* [PATCH v2 bpf-next 00/12] CO-RE offset relocations
@ 2019-07-30 19:53 Andrii Nakryiko
2019-07-30 19:53 ` [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading Andrii Nakryiko
` (11 more replies)
0 siblings, 12 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:53 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
This patch set implements central part of CO-RE (Compile Once - Run
Everywhere, see [0] and [1] for slides and video): relocating fields offsets.
Most of the details are written down as comments to corresponding parts of the
code.
Patch #1 adds loading of .BTF.ext offset relocations section and macros to
work with its contents.
Patch #2 implements CO-RE relocations algorithm in libbpf.
Patch #3 introduced BPF_CORE_READ macro, hiding usage of Clang's
__builtin_preserve_access_index intrinsic that records offset relocation.
Patches #4-#12 adds selftests validating various parts of relocation handling,
type compatibility, etc.
For all tests to work, you'll need latest Clang/LLVM supporting
__builtin_preserve_access_index intrinsic, used for recording offset
relocations. Kernel on which selftests run should have BTF information built
in (CONFIG_DEBUG_INFO_BTF=y).
[0] http://vger.kernel.org/bpfconf2019.html#session-2
[1] http://vger.kernel.org/lpc-bpf2018.html#session-2
v1->v2:
- add offsetofend(), fix btf_ext optional fields checks (Song);
- add bpf_core_dump_spec() for logging spec representation;
- move special first element processing out of the loop (Song);
- typo fixes (Song);
- drop BPF_ST | BPF_MEM insn relocation (Alexei);
- extracted BPF_CORE_READ into bpf_helpers (Alexei);
- added extra tests validating Clang capturing relocs correctly (Yonghong);
- switch core_relocs.c to use sub-tests;
- updated mods tests after Clang bug was fixed (Yonghong);
- fix bug enumerating candidate types;
Andrii Nakryiko (12):
libbpf: add .BTF.ext offset relocation section loading
libbpf: implement BPF CO-RE offset relocation algorithm
selftests/bpf: add BPF_CORE_READ relocatable read macro
selftests/bpf: add CO-RE relocs testing setup
selftests/bpf: add CO-RE relocs struct flavors tests
selftests/bpf: add CO-RE relocs nesting tests
selftests/bpf: add CO-RE relocs array tests
selftests/bpf: add CO-RE relocs enum/ptr/func_proto tests
selftests/bpf: add CO-RE relocs modifiers/typedef tests
selftests/bpf: add CO-RE relocs ptr-as-array tests
selftests/bpf: add CO-RE relocs ints tests
selftests/bpf: add CO-RE relocs misc tests
tools/lib/bpf/btf.c | 69 +-
tools/lib/bpf/btf.h | 4 +
tools/lib/bpf/libbpf.c | 915 +++++++++++++++++-
tools/lib/bpf/libbpf.h | 1 +
tools/lib/bpf/libbpf_internal.h | 105 ++
tools/testing/selftests/bpf/bpf_helpers.h | 19 +
.../selftests/bpf/prog_tests/core_reloc.c | 381 ++++++++
.../bpf/progs/btf__core_reloc_arrays.c | 3 +
.../btf__core_reloc_arrays___diff_arr_dim.c | 3 +
...btf__core_reloc_arrays___diff_arr_val_sz.c | 3 +
.../btf__core_reloc_arrays___err_non_array.c | 3 +
...btf__core_reloc_arrays___err_too_shallow.c | 3 +
.../btf__core_reloc_arrays___err_too_small.c | 3 +
..._core_reloc_arrays___err_wrong_val_type1.c | 3 +
..._core_reloc_arrays___err_wrong_val_type2.c | 3 +
.../bpf/progs/btf__core_reloc_flavors.c | 3 +
.../btf__core_reloc_flavors__err_wrong_name.c | 3 +
.../bpf/progs/btf__core_reloc_ints.c | 3 +
.../bpf/progs/btf__core_reloc_ints___bool.c | 3 +
.../btf__core_reloc_ints___err_bitfield.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_16.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_32.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_64.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_8.c | 3 +
.../btf__core_reloc_ints___reverse_sign.c | 3 +
.../bpf/progs/btf__core_reloc_misc.c | 4 +
.../bpf/progs/btf__core_reloc_mods.c | 3 +
.../progs/btf__core_reloc_mods___mod_swap.c | 3 +
.../progs/btf__core_reloc_mods___typedefs.c | 3 +
.../bpf/progs/btf__core_reloc_nesting.c | 3 +
.../btf__core_reloc_nesting___anon_embed.c | 3 +
...f__core_reloc_nesting___dup_compat_types.c | 5 +
...core_reloc_nesting___err_array_container.c | 3 +
...tf__core_reloc_nesting___err_array_field.c | 3 +
...e_reloc_nesting___err_dup_incompat_types.c | 4 +
...re_reloc_nesting___err_missing_container.c | 3 +
...__core_reloc_nesting___err_missing_field.c | 3 +
..._reloc_nesting___err_nonstruct_container.c | 3 +
...e_reloc_nesting___err_partial_match_dups.c | 4 +
.../btf__core_reloc_nesting___err_too_deep.c | 3 +
.../btf__core_reloc_nesting___extra_nesting.c | 3 +
..._core_reloc_nesting___struct_union_mixup.c | 3 +
.../bpf/progs/btf__core_reloc_primitives.c | 3 +
...f__core_reloc_primitives___diff_enum_def.c | 3 +
..._core_reloc_primitives___diff_func_proto.c | 3 +
...f__core_reloc_primitives___diff_ptr_type.c | 3 +
...tf__core_reloc_primitives___err_non_enum.c | 3 +
...btf__core_reloc_primitives___err_non_int.c | 3 +
...btf__core_reloc_primitives___err_non_ptr.c | 3 +
.../bpf/progs/btf__core_reloc_ptr_as_arr.c | 3 +
.../btf__core_reloc_ptr_as_arr___diff_sz.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 667 +++++++++++++
.../bpf/progs/test_core_reloc_arrays.c | 55 ++
.../bpf/progs/test_core_reloc_flavors.c | 62 ++
.../bpf/progs/test_core_reloc_ints.c | 44 +
.../bpf/progs/test_core_reloc_kernel.c | 36 +
.../bpf/progs/test_core_reloc_misc.c | 58 ++
.../bpf/progs/test_core_reloc_mods.c | 62 ++
.../bpf/progs/test_core_reloc_nesting.c | 46 +
.../bpf/progs/test_core_reloc_primitives.c | 43 +
.../bpf/progs/test_core_reloc_ptr_as_arr.c | 30 +
61 files changed, 2685 insertions(+), 49 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/core_reloc.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_dim.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_val_sz.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_non_array.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_shallow.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_small.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type1.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type2.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_flavors.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_flavors__err_wrong_name.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___bool.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_bitfield.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_16.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_32.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_64.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_8.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___reverse_sign.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_misc.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_mods.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_mods___mod_swap.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_mods___typedefs.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___anon_embed.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___dup_compat_types.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_container.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_field.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_dup_incompat_types.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_container.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_field.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_nonstruct_container.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_partial_match_dups.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_too_deep.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___extra_nesting.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___struct_union_mixup.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_enum_def.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_func_proto.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_ptr_type.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_enum.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_int.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_ptr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr___diff_sz.c
create mode 100644 tools/testing/selftests/bpf/progs/core_reloc_types.h
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_flavors.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_ints.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_misc.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_mods.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_nesting.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_primitives.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_ptr_as_arr.c
--
2.17.1
^ permalink raw reply [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
@ 2019-07-30 19:53 ` Andrii Nakryiko
2019-07-30 21:19 ` Song Liu
2019-07-30 19:53 ` [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm Andrii Nakryiko
` (10 subsequent siblings)
11 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:53 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add support for BPF CO-RE offset relocations. Add section/record
iteration macros for .BTF.ext. These macro are useful for iterating over
each .BTF.ext record, either for dumping out contents or later for BPF
CO-RE relocation handling.
To enable other parts of libbpf to work with .BTF.ext contents, moved
a bunch of type definitions into libbpf_internal.h.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/lib/bpf/btf.c | 69 ++++++++-------------
tools/lib/bpf/btf.h | 4 ++
tools/lib/bpf/libbpf_internal.h | 105 ++++++++++++++++++++++++++++++++
3 files changed, 136 insertions(+), 42 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 467224feb43b..f2a3c356b388 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -42,47 +42,6 @@ struct btf {
int fd;
};
-struct btf_ext_info {
- /*
- * info points to the individual info section (e.g. func_info and
- * line_info) from the .BTF.ext. It does not include the __u32 rec_size.
- */
- void *info;
- __u32 rec_size;
- __u32 len;
-};
-
-struct btf_ext {
- union {
- struct btf_ext_header *hdr;
- void *data;
- };
- struct btf_ext_info func_info;
- struct btf_ext_info line_info;
- __u32 data_size;
-};
-
-struct btf_ext_info_sec {
- __u32 sec_name_off;
- __u32 num_info;
- /* Followed by num_info * record_size number of bytes */
- __u8 data[0];
-};
-
-/* The minimum bpf_func_info checked by the loader */
-struct bpf_func_info_min {
- __u32 insn_off;
- __u32 type_id;
-};
-
-/* The minimum bpf_line_info checked by the loader */
-struct bpf_line_info_min {
- __u32 insn_off;
- __u32 file_name_off;
- __u32 line_off;
- __u32 line_col;
-};
-
static inline __u64 ptr_to_u64(const void *ptr)
{
return (__u64) (unsigned long) ptr;
@@ -831,6 +790,9 @@ static int btf_ext_setup_info(struct btf_ext *btf_ext,
/* The start of the info sec (including the __u32 record_size). */
void *info;
+ if (ext_sec->len == 0)
+ return 0;
+
if (ext_sec->off & 0x03) {
pr_debug(".BTF.ext %s section is not aligned to 4 bytes\n",
ext_sec->desc);
@@ -934,11 +896,24 @@ static int btf_ext_setup_line_info(struct btf_ext *btf_ext)
return btf_ext_setup_info(btf_ext, ¶m);
}
+static int btf_ext_setup_offset_reloc(struct btf_ext *btf_ext)
+{
+ struct btf_ext_sec_setup_param param = {
+ .off = btf_ext->hdr->offset_reloc_off,
+ .len = btf_ext->hdr->offset_reloc_len,
+ .min_rec_size = sizeof(struct bpf_offset_reloc),
+ .ext_info = &btf_ext->offset_reloc_info,
+ .desc = "offset_reloc",
+ };
+
+ return btf_ext_setup_info(btf_ext, ¶m);
+}
+
static int btf_ext_parse_hdr(__u8 *data, __u32 data_size)
{
const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
- if (data_size < offsetof(struct btf_ext_header, func_info_off) ||
+ if (data_size < offsetofend(struct btf_ext_header, hdr_len) ||
data_size < hdr->hdr_len) {
pr_debug("BTF.ext header not found");
return -EINVAL;
@@ -996,6 +971,9 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
}
memcpy(btf_ext->data, data, size);
+ if (btf_ext->hdr->hdr_len <
+ offsetofend(struct btf_ext_header, line_info_len))
+ goto done;
err = btf_ext_setup_func_info(btf_ext);
if (err)
goto done;
@@ -1004,6 +982,13 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
if (err)
goto done;
+ if (btf_ext->hdr->hdr_len <
+ offsetofend(struct btf_ext_header, offset_reloc_len))
+ goto done;
+ err = btf_ext_setup_offset_reloc(btf_ext);
+ if (err)
+ goto done;
+
done:
if (err) {
btf_ext__free(btf_ext);
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 88a52ae56fc6..287361ee1f6b 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -57,6 +57,10 @@ struct btf_ext_header {
__u32 func_info_len;
__u32 line_info_off;
__u32 line_info_len;
+
+ /* optional part of .BTF.ext header */
+ __u32 offset_reloc_off;
+ __u32 offset_reloc_len;
};
LIBBPF_API void btf__free(struct btf *btf);
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 2ac29bd36226..2e83a34f8c79 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -29,6 +29,10 @@
#ifndef max
# define max(x, y) ((x) < (y) ? (y) : (x))
#endif
+#ifndef offsetofend
+# define offsetofend(TYPE, FIELD) \
+ (offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD))
+#endif
extern void libbpf_print(enum libbpf_print_level level,
const char *format, ...)
@@ -46,4 +50,105 @@ do { \
int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
const char *str_sec, size_t str_len);
+struct btf_ext_info {
+ /*
+ * info points to the individual info section (e.g. func_info and
+ * line_info) from the .BTF.ext. It does not include the __u32 rec_size.
+ */
+ void *info;
+ __u32 rec_size;
+ __u32 len;
+};
+
+#define for_each_btf_ext_sec(seg, sec) \
+ for (sec = (seg)->info; \
+ (void *)sec < (seg)->info + (seg)->len; \
+ sec = (void *)sec + sizeof(struct btf_ext_info_sec) + \
+ (seg)->rec_size * sec->num_info)
+
+#define for_each_btf_ext_rec(seg, sec, i, rec) \
+ for (i = 0, rec = (void *)&(sec)->data; \
+ i < (sec)->num_info; \
+ i++, rec = (void *)rec + (seg)->rec_size)
+
+struct btf_ext {
+ union {
+ struct btf_ext_header *hdr;
+ void *data;
+ };
+ struct btf_ext_info func_info;
+ struct btf_ext_info line_info;
+ struct btf_ext_info offset_reloc_info;
+ __u32 data_size;
+};
+
+struct btf_ext_info_sec {
+ __u32 sec_name_off;
+ __u32 num_info;
+ /* Followed by num_info * record_size number of bytes */
+ __u8 data[0];
+};
+
+/* The minimum bpf_func_info checked by the loader */
+struct bpf_func_info_min {
+ __u32 insn_off;
+ __u32 type_id;
+};
+
+/* The minimum bpf_line_info checked by the loader */
+struct bpf_line_info_min {
+ __u32 insn_off;
+ __u32 file_name_off;
+ __u32 line_off;
+ __u32 line_col;
+};
+
+/* The minimum bpf_offset_reloc checked by the loader
+ *
+ * Offset relocation captures the following data:
+ * - insn_off - instruction offset (in bytes) within a BPF program that needs
+ * its insn->imm field to be relocated with actual offset;
+ * - type_id - BTF type ID of the "root" (containing) entity of a relocatable
+ * offset;
+ * - access_str_off - offset into corresponding .BTF string section. String
+ * itself encodes an accessed field using a sequence of field and array
+ * indicies, separated by colon (:). It's conceptually very close to LLVM's
+ * getelementptr ([0]) instruction's arguments for identifying offset to
+ * a field.
+ *
+ * Example to provide a better feel.
+ *
+ * struct sample {
+ * int a;
+ * struct {
+ * int b[10];
+ * };
+ * };
+ *
+ * struct sample *s = ...;
+ * int x = &s->a; // encoded as "0:0" (a is field #0)
+ * int y = &s->b[5]; // encoded as "0:1:0:5" (anon struct is field #1,
+ * // b is field #0 inside anon struct, accessing elem #5)
+ * int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array)
+ *
+ * type_id for all relocs in this example will capture BTF type id of
+ * `struct sample`.
+ *
+ * Such relocation is emitted when using __builtin_preserve_access_index()
+ * Clang built-in, passing expression that captures field address, e.g.:
+ *
+ * bpf_probe_read(&dst, sizeof(dst),
+ * __builtin_preserve_access_index(&src->a.b.c));
+ *
+ * In this case Clang will emit offset relocation recording necessary data to
+ * be able to find offset of embedded `a.b.c` field within `src` struct.
+ *
+ * [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction
+ */
+struct bpf_offset_reloc {
+ __u32 insn_off;
+ __u32 type_id;
+ __u32 access_str_off;
+};
+
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
2019-07-30 19:53 ` [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading Andrii Nakryiko
@ 2019-07-30 19:53 ` Andrii Nakryiko
2019-07-30 23:43 ` Song Liu
2019-07-31 0:39 ` Song Liu
2019-07-30 19:53 ` [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro Andrii Nakryiko
` (9 subsequent siblings)
11 siblings, 2 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:53 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
This patch implements the core logic for BPF CO-RE offsets relocations.
Every instruction that needs to be relocated has corresponding
bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
to match recorded "local" relocation spec against potentially many
compatible "target" types, creating corresponding spec. Details of the
algorithm are noted in corresponding comments in the code.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
tools/lib/bpf/libbpf.h | 1 +
2 files changed, 909 insertions(+), 7 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ead915aec349..75da90928257 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -38,6 +38,7 @@
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/vfs.h>
+#include <sys/utsname.h>
#include <tools/libc_compat.h>
#include <libelf.h>
#include <gelf.h>
@@ -47,6 +48,7 @@
#include "btf.h"
#include "str_error.h"
#include "libbpf_internal.h"
+#include "hashmap.h"
#ifndef EM_BPF
#define EM_BPF 247
@@ -1015,17 +1017,22 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict)
return 0;
}
-static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
- __u32 id)
+static const struct btf_type *
+skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
{
const struct btf_type *t = btf__type_by_id(btf, id);
+ if (res_id)
+ *res_id = id;
+
while (true) {
switch (BTF_INFO_KIND(t->info)) {
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
case BTF_KIND_TYPEDEF:
+ if (res_id)
+ *res_id = t->type;
t = btf__type_by_id(btf, t->type);
break;
default:
@@ -1044,7 +1051,7 @@ static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
static bool get_map_field_int(const char *map_name, const struct btf *btf,
const struct btf_type *def,
const struct btf_member *m, __u32 *res) {
- const struct btf_type *t = skip_mods_and_typedefs(btf, m->type);
+ const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
const char *name = btf__name_by_offset(btf, m->name_off);
const struct btf_array *arr_info;
const struct btf_type *arr_t;
@@ -1110,7 +1117,7 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
return -EOPNOTSUPP;
}
- def = skip_mods_and_typedefs(obj->btf, var->type);
+ def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
if (BTF_INFO_KIND(def->info) != BTF_KIND_STRUCT) {
pr_warning("map '%s': unexpected def kind %u.\n",
map_name, BTF_INFO_KIND(var->info));
@@ -2292,6 +2299,893 @@ bpf_program_reloc_btf_ext(struct bpf_program *prog, struct bpf_object *obj,
return 0;
}
+#define BPF_CORE_SPEC_MAX_LEN 64
+
+/* represents BPF CO-RE field or array element accessor */
+struct bpf_core_accessor {
+ __u32 type_id; /* struct/union type or array element type */
+ __u32 idx; /* field index or array index */
+ const char *name; /* field name or NULL for array accessor */
+};
+
+struct bpf_core_spec {
+ const struct btf *btf;
+ /* high-level spec: named fields and array indices only */
+ struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
+ /* high-level spec length */
+ int len;
+ /* raw, low-level spec: 1-to-1 with accessor spec string */
+ int raw_spec[BPF_CORE_SPEC_MAX_LEN];
+ /* raw spec length */
+ int raw_len;
+ /* field byte offset represented by spec */
+ __u32 offset;
+};
+
+static bool str_is_empty(const char *s)
+{
+ return !s || !s[0];
+}
+
+static int btf_kind(const struct btf_type *t)
+{
+ return BTF_INFO_KIND(t->info);
+}
+
+static bool btf_is_composite(const struct btf_type *t)
+{
+ int kind = btf_kind(t);
+
+ return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
+}
+
+static bool btf_is_array(const struct btf_type *t)
+{
+ return btf_kind(t) == BTF_KIND_ARRAY;
+}
+
+/*
+ * Turn bpf_offset_reloc into a low- and high-level spec representation,
+ * validating correctness along the way, as well as calculating resulting
+ * field offset (in bytes), specified by accessor string. Low-level spec
+ * captures every single level of nestedness, including traversing anonymous
+ * struct/union members. High-level one only captures semantically meaningful
+ * "turning points": named fields and array indicies.
+ * E.g., for this case:
+ *
+ * struct sample {
+ * int __unimportant;
+ * struct {
+ * int __1;
+ * int __2;
+ * int a[7];
+ * };
+ * };
+ *
+ * struct sample *s = ...;
+ *
+ * int x = &s->a[3]; // access string = '0:1:2:3'
+ *
+ * Low-level spec has 1:1 mapping with each element of access string (it's
+ * just a parsed access string representation): [0, 1, 2, 3].
+ *
+ * High-level spec will capture only 3 points:
+ * - intial zero-index access by pointer (&s->... is the same as &s[0]...);
+ * - field 'a' access (corresponds to '2' in low-level spec);
+ * - array element #3 access (corresponds to '3' in low-level spec).
+ *
+ */
+static int bpf_core_spec_parse(const struct btf *btf,
+ __u32 type_id,
+ const char *spec_str,
+ struct bpf_core_spec *spec)
+{
+ int access_idx, parsed_len, i;
+ const struct btf_type *t;
+ const char *name;
+ __u32 id;
+ __s64 sz;
+
+ if (str_is_empty(spec_str) || *spec_str == ':')
+ return -EINVAL;
+
+ memset(spec, 0, sizeof(*spec));
+ spec->btf = btf;
+
+ /* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
+ while (*spec_str) {
+ if (*spec_str == ':')
+ ++spec_str;
+ if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
+ return -EINVAL;
+ if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
+ return -E2BIG;
+ spec_str += parsed_len;
+ spec->raw_spec[spec->raw_len++] = access_idx;
+ }
+
+ if (spec->raw_len == 0)
+ return -EINVAL;
+
+ /* first spec value is always reloc type array index */
+ t = skip_mods_and_typedefs(btf, type_id, &id);
+ if (!t)
+ return -EINVAL;
+
+ access_idx = spec->raw_spec[0];
+ spec->spec[0].type_id = id;
+ spec->spec[0].idx = access_idx;
+ spec->len++;
+
+ sz = btf__resolve_size(btf, id);
+ if (sz < 0)
+ return sz;
+ spec->offset = access_idx * sz;
+
+ for (i = 1; i < spec->raw_len; i++) {
+ t = skip_mods_and_typedefs(btf, id, &id);
+ if (!t)
+ return -EINVAL;
+
+ access_idx = spec->raw_spec[i];
+
+ if (btf_is_composite(t)) {
+ const struct btf_member *m = (void *)(t + 1);
+ __u32 offset;
+
+ if (access_idx >= BTF_INFO_VLEN(t->info))
+ return -EINVAL;
+
+ m = &m[access_idx];
+
+ if (BTF_INFO_KFLAG(t->info)) {
+ if (BTF_MEMBER_BITFIELD_SIZE(m->offset))
+ return -EINVAL;
+ offset = BTF_MEMBER_BIT_OFFSET(m->offset);
+ } else {
+ offset = m->offset;
+ }
+ if (m->offset % 8)
+ return -EINVAL;
+ spec->offset += offset / 8;
+
+ if (m->name_off) {
+ name = btf__name_by_offset(btf, m->name_off);
+ if (str_is_empty(name))
+ return -EINVAL;
+
+ spec->spec[spec->len].type_id = id;
+ spec->spec[spec->len].idx = access_idx;
+ spec->spec[spec->len].name = name;
+ spec->len++;
+ }
+
+ id = m->type;
+ } else if (btf_is_array(t)) {
+ const struct btf_array *a = (void *)(t + 1);
+
+ t = skip_mods_and_typedefs(btf, a->type, &id);
+ if (!t || access_idx >= a->nelems)
+ return -EINVAL;
+
+ spec->spec[spec->len].type_id = id;
+ spec->spec[spec->len].idx = access_idx;
+ spec->len++;
+
+ sz = btf__resolve_size(btf, id);
+ if (sz < 0)
+ return sz;
+ spec->offset += access_idx * sz;
+ } else {
+ pr_warning("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %d\n",
+ type_id, spec_str, i, id, btf_kind(t));
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+/* Given 'some_struct_name___with_flavor' return the length of a name prefix
+ * before last triple underscore. Struct name part after last triple
+ * underscore is ignored by BPF CO-RE relocation during relocation matching.
+ */
+static size_t bpf_core_essential_name_len(const char *name)
+{
+ size_t n = strlen(name);
+ int i = n - 3;
+
+ while (i > 0) {
+ if (name[i] == '_' && name[i + 1] == '_' && name[i + 2] == '_')
+ return i;
+ i--;
+ }
+ return n;
+}
+
+/* dynamically sized list of type IDs */
+struct ids_vec {
+ __u32 *data;
+ int len;
+};
+
+static void bpf_core_free_cands(struct ids_vec *cand_ids)
+{
+ free(cand_ids->data);
+ free(cand_ids);
+}
+
+static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
+ __u32 local_type_id,
+ const struct btf *targ_btf)
+{
+ size_t local_essent_len, targ_essent_len;
+ const char *local_name, *targ_name;
+ const struct btf_type *t;
+ struct ids_vec *cand_ids;
+ __u32 *new_ids;
+ int i, err, n;
+
+ t = btf__type_by_id(local_btf, local_type_id);
+ if (!t)
+ return ERR_PTR(-EINVAL);
+
+ local_name = btf__name_by_offset(local_btf, t->name_off);
+ if (str_is_empty(local_name))
+ return ERR_PTR(-EINVAL);
+ local_essent_len = bpf_core_essential_name_len(local_name);
+
+ cand_ids = calloc(1, sizeof(*cand_ids));
+ if (!cand_ids)
+ return ERR_PTR(-ENOMEM);
+
+ n = btf__get_nr_types(targ_btf);
+ for (i = 1; i <= n; i++) {
+ t = btf__type_by_id(targ_btf, i);
+ targ_name = btf__name_by_offset(targ_btf, t->name_off);
+ if (str_is_empty(targ_name))
+ continue;
+
+ targ_essent_len = bpf_core_essential_name_len(targ_name);
+ if (targ_essent_len != local_essent_len)
+ continue;
+
+ if (strncmp(local_name, targ_name, local_essent_len) == 0) {
+ pr_debug("[%d] (%s): found candidate [%d] (%s)\n",
+ local_type_id, local_name, i, targ_name);
+ new_ids = realloc(cand_ids->data, cand_ids->len + 1);
+ if (!new_ids) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ cand_ids->data = new_ids;
+ cand_ids->data[cand_ids->len++] = i;
+ }
+ }
+ return cand_ids;
+err_out:
+ bpf_core_free_cands(cand_ids);
+ return ERR_PTR(err);
+}
+
+/* Check two types for compatibility, skipping const/volatile/restrict and
+ * typedefs, to ensure we are relocating offset to the compatible entities:
+ * - any two STRUCTs/UNIONs are compatible and can be mixed;
+ * - any two FWDs are compatible;
+ * - any two PTRs are always compatible;
+ * - for ENUMs, check sizes, names are ignored;
+ * - for INT, size and bitness should match, signedness is ignored;
+ * - for ARRAY, dimensionality is ignored, element types are checked for
+ * compatibility recursively;
+ * - everything else shouldn't be ever a target of relocation.
+ * These rules are not set in stone and probably will be adjusted as we get
+ * more experience with using BPF CO-RE relocations.
+ */
+static int bpf_core_fields_are_compat(const struct btf *local_btf,
+ __u32 local_id,
+ const struct btf *targ_btf,
+ __u32 targ_id)
+{
+ const struct btf_type *local_type, *targ_type;
+ __u16 kind;
+
+recur:
+ local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
+ targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
+ if (!local_type || !targ_type)
+ return -EINVAL;
+
+ if (btf_is_composite(local_type) && btf_is_composite(targ_type))
+ return 1;
+ if (BTF_INFO_KIND(local_type->info) != BTF_INFO_KIND(targ_type->info))
+ return 0;
+
+ kind = BTF_INFO_KIND(local_type->info);
+ switch (kind) {
+ case BTF_KIND_FWD:
+ case BTF_KIND_PTR:
+ return 1;
+ case BTF_KIND_ENUM:
+ return local_type->size == targ_type->size;
+ case BTF_KIND_INT: {
+ __u32 loc_int = *(__u32 *)(local_type + 1);
+ __u32 targ_int = *(__u32 *)(targ_type + 1);
+
+ return BTF_INT_OFFSET(loc_int) == 0 &&
+ BTF_INT_OFFSET(targ_int) == 0 &&
+ local_type->size == targ_type->size &&
+ BTF_INT_BITS(loc_int) == BTF_INT_BITS(targ_int);
+ }
+ case BTF_KIND_ARRAY: {
+ const struct btf_array *loc_a, *targ_a;
+
+ loc_a = (void *)(local_type + 1);
+ targ_a = (void *)(targ_type + 1);
+ local_id = loc_a->type;
+ targ_id = targ_a->type;
+ goto recur;
+ }
+ default:
+ pr_warning("unexpected kind %d relocated, local [%d], target [%d]\n",
+ kind, local_id, targ_id);
+ return 0;
+ }
+}
+
+/*
+ * Given single high-level named field accessor in local type, find
+ * corresponding high-level accessor for a target type. Along the way,
+ * maintain low-level spec for target as well. Also keep updating target
+ * offset.
+ *
+ * Searching is performed through recursive exhaustive enumeration of all
+ * fields of a struct/union. If there are any anonymous (embedded)
+ * structs/unions, they are recursively searched as well. If field with
+ * desired name is found, check compatibility between local and target types,
+ * before returning result.
+ *
+ * 1 is returned, if field is found.
+ * 0 is returned if no compatible field is found.
+ * <0 is returned on error.
+ */
+static int bpf_core_match_member(const struct btf *local_btf,
+ const struct bpf_core_accessor *local_acc,
+ const struct btf *targ_btf,
+ __u32 targ_id,
+ struct bpf_core_spec *spec,
+ __u32 *next_targ_id)
+{
+ const struct btf_type *local_type, *targ_type;
+ const struct btf_member *local_member, *m;
+ const char *local_name, *targ_name;
+ __u32 local_id;
+ int i, n, found;
+
+ targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
+ if (!targ_type)
+ return -EINVAL;
+ if (!btf_is_composite(targ_type))
+ return 0;
+
+ local_id = local_acc->type_id;
+ local_type = btf__type_by_id(local_btf, local_id);
+ local_member = (void *)(local_type + 1);
+ local_member += local_acc->idx;
+ local_name = btf__name_by_offset(local_btf, local_member->name_off);
+
+ n = BTF_INFO_VLEN(targ_type->info);
+ m = (void *)(targ_type + 1);
+ for (i = 0; i < n; i++, m++) {
+ __u32 offset;
+
+ /* bitfield relocations not supported */
+ if (BTF_INFO_KFLAG(targ_type->info)) {
+ if (BTF_MEMBER_BITFIELD_SIZE(m->offset))
+ continue;
+ offset = BTF_MEMBER_BIT_OFFSET(m->offset);
+ } else {
+ offset = m->offset;
+ }
+ if (offset % 8)
+ continue;
+
+ /* too deep struct/union/array nesting */
+ if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
+ return -E2BIG;
+
+ /* speculate this member will be the good one */
+ spec->offset += offset / 8;
+ spec->raw_spec[spec->raw_len++] = i;
+
+ targ_name = btf__name_by_offset(targ_btf, m->name_off);
+ if (str_is_empty(targ_name)) {
+ /* embedded struct/union, we need to go deeper */
+ found = bpf_core_match_member(local_btf, local_acc,
+ targ_btf, m->type,
+ spec, next_targ_id);
+ if (found) /* either found or error */
+ return found;
+ } else if (strcmp(local_name, targ_name) == 0) {
+ /* matching named field */
+ struct bpf_core_accessor *targ_acc;
+
+ targ_acc = &spec->spec[spec->len++];
+ targ_acc->type_id = targ_id;
+ targ_acc->idx = i;
+ targ_acc->name = targ_name;
+
+ *next_targ_id = m->type;
+ found = bpf_core_fields_are_compat(local_btf,
+ local_member->type,
+ targ_btf, m->type);
+ if (!found)
+ spec->len--; /* pop accessor */
+ return found;
+ }
+ /* member turned out not to be what we looked for */
+ spec->offset -= offset / 8;
+ spec->raw_len--;
+ }
+
+ return 0;
+}
+
+/*
+ * Try to match local spec to a target type and, if successful, produce full
+ * target spec (high-level, low-level + offset).
+ */
+static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
+ const struct btf *targ_btf, __u32 targ_id,
+ struct bpf_core_spec *targ_spec)
+{
+ const struct btf_type *targ_type;
+ const struct bpf_core_accessor *local_acc;
+ struct bpf_core_accessor *targ_acc;
+ int i, sz, matched;
+
+ memset(targ_spec, 0, sizeof(*targ_spec));
+ targ_spec->btf = targ_btf;
+
+ local_acc = &local_spec->spec[0];
+ targ_acc = &targ_spec->spec[0];
+
+ for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
+ targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
+ &targ_id);
+ if (!targ_type)
+ return -EINVAL;
+
+ if (local_acc->name) {
+ matched = bpf_core_match_member(local_spec->btf,
+ local_acc,
+ targ_btf, targ_id,
+ targ_spec, &targ_id);
+ if (matched <= 0)
+ return matched;
+ } else {
+ /* for i=0, targ_id is already treated as array element
+ * type (because it's the original struct), for others
+ * we should find array element type first
+ */
+ if (i > 0) {
+ const struct btf_array *a;
+
+ if (!btf_is_array(targ_type))
+ return 0;
+
+ a = (void *)(targ_type + 1);
+ if (local_acc->idx >= a->nelems)
+ return 0;
+ if (!skip_mods_and_typedefs(targ_btf, a->type,
+ &targ_id))
+ return -EINVAL;
+ }
+
+ /* too deep struct/union/array nesting */
+ if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
+ return -E2BIG;
+
+ targ_acc->type_id = targ_id;
+ targ_acc->idx = local_acc->idx;
+ targ_acc->name = NULL;
+ targ_spec->len++;
+ targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
+ targ_spec->raw_len++;
+
+ sz = btf__resolve_size(targ_btf, targ_id);
+ if (sz < 0)
+ return sz;
+ targ_spec->offset += local_acc->idx * sz;
+ }
+ }
+
+ return 1;
+}
+
+/*
+ * Patch relocatable BPF instruction.
+ * Expected insn->imm value is provided for validation, as well as the new
+ * relocated value.
+ *
+ * Currently three kinds of BPF instructions are supported:
+ * 1. rX = <imm> (assignment with immediate operand);
+ * 2. rX += <imm> (arithmetic operations with immediate operand);
+ * 3. *(rX) = <imm> (indirect memory assignment with immediate operand).
+ *
+ * If actual insn->imm value is wrong, bail out.
+ */
+static int bpf_core_reloc_insn(struct bpf_program *prog, int insn_off,
+ __u32 orig_off, __u32 new_off)
+{
+ struct bpf_insn *insn;
+ int insn_idx;
+ __u8 class;
+
+ if (insn_off % sizeof(struct bpf_insn))
+ return -EINVAL;
+ insn_idx = insn_off / sizeof(struct bpf_insn);
+
+ insn = &prog->insns[insn_idx];
+ class = BPF_CLASS(insn->code);
+
+ if (class == BPF_ALU || class == BPF_ALU64) {
+ if (BPF_SRC(insn->code) != BPF_K)
+ return -EINVAL;
+ if (insn->imm != orig_off)
+ return -EINVAL;
+ insn->imm = new_off;
+ pr_debug("prog '%s': patched insn #%d (ALU/ALU64) imm %d -> %d\n",
+ bpf_program__title(prog, false),
+ insn_idx, orig_off, new_off);
+ } else {
+ pr_warning("prog '%s': trying to relocate unrecognized insn #%d, code:%x, src:%x, dst:%x, off:%x, imm:%x\n",
+ bpf_program__title(prog, false),
+ insn_idx, insn->code, insn->src_reg, insn->dst_reg,
+ insn->off, insn->imm);
+ return -EINVAL;
+ }
+ return 0;
+}
+
+/*
+ * Probe few well-known locations for vmlinux kernel image and try to load BTF
+ * data out of it to use for target BTF.
+ */
+static struct btf *bpf_core_find_kernel_btf(void)
+{
+ const char *locations[] = {
+ "/lib/modules/%1$s/vmlinux-%1$s",
+ "/usr/lib/modules/%1$s/kernel/vmlinux",
+ };
+ char path[PATH_MAX + 1];
+ struct utsname buf;
+ struct btf *btf;
+ int i, err;
+
+ err = uname(&buf);
+ if (err) {
+ pr_warning("failed to uname(): %d\n", err);
+ return ERR_PTR(err);
+ }
+
+ for (i = 0; i < ARRAY_SIZE(locations); i++) {
+ snprintf(path, PATH_MAX, locations[i], buf.release);
+ pr_debug("attempting to load kernel BTF from '%s'\n", path);
+
+ if (access(path, R_OK))
+ continue;
+
+ btf = btf__parse_elf(path, NULL);
+ if (IS_ERR(btf))
+ continue;
+
+ pr_debug("successfully loaded kernel BTF from '%s'\n", path);
+ return btf;
+ }
+
+ pr_warning("failed to find valid kernel BTF\n");
+ return ERR_PTR(-ESRCH);
+}
+
+/* Output spec definition in the format:
+ * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
+ * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
+ */
+static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
+{
+ const struct btf_type *t;
+ const char *s;
+ __u32 type_id;
+ int i;
+
+ type_id = spec->spec[0].type_id;
+ t = btf__type_by_id(spec->btf, type_id);
+ s = btf__name_by_offset(spec->btf, t->name_off);
+ libbpf_print(level, "[%u] (%s) + ", type_id, s);
+
+ for (i = 0; i < spec->raw_len; i++)
+ libbpf_print(level, "%d%s", spec->raw_spec[i],
+ i == spec->raw_len - 1 ? " => " : ":");
+
+ libbpf_print(level, "%u @ &x", spec->offset);
+
+ for (i = 0; i < spec->len; i++) {
+ if (spec->spec[i].name)
+ libbpf_print(level, ".%s", spec->spec[i].name);
+ else
+ libbpf_print(level, "[%u]", spec->spec[i].idx);
+ }
+
+}
+
+static size_t bpf_core_hash_fn(const void *key, void *ctx)
+{
+ return (size_t)key;
+}
+
+static bool bpf_core_equal_fn(const void *k1, const void *k2, void *ctx)
+{
+ return k1 == k2;
+}
+
+static void *u32_to_ptr(__u32 x)
+{
+ return (void *)(uintptr_t)x;
+}
+
+/*
+ * CO-RE relocate single instruction.
+ *
+ * The outline and important points of the algorithm:
+ * 1. For given local type, find corresponding candidate target types.
+ * Candidate type is a type with the same "essential" name, ignoring
+ * everything after last triple underscore (___). E.g., `sample`,
+ * `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
+ * for each other. Names with triple underscore are referred to as
+ * "flavors" and are useful, among other things, to allow to
+ * specify/support incompatible variations of the same kernel struct, which
+ * might differ between different kernel versions and/or build
+ * configurations.
+ *
+ * N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
+ * converter, when deduplicated BTF of a kernel still contains more than
+ * one different types with the same name. In that case, ___2, ___3, etc
+ * are appended starting from second name conflict. But start flavors are
+ * also useful to be defined "locally", in BPF program, to extract same
+ * data from incompatible changes between different kernel
+ * versions/configurations. For instance, to handle field renames between
+ * kernel versions, one can use two flavors of the struct name with the
+ * same common name and use conditional relocations to extract that field,
+ * depending on target kernel version.
+ * 2. For each candidate type, try to match local specification to this
+ * candidate target type. Matching involves finding corresponding
+ * high-level spec accessors, meaning that all named fields should match,
+ * as well as all array accesses should be within the actual bounds. Also,
+ * types should be compatible (see bpf_core_fields_are_compat for details).
+ * 3. It is supported and expected that there might be multiple flavors
+ * matching the spec. As long as all the specs resolve to the same set of
+ * offsets across all candidates, there is not error. If there is any
+ * ambiguity, CO-RE relocation will fail. This is necessary to accomodate
+ * imprefection of BTF deduplication, which can cause slight duplication of
+ * the same BTF type, if some directly or indirectly referenced (by
+ * pointer) type gets resolved to different actual types in different
+ * object files. If such situation occurs, deduplicated BTF will end up
+ * with two (or more) structurally identical types, which differ only in
+ * types they refer to through pointer. This should be OK in most cases and
+ * is not an error.
+ * 4. Candidate types search is performed by linearly scanning through all
+ * types in target BTF. It is anticipated that this is overall more
+ * efficient memory-wise and not significantly worse (if not better)
+ * CPU-wise compared to prebuilding a map from all local type names to
+ * a list of candidate type names. It's also sped up by caching resolved
+ * list of matching candidates per each local "root" type ID, that has at
+ * least one bpf_offset_reloc associated with it. This list is shared
+ * between multiple relocations for the same type ID and is updated as some
+ * of the candidates are pruned due to structural incompatibility.
+ */
+static int bpf_core_reloc_offset(struct bpf_program *prog,
+ const struct bpf_offset_reloc *relo,
+ int relo_idx,
+ const struct btf *local_btf,
+ const struct btf *targ_btf,
+ struct hashmap *cand_cache)
+{
+ const char *prog_name = bpf_program__title(prog, false);
+ struct bpf_core_spec local_spec, cand_spec, targ_spec;
+ const void *type_key = u32_to_ptr(relo->type_id);
+ const struct btf_type *local_type, *cand_type;
+ const char *local_name, *cand_name;
+ struct ids_vec *cand_ids;
+ __u32 local_id, cand_id;
+ const char *spec_str;
+ int i, j, err;
+
+ local_id = relo->type_id;
+ local_type = btf__type_by_id(local_btf, local_id);
+ if (!local_type)
+ return -EINVAL;
+
+ local_name = btf__name_by_offset(local_btf, local_type->name_off);
+ if (str_is_empty(local_name))
+ return -EINVAL;
+
+ spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
+ if (str_is_empty(spec_str))
+ return -EINVAL;
+
+ err = bpf_core_spec_parse(local_btf, local_id, spec_str, &local_spec);
+ if (err) {
+ pr_warning("prog '%s': relo #%d: parsing [%d] (%s) + %s failed: %d\n",
+ prog_name, relo_idx, local_id, local_name, spec_str,
+ err);
+ return -EINVAL;
+ }
+
+ pr_debug("prog '%s': relo #%d: spec is ", prog_name, relo_idx);
+ bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
+ libbpf_print(LIBBPF_DEBUG, "\n");
+
+ if (!hashmap__find(cand_cache, type_key, (void **)&cand_ids)) {
+ cand_ids = bpf_core_find_cands(local_btf, local_id, targ_btf);
+ if (IS_ERR(cand_ids)) {
+ pr_warning("prog '%s': relo #%d: target candidate search failed for [%d] (%s): %ld",
+ prog_name, relo_idx, local_id, local_name,
+ PTR_ERR(cand_ids));
+ return PTR_ERR(cand_ids);
+ }
+ err = hashmap__set(cand_cache, type_key, cand_ids, NULL, NULL);
+ if (err) {
+ bpf_core_free_cands(cand_ids);
+ return err;
+ }
+ }
+
+ for (i = 0, j = 0; i < cand_ids->len; i++) {
+ cand_id = cand_ids->data[i];
+ cand_type = btf__type_by_id(targ_btf, cand_id);
+ cand_name = btf__name_by_offset(targ_btf, cand_type->name_off);
+
+ err = bpf_core_spec_match(&local_spec, targ_btf,
+ cand_id, &cand_spec);
+ if (err < 0) {
+ pr_warning("prog '%s': relo #%d: failed to match spec ",
+ prog_name, relo_idx);
+ bpf_core_dump_spec(LIBBPF_WARN, &local_spec);
+ libbpf_print(LIBBPF_WARN,
+ " to candidate #%d [%d] (%s): %d\n",
+ i, cand_id, cand_name, err);
+ return err;
+ }
+ if (err == 0) {
+ pr_debug("prog '%s': relo #%d: candidate #%d [%d] (%s) doesn't match spec ",
+ prog_name, relo_idx, i, cand_id, cand_name);
+ bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
+ libbpf_print(LIBBPF_DEBUG, "\n");
+ continue;
+ }
+
+ pr_debug("prog '%s': relo #%d: candidate #%d matched as spec ",
+ prog_name, relo_idx, i);
+ bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
+ libbpf_print(LIBBPF_DEBUG, "\n");
+
+ if (j == 0) {
+ targ_spec = cand_spec;
+ } else if (cand_spec.offset != targ_spec.offset) {
+ /* if there are many candidates, they should all
+ * resolve to the same offset
+ */
+ pr_warning("prog '%s': relo #%d: candidate #%d spec ",
+ prog_name, relo_idx, i);
+ bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
+ libbpf_print(LIBBPF_WARN,
+ " conflicts with target spec ");
+ bpf_core_dump_spec(LIBBPF_WARN, &targ_spec);
+ libbpf_print(LIBBPF_WARN, "\n");
+ return -EINVAL;
+ }
+
+ cand_ids->data[j++] = cand_spec.spec[0].type_id;
+ }
+
+ cand_ids->len = j;
+ if (cand_ids->len == 0) {
+ pr_warning("prog '%s': relo #%d: no matching targets found for [%d] (%s) + %s\n",
+ prog_name, relo_idx, local_id, local_name, spec_str);
+ return -ESRCH;
+ }
+
+ err = bpf_core_reloc_insn(prog, relo->insn_off,
+ local_spec.offset, targ_spec.offset);
+ if (err) {
+ pr_warning("prog '%s': relo #%d: failed to patch insn at offset %d: %d\n",
+ prog_name, relo_idx, relo->insn_off, err);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int
+bpf_core_reloc_offsets(struct bpf_object *obj, const char *targ_btf_path)
+{
+ const struct btf_ext_info_sec *sec;
+ const struct bpf_offset_reloc *rec;
+ const struct btf_ext_info *seg;
+ struct hashmap_entry *entry;
+ struct hashmap *cand_cache = NULL;
+ struct bpf_program *prog;
+ struct btf *targ_btf;
+ const char *sec_name;
+ int i, err = 0;
+
+ if (targ_btf_path)
+ targ_btf = btf__parse_elf(targ_btf_path, NULL);
+ else
+ targ_btf = bpf_core_find_kernel_btf();
+ if (IS_ERR(targ_btf)) {
+ pr_warning("failed to get target BTF: %ld\n",
+ PTR_ERR(targ_btf));
+ return PTR_ERR(targ_btf);
+ }
+
+ cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
+ if (IS_ERR(cand_cache)) {
+ err = PTR_ERR(cand_cache);
+ goto out;
+ }
+
+ seg = &obj->btf_ext->offset_reloc_info;
+ for_each_btf_ext_sec(seg, sec) {
+ sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
+ if (str_is_empty(sec_name)) {
+ err = -EINVAL;
+ goto out;
+ }
+ prog = bpf_object__find_program_by_title(obj, sec_name);
+ if (!prog) {
+ pr_warning("failed to find program '%s' for CO-RE offset relocation\n",
+ sec_name);
+ err = -EINVAL;
+ goto out;
+ }
+
+ pr_debug("prog '%s': performing %d CO-RE offset relocs\n",
+ sec_name, sec->num_info);
+
+ for_each_btf_ext_rec(seg, sec, i, rec) {
+ err = bpf_core_reloc_offset(prog, rec, i, obj->btf,
+ targ_btf, cand_cache);
+ if (err) {
+ pr_warning("prog '%s': relo #%d: failed to relocate: %d\n",
+ sec_name, i, err);
+ goto out;
+ }
+ }
+ }
+
+out:
+ btf__free(targ_btf);
+ if (!IS_ERR_OR_NULL(cand_cache)) {
+ hashmap__for_each_entry(cand_cache, entry, i) {
+ bpf_core_free_cands(entry->value);
+ }
+ hashmap__free(cand_cache);
+ }
+ return err;
+}
+
+static int
+bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
+{
+ int err = 0;
+
+ if (obj->btf_ext->offset_reloc_info.len)
+ err = bpf_core_reloc_offsets(obj, targ_btf_path);
+
+ return err;
+}
+
static int
bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
struct reloc_desc *relo)
@@ -2399,14 +3293,21 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
return 0;
}
-
static int
-bpf_object__relocate(struct bpf_object *obj)
+bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
{
struct bpf_program *prog;
size_t i;
int err;
+ if (obj->btf_ext) {
+ err = bpf_object__relocate_core(obj, targ_btf_path);
+ if (err) {
+ pr_warning("failed to perform CO-RE relocations: %d\n",
+ err);
+ return err;
+ }
+ }
for (i = 0; i < obj->nr_programs; i++) {
prog = &obj->programs[i];
@@ -2807,7 +3708,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
obj->loaded = true;
CHECK_ERR(bpf_object__create_maps(obj), err, out);
- CHECK_ERR(bpf_object__relocate(obj), err, out);
+ CHECK_ERR(bpf_object__relocate(obj, attr->target_btf_path), err, out);
CHECK_ERR(bpf_object__load_progs(obj, attr->log_level), err, out);
return 0;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 8a9d462a6f6d..e8f70977d137 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -92,6 +92,7 @@ LIBBPF_API void bpf_object__close(struct bpf_object *object);
struct bpf_object_load_attr {
struct bpf_object *obj;
int log_level;
+ const char *target_btf_path;
};
/* Load/unload object into/from kernel */
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
2019-07-30 19:53 ` [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading Andrii Nakryiko
2019-07-30 19:53 ` [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm Andrii Nakryiko
@ 2019-07-30 19:53 ` Andrii Nakryiko
2019-07-30 21:24 ` Song Liu
2019-07-30 19:54 ` [PATCH v2 bpf-next 04/12] selftests/bpf: add CO-RE relocs testing setup Andrii Nakryiko
` (8 subsequent siblings)
11 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:53 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add BPF_CORE_READ macro used in tests to do bpf_core_read(), which
automatically captures offset relocation.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/testing/selftests/bpf/bpf_helpers.h | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index f804f210244e..81bc51293d11 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -501,4 +501,23 @@ struct pt_regs;
(void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
#endif
+/*
+ * BPF_CORE_READ abstracts away bpf_probe_read() call and captures offset
+ * relocation for source address using __builtin_preserve_access_index()
+ * built-in, provided by Clang.
+ *
+ * __builtin_preserve_access_index() takes as an argument an expression of
+ * taking an address of a field within struct/union. It makes compiler emit
+ * a relocation, which records BTF type ID describing root struct/union and an
+ * accessor string which describes exact embedded field that was used to take
+ * an address. See detailed description of this relocation format and
+ * semantics in comments to struct bpf_offset_reloc in libbpf_internal.h.
+ *
+ * This relocation allows libbpf to adjust BPF instruction to use correct
+ * actual field offset, based on target kernel BTF type that matches original
+ * (local) BTF, used to record relocation.
+ */
+#define BPF_CORE_READ(dst, src) \
+ bpf_probe_read(dst, sizeof(*src), __builtin_preserve_access_index(src))
+
#endif
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 04/12] selftests/bpf: add CO-RE relocs testing setup
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (2 preceding siblings ...)
2019-07-30 19:53 ` [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 05/12] selftests/bpf: add CO-RE relocs struct flavors tests Andrii Nakryiko
` (7 subsequent siblings)
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add CO-RE relocation test runner. Add one simple test validating that
libbpf's logic for searching for kernel image and loading BTF out of it
works.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 125 ++++++++++++++++++
.../bpf/progs/test_core_reloc_kernel.c | 36 +++++
2 files changed, 161 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/core_reloc.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
new file mode 100644
index 000000000000..fab7492a8714
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+
+struct core_reloc_test_case {
+ const char *case_name;
+ const char *bpf_obj_file;
+ const char *btf_src_file;
+ const char *input;
+ int input_len;
+ const char *output;
+ int output_len;
+ bool fails;
+};
+
+static struct core_reloc_test_case test_cases[] = {
+ /* validate we can find kernel image and use its BTF for relocs */
+ {
+ .case_name = "kernel",
+ .bpf_obj_file = "test_core_reloc_kernel.o",
+ .btf_src_file = NULL, /* load from /lib/modules/$(uname -r) */
+ .input = "",
+ .input_len = 0,
+ .output = "\1", /* true */
+ .output_len = 1,
+ },
+};
+
+struct data {
+ char in[256];
+ char out[256];
+};
+
+void test_core_reloc(void)
+{
+ const char *probe_name = "raw_tracepoint/sys_enter";
+ struct bpf_object_load_attr load_attr = {};
+ struct core_reloc_test_case *test_case;
+ int err, duration = 0, i, equal;
+ struct bpf_link *link = NULL;
+ struct bpf_map *data_map;
+ struct bpf_program *prog;
+ struct bpf_object *obj;
+ const int zero = 0;
+ struct data data;
+
+ for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+ test_case = &test_cases[i];
+
+ if (!test__start_subtest(test_case->case_name))
+ continue;
+
+ obj = bpf_object__open(test_case->bpf_obj_file);
+ if (CHECK(IS_ERR_OR_NULL(obj), "obj_open",
+ "failed to open '%s': %ld\n",
+ test_case->bpf_obj_file, PTR_ERR(obj)))
+ continue;
+
+ prog = bpf_object__find_program_by_title(obj, probe_name);
+ if (CHECK(!prog, "find_probe",
+ "prog '%s' not found\n", probe_name))
+ goto cleanup;
+ bpf_program__set_type(prog, BPF_PROG_TYPE_RAW_TRACEPOINT);
+
+ load_attr.obj = obj;
+ load_attr.log_level = 0;
+ load_attr.target_btf_path = test_case->btf_src_file;
+ err = bpf_object__load_xattr(&load_attr);
+ if (test_case->fails) {
+ CHECK(!err, "obj_load_fail",
+ "should fail to load prog '%s'\n", probe_name);
+ goto cleanup;
+ } else {
+ if (CHECK(err, "obj_load",
+ "failed to load prog '%s': %d\n",
+ probe_name, err))
+ goto cleanup;
+ }
+
+ link = bpf_program__attach_raw_tracepoint(prog, "sys_enter");
+ if (CHECK(IS_ERR(link), "attach_raw_tp", "err %ld\n",
+ PTR_ERR(link)))
+ goto cleanup;
+
+ data_map = bpf_object__find_map_by_name(obj, "test_cor.bss");
+ if (CHECK(!data_map, "find_data_map", "data map not found\n"))
+ goto cleanup;
+
+ memset(&data, 0, sizeof(data));
+ memcpy(data.in, test_case->input, test_case->input_len);
+
+ err = bpf_map_update_elem(bpf_map__fd(data_map),
+ &zero, &data, 0);
+ if (CHECK(err, "update_data_map",
+ "failed to update .data map: %d\n", err))
+ goto cleanup;
+
+ /* trigger test run */
+ usleep(1);
+
+ err = bpf_map_lookup_elem(bpf_map__fd(data_map), &zero, &data);
+ if (CHECK(err, "get_result",
+ "failed to get output data: %d\n", err))
+ goto cleanup;
+
+ equal = memcmp(data.out, test_case->output,
+ test_case->output_len) == 0;
+ if (CHECK(!equal, "check_result",
+ "input/output data don't match\n")) {
+ int j;
+
+ for (j = 0; j < test_case->output_len; j++) {
+ test__printf("byte #%d, EXP 0x%02hhx GOT 0x%02hhx\n",
+ j, test_case->output[j], data.out[j]);
+ }
+ goto cleanup;
+ }
+
+cleanup:
+ if (!IS_ERR_OR_NULL(link)) {
+ bpf_link__destroy(link);
+ link = NULL;
+ }
+ bpf_object__close(obj);
+ }
+}
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c b/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
new file mode 100644
index 000000000000..37e02aa3f0c8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct task_struct {
+ int pid;
+ int tgid;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_kernel(void *ctx)
+{
+ struct task_struct *task = (void *)bpf_get_current_task();
+ uint64_t pid_tgid = bpf_get_current_pid_tgid();
+ int pid, tgid;
+
+ if (BPF_CORE_READ(&pid, &task->pid) ||
+ BPF_CORE_READ(&tgid, &task->tgid))
+ return 1;
+
+ /* validate pid + tgid matches */
+ data.out[0] = (((uint64_t)pid << 32) | tgid) == pid_tgid;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 05/12] selftests/bpf: add CO-RE relocs struct flavors tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (3 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 04/12] selftests/bpf: add CO-RE relocs testing setup Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 06/12] selftests/bpf: add CO-RE relocs nesting tests Andrii Nakryiko
` (6 subsequent siblings)
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add tests verifying that BPF program can use various struct/union
"flavors" to extract data from the same target struct/union.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 34 ++++++++++
.../bpf/progs/btf__core_reloc_flavors.c | 3 +
.../btf__core_reloc_flavors__err_wrong_name.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 15 +++++
.../bpf/progs/test_core_reloc_flavors.c | 62 +++++++++++++++++++
5 files changed, 117 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_flavors.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_flavors__err_wrong_name.c
create mode 100644 tools/testing/selftests/bpf/progs/core_reloc_types.h
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_flavors.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index fab7492a8714..c147271deee6 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -1,5 +1,32 @@
// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
+#include "progs/core_reloc_types.h"
+
+#define STRUCT_TO_CHAR_PTR(struct_name) (const char *)&(struct struct_name)
+
+#define FLAVORS_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) { \
+ .a = 42, \
+ .b = 0xc001, \
+ .c = 0xbeef, \
+}
+
+#define FLAVORS_CASE_COMMON(name) \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_flavors.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o" \
+
+#define FLAVORS_CASE(name) { \
+ FLAVORS_CASE_COMMON(name), \
+ .input = FLAVORS_DATA(core_reloc_##name), \
+ .input_len = sizeof(struct core_reloc_##name), \
+ .output = FLAVORS_DATA(core_reloc_flavors), \
+ .output_len = sizeof(struct core_reloc_flavors), \
+}
+
+#define FLAVORS_ERR_CASE(name) { \
+ FLAVORS_CASE_COMMON(name), \
+ .fails = true, \
+}
struct core_reloc_test_case {
const char *case_name;
@@ -23,6 +50,13 @@ static struct core_reloc_test_case test_cases[] = {
.output = "\1", /* true */
.output_len = 1,
},
+
+ /* validate BPF program can use multiple flavors to match against
+ * single target BTF type
+ */
+ FLAVORS_CASE(flavors),
+
+ FLAVORS_ERR_CASE(flavors__err_wrong_name),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_flavors.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_flavors.c
new file mode 100644
index 000000000000..b74455b91227
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_flavors.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_flavors x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_flavors__err_wrong_name.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_flavors__err_wrong_name.c
new file mode 100644
index 000000000000..7b6035f86ee6
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_flavors__err_wrong_name.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_flavors__err_wrong_name x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
new file mode 100644
index 000000000000..33b0c6a61912
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -0,0 +1,15 @@
+/*
+ * FLAVORS
+ */
+struct core_reloc_flavors {
+ int a;
+ int b;
+ int c;
+};
+
+/* this is not a flavor, as it doesn't have triple underscore */
+struct core_reloc_flavors__err_wrong_name {
+ int a;
+ int b;
+ int c;
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_flavors.c b/tools/testing/selftests/bpf/progs/test_core_reloc_flavors.c
new file mode 100644
index 000000000000..9fda73e87972
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_flavors.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_flavors {
+ int a;
+ int b;
+ int c;
+};
+
+/* local flavor with reversed layout */
+struct core_reloc_flavors___reversed {
+ int c;
+ int b;
+ int a;
+};
+
+/* local flavor with nested/overlapping layout */
+struct core_reloc_flavors___weird {
+ struct {
+ int b;
+ };
+ /* a and c overlap in local flavor, but this should still work
+ * correctly with target original flavor
+ */
+ union {
+ int a;
+ int c;
+ };
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_flavors(void *ctx)
+{
+ struct core_reloc_flavors *in_orig = (void *)&data.in;
+ struct core_reloc_flavors___reversed *in_rev = (void *)&data.in;
+ struct core_reloc_flavors___weird *in_weird = (void *)&data.in;
+ struct core_reloc_flavors *out = (void *)&data.out;
+
+ /* read a using weird layout */
+ if (BPF_CORE_READ(&out->a, &in_weird->a))
+ return 1;
+ /* read b using reversed layout */
+ if (BPF_CORE_READ(&out->b, &in_rev->b))
+ return 1;
+ /* read c using original layout */
+ if (BPF_CORE_READ(&out->c, &in_orig->c))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 06/12] selftests/bpf: add CO-RE relocs nesting tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (4 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 05/12] selftests/bpf: add CO-RE relocs struct flavors tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 07/12] selftests/bpf: add CO-RE relocs array tests Andrii Nakryiko
` (5 subsequent siblings)
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add a bunch of test validating correct handling of nested
structs/unions.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 39 +++
.../bpf/progs/btf__core_reloc_nesting.c | 3 +
.../btf__core_reloc_nesting___anon_embed.c | 3 +
...f__core_reloc_nesting___dup_compat_types.c | 5 +
...core_reloc_nesting___err_array_container.c | 3 +
...tf__core_reloc_nesting___err_array_field.c | 3 +
...e_reloc_nesting___err_dup_incompat_types.c | 4 +
...re_reloc_nesting___err_missing_container.c | 3 +
...__core_reloc_nesting___err_missing_field.c | 3 +
..._reloc_nesting___err_nonstruct_container.c | 3 +
...e_reloc_nesting___err_partial_match_dups.c | 4 +
.../btf__core_reloc_nesting___err_too_deep.c | 3 +
.../btf__core_reloc_nesting___extra_nesting.c | 3 +
..._core_reloc_nesting___struct_union_mixup.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 293 ++++++++++++++++++
.../bpf/progs/test_core_reloc_nesting.c | 46 +++
16 files changed, 421 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___anon_embed.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___dup_compat_types.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_container.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_field.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_dup_incompat_types.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_container.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_field.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_nonstruct_container.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_partial_match_dups.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_too_deep.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___extra_nesting.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___struct_union_mixup.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_nesting.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index c147271deee6..226c5af28d6b 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -28,6 +28,29 @@
.fails = true, \
}
+#define NESTING_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) { \
+ .a = { .a = { .a = 42 } }, \
+ .b = { .b = { .b = 0xc001 } }, \
+}
+
+#define NESTING_CASE_COMMON(name) \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_nesting.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o"
+
+#define NESTING_CASE(name) { \
+ NESTING_CASE_COMMON(name), \
+ .input = NESTING_DATA(core_reloc_##name), \
+ .input_len = sizeof(struct core_reloc_##name), \
+ .output = NESTING_DATA(core_reloc_nesting), \
+ .output_len = sizeof(struct core_reloc_nesting) \
+}
+
+#define NESTING_ERR_CASE(name) { \
+ NESTING_CASE_COMMON(name), \
+ .fails = true, \
+}
+
struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
@@ -57,6 +80,22 @@ static struct core_reloc_test_case test_cases[] = {
FLAVORS_CASE(flavors),
FLAVORS_ERR_CASE(flavors__err_wrong_name),
+
+ /* various struct/enum nesting and resolution scenarios */
+ NESTING_CASE(nesting),
+ NESTING_CASE(nesting___anon_embed),
+ NESTING_CASE(nesting___struct_union_mixup),
+ NESTING_CASE(nesting___extra_nesting),
+ NESTING_CASE(nesting___dup_compat_types),
+
+ NESTING_ERR_CASE(nesting___err_missing_field),
+ NESTING_ERR_CASE(nesting___err_array_field),
+ NESTING_ERR_CASE(nesting___err_missing_container),
+ NESTING_ERR_CASE(nesting___err_nonstruct_container),
+ NESTING_ERR_CASE(nesting___err_array_container),
+ NESTING_ERR_CASE(nesting___err_dup_incompat_types),
+ NESTING_ERR_CASE(nesting___err_partial_match_dups),
+ NESTING_ERR_CASE(nesting___err_too_deep),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting.c
new file mode 100644
index 000000000000..4480fcc0f183
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___anon_embed.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___anon_embed.c
new file mode 100644
index 000000000000..13e108f76ece
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___anon_embed.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___anon_embed x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___dup_compat_types.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___dup_compat_types.c
new file mode 100644
index 000000000000..76b54fda5fbb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___dup_compat_types.c
@@ -0,0 +1,5 @@
+#include "core_reloc_types.h"
+
+void f1(struct core_reloc_nesting___dup_compat_types x) {}
+void f2(struct core_reloc_nesting___dup_compat_types__2 x) {}
+void f3(struct core_reloc_nesting___dup_compat_types__3 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_container.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_container.c
new file mode 100644
index 000000000000..975fb95db810
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_container.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___err_array_container x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_field.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_field.c
new file mode 100644
index 000000000000..ad66c67e7980
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_array_field.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___err_array_field x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_dup_incompat_types.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_dup_incompat_types.c
new file mode 100644
index 000000000000..35c5f8da6812
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_dup_incompat_types.c
@@ -0,0 +1,4 @@
+#include "core_reloc_types.h"
+
+void f1(struct core_reloc_nesting___err_dup_incompat_types__1 x) {}
+void f2(struct core_reloc_nesting___err_dup_incompat_types__2 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_container.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_container.c
new file mode 100644
index 000000000000..142e332041db
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_container.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___err_missing_container x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_field.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_field.c
new file mode 100644
index 000000000000..efcae167fab9
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_missing_field.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___err_missing_field x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_nonstruct_container.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_nonstruct_container.c
new file mode 100644
index 000000000000..97aaaedd8ada
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_nonstruct_container.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___err_nonstruct_container x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_partial_match_dups.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_partial_match_dups.c
new file mode 100644
index 000000000000..ffde35086e90
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_partial_match_dups.c
@@ -0,0 +1,4 @@
+#include "core_reloc_types.h"
+
+void f1(struct core_reloc_nesting___err_partial_match_dups__a x) {}
+void f2(struct core_reloc_nesting___err_partial_match_dups__b x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_too_deep.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_too_deep.c
new file mode 100644
index 000000000000..39a2fadd8e95
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___err_too_deep.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___err_too_deep x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___extra_nesting.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___extra_nesting.c
new file mode 100644
index 000000000000..a09d9dfb20df
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___extra_nesting.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___extra_nesting x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___struct_union_mixup.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___struct_union_mixup.c
new file mode 100644
index 000000000000..3d8a1a74012f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_nesting___struct_union_mixup.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_nesting___struct_union_mixup x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 33b0c6a61912..340ee2bcd463 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -13,3 +13,296 @@ struct core_reloc_flavors__err_wrong_name {
int b;
int c;
};
+
+/*
+ * NESTING
+ */
+/* original set up, used to record relocations in BPF program */
+struct core_reloc_nesting_substruct {
+ int a;
+};
+
+union core_reloc_nesting_subunion {
+ int b;
+};
+
+struct core_reloc_nesting {
+ union {
+ struct core_reloc_nesting_substruct a;
+ } a;
+ struct {
+ union core_reloc_nesting_subunion b;
+ } b;
+};
+
+/* inlined anonymous struct/union instead of named structs in original */
+struct core_reloc_nesting___anon_embed {
+ int __just_for_padding;
+ union {
+ struct {
+ int a;
+ } a;
+ } a;
+ struct {
+ union {
+ int b;
+ } b;
+ } b;
+};
+
+/* different mix of nested structs/unions than in original */
+struct core_reloc_nesting___struct_union_mixup {
+ int __a;
+ struct {
+ int __a;
+ union {
+ char __a;
+ int a;
+ } a;
+ } a;
+ int __b;
+ union {
+ int __b;
+ union {
+ char __b;
+ int b;
+ } b;
+ } b;
+};
+
+/* extra anon structs/unions, but still valid a.a.a and b.b.b accessors */
+struct core_reloc_nesting___extra_nesting {
+ int __padding;
+ struct {
+ struct {
+ struct {
+ struct {
+ union {
+ int a;
+ } a;
+ };
+ };
+ } a;
+ int __some_more;
+ struct {
+ union {
+ union {
+ union {
+ struct {
+ int b;
+ };
+ } b;
+ };
+ } b;
+ };
+ };
+};
+
+/* three flavors of same struct with different structure but same layout for
+ * a.a.a and b.b.b, thus successfully resolved and relocatable */
+struct core_reloc_nesting___dup_compat_types {
+ char __just_for_padding;
+ /* 3 more bytes of padding */
+ struct {
+ struct {
+ int a; /* offset 4 */
+ } a;
+ } a;
+ long long __more_padding;
+ struct {
+ struct {
+ int b; /* offset 16 */
+ } b;
+ } b;
+};
+
+struct core_reloc_nesting___dup_compat_types__2 {
+ int __aligned_padding;
+ struct {
+ int __trickier_noop[0];
+ struct {
+ char __some_more_noops[0];
+ int a; /* offset 4 */
+ } a;
+ } a;
+ int __more_padding;
+ struct {
+ struct {
+ struct {
+ int __critical_padding;
+ int b; /* offset 16 */
+ } b;
+ int __does_not_matter;
+ };
+ } b;
+ int __more_irrelevant_stuff;
+};
+
+struct core_reloc_nesting___dup_compat_types__3 {
+ char __correct_padding[4];
+ struct {
+ struct {
+ int a; /* offset 4 */
+ } a;
+ } a;
+ /* 8 byte padding due to next struct's alignment */
+ struct {
+ struct {
+ int b;
+ } b;
+ } b __attribute__((aligned(16)));
+};
+
+/* b.b.b field is missing */
+struct core_reloc_nesting___err_missing_field {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+ struct {
+ struct {
+ int x;
+ } b;
+ } b;
+};
+
+/* b.b.b field is an array of integers instead of plain int */
+struct core_reloc_nesting___err_array_field {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+ struct {
+ struct {
+ int b[1];
+ } b;
+ } b;
+};
+
+/* middle b container is missing */
+struct core_reloc_nesting___err_missing_container {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+ struct {
+ int x;
+ } b;
+};
+
+/* middle b container is referenced through pointer instead of being embedded */
+struct core_reloc_nesting___err_nonstruct_container {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+ struct {
+ struct {
+ int b;
+ } *b;
+ } b;
+};
+
+/* middle b container is an array of structs instead of plain struct */
+struct core_reloc_nesting___err_array_container {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+ struct {
+ struct {
+ int b;
+ } b[1];
+ } b;
+};
+
+/* two flavors of same struct with incompatible layout for b.b.b */
+struct core_reloc_nesting___err_dup_incompat_types__1 {
+ struct {
+ struct {
+ int a; /* offset 0 */
+ } a;
+ } a;
+ struct {
+ struct {
+ int b; /* offset 4 */
+ } b;
+ } b;
+};
+
+struct core_reloc_nesting___err_dup_incompat_types__2 {
+ struct {
+ struct {
+ int a; /* offset 0 */
+ } a;
+ } a;
+ int __extra_padding;
+ struct {
+ struct {
+ int b; /* offset 8 (!) */
+ } b;
+ } b;
+};
+
+/* two flavors of same struct having one of a.a.a and b.b.b, but not both */
+struct core_reloc_nesting___err_partial_match_dups__a {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+};
+
+struct core_reloc_nesting___err_partial_match_dups__b {
+ struct {
+ struct {
+ int b;
+ } b;
+ } b;
+};
+
+struct core_reloc_nesting___err_too_deep {
+ struct {
+ struct {
+ int a;
+ } a;
+ } a;
+ /* 65 levels of nestedness for b.b.b */
+ struct {
+ struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ struct { struct { struct { struct { struct {
+ /* this one is one too much */
+ struct {
+ int b;
+ };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ }; }; }; }; };
+ } b;
+ } b;
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_nesting.c b/tools/testing/selftests/bpf/progs/test_core_reloc_nesting.c
new file mode 100644
index 000000000000..3ca30cec2b39
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_nesting.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_nesting_substruct {
+ int a;
+};
+
+union core_reloc_nesting_subunion {
+ int b;
+};
+
+/* int a.a.a and b.b.b accesses */
+struct core_reloc_nesting {
+ union {
+ struct core_reloc_nesting_substruct a;
+ } a;
+ struct {
+ union core_reloc_nesting_subunion b;
+ } b;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_nesting(void *ctx)
+{
+ struct core_reloc_nesting *in = (void *)&data.in;
+ struct core_reloc_nesting *out = (void *)&data.out;
+
+ if (BPF_CORE_READ(&out->a.a.a, &in->a.a.a))
+ return 1;
+ if (BPF_CORE_READ(&out->b.b.b, &in->b.b.b))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 07/12] selftests/bpf: add CO-RE relocs array tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (5 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 06/12] selftests/bpf: add CO-RE relocs nesting tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 08/12] selftests/bpf: add CO-RE relocs enum/ptr/func_proto tests Andrii Nakryiko
` (4 subsequent siblings)
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add tests for various array handling/relocation scenarios.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 41 ++++++++++
.../bpf/progs/btf__core_reloc_arrays.c | 3 +
.../btf__core_reloc_arrays___diff_arr_dim.c | 3 +
...btf__core_reloc_arrays___diff_arr_val_sz.c | 3 +
.../btf__core_reloc_arrays___err_non_array.c | 3 +
...btf__core_reloc_arrays___err_too_shallow.c | 3 +
.../btf__core_reloc_arrays___err_too_small.c | 3 +
..._core_reloc_arrays___err_wrong_val_type1.c | 3 +
..._core_reloc_arrays___err_wrong_val_type2.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 81 +++++++++++++++++++
.../bpf/progs/test_core_reloc_arrays.c | 55 +++++++++++++
11 files changed, 201 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_dim.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_val_sz.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_non_array.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_shallow.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_small.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type1.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type2.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index 226c5af28d6b..13e1aaeb1c99 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -51,6 +51,36 @@
.fails = true, \
}
+#define ARRAYS_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) { \
+ .a = { [2] = 1 }, \
+ .b = { [1] = { [2] = { [3] = 2 } } }, \
+ .c = { [1] = { .c = 3 } }, \
+ .d = { [0] = { [0] = { .d = 4 } } }, \
+}
+
+#define ARRAYS_CASE_COMMON(name) \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_arrays.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o"
+
+#define ARRAYS_CASE(name) { \
+ ARRAYS_CASE_COMMON(name), \
+ .input = ARRAYS_DATA(core_reloc_##name), \
+ .input_len = sizeof(struct core_reloc_##name), \
+ .output = STRUCT_TO_CHAR_PTR(core_reloc_arrays_output) { \
+ .a2 = 1, \
+ .b123 = 2, \
+ .c1c = 3, \
+ .d00d = 4, \
+ }, \
+ .output_len = sizeof(struct core_reloc_arrays_output) \
+}
+
+#define ARRAYS_ERR_CASE(name) { \
+ ARRAYS_CASE_COMMON(name), \
+ .fails = true, \
+}
+
struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
@@ -96,6 +126,17 @@ static struct core_reloc_test_case test_cases[] = {
NESTING_ERR_CASE(nesting___err_dup_incompat_types),
NESTING_ERR_CASE(nesting___err_partial_match_dups),
NESTING_ERR_CASE(nesting___err_too_deep),
+
+ /* various array access relocation scenarios */
+ ARRAYS_CASE(arrays),
+ ARRAYS_CASE(arrays___diff_arr_dim),
+ ARRAYS_CASE(arrays___diff_arr_val_sz),
+
+ ARRAYS_ERR_CASE(arrays___err_too_small),
+ ARRAYS_ERR_CASE(arrays___err_too_shallow),
+ ARRAYS_ERR_CASE(arrays___err_non_array),
+ ARRAYS_ERR_CASE(arrays___err_wrong_val_type1),
+ ARRAYS_ERR_CASE(arrays___err_wrong_val_type2),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays.c
new file mode 100644
index 000000000000..018ed7fbba3a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_dim.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_dim.c
new file mode 100644
index 000000000000..13d662c57014
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_dim.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___diff_arr_dim x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_val_sz.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_val_sz.c
new file mode 100644
index 000000000000..a351f418c85d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___diff_arr_val_sz.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___diff_arr_val_sz x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_non_array.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_non_array.c
new file mode 100644
index 000000000000..a8735009becc
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_non_array.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_non_array x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_shallow.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_shallow.c
new file mode 100644
index 000000000000..2a67c28b1e75
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_shallow.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_too_shallow x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_small.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_small.c
new file mode 100644
index 000000000000..1142c08c925f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_too_small.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_too_small x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type1.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type1.c
new file mode 100644
index 000000000000..795a5b729176
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type1.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_wrong_val_type1 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type2.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type2.c
new file mode 100644
index 000000000000..3af74b837c4d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_wrong_val_type2.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_wrong_val_type2 x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 340ee2bcd463..45de7986ea2e 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -306,3 +306,84 @@ struct core_reloc_nesting___err_too_deep {
} b;
} b;
};
+
+/*
+ * ARRAYS
+ */
+struct core_reloc_arrays_output {
+ int a2;
+ char b123;
+ int c1c;
+ int d00d;
+};
+
+struct core_reloc_arrays_substruct {
+ int c;
+ int d;
+};
+
+struct core_reloc_arrays {
+ int a[5];
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+};
+
+/* bigger array dimensions */
+struct core_reloc_arrays___diff_arr_dim {
+ int a[7];
+ char b[3][4][5];
+ struct core_reloc_arrays_substruct c[4];
+ struct core_reloc_arrays_substruct d[2][3];
+};
+
+/* different size of array's value (struct) */
+struct core_reloc_arrays___diff_arr_val_sz {
+ int a[5];
+ char b[2][3][4];
+ struct {
+ int __padding1;
+ int c;
+ int __padding2;
+ } c[3];
+ struct {
+ int __padding1;
+ int d;
+ int __padding2;
+ } d[1][2];
+};
+
+struct core_reloc_arrays___err_too_small {
+ int a[2]; /* this one is too small */
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+};
+
+struct core_reloc_arrays___err_too_shallow {
+ int a[5];
+ char b[2][3]; /* this one lacks one dimension */
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+};
+
+struct core_reloc_arrays___err_non_array {
+ int a; /* not an array */
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+};
+
+struct core_reloc_arrays___err_wrong_val_type1 {
+ char a[5]; /* char instead of int */
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+};
+
+struct core_reloc_arrays___err_wrong_val_type2 {
+ int a[5];
+ char b[2][3][4];
+ int c[3]; /* value is not a struct */
+ struct core_reloc_arrays_substruct d[1][2];
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c b/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
new file mode 100644
index 000000000000..bf67f0fdf743
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_arrays_output {
+ int a2;
+ char b123;
+ int c1c;
+ int d00d;
+};
+
+struct core_reloc_arrays_substruct {
+ int c;
+ int d;
+};
+
+struct core_reloc_arrays {
+ int a[5];
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_arrays(void *ctx)
+{
+ struct core_reloc_arrays *in = (void *)&data.in;
+ struct core_reloc_arrays_output *out = (void *)&data.out;
+
+ /* in->a[2] */
+ if (BPF_CORE_READ(&out->a2, &in->a[2]))
+ return 1;
+ /* in->b[1][2][3] */
+ if (BPF_CORE_READ(&out->b123, &in->b[1][2][3]))
+ return 1;
+ /* in->c[1].c */
+ if (BPF_CORE_READ(&out->c1c, &in->c[1].c))
+ return 1;
+ /* in->d[0][0].d */
+ if (BPF_CORE_READ(&out->d00d, &in->d[0][0].d))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 08/12] selftests/bpf: add CO-RE relocs enum/ptr/func_proto tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (6 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 07/12] selftests/bpf: add CO-RE relocs array tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 09/12] selftests/bpf: add CO-RE relocs modifiers/typedef tests Andrii Nakryiko
` (3 subsequent siblings)
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Test CO-RE relocation handling of ints, enums, pointers, func protos, etc.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 36 ++++++++++
.../bpf/progs/btf__core_reloc_primitives.c | 3 +
...f__core_reloc_primitives___diff_enum_def.c | 3 +
..._core_reloc_primitives___diff_func_proto.c | 3 +
...f__core_reloc_primitives___diff_ptr_type.c | 3 +
...tf__core_reloc_primitives___err_non_enum.c | 3 +
...btf__core_reloc_primitives___err_non_int.c | 3 +
...btf__core_reloc_primitives___err_non_ptr.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 67 +++++++++++++++++++
.../bpf/progs/test_core_reloc_primitives.c | 43 ++++++++++++
10 files changed, 167 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_enum_def.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_func_proto.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_ptr_type.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_enum.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_int.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_ptr.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_primitives.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index 13e1aaeb1c99..dd2bab1b2e7d 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -81,6 +81,32 @@
.fails = true, \
}
+#define PRIMITIVES_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) { \
+ .a = 1, \
+ .b = 2, \
+ .c = 3, \
+ .d = (void *)4, \
+ .f = (void *)5, \
+}
+
+#define PRIMITIVES_CASE_COMMON(name) \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_primitives.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o"
+
+#define PRIMITIVES_CASE(name) { \
+ PRIMITIVES_CASE_COMMON(name), \
+ .input = PRIMITIVES_DATA(core_reloc_##name), \
+ .input_len = sizeof(struct core_reloc_##name), \
+ .output = PRIMITIVES_DATA(core_reloc_primitives), \
+ .output_len = sizeof(struct core_reloc_primitives), \
+}
+
+#define PRIMITIVES_ERR_CASE(name) { \
+ PRIMITIVES_CASE_COMMON(name), \
+ .fails = true, \
+}
+
struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
@@ -137,6 +163,16 @@ static struct core_reloc_test_case test_cases[] = {
ARRAYS_ERR_CASE(arrays___err_non_array),
ARRAYS_ERR_CASE(arrays___err_wrong_val_type1),
ARRAYS_ERR_CASE(arrays___err_wrong_val_type2),
+
+ /* enum/ptr/int handling scenarios */
+ PRIMITIVES_CASE(primitives),
+ PRIMITIVES_CASE(primitives___diff_enum_def),
+ PRIMITIVES_CASE(primitives___diff_func_proto),
+ PRIMITIVES_CASE(primitives___diff_ptr_type),
+
+ PRIMITIVES_ERR_CASE(primitives___err_non_enum),
+ PRIMITIVES_ERR_CASE(primitives___err_non_int),
+ PRIMITIVES_ERR_CASE(primitives___err_non_ptr),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives.c
new file mode 100644
index 000000000000..96b90e39242a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_enum_def.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_enum_def.c
new file mode 100644
index 000000000000..6e87233a3ed0
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_enum_def.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives___diff_enum_def x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_func_proto.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_func_proto.c
new file mode 100644
index 000000000000..d9f48e80b9d9
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_func_proto.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives___diff_func_proto x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_ptr_type.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_ptr_type.c
new file mode 100644
index 000000000000..c718f75f8f3b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___diff_ptr_type.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives___diff_ptr_type x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_enum.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_enum.c
new file mode 100644
index 000000000000..b8a120830891
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_enum.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives___err_non_enum x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_int.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_int.c
new file mode 100644
index 000000000000..ad8b3c9aa76f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_int.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives___err_non_int x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_ptr.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_ptr.c
new file mode 100644
index 000000000000..e20bc1d42d0a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_primitives___err_non_ptr.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_primitives___err_non_ptr x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 45de7986ea2e..7526a5f5755b 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -387,3 +387,70 @@ struct core_reloc_arrays___err_wrong_val_type2 {
int c[3]; /* value is not a struct */
struct core_reloc_arrays_substruct d[1][2];
};
+
+/*
+ * PRIMITIVES
+ */
+enum core_reloc_primitives_enum {
+ A = 0,
+ B = 1,
+};
+
+struct core_reloc_primitives {
+ char a;
+ int b;
+ enum core_reloc_primitives_enum c;
+ void *d;
+ int (*f)(const char *);
+};
+
+struct core_reloc_primitives___diff_enum_def {
+ char a;
+ int b;
+ void *d;
+ int (*f)(const char *);
+ enum {
+ X = 100,
+ Y = 200,
+ } c; /* inline enum def with differing set of values */
+};
+
+struct core_reloc_primitives___diff_func_proto {
+ void (*f)(int); /* incompatible function prototype */
+ void *d;
+ enum core_reloc_primitives_enum c;
+ int b;
+ char a;
+};
+
+struct core_reloc_primitives___diff_ptr_type {
+ const char * const d; /* different pointee type + modifiers */
+ char a;
+ int b;
+ enum core_reloc_primitives_enum c;
+ int (*f)(const char *);
+};
+
+struct core_reloc_primitives___err_non_enum {
+ char a[1];
+ int b;
+ int c; /* int instead of enum */
+ void *d;
+ int (*f)(const char *);
+};
+
+struct core_reloc_primitives___err_non_int {
+ char a[1];
+ int *b; /* ptr instead of int */
+ enum core_reloc_primitives_enum c;
+ void *d;
+ int (*f)(const char *);
+};
+
+struct core_reloc_primitives___err_non_ptr {
+ char a[1];
+ int b;
+ enum core_reloc_primitives_enum c;
+ int d; /* int instead of ptr */
+ int (*f)(const char *);
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_primitives.c b/tools/testing/selftests/bpf/progs/test_core_reloc_primitives.c
new file mode 100644
index 000000000000..add52f23ab35
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_primitives.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+enum core_reloc_primitives_enum {
+ A = 0,
+ B = 1,
+};
+
+struct core_reloc_primitives {
+ char a;
+ int b;
+ enum core_reloc_primitives_enum c;
+ void *d;
+ int (*f)(const char *);
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_primitives(void *ctx)
+{
+ struct core_reloc_primitives *in = (void *)&data.in;
+ struct core_reloc_primitives *out = (void *)&data.out;
+
+ if (BPF_CORE_READ(&out->a, &in->a) ||
+ BPF_CORE_READ(&out->b, &in->b) ||
+ BPF_CORE_READ(&out->c, &in->c) ||
+ BPF_CORE_READ(&out->d, &in->d) ||
+ BPF_CORE_READ(&out->f, &in->f))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 09/12] selftests/bpf: add CO-RE relocs modifiers/typedef tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (7 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 08/12] selftests/bpf: add CO-RE relocs enum/ptr/func_proto tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 10/12] selftests/bpf: add CO-RE relocs ptr-as-array tests Andrii Nakryiko
` (2 subsequent siblings)
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add tests validating correct handling of various combinations of
typedefs and const/volatile/restrict modifiers.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 27 +++++++
.../bpf/progs/btf__core_reloc_mods.c | 3 +
.../progs/btf__core_reloc_mods___mod_swap.c | 3 +
.../progs/btf__core_reloc_mods___typedefs.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 72 +++++++++++++++++++
.../bpf/progs/test_core_reloc_mods.c | 62 ++++++++++++++++
6 files changed, 170 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_mods.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_mods___mod_swap.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_mods___typedefs.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_mods.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index dd2bab1b2e7d..adb8480d14dc 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -107,6 +107,28 @@
.fails = true, \
}
+#define MODS_CASE(name) { \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_mods.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o", \
+ .input = STRUCT_TO_CHAR_PTR(core_reloc_##name) { \
+ .a = 1, \
+ .b = 2, \
+ .c = (void *)3, \
+ .d = (void *)4, \
+ .e = { [2] = 5 }, \
+ .f = { [1] = 6 }, \
+ .g = { .x = 7 }, \
+ .h = { .y = 8 }, \
+ }, \
+ .input_len = sizeof(struct core_reloc_##name), \
+ .output = STRUCT_TO_CHAR_PTR(core_reloc_mods_output) { \
+ .a = 1, .b = 2, .c = 3, .d = 4, \
+ .e = 5, .f = 6, .g = 7, .h = 8, \
+ }, \
+ .output_len = sizeof(struct core_reloc_mods_output), \
+}
+
struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
@@ -173,6 +195,11 @@ static struct core_reloc_test_case test_cases[] = {
PRIMITIVES_ERR_CASE(primitives___err_non_enum),
PRIMITIVES_ERR_CASE(primitives___err_non_int),
PRIMITIVES_ERR_CASE(primitives___err_non_ptr),
+
+ /* const/volatile/restrict and typedefs scenarios */
+ MODS_CASE(mods),
+ MODS_CASE(mods___mod_swap),
+ MODS_CASE(mods___typedefs),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_mods.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_mods.c
new file mode 100644
index 000000000000..124197a2e813
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_mods.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_mods x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_mods___mod_swap.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_mods___mod_swap.c
new file mode 100644
index 000000000000..f8a6592ca75f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_mods___mod_swap.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_mods___mod_swap x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_mods___typedefs.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_mods___typedefs.c
new file mode 100644
index 000000000000..5c0d73687247
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_mods___typedefs.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_mods___typedefs x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 7526a5f5755b..3401e8342e57 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -454,3 +454,75 @@ struct core_reloc_primitives___err_non_ptr {
int d; /* int instead of ptr */
int (*f)(const char *);
};
+
+/*
+ * MODS
+ */
+struct core_reloc_mods_output {
+ int a, b, c, d, e, f, g, h;
+};
+
+typedef const int int_t;
+typedef const char *char_ptr_t;
+typedef const int arr_t[7];
+
+struct core_reloc_mods_substruct {
+ int x;
+ int y;
+};
+
+typedef struct {
+ int x;
+ int y;
+} core_reloc_mods_substruct_t;
+
+struct core_reloc_mods {
+ int a;
+ int_t b;
+ char *c;
+ char_ptr_t d;
+ int e[3];
+ arr_t f;
+ struct core_reloc_mods_substruct g;
+ core_reloc_mods_substruct_t h;
+};
+
+/* a/b, c/d, e/f, and g/h pairs are swapped */
+struct core_reloc_mods___mod_swap {
+ int b;
+ int_t a;
+ char *d;
+ char_ptr_t c;
+ int f[3];
+ arr_t e;
+ struct {
+ int y;
+ int x;
+ } h;
+ core_reloc_mods_substruct_t g;
+};
+
+typedef int int1_t;
+typedef int1_t int2_t;
+typedef int2_t int3_t;
+
+typedef int arr1_t[5];
+typedef arr1_t arr2_t;
+typedef arr2_t arr3_t;
+typedef arr3_t arr4_t;
+
+typedef const char * const volatile restrict fancy_char_ptr_t;
+
+typedef core_reloc_mods_substruct_t core_reloc_mods_substruct_tt;
+
+/* we need more typedefs */
+struct core_reloc_mods___typedefs {
+ core_reloc_mods_substruct_tt g;
+ core_reloc_mods_substruct_tt h;
+ arr4_t f;
+ arr4_t e;
+ fancy_char_ptr_t d;
+ fancy_char_ptr_t c;
+ int3_t b;
+ int3_t a;
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_mods.c b/tools/testing/selftests/bpf/progs/test_core_reloc_mods.c
new file mode 100644
index 000000000000..f98b942c062b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_mods.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_mods_output {
+ int a, b, c, d, e, f, g, h;
+};
+
+typedef const int int_t;
+typedef const char *char_ptr_t;
+typedef const int arr_t[7];
+
+struct core_reloc_mods_substruct {
+ int x;
+ int y;
+};
+
+typedef struct {
+ int x;
+ int y;
+} core_reloc_mods_substruct_t;
+
+struct core_reloc_mods {
+ int a;
+ int_t b;
+ char *c;
+ char_ptr_t d;
+ int e[3];
+ arr_t f;
+ struct core_reloc_mods_substruct g;
+ core_reloc_mods_substruct_t h;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_mods(void *ctx)
+{
+ struct core_reloc_mods *in = (void *)&data.in;
+ struct core_reloc_mods_output *out = (void *)&data.out;
+
+ if (BPF_CORE_READ(&out->a, &in->a) ||
+ BPF_CORE_READ(&out->b, &in->b) ||
+ BPF_CORE_READ(&out->c, &in->c) ||
+ BPF_CORE_READ(&out->d, &in->d) ||
+ BPF_CORE_READ(&out->e, &in->e[2]) ||
+ BPF_CORE_READ(&out->f, &in->f[1]) ||
+ BPF_CORE_READ(&out->g, &in->g.x) ||
+ BPF_CORE_READ(&out->h, &in->h.y))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 10/12] selftests/bpf: add CO-RE relocs ptr-as-array tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (8 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 09/12] selftests/bpf: add CO-RE relocs modifiers/typedef tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 11/12] selftests/bpf: add CO-RE relocs ints tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 12/12] selftests/bpf: add CO-RE relocs misc tests Andrii Nakryiko
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add test validating correct relocation handling for cases where pointer
to something is used as an array. E.g.:
int *ptr = ...;
int x = ptr[42];
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 20 +++++++++++++
.../bpf/progs/btf__core_reloc_ptr_as_arr.c | 3 ++
.../btf__core_reloc_ptr_as_arr___diff_sz.c | 3 ++
.../selftests/bpf/progs/core_reloc_types.h | 13 ++++++++
.../bpf/progs/test_core_reloc_ptr_as_arr.c | 30 +++++++++++++++++++
5 files changed, 69 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr___diff_sz.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_ptr_as_arr.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index adb8480d14dc..ad663978be15 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -129,6 +129,22 @@
.output_len = sizeof(struct core_reloc_mods_output), \
}
+#define PTR_AS_ARR_CASE(name) { \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_ptr_as_arr.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o", \
+ .input = (const char *)&(struct core_reloc_##name []){ \
+ { .a = 1 }, \
+ { .a = 2 }, \
+ { .a = 3 }, \
+ }, \
+ .input_len = 3 * sizeof(struct core_reloc_##name), \
+ .output = STRUCT_TO_CHAR_PTR(core_reloc_ptr_as_arr) { \
+ .a = 3, \
+ }, \
+ .output_len = sizeof(struct core_reloc_ptr_as_arr), \
+}
+
struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
@@ -200,6 +216,10 @@ static struct core_reloc_test_case test_cases[] = {
MODS_CASE(mods),
MODS_CASE(mods___mod_swap),
MODS_CASE(mods___typedefs),
+
+ /* handling "ptr is an array" semantics */
+ PTR_AS_ARR_CASE(ptr_as_arr),
+ PTR_AS_ARR_CASE(ptr_as_arr___diff_sz),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr.c
new file mode 100644
index 000000000000..8da52432ba17
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ptr_as_arr x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr___diff_sz.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr___diff_sz.c
new file mode 100644
index 000000000000..003acfc9a3e7
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ptr_as_arr___diff_sz.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ptr_as_arr___diff_sz x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 3401e8342e57..c17c9279deae 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -526,3 +526,16 @@ struct core_reloc_mods___typedefs {
int3_t b;
int3_t a;
};
+
+/*
+ * PTR_AS_ARR
+ */
+struct core_reloc_ptr_as_arr {
+ int a;
+};
+
+struct core_reloc_ptr_as_arr___diff_sz {
+ int :32; /* padding */
+ char __some_more_padding;
+ int a;
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_ptr_as_arr.c b/tools/testing/selftests/bpf/progs/test_core_reloc_ptr_as_arr.c
new file mode 100644
index 000000000000..526b7ddc7ea1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_ptr_as_arr.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_ptr_as_arr {
+ int a;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_ptr_as_arr(void *ctx)
+{
+ struct core_reloc_ptr_as_arr *in = (void *)&data.in;
+ struct core_reloc_ptr_as_arr *out = (void *)&data.out;
+
+ if (BPF_CORE_READ(&out->a, &in[2].a))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 11/12] selftests/bpf: add CO-RE relocs ints tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (9 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 10/12] selftests/bpf: add CO-RE relocs ptr-as-array tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 12/12] selftests/bpf: add CO-RE relocs misc tests Andrii Nakryiko
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add various tests validating handling compatible/incompatible integer
types.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 40 +++++++
.../bpf/progs/btf__core_reloc_ints.c | 3 +
.../bpf/progs/btf__core_reloc_ints___bool.c | 3 +
.../btf__core_reloc_ints___err_bitfield.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_16.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_32.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_64.c | 3 +
.../btf__core_reloc_ints___err_wrong_sz_8.c | 3 +
.../btf__core_reloc_ints___reverse_sign.c | 3 +
.../selftests/bpf/progs/core_reloc_types.h | 101 ++++++++++++++++++
.../bpf/progs/test_core_reloc_ints.c | 44 ++++++++
11 files changed, 209 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___bool.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_bitfield.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_16.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_32.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_64.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_8.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_ints___reverse_sign.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_ints.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index ad663978be15..46abb4df5b1c 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -145,6 +145,35 @@
.output_len = sizeof(struct core_reloc_ptr_as_arr), \
}
+#define INTS_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) { \
+ .u8_field = 1, \
+ .s8_field = 2, \
+ .u16_field = 3, \
+ .s16_field = 4, \
+ .u32_field = 5, \
+ .s32_field = 6, \
+ .u64_field = 7, \
+ .s64_field = 8, \
+}
+
+#define INTS_CASE_COMMON(name) \
+ .case_name = #name, \
+ .bpf_obj_file = "test_core_reloc_ints.o", \
+ .btf_src_file = "btf__core_reloc_" #name ".o"
+
+#define INTS_CASE(name) { \
+ INTS_CASE_COMMON(name), \
+ .input = INTS_DATA(core_reloc_##name), \
+ .input_len = sizeof(struct core_reloc_##name), \
+ .output = INTS_DATA(core_reloc_ints), \
+ .output_len = sizeof(struct core_reloc_ints), \
+}
+
+#define INTS_ERR_CASE(name) { \
+ INTS_CASE_COMMON(name), \
+ .fails = true, \
+}
+
struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
@@ -220,6 +249,17 @@ static struct core_reloc_test_case test_cases[] = {
/* handling "ptr is an array" semantics */
PTR_AS_ARR_CASE(ptr_as_arr),
PTR_AS_ARR_CASE(ptr_as_arr___diff_sz),
+
+ /* int signedness/sizing/bitfield handling */
+ INTS_CASE(ints),
+ INTS_CASE(ints___bool),
+ INTS_CASE(ints___reverse_sign),
+
+ INTS_ERR_CASE(ints___err_bitfield),
+ INTS_ERR_CASE(ints___err_wrong_sz_8),
+ INTS_ERR_CASE(ints___err_wrong_sz_16),
+ INTS_ERR_CASE(ints___err_wrong_sz_32),
+ INTS_ERR_CASE(ints___err_wrong_sz_64),
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints.c
new file mode 100644
index 000000000000..7d0f041042c5
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___bool.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___bool.c
new file mode 100644
index 000000000000..f9359450186e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___bool.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___bool x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_bitfield.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_bitfield.c
new file mode 100644
index 000000000000..50369e8320a0
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_bitfield.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___err_bitfield x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_16.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_16.c
new file mode 100644
index 000000000000..823bac13d641
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_16.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___err_wrong_sz_16 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_32.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_32.c
new file mode 100644
index 000000000000..b44f3be18535
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_32.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___err_wrong_sz_32 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_64.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_64.c
new file mode 100644
index 000000000000..9a3dd2099c0f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_64.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___err_wrong_sz_64 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_8.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_8.c
new file mode 100644
index 000000000000..9f11ef5f6e88
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___err_wrong_sz_8.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___err_wrong_sz_8 x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___reverse_sign.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___reverse_sign.c
new file mode 100644
index 000000000000..aafb1c5819d7
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_ints___reverse_sign.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_ints___reverse_sign x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index c17c9279deae..5f3ebd4f6dc3 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -1,3 +1,6 @@
+#include <stdint.h>
+#include <stdbool.h>
+
/*
* FLAVORS
*/
@@ -539,3 +542,101 @@ struct core_reloc_ptr_as_arr___diff_sz {
char __some_more_padding;
int a;
};
+
+/*
+ * INTS
+ */
+struct core_reloc_ints {
+ uint8_t u8_field;
+ int8_t s8_field;
+ uint16_t u16_field;
+ int16_t s16_field;
+ uint32_t u32_field;
+ int32_t s32_field;
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+/* signed/unsigned types swap */
+struct core_reloc_ints___reverse_sign {
+ int8_t u8_field;
+ uint8_t s8_field;
+ int16_t u16_field;
+ uint16_t s16_field;
+ int32_t u32_field;
+ uint32_t s32_field;
+ int64_t u64_field;
+ uint64_t s64_field;
+};
+
+struct core_reloc_ints___bool {
+ bool u8_field; /* bool instead of uint8 */
+ int8_t s8_field;
+ uint16_t u16_field;
+ int16_t s16_field;
+ uint32_t u32_field;
+ int32_t s32_field;
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+struct core_reloc_ints___err_bitfield {
+ uint8_t u8_field;
+ int8_t s8_field;
+ uint16_t u16_field;
+ int16_t s16_field;
+ uint32_t u32_field: 32; /* bitfields are not supported */
+ int32_t s32_field;
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+struct core_reloc_ints___err_wrong_sz_8 {
+ uint16_t u8_field; /* not 8-bit anymore */
+ int16_t s8_field; /* not 8-bit anymore */
+
+ uint16_t u16_field;
+ int16_t s16_field;
+ uint32_t u32_field;
+ int32_t s32_field;
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+struct core_reloc_ints___err_wrong_sz_16 {
+ uint8_t u8_field;
+ int8_t s8_field;
+
+ uint32_t u16_field; /* not 16-bit anymore */
+ int32_t s16_field; /* not 16-bit anymore */
+
+ uint32_t u32_field;
+ int32_t s32_field;
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+struct core_reloc_ints___err_wrong_sz_32 {
+ uint8_t u8_field;
+ int8_t s8_field;
+ uint16_t u16_field;
+ int16_t s16_field;
+
+ uint64_t u32_field; /* not 32-bit anymore */
+ int64_t s32_field; /* not 32-bit anymore */
+
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+struct core_reloc_ints___err_wrong_sz_64 {
+ uint8_t u8_field;
+ int8_t s8_field;
+ uint16_t u16_field;
+ int16_t s16_field;
+ uint32_t u32_field;
+ int32_t s32_field;
+
+ uint32_t u64_field; /* not 64-bit anymore */
+ int32_t s64_field; /* not 64-bit anymore */
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_ints.c b/tools/testing/selftests/bpf/progs/test_core_reloc_ints.c
new file mode 100644
index 000000000000..d99233c8008a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_ints.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_ints {
+ uint8_t u8_field;
+ int8_t s8_field;
+ uint16_t u16_field;
+ int16_t s16_field;
+ uint32_t u32_field;
+ int32_t s32_field;
+ uint64_t u64_field;
+ int64_t s64_field;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_ints(void *ctx)
+{
+ struct core_reloc_ints *in = (void *)&data.in;
+ struct core_reloc_ints *out = (void *)&data.out;
+
+ if (BPF_CORE_READ(&out->u8_field, &in->u8_field) ||
+ BPF_CORE_READ(&out->s8_field, &in->s8_field) ||
+ BPF_CORE_READ(&out->u16_field, &in->u16_field) ||
+ BPF_CORE_READ(&out->s16_field, &in->s16_field) ||
+ BPF_CORE_READ(&out->u32_field, &in->u32_field) ||
+ BPF_CORE_READ(&out->s32_field, &in->s32_field) ||
+ BPF_CORE_READ(&out->u64_field, &in->u64_field) ||
+ BPF_CORE_READ(&out->s64_field, &in->s64_field))
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* [PATCH v2 bpf-next 12/12] selftests/bpf: add CO-RE relocs misc tests
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
` (10 preceding siblings ...)
2019-07-30 19:54 ` [PATCH v2 bpf-next 11/12] selftests/bpf: add CO-RE relocs ints tests Andrii Nakryiko
@ 2019-07-30 19:54 ` Andrii Nakryiko
11 siblings, 0 replies; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 19:54 UTC (permalink / raw)
To: bpf, netdev, ast, daniel, yhs
Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add tests validating few edge-cases of capturing offset relocations.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 19 ++++++
.../bpf/progs/btf__core_reloc_misc.c | 4 ++
.../selftests/bpf/progs/core_reloc_types.h | 25 ++++++++
.../bpf/progs/test_core_reloc_misc.c | 58 +++++++++++++++++++
4 files changed, 106 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_misc.c
create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_misc.c
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index 46abb4df5b1c..a50ad439ea90 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -260,6 +260,25 @@ static struct core_reloc_test_case test_cases[] = {
INTS_ERR_CASE(ints___err_wrong_sz_16),
INTS_ERR_CASE(ints___err_wrong_sz_32),
INTS_ERR_CASE(ints___err_wrong_sz_64),
+
+ /* validate edge cases of capturing relocations */
+ {
+ .case_name = "misc",
+ .bpf_obj_file = "test_core_reloc_misc.o",
+ .btf_src_file = "btf__core_reloc_misc.o",
+ .input = (const char *)&(struct core_reloc_misc_extensible[]){
+ { .a = 1 },
+ { .a = 2 }, /* not read */
+ { .a = 3 },
+ },
+ .input_len = 4 * sizeof(int),
+ .output = STRUCT_TO_CHAR_PTR(core_reloc_misc_output) {
+ .a = 1,
+ .b = 1,
+ .c = 0, /* BUG in clang, should be 3 */
+ },
+ .output_len = sizeof(struct core_reloc_misc_output),
+ },
};
struct data {
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_misc.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_misc.c
new file mode 100644
index 000000000000..e379831d31a8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_misc.c
@@ -0,0 +1,4 @@
+#include "core_reloc_types.h"
+
+void f1(struct core_reloc_misc___a x) {}
+void f2(struct core_reloc_misc___b x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 5f3ebd4f6dc3..10a252b6da55 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -640,3 +640,28 @@ struct core_reloc_ints___err_wrong_sz_64 {
uint32_t u64_field; /* not 64-bit anymore */
int32_t s64_field; /* not 64-bit anymore */
};
+
+/*
+ * MISC
+ */
+struct core_reloc_misc_output {
+ int a, b, c;
+};
+
+struct core_reloc_misc___a {
+ int a1;
+ int a2;
+};
+
+struct core_reloc_misc___b {
+ int b1;
+ int b2;
+};
+
+/* this one extends core_reloc_misc_extensible struct from BPF prog */
+struct core_reloc_misc_extensible {
+ int a;
+ int b;
+ int c;
+ int d;
+};
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_misc.c b/tools/testing/selftests/bpf/progs/test_core_reloc_misc.c
new file mode 100644
index 000000000000..bfd295f23d5f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_misc.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+ char in[256];
+ char out[256];
+} data;
+
+struct core_reloc_misc_output {
+ int a, b, c;
+};
+
+struct core_reloc_misc___a {
+ int a1;
+ int a2;
+};
+
+struct core_reloc_misc___b {
+ int b1;
+ int b2;
+};
+
+/* fixed two first members, can be extended with new fields */
+struct core_reloc_misc_extensible {
+ int a;
+ int b;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_misc(void *ctx)
+{
+ struct core_reloc_misc___a *in_a = (void *)&data.in;
+ struct core_reloc_misc___b *in_b = (void *)&data.in;
+ struct core_reloc_misc_extensible *in_ext = (void *)&data.in;
+ struct core_reloc_misc_output *out = (void *)&data.out;
+
+ /* record two different relocations with the same accessor string */
+ if (BPF_CORE_READ(&out->a, &in_a->a1) || /* accessor: 0:0 */
+ BPF_CORE_READ(&out->b, &in_b->b1)) /* accessor: 0:0 */
+ return 1;
+
+ /* Validate relocations capture array-only accesses for structs with
+ * fixed header, but with potentially extendable tail. This will read
+ * first 4 bytes of 2nd element of in_ext array of potentially
+ * variably sized struct core_reloc_misc_extensible. */
+ /* BUG in Clang, isn't captured right now */
+ if (BPF_CORE_READ(&out->c, &in_ext[2])) /* accessor: 2 */
+ return 1;
+
+ return 0;
+}
+
--
2.17.1
^ permalink raw reply related [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading
2019-07-30 19:53 ` [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading Andrii Nakryiko
@ 2019-07-30 21:19 ` Song Liu
0 siblings, 0 replies; 27+ messages in thread
From: Song Liu @ 2019-07-30 21:19 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Yonghong Song, Andrii Nakryiko, Kernel Team
> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>
> Add support for BPF CO-RE offset relocations. Add section/record
> iteration macros for .BTF.ext. These macro are useful for iterating over
> each .BTF.ext record, either for dumping out contents or later for BPF
> CO-RE relocation handling.
>
> To enable other parts of libbpf to work with .BTF.ext contents, moved
> a bunch of type definitions into libbpf_internal.h.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro
2019-07-30 19:53 ` [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro Andrii Nakryiko
@ 2019-07-30 21:24 ` Song Liu
2019-07-30 21:26 ` Andrii Nakryiko
0 siblings, 1 reply; 27+ messages in thread
From: Song Liu @ 2019-07-30 21:24 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, Networking, Alexei Starovoitov, daniel, Yonghong Song,
andrii.nakryiko, Kernel Team
> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>
> Add BPF_CORE_READ macro used in tests to do bpf_core_read(), which
> automatically captures offset relocation.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
> tools/testing/selftests/bpf/bpf_helpers.h | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
> index f804f210244e..81bc51293d11 100644
> --- a/tools/testing/selftests/bpf/bpf_helpers.h
> +++ b/tools/testing/selftests/bpf/bpf_helpers.h
> @@ -501,4 +501,23 @@ struct pt_regs;
> (void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
> #endif
>
> +/*
> + * BPF_CORE_READ abstracts away bpf_probe_read() call and captures offset
> + * relocation for source address using __builtin_preserve_access_index()
> + * built-in, provided by Clang.
> + *
> + * __builtin_preserve_access_index() takes as an argument an expression of
> + * taking an address of a field within struct/union. It makes compiler emit
> + * a relocation, which records BTF type ID describing root struct/union and an
> + * accessor string which describes exact embedded field that was used to take
> + * an address. See detailed description of this relocation format and
> + * semantics in comments to struct bpf_offset_reloc in libbpf_internal.h.
> + *
> + * This relocation allows libbpf to adjust BPF instruction to use correct
> + * actual field offset, based on target kernel BTF type that matches original
> + * (local) BTF, used to record relocation.
> + */
> +#define BPF_CORE_READ(dst, src) \
> + bpf_probe_read(dst, sizeof(*src), __builtin_preserve_access_index(src))
We should use "sizeof(*(src))"
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro
2019-07-30 21:24 ` Song Liu
@ 2019-07-30 21:26 ` Andrii Nakryiko
2019-07-30 21:33 ` Song Liu
0 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 21:26 UTC (permalink / raw)
To: Song Liu
Cc: Andrii Nakryiko, bpf, Networking, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
On Tue, Jul 30, 2019 at 2:24 PM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
> >
> > Add BPF_CORE_READ macro used in tests to do bpf_core_read(), which
> > automatically captures offset relocation.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> > tools/testing/selftests/bpf/bpf_helpers.h | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
> > index f804f210244e..81bc51293d11 100644
> > --- a/tools/testing/selftests/bpf/bpf_helpers.h
> > +++ b/tools/testing/selftests/bpf/bpf_helpers.h
> > @@ -501,4 +501,23 @@ struct pt_regs;
> > (void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
> > #endif
> >
> > +/*
> > + * BPF_CORE_READ abstracts away bpf_probe_read() call and captures offset
> > + * relocation for source address using __builtin_preserve_access_index()
> > + * built-in, provided by Clang.
> > + *
> > + * __builtin_preserve_access_index() takes as an argument an expression of
> > + * taking an address of a field within struct/union. It makes compiler emit
> > + * a relocation, which records BTF type ID describing root struct/union and an
> > + * accessor string which describes exact embedded field that was used to take
> > + * an address. See detailed description of this relocation format and
> > + * semantics in comments to struct bpf_offset_reloc in libbpf_internal.h.
> > + *
> > + * This relocation allows libbpf to adjust BPF instruction to use correct
> > + * actual field offset, based on target kernel BTF type that matches original
> > + * (local) BTF, used to record relocation.
> > + */
> > +#define BPF_CORE_READ(dst, src) \
> > + bpf_probe_read(dst, sizeof(*src), __builtin_preserve_access_index(src))
>
> We should use "sizeof(*(src))"
>
Good point. Also (dst) instead of just (dst). Will update.
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro
2019-07-30 21:26 ` Andrii Nakryiko
@ 2019-07-30 21:33 ` Song Liu
0 siblings, 0 replies; 27+ messages in thread
From: Song Liu @ 2019-07-30 21:33 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Andrii Nakryiko, bpf, Networking, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
> On Jul 30, 2019, at 2:26 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Jul 30, 2019 at 2:24 PM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>>>
>>> Add BPF_CORE_READ macro used in tests to do bpf_core_read(), which
>>> automatically captures offset relocation.
>>>
>>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
>>> ---
>>> tools/testing/selftests/bpf/bpf_helpers.h | 19 +++++++++++++++++++
>>> 1 file changed, 19 insertions(+)
>>>
>>> diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
>>> index f804f210244e..81bc51293d11 100644
>>> --- a/tools/testing/selftests/bpf/bpf_helpers.h
>>> +++ b/tools/testing/selftests/bpf/bpf_helpers.h
>>> @@ -501,4 +501,23 @@ struct pt_regs;
>>> (void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
>>> #endif
>>>
>>> +/*
>>> + * BPF_CORE_READ abstracts away bpf_probe_read() call and captures offset
>>> + * relocation for source address using __builtin_preserve_access_index()
>>> + * built-in, provided by Clang.
>>> + *
>>> + * __builtin_preserve_access_index() takes as an argument an expression of
>>> + * taking an address of a field within struct/union. It makes compiler emit
>>> + * a relocation, which records BTF type ID describing root struct/union and an
>>> + * accessor string which describes exact embedded field that was used to take
>>> + * an address. See detailed description of this relocation format and
>>> + * semantics in comments to struct bpf_offset_reloc in libbpf_internal.h.
>>> + *
>>> + * This relocation allows libbpf to adjust BPF instruction to use correct
>>> + * actual field offset, based on target kernel BTF type that matches original
>>> + * (local) BTF, used to record relocation.
>>> + */
>>> +#define BPF_CORE_READ(dst, src) \
>>> + bpf_probe_read(dst, sizeof(*src), __builtin_preserve_access_index(src))
>>
>> We should use "sizeof(*(src))"
>>
>
> Good point. Also (dst) instead of just (dst). Will update.
I think dst as-is is fine. "," is the very last in precedence list.
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-30 19:53 ` [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm Andrii Nakryiko
@ 2019-07-30 23:43 ` Song Liu
2019-07-30 23:55 ` Andrii Nakryiko
2019-07-31 0:39 ` Song Liu
1 sibling, 1 reply; 27+ messages in thread
From: Song Liu @ 2019-07-30 23:43 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, netdev, Alexei Starovoitov, daniel, Yonghong Song,
andrii.nakryiko, Kernel Team
> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>
> This patch implements the core logic for BPF CO-RE offsets relocations.
> Every instruction that needs to be relocated has corresponding
> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> to match recorded "local" relocation spec against potentially many
> compatible "target" types, creating corresponding spec. Details of the
> algorithm are noted in corresponding comments in the code.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
> tools/lib/bpf/libbpf.h | 1 +
> 2 files changed, 909 insertions(+), 7 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ead915aec349..75da90928257 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -38,6 +38,7 @@
> #include <sys/stat.h>
> #include <sys/types.h>
> #include <sys/vfs.h>
> +#include <sys/utsname.h>
> #include <tools/libc_compat.h>
> #include <libelf.h>
> #include <gelf.h>
> @@ -47,6 +48,7 @@
> #include "btf.h"
> #include "str_error.h"
> #include "libbpf_internal.h"
> +#include "hashmap.h"
>
> #ifndef EM_BPF
> #define EM_BPF 247
> @@ -1015,17 +1017,22 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict)
> return 0;
> }
>
> -static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
> - __u32 id)
> +static const struct btf_type *
> +skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
> {
> const struct btf_type *t = btf__type_by_id(btf, id);
>
> + if (res_id)
> + *res_id = id;
> +
> while (true) {
> switch (BTF_INFO_KIND(t->info)) {
> case BTF_KIND_VOLATILE:
> case BTF_KIND_CONST:
> case BTF_KIND_RESTRICT:
> case BTF_KIND_TYPEDEF:
> + if (res_id)
> + *res_id = t->type;
> t = btf__type_by_id(btf, t->type);
So btf->types[*res_id] == retval, right? Then with retval and btf, we can
calculate *res_id without this change?
> break;
> default:
> @@ -1044,7 +1051,7 @@ static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
> static bool get_map_field_int(const char *map_name, const struct btf *btf,
> const struct btf_type *def,
> const struct btf_member *m, __u32 *res) {
> - const struct btf_type *t = skip_mods_and_typedefs(btf, m->type);
> + const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
> const char *name = btf__name_by_offset(btf, m->name_off);
> const struct btf_array *arr_info;
> const struct btf_type *arr_t;
> @@ -1110,7 +1117,7 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
> return -EOPNOTSUPP;
> }
>
> - def = skip_mods_and_typedefs(obj->btf, var->type);
> + def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
> if (BTF_INFO_KIND(def->info) != BTF_KIND_STRUCT) {
> pr_warning("map '%s': unexpected def kind %u.\n",
> map_name, BTF_INFO_KIND(var->info));
> @@ -2292,6 +2299,893 @@ bpf_program_reloc_btf_ext(struct bpf_program *prog, struct bpf_object *obj,
> return 0;
> }
>
> +#define BPF_CORE_SPEC_MAX_LEN 64
> +
> +/* represents BPF CO-RE field or array element accessor */
> +struct bpf_core_accessor {
> + __u32 type_id; /* struct/union type or array element type */
> + __u32 idx; /* field index or array index */
> + const char *name; /* field name or NULL for array accessor */
> +};
> +
> +struct bpf_core_spec {
> + const struct btf *btf;
> + /* high-level spec: named fields and array indices only */
> + struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
> + /* high-level spec length */
> + int len;
> + /* raw, low-level spec: 1-to-1 with accessor spec string */
> + int raw_spec[BPF_CORE_SPEC_MAX_LEN];
> + /* raw spec length */
> + int raw_len;
> + /* field byte offset represented by spec */
> + __u32 offset;
> +};
> +
> +static bool str_is_empty(const char *s)
> +{
> + return !s || !s[0];
> +}
> +
> +static int btf_kind(const struct btf_type *t)
> +{
> + return BTF_INFO_KIND(t->info);
> +}
> +
> +static bool btf_is_composite(const struct btf_type *t)
> +{
> + int kind = btf_kind(t);
> +
> + return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
> +}
> +
> +static bool btf_is_array(const struct btf_type *t)
> +{
> + return btf_kind(t) == BTF_KIND_ARRAY;
> +}
> +
> +/*
> + * Turn bpf_offset_reloc into a low- and high-level spec representation,
> + * validating correctness along the way, as well as calculating resulting
> + * field offset (in bytes), specified by accessor string. Low-level spec
> + * captures every single level of nestedness, including traversing anonymous
> + * struct/union members. High-level one only captures semantically meaningful
> + * "turning points": named fields and array indicies.
> + * E.g., for this case:
> + *
> + * struct sample {
> + * int __unimportant;
> + * struct {
> + * int __1;
> + * int __2;
> + * int a[7];
> + * };
> + * };
> + *
> + * struct sample *s = ...;
> + *
> + * int x = &s->a[3]; // access string = '0:1:2:3'
> + *
> + * Low-level spec has 1:1 mapping with each element of access string (it's
> + * just a parsed access string representation): [0, 1, 2, 3].
> + *
> + * High-level spec will capture only 3 points:
> + * - intial zero-index access by pointer (&s->... is the same as &s[0]...);
> + * - field 'a' access (corresponds to '2' in low-level spec);
> + * - array element #3 access (corresponds to '3' in low-level spec).
> + *
> + */
> +static int bpf_core_spec_parse(const struct btf *btf,
> + __u32 type_id,
> + const char *spec_str,
> + struct bpf_core_spec *spec)
> +{
> + int access_idx, parsed_len, i;
> + const struct btf_type *t;
> + const char *name;
> + __u32 id;
> + __s64 sz;
> +
> + if (str_is_empty(spec_str) || *spec_str == ':')
> + return -EINVAL;
> +
> + memset(spec, 0, sizeof(*spec));
> + spec->btf = btf;
> +
> + /* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
> + while (*spec_str) {
> + if (*spec_str == ':')
> + ++spec_str;
> + if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
> + return -EINVAL;
> + if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
> + return -E2BIG;
> + spec_str += parsed_len;
> + spec->raw_spec[spec->raw_len++] = access_idx;
> + }
> +
> + if (spec->raw_len == 0)
> + return -EINVAL;
> +
> + /* first spec value is always reloc type array index */
> + t = skip_mods_and_typedefs(btf, type_id, &id);
> + if (!t)
> + return -EINVAL;
> +
> + access_idx = spec->raw_spec[0];
> + spec->spec[0].type_id = id;
> + spec->spec[0].idx = access_idx;
> + spec->len++;
> +
> + sz = btf__resolve_size(btf, id);
> + if (sz < 0)
> + return sz;
> + spec->offset = access_idx * sz;
> +
> + for (i = 1; i < spec->raw_len; i++) {
> + t = skip_mods_and_typedefs(btf, id, &id);
> + if (!t)
> + return -EINVAL;
> +
> + access_idx = spec->raw_spec[i];
> +
> + if (btf_is_composite(t)) {
> + const struct btf_member *m = (void *)(t + 1);
> + __u32 offset;
> +
> + if (access_idx >= BTF_INFO_VLEN(t->info))
> + return -EINVAL;
> +
> + m = &m[access_idx];
> +
> + if (BTF_INFO_KFLAG(t->info)) {
> + if (BTF_MEMBER_BITFIELD_SIZE(m->offset))
> + return -EINVAL;
> + offset = BTF_MEMBER_BIT_OFFSET(m->offset);
> + } else {
> + offset = m->offset;
> + }
> + if (m->offset % 8)
> + return -EINVAL;
> + spec->offset += offset / 8;
> +
> + if (m->name_off) {
> + name = btf__name_by_offset(btf, m->name_off);
> + if (str_is_empty(name))
> + return -EINVAL;
> +
> + spec->spec[spec->len].type_id = id;
> + spec->spec[spec->len].idx = access_idx;
> + spec->spec[spec->len].name = name;
> + spec->len++;
> + }
> +
> + id = m->type;
> + } else if (btf_is_array(t)) {
> + const struct btf_array *a = (void *)(t + 1);
> +
> + t = skip_mods_and_typedefs(btf, a->type, &id);
> + if (!t || access_idx >= a->nelems)
> + return -EINVAL;
> +
> + spec->spec[spec->len].type_id = id;
> + spec->spec[spec->len].idx = access_idx;
> + spec->len++;
> +
> + sz = btf__resolve_size(btf, id);
> + if (sz < 0)
> + return sz;
> + spec->offset += access_idx * sz;
> + } else {
> + pr_warning("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %d\n",
> + type_id, spec_str, i, id, btf_kind(t));
> + return -EINVAL;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/* Given 'some_struct_name___with_flavor' return the length of a name prefix
> + * before last triple underscore. Struct name part after last triple
> + * underscore is ignored by BPF CO-RE relocation during relocation matching.
> + */
> +static size_t bpf_core_essential_name_len(const char *name)
> +{
> + size_t n = strlen(name);
> + int i = n - 3;
> +
> + while (i > 0) {
> + if (name[i] == '_' && name[i + 1] == '_' && name[i + 2] == '_')
> + return i;
> + i--;
> + }
> + return n;
> +}
> +
> +/* dynamically sized list of type IDs */
> +struct ids_vec {
> + __u32 *data;
> + int len;
> +};
> +
> +static void bpf_core_free_cands(struct ids_vec *cand_ids)
> +{
> + free(cand_ids->data);
> + free(cand_ids);
> +}
> +
> +static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
> + __u32 local_type_id,
> + const struct btf *targ_btf)
> +{
> + size_t local_essent_len, targ_essent_len;
> + const char *local_name, *targ_name;
> + const struct btf_type *t;
> + struct ids_vec *cand_ids;
> + __u32 *new_ids;
> + int i, err, n;
> +
> + t = btf__type_by_id(local_btf, local_type_id);
> + if (!t)
> + return ERR_PTR(-EINVAL);
> +
> + local_name = btf__name_by_offset(local_btf, t->name_off);
> + if (str_is_empty(local_name))
> + return ERR_PTR(-EINVAL);
> + local_essent_len = bpf_core_essential_name_len(local_name);
> +
> + cand_ids = calloc(1, sizeof(*cand_ids));
> + if (!cand_ids)
> + return ERR_PTR(-ENOMEM);
> +
> + n = btf__get_nr_types(targ_btf);
> + for (i = 1; i <= n; i++) {
> + t = btf__type_by_id(targ_btf, i);
> + targ_name = btf__name_by_offset(targ_btf, t->name_off);
> + if (str_is_empty(targ_name))
> + continue;
> +
> + targ_essent_len = bpf_core_essential_name_len(targ_name);
> + if (targ_essent_len != local_essent_len)
> + continue;
> +
> + if (strncmp(local_name, targ_name, local_essent_len) == 0) {
> + pr_debug("[%d] (%s): found candidate [%d] (%s)\n",
> + local_type_id, local_name, i, targ_name);
> + new_ids = realloc(cand_ids->data, cand_ids->len + 1);
> + if (!new_ids) {
> + err = -ENOMEM;
> + goto err_out;
> + }
> + cand_ids->data = new_ids;
> + cand_ids->data[cand_ids->len++] = i;
> + }
> + }
> + return cand_ids;
> +err_out:
> + bpf_core_free_cands(cand_ids);
> + return ERR_PTR(err);
> +}
> +
> +/* Check two types for compatibility, skipping const/volatile/restrict and
> + * typedefs, to ensure we are relocating offset to the compatible entities:
> + * - any two STRUCTs/UNIONs are compatible and can be mixed;
> + * - any two FWDs are compatible;
> + * - any two PTRs are always compatible;
> + * - for ENUMs, check sizes, names are ignored;
> + * - for INT, size and bitness should match, signedness is ignored;
> + * - for ARRAY, dimensionality is ignored, element types are checked for
> + * compatibility recursively;
> + * - everything else shouldn't be ever a target of relocation.
> + * These rules are not set in stone and probably will be adjusted as we get
> + * more experience with using BPF CO-RE relocations.
> + */
> +static int bpf_core_fields_are_compat(const struct btf *local_btf,
> + __u32 local_id,
> + const struct btf *targ_btf,
> + __u32 targ_id)
> +{
> + const struct btf_type *local_type, *targ_type;
> + __u16 kind;
> +
> +recur:
> + local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
> + targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
> + if (!local_type || !targ_type)
> + return -EINVAL;
> +
> + if (btf_is_composite(local_type) && btf_is_composite(targ_type))
> + return 1;
> + if (BTF_INFO_KIND(local_type->info) != BTF_INFO_KIND(targ_type->info))
> + return 0;
> +
> + kind = BTF_INFO_KIND(local_type->info);
> + switch (kind) {
> + case BTF_KIND_FWD:
> + case BTF_KIND_PTR:
> + return 1;
> + case BTF_KIND_ENUM:
> + return local_type->size == targ_type->size;
> + case BTF_KIND_INT: {
> + __u32 loc_int = *(__u32 *)(local_type + 1);
> + __u32 targ_int = *(__u32 *)(targ_type + 1);
> +
> + return BTF_INT_OFFSET(loc_int) == 0 &&
> + BTF_INT_OFFSET(targ_int) == 0 &&
> + local_type->size == targ_type->size &&
> + BTF_INT_BITS(loc_int) == BTF_INT_BITS(targ_int);
> + }
> + case BTF_KIND_ARRAY: {
> + const struct btf_array *loc_a, *targ_a;
> +
> + loc_a = (void *)(local_type + 1);
> + targ_a = (void *)(targ_type + 1);
> + local_id = loc_a->type;
> + targ_id = targ_a->type;
> + goto recur;
> + }
> + default:
> + pr_warning("unexpected kind %d relocated, local [%d], target [%d]\n",
> + kind, local_id, targ_id);
> + return 0;
> + }
> +}
> +
> +/*
> + * Given single high-level named field accessor in local type, find
> + * corresponding high-level accessor for a target type. Along the way,
> + * maintain low-level spec for target as well. Also keep updating target
> + * offset.
> + *
> + * Searching is performed through recursive exhaustive enumeration of all
> + * fields of a struct/union. If there are any anonymous (embedded)
> + * structs/unions, they are recursively searched as well. If field with
> + * desired name is found, check compatibility between local and target types,
> + * before returning result.
> + *
> + * 1 is returned, if field is found.
> + * 0 is returned if no compatible field is found.
> + * <0 is returned on error.
> + */
> +static int bpf_core_match_member(const struct btf *local_btf,
> + const struct bpf_core_accessor *local_acc,
> + const struct btf *targ_btf,
> + __u32 targ_id,
> + struct bpf_core_spec *spec,
> + __u32 *next_targ_id)
> +{
> + const struct btf_type *local_type, *targ_type;
> + const struct btf_member *local_member, *m;
> + const char *local_name, *targ_name;
> + __u32 local_id;
> + int i, n, found;
> +
> + targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
> + if (!targ_type)
> + return -EINVAL;
> + if (!btf_is_composite(targ_type))
> + return 0;
> +
> + local_id = local_acc->type_id;
> + local_type = btf__type_by_id(local_btf, local_id);
> + local_member = (void *)(local_type + 1);
> + local_member += local_acc->idx;
> + local_name = btf__name_by_offset(local_btf, local_member->name_off);
> +
> + n = BTF_INFO_VLEN(targ_type->info);
> + m = (void *)(targ_type + 1);
> + for (i = 0; i < n; i++, m++) {
> + __u32 offset;
> +
> + /* bitfield relocations not supported */
> + if (BTF_INFO_KFLAG(targ_type->info)) {
> + if (BTF_MEMBER_BITFIELD_SIZE(m->offset))
> + continue;
> + offset = BTF_MEMBER_BIT_OFFSET(m->offset);
> + } else {
> + offset = m->offset;
> + }
> + if (offset % 8)
> + continue;
> +
> + /* too deep struct/union/array nesting */
> + if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
> + return -E2BIG;
> +
> + /* speculate this member will be the good one */
> + spec->offset += offset / 8;
> + spec->raw_spec[spec->raw_len++] = i;
> +
> + targ_name = btf__name_by_offset(targ_btf, m->name_off);
> + if (str_is_empty(targ_name)) {
> + /* embedded struct/union, we need to go deeper */
> + found = bpf_core_match_member(local_btf, local_acc,
> + targ_btf, m->type,
> + spec, next_targ_id);
> + if (found) /* either found or error */
> + return found;
> + } else if (strcmp(local_name, targ_name) == 0) {
> + /* matching named field */
> + struct bpf_core_accessor *targ_acc;
> +
> + targ_acc = &spec->spec[spec->len++];
> + targ_acc->type_id = targ_id;
> + targ_acc->idx = i;
> + targ_acc->name = targ_name;
> +
> + *next_targ_id = m->type;
> + found = bpf_core_fields_are_compat(local_btf,
> + local_member->type,
> + targ_btf, m->type);
> + if (!found)
> + spec->len--; /* pop accessor */
> + return found;
> + }
> + /* member turned out not to be what we looked for */
> + spec->offset -= offset / 8;
> + spec->raw_len--;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Try to match local spec to a target type and, if successful, produce full
> + * target spec (high-level, low-level + offset).
> + */
> +static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
> + const struct btf *targ_btf, __u32 targ_id,
> + struct bpf_core_spec *targ_spec)
> +{
> + const struct btf_type *targ_type;
> + const struct bpf_core_accessor *local_acc;
> + struct bpf_core_accessor *targ_acc;
> + int i, sz, matched;
> +
> + memset(targ_spec, 0, sizeof(*targ_spec));
> + targ_spec->btf = targ_btf;
> +
> + local_acc = &local_spec->spec[0];
> + targ_acc = &targ_spec->spec[0];
> +
> + for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
> + targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
> + &targ_id);
> + if (!targ_type)
> + return -EINVAL;
> +
> + if (local_acc->name) {
> + matched = bpf_core_match_member(local_spec->btf,
> + local_acc,
> + targ_btf, targ_id,
> + targ_spec, &targ_id);
> + if (matched <= 0)
> + return matched;
> + } else {
> + /* for i=0, targ_id is already treated as array element
> + * type (because it's the original struct), for others
> + * we should find array element type first
> + */
> + if (i > 0) {
> + const struct btf_array *a;
> +
> + if (!btf_is_array(targ_type))
> + return 0;
> +
> + a = (void *)(targ_type + 1);
> + if (local_acc->idx >= a->nelems)
> + return 0;
> + if (!skip_mods_and_typedefs(targ_btf, a->type,
> + &targ_id))
> + return -EINVAL;
> + }
> +
> + /* too deep struct/union/array nesting */
> + if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
> + return -E2BIG;
> +
> + targ_acc->type_id = targ_id;
> + targ_acc->idx = local_acc->idx;
> + targ_acc->name = NULL;
> + targ_spec->len++;
> + targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
> + targ_spec->raw_len++;
> +
> + sz = btf__resolve_size(targ_btf, targ_id);
> + if (sz < 0)
> + return sz;
> + targ_spec->offset += local_acc->idx * sz;
> + }
> + }
> +
> + return 1;
> +}
> +
> +/*
> + * Patch relocatable BPF instruction.
> + * Expected insn->imm value is provided for validation, as well as the new
> + * relocated value.
> + *
> + * Currently three kinds of BPF instructions are supported:
> + * 1. rX = <imm> (assignment with immediate operand);
> + * 2. rX += <imm> (arithmetic operations with immediate operand);
> + * 3. *(rX) = <imm> (indirect memory assignment with immediate operand).
> + *
> + * If actual insn->imm value is wrong, bail out.
> + */
> +static int bpf_core_reloc_insn(struct bpf_program *prog, int insn_off,
> + __u32 orig_off, __u32 new_off)
> +{
> + struct bpf_insn *insn;
> + int insn_idx;
> + __u8 class;
> +
> + if (insn_off % sizeof(struct bpf_insn))
> + return -EINVAL;
> + insn_idx = insn_off / sizeof(struct bpf_insn);
> +
> + insn = &prog->insns[insn_idx];
> + class = BPF_CLASS(insn->code);
> +
> + if (class == BPF_ALU || class == BPF_ALU64) {
> + if (BPF_SRC(insn->code) != BPF_K)
> + return -EINVAL;
> + if (insn->imm != orig_off)
> + return -EINVAL;
> + insn->imm = new_off;
> + pr_debug("prog '%s': patched insn #%d (ALU/ALU64) imm %d -> %d\n",
> + bpf_program__title(prog, false),
> + insn_idx, orig_off, new_off);
> + } else {
> + pr_warning("prog '%s': trying to relocate unrecognized insn #%d, code:%x, src:%x, dst:%x, off:%x, imm:%x\n",
> + bpf_program__title(prog, false),
> + insn_idx, insn->code, insn->src_reg, insn->dst_reg,
> + insn->off, insn->imm);
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +/*
> + * Probe few well-known locations for vmlinux kernel image and try to load BTF
> + * data out of it to use for target BTF.
> + */
> +static struct btf *bpf_core_find_kernel_btf(void)
> +{
> + const char *locations[] = {
> + "/lib/modules/%1$s/vmlinux-%1$s",
> + "/usr/lib/modules/%1$s/kernel/vmlinux",
> + };
> + char path[PATH_MAX + 1];
> + struct utsname buf;
> + struct btf *btf;
> + int i, err;
> +
> + err = uname(&buf);
> + if (err) {
> + pr_warning("failed to uname(): %d\n", err);
> + return ERR_PTR(err);
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(locations); i++) {
> + snprintf(path, PATH_MAX, locations[i], buf.release);
> + pr_debug("attempting to load kernel BTF from '%s'\n", path);
> +
> + if (access(path, R_OK))
> + continue;
> +
> + btf = btf__parse_elf(path, NULL);
> + if (IS_ERR(btf))
> + continue;
> +
> + pr_debug("successfully loaded kernel BTF from '%s'\n", path);
> + return btf;
> + }
> +
> + pr_warning("failed to find valid kernel BTF\n");
> + return ERR_PTR(-ESRCH);
> +}
> +
> +/* Output spec definition in the format:
> + * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
> + * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
> + */
> +static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
> +{
> + const struct btf_type *t;
> + const char *s;
> + __u32 type_id;
> + int i;
> +
> + type_id = spec->spec[0].type_id;
> + t = btf__type_by_id(spec->btf, type_id);
> + s = btf__name_by_offset(spec->btf, t->name_off);
> + libbpf_print(level, "[%u] (%s) + ", type_id, s);
> +
> + for (i = 0; i < spec->raw_len; i++)
> + libbpf_print(level, "%d%s", spec->raw_spec[i],
> + i == spec->raw_len - 1 ? " => " : ":");
> +
> + libbpf_print(level, "%u @ &x", spec->offset);
> +
> + for (i = 0; i < spec->len; i++) {
> + if (spec->spec[i].name)
> + libbpf_print(level, ".%s", spec->spec[i].name);
> + else
> + libbpf_print(level, "[%u]", spec->spec[i].idx);
> + }
> +
> +}
> +
> +static size_t bpf_core_hash_fn(const void *key, void *ctx)
> +{
> + return (size_t)key;
> +}
> +
> +static bool bpf_core_equal_fn(const void *k1, const void *k2, void *ctx)
> +{
> + return k1 == k2;
> +}
> +
> +static void *u32_to_ptr(__u32 x)
> +{
> + return (void *)(uintptr_t)x;
> +}
> +
> +/*
> + * CO-RE relocate single instruction.
> + *
> + * The outline and important points of the algorithm:
> + * 1. For given local type, find corresponding candidate target types.
> + * Candidate type is a type with the same "essential" name, ignoring
> + * everything after last triple underscore (___). E.g., `sample`,
> + * `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
> + * for each other. Names with triple underscore are referred to as
> + * "flavors" and are useful, among other things, to allow to
> + * specify/support incompatible variations of the same kernel struct, which
> + * might differ between different kernel versions and/or build
> + * configurations.
> + *
> + * N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
> + * converter, when deduplicated BTF of a kernel still contains more than
> + * one different types with the same name. In that case, ___2, ___3, etc
> + * are appended starting from second name conflict. But start flavors are
> + * also useful to be defined "locally", in BPF program, to extract same
> + * data from incompatible changes between different kernel
> + * versions/configurations. For instance, to handle field renames between
> + * kernel versions, one can use two flavors of the struct name with the
> + * same common name and use conditional relocations to extract that field,
> + * depending on target kernel version.
> + * 2. For each candidate type, try to match local specification to this
> + * candidate target type. Matching involves finding corresponding
> + * high-level spec accessors, meaning that all named fields should match,
> + * as well as all array accesses should be within the actual bounds. Also,
> + * types should be compatible (see bpf_core_fields_are_compat for details).
> + * 3. It is supported and expected that there might be multiple flavors
> + * matching the spec. As long as all the specs resolve to the same set of
> + * offsets across all candidates, there is not error. If there is any
> + * ambiguity, CO-RE relocation will fail. This is necessary to accomodate
> + * imprefection of BTF deduplication, which can cause slight duplication of
> + * the same BTF type, if some directly or indirectly referenced (by
> + * pointer) type gets resolved to different actual types in different
> + * object files. If such situation occurs, deduplicated BTF will end up
> + * with two (or more) structurally identical types, which differ only in
> + * types they refer to through pointer. This should be OK in most cases and
> + * is not an error.
> + * 4. Candidate types search is performed by linearly scanning through all
> + * types in target BTF. It is anticipated that this is overall more
> + * efficient memory-wise and not significantly worse (if not better)
> + * CPU-wise compared to prebuilding a map from all local type names to
> + * a list of candidate type names. It's also sped up by caching resolved
> + * list of matching candidates per each local "root" type ID, that has at
> + * least one bpf_offset_reloc associated with it. This list is shared
> + * between multiple relocations for the same type ID and is updated as some
> + * of the candidates are pruned due to structural incompatibility.
> + */
> +static int bpf_core_reloc_offset(struct bpf_program *prog,
> + const struct bpf_offset_reloc *relo,
> + int relo_idx,
> + const struct btf *local_btf,
> + const struct btf *targ_btf,
> + struct hashmap *cand_cache)
> +{
> + const char *prog_name = bpf_program__title(prog, false);
> + struct bpf_core_spec local_spec, cand_spec, targ_spec;
> + const void *type_key = u32_to_ptr(relo->type_id);
> + const struct btf_type *local_type, *cand_type;
> + const char *local_name, *cand_name;
> + struct ids_vec *cand_ids;
> + __u32 local_id, cand_id;
> + const char *spec_str;
> + int i, j, err;
> +
> + local_id = relo->type_id;
> + local_type = btf__type_by_id(local_btf, local_id);
> + if (!local_type)
> + return -EINVAL;
> +
> + local_name = btf__name_by_offset(local_btf, local_type->name_off);
> + if (str_is_empty(local_name))
> + return -EINVAL;
> +
> + spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
> + if (str_is_empty(spec_str))
> + return -EINVAL;
> +
> + err = bpf_core_spec_parse(local_btf, local_id, spec_str, &local_spec);
> + if (err) {
> + pr_warning("prog '%s': relo #%d: parsing [%d] (%s) + %s failed: %d\n",
> + prog_name, relo_idx, local_id, local_name, spec_str,
> + err);
> + return -EINVAL;
> + }
> +
> + pr_debug("prog '%s': relo #%d: spec is ", prog_name, relo_idx);
> + bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
> + libbpf_print(LIBBPF_DEBUG, "\n");
> +
> + if (!hashmap__find(cand_cache, type_key, (void **)&cand_ids)) {
> + cand_ids = bpf_core_find_cands(local_btf, local_id, targ_btf);
> + if (IS_ERR(cand_ids)) {
> + pr_warning("prog '%s': relo #%d: target candidate search failed for [%d] (%s): %ld",
> + prog_name, relo_idx, local_id, local_name,
> + PTR_ERR(cand_ids));
> + return PTR_ERR(cand_ids);
> + }
> + err = hashmap__set(cand_cache, type_key, cand_ids, NULL, NULL);
> + if (err) {
> + bpf_core_free_cands(cand_ids);
> + return err;
> + }
> + }
> +
> + for (i = 0, j = 0; i < cand_ids->len; i++) {
> + cand_id = cand_ids->data[i];
> + cand_type = btf__type_by_id(targ_btf, cand_id);
> + cand_name = btf__name_by_offset(targ_btf, cand_type->name_off);
> +
> + err = bpf_core_spec_match(&local_spec, targ_btf,
> + cand_id, &cand_spec);
> + if (err < 0) {
> + pr_warning("prog '%s': relo #%d: failed to match spec ",
> + prog_name, relo_idx);
> + bpf_core_dump_spec(LIBBPF_WARN, &local_spec);
> + libbpf_print(LIBBPF_WARN,
> + " to candidate #%d [%d] (%s): %d\n",
> + i, cand_id, cand_name, err);
> + return err;
> + }
> + if (err == 0) {
> + pr_debug("prog '%s': relo #%d: candidate #%d [%d] (%s) doesn't match spec ",
> + prog_name, relo_idx, i, cand_id, cand_name);
> + bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
> + libbpf_print(LIBBPF_DEBUG, "\n");
> + continue;
> + }
> +
> + pr_debug("prog '%s': relo #%d: candidate #%d matched as spec ",
> + prog_name, relo_idx, i);
> + bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
> + libbpf_print(LIBBPF_DEBUG, "\n");
> +
> + if (j == 0) {
> + targ_spec = cand_spec;
> + } else if (cand_spec.offset != targ_spec.offset) {
> + /* if there are many candidates, they should all
> + * resolve to the same offset
> + */
> + pr_warning("prog '%s': relo #%d: candidate #%d spec ",
> + prog_name, relo_idx, i);
> + bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
> + libbpf_print(LIBBPF_WARN,
> + " conflicts with target spec ");
> + bpf_core_dump_spec(LIBBPF_WARN, &targ_spec);
> + libbpf_print(LIBBPF_WARN, "\n");
> + return -EINVAL;
> + }
> +
> + cand_ids->data[j++] = cand_spec.spec[0].type_id;
> + }
> +
> + cand_ids->len = j;
> + if (cand_ids->len == 0) {
> + pr_warning("prog '%s': relo #%d: no matching targets found for [%d] (%s) + %s\n",
> + prog_name, relo_idx, local_id, local_name, spec_str);
> + return -ESRCH;
> + }
> +
> + err = bpf_core_reloc_insn(prog, relo->insn_off,
> + local_spec.offset, targ_spec.offset);
> + if (err) {
> + pr_warning("prog '%s': relo #%d: failed to patch insn at offset %d: %d\n",
> + prog_name, relo_idx, relo->insn_off, err);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int
> +bpf_core_reloc_offsets(struct bpf_object *obj, const char *targ_btf_path)
> +{
> + const struct btf_ext_info_sec *sec;
> + const struct bpf_offset_reloc *rec;
> + const struct btf_ext_info *seg;
> + struct hashmap_entry *entry;
> + struct hashmap *cand_cache = NULL;
> + struct bpf_program *prog;
> + struct btf *targ_btf;
> + const char *sec_name;
> + int i, err = 0;
> +
> + if (targ_btf_path)
> + targ_btf = btf__parse_elf(targ_btf_path, NULL);
> + else
> + targ_btf = bpf_core_find_kernel_btf();
> + if (IS_ERR(targ_btf)) {
> + pr_warning("failed to get target BTF: %ld\n",
> + PTR_ERR(targ_btf));
> + return PTR_ERR(targ_btf);
> + }
> +
> + cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
> + if (IS_ERR(cand_cache)) {
> + err = PTR_ERR(cand_cache);
> + goto out;
> + }
> +
> + seg = &obj->btf_ext->offset_reloc_info;
> + for_each_btf_ext_sec(seg, sec) {
> + sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
> + if (str_is_empty(sec_name)) {
> + err = -EINVAL;
> + goto out;
> + }
> + prog = bpf_object__find_program_by_title(obj, sec_name);
> + if (!prog) {
> + pr_warning("failed to find program '%s' for CO-RE offset relocation\n",
> + sec_name);
> + err = -EINVAL;
> + goto out;
> + }
> +
> + pr_debug("prog '%s': performing %d CO-RE offset relocs\n",
> + sec_name, sec->num_info);
> +
> + for_each_btf_ext_rec(seg, sec, i, rec) {
> + err = bpf_core_reloc_offset(prog, rec, i, obj->btf,
> + targ_btf, cand_cache);
> + if (err) {
> + pr_warning("prog '%s': relo #%d: failed to relocate: %d\n",
> + sec_name, i, err);
> + goto out;
> + }
> + }
> + }
> +
> +out:
> + btf__free(targ_btf);
> + if (!IS_ERR_OR_NULL(cand_cache)) {
> + hashmap__for_each_entry(cand_cache, entry, i) {
> + bpf_core_free_cands(entry->value);
> + }
> + hashmap__free(cand_cache);
> + }
> + return err;
> +}
> +
> +static int
> +bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
> +{
> + int err = 0;
> +
> + if (obj->btf_ext->offset_reloc_info.len)
> + err = bpf_core_reloc_offsets(obj, targ_btf_path);
> +
> + return err;
> +}
> +
> static int
> bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
> struct reloc_desc *relo)
> @@ -2399,14 +3293,21 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
> return 0;
> }
>
> -
> static int
> -bpf_object__relocate(struct bpf_object *obj)
> +bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
> {
> struct bpf_program *prog;
> size_t i;
> int err;
>
> + if (obj->btf_ext) {
> + err = bpf_object__relocate_core(obj, targ_btf_path);
> + if (err) {
> + pr_warning("failed to perform CO-RE relocations: %d\n",
> + err);
> + return err;
> + }
> + }
> for (i = 0; i < obj->nr_programs; i++) {
> prog = &obj->programs[i];
>
> @@ -2807,7 +3708,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
> obj->loaded = true;
>
> CHECK_ERR(bpf_object__create_maps(obj), err, out);
> - CHECK_ERR(bpf_object__relocate(obj), err, out);
> + CHECK_ERR(bpf_object__relocate(obj, attr->target_btf_path), err, out);
> CHECK_ERR(bpf_object__load_progs(obj, attr->log_level), err, out);
>
> return 0;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8a9d462a6f6d..e8f70977d137 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -92,6 +92,7 @@ LIBBPF_API void bpf_object__close(struct bpf_object *object);
> struct bpf_object_load_attr {
> struct bpf_object *obj;
> int log_level;
> + const char *target_btf_path;
> };
>
> /* Load/unload object into/from kernel */
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-30 23:43 ` Song Liu
@ 2019-07-30 23:55 ` Andrii Nakryiko
2019-07-31 0:16 ` Song Liu
0 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-30 23:55 UTC (permalink / raw)
To: Song Liu
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
On Tue, Jul 30, 2019 at 4:44 PM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
> >
> > This patch implements the core logic for BPF CO-RE offsets relocations.
> > Every instruction that needs to be relocated has corresponding
> > bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> > to match recorded "local" relocation spec against potentially many
> > compatible "target" types, creating corresponding spec. Details of the
> > algorithm are noted in corresponding comments in the code.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> > tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
> > tools/lib/bpf/libbpf.h | 1 +
> > 2 files changed, 909 insertions(+), 7 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index ead915aec349..75da90928257 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -38,6 +38,7 @@
[...]
> >
> > -static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
> > - __u32 id)
> > +static const struct btf_type *
> > +skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
> > {
> > const struct btf_type *t = btf__type_by_id(btf, id);
> >
> > + if (res_id)
> > + *res_id = id;
> > +
> > while (true) {
> > switch (BTF_INFO_KIND(t->info)) {
> > case BTF_KIND_VOLATILE:
> > case BTF_KIND_CONST:
> > case BTF_KIND_RESTRICT:
> > case BTF_KIND_TYPEDEF:
> > + if (res_id)
> > + *res_id = t->type;
> > t = btf__type_by_id(btf, t->type);
>
> So btf->types[*res_id] == retval, right? Then with retval and btf, we can
> calculate *res_id without this change?
Unless I'm missing something very clever here, no. btf->types is array
of pointers (it's an index into a variable-sized types). This function
returns `struct btf_type *`, which is one of the **values** stored in
that array. You are claiming that by having value of one of array
elements you can easily find element's index? If it was possible to do
in O(1), we wouldn't have so many algorithms and data structures for
search and indexing. You can do that only with linear search, not some
clever pointer arithmetic or at least binary search. So I'm not sure
what you are proposing here...
The way BTF is defined, struct btf_type doesn't know its own type ID,
which is often inconvenient and requires to keep track of that ID, if
it's necessary, but that's how it is.
But then again, what are we trying to achieve here? Eliminate
returning id and pointer? I could always return id and easily look up
pointer, but having both is super convenient and makes code simpler
and shorter, so I'd like to keep it.
>
> > break;
> > default:
> > @@ -1044,7 +1051,7 @@ static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
> > static bool get_map_field_int(const char *map_name, const struct btf *btf,
> > const struct btf_type *def,
> > const struct btf_member *m, __u32 *res) {
[...]
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-30 23:55 ` Andrii Nakryiko
@ 2019-07-31 0:16 ` Song Liu
0 siblings, 0 replies; 27+ messages in thread
From: Song Liu @ 2019-07-31 0:16 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
> On Jul 30, 2019, at 4:55 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Jul 30, 2019 at 4:44 PM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>>>
>>> This patch implements the core logic for BPF CO-RE offsets relocations.
>>> Every instruction that needs to be relocated has corresponding
>>> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
>>> to match recorded "local" relocation spec against potentially many
>>> compatible "target" types, creating corresponding spec. Details of the
>>> algorithm are noted in corresponding comments in the code.
>>>
>>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
>>> ---
>>> tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
>>> tools/lib/bpf/libbpf.h | 1 +
>>> 2 files changed, 909 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>>> index ead915aec349..75da90928257 100644
>>> --- a/tools/lib/bpf/libbpf.c
>>> +++ b/tools/lib/bpf/libbpf.c
>>> @@ -38,6 +38,7 @@
>
> [...]
>
>>>
>>> -static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
>>> - __u32 id)
>>> +static const struct btf_type *
>>> +skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
>>> {
>>> const struct btf_type *t = btf__type_by_id(btf, id);
>>>
>>> + if (res_id)
>>> + *res_id = id;
>>> +
>>> while (true) {
>>> switch (BTF_INFO_KIND(t->info)) {
>>> case BTF_KIND_VOLATILE:
>>> case BTF_KIND_CONST:
>>> case BTF_KIND_RESTRICT:
>>> case BTF_KIND_TYPEDEF:
>>> + if (res_id)
>>> + *res_id = t->type;
>>> t = btf__type_by_id(btf, t->type);
>>
>> So btf->types[*res_id] == retval, right? Then with retval and btf, we can
>> calculate *res_id without this change?
>
> Unless I'm missing something very clever here, no. btf->types is array
> of pointers (it's an index into a variable-sized types). This function
> returns `struct btf_type *`, which is one of the **values** stored in
> that array. You are claiming that by having value of one of array
> elements you can easily find element's index? If it was possible to do
> in O(1), we wouldn't have so many algorithms and data structures for
> search and indexing. You can do that only with linear search, not some
> clever pointer arithmetic or at least binary search. So I'm not sure
> what you are proposing here...
oops.. Clearly, I made some silly mistake. Sorry for the noise.
Song
>
> The way BTF is defined, struct btf_type doesn't know its own type ID,
> which is often inconvenient and requires to keep track of that ID, if
> it's necessary, but that's how it is.
>
> But then again, what are we trying to achieve here? Eliminate
> returning id and pointer? I could always return id and easily look up
> pointer, but having both is super convenient and makes code simpler
> and shorter, so I'd like to keep it.
>
>>
>>> break;
>>> default:
>>> @@ -1044,7 +1051,7 @@ static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
>>> static bool get_map_field_int(const char *map_name, const struct btf *btf,
>>> const struct btf_type *def,
>>> const struct btf_member *m, __u32 *res) {
>
> [...]
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-30 19:53 ` [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm Andrii Nakryiko
2019-07-30 23:43 ` Song Liu
@ 2019-07-31 0:39 ` Song Liu
2019-07-31 1:00 ` Andrii Nakryiko
1 sibling, 1 reply; 27+ messages in thread
From: Song Liu @ 2019-07-31 0:39 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, netdev, Alexei Starovoitov, daniel, Yonghong Song,
andrii.nakryiko, Kernel Team
> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>
> This patch implements the core logic for BPF CO-RE offsets relocations.
> Every instruction that needs to be relocated has corresponding
> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> to match recorded "local" relocation spec against potentially many
> compatible "target" types, creating corresponding spec. Details of the
> algorithm are noted in corresponding comments in the code.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
> tools/lib/bpf/libbpf.h | 1 +
> 2 files changed, 909 insertions(+), 7 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ead915aec349..75da90928257 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -38,6 +38,7 @@
> #include <sys/stat.h>
> #include <sys/types.h>
> #include <sys/vfs.h>
> +#include <sys/utsname.h>
> #include <tools/libc_compat.h>
> #include <libelf.h>
> #include <gelf.h>
> @@ -47,6 +48,7 @@
> #include "btf.h"
> #include "str_error.h"
> #include "libbpf_internal.h"
> +#include "hashmap.h"
>
> #ifndef EM_BPF
> #define EM_BPF 247
> @@ -1015,17 +1017,22 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict)
> return 0;
> }
>
> -static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
> - __u32 id)
> +static const struct btf_type *
> +skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
> {
> const struct btf_type *t = btf__type_by_id(btf, id);
>
> + if (res_id)
> + *res_id = id;
> +
> while (true) {
> switch (BTF_INFO_KIND(t->info)) {
> case BTF_KIND_VOLATILE:
> case BTF_KIND_CONST:
> case BTF_KIND_RESTRICT:
> case BTF_KIND_TYPEDEF:
> + if (res_id)
> + *res_id = t->type;
> t = btf__type_by_id(btf, t->type);
> break;
> default:
> @@ -1044,7 +1051,7 @@ static const struct btf_type *skip_mods_and_typedefs(const struct btf *btf,
> static bool get_map_field_int(const char *map_name, const struct btf *btf,
> const struct btf_type *def,
> const struct btf_member *m, __u32 *res) {
> - const struct btf_type *t = skip_mods_and_typedefs(btf, m->type);
> + const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
> const char *name = btf__name_by_offset(btf, m->name_off);
> const struct btf_array *arr_info;
> const struct btf_type *arr_t;
> @@ -1110,7 +1117,7 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
> return -EOPNOTSUPP;
> }
>
> - def = skip_mods_and_typedefs(obj->btf, var->type);
> + def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
> if (BTF_INFO_KIND(def->info) != BTF_KIND_STRUCT) {
> pr_warning("map '%s': unexpected def kind %u.\n",
> map_name, BTF_INFO_KIND(var->info));
> @@ -2292,6 +2299,893 @@ bpf_program_reloc_btf_ext(struct bpf_program *prog, struct bpf_object *obj,
> return 0;
> }
>
> +#define BPF_CORE_SPEC_MAX_LEN 64
> +
> +/* represents BPF CO-RE field or array element accessor */
> +struct bpf_core_accessor {
> + __u32 type_id; /* struct/union type or array element type */
> + __u32 idx; /* field index or array index */
> + const char *name; /* field name or NULL for array accessor */
> +};
> +
> +struct bpf_core_spec {
> + const struct btf *btf;
> + /* high-level spec: named fields and array indices only */
> + struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
> + /* high-level spec length */
> + int len;
> + /* raw, low-level spec: 1-to-1 with accessor spec string */
> + int raw_spec[BPF_CORE_SPEC_MAX_LEN];
> + /* raw spec length */
> + int raw_len;
> + /* field byte offset represented by spec */
> + __u32 offset;
> +};
> +
> +static bool str_is_empty(const char *s)
> +{
> + return !s || !s[0];
> +}
> +
> +static int btf_kind(const struct btf_type *t)
> +{
> + return BTF_INFO_KIND(t->info);
> +}
> +
> +static bool btf_is_composite(const struct btf_type *t)
> +{
> + int kind = btf_kind(t);
> +
> + return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
> +}
> +
> +static bool btf_is_array(const struct btf_type *t)
> +{
> + return btf_kind(t) == BTF_KIND_ARRAY;
> +}
> +
> +/*
> + * Turn bpf_offset_reloc into a low- and high-level spec representation,
> + * validating correctness along the way, as well as calculating resulting
> + * field offset (in bytes), specified by accessor string. Low-level spec
> + * captures every single level of nestedness, including traversing anonymous
> + * struct/union members. High-level one only captures semantically meaningful
> + * "turning points": named fields and array indicies.
> + * E.g., for this case:
> + *
> + * struct sample {
> + * int __unimportant;
> + * struct {
> + * int __1;
> + * int __2;
> + * int a[7];
> + * };
> + * };
> + *
> + * struct sample *s = ...;
> + *
> + * int x = &s->a[3]; // access string = '0:1:2:3'
> + *
> + * Low-level spec has 1:1 mapping with each element of access string (it's
> + * just a parsed access string representation): [0, 1, 2, 3].
> + *
> + * High-level spec will capture only 3 points:
> + * - intial zero-index access by pointer (&s->... is the same as &s[0]...);
> + * - field 'a' access (corresponds to '2' in low-level spec);
> + * - array element #3 access (corresponds to '3' in low-level spec).
> + *
> + */
> +static int bpf_core_spec_parse(const struct btf *btf,
> + __u32 type_id,
> + const char *spec_str,
> + struct bpf_core_spec *spec)
> +{
> + int access_idx, parsed_len, i;
> + const struct btf_type *t;
> + const char *name;
> + __u32 id;
> + __s64 sz;
> +
> + if (str_is_empty(spec_str) || *spec_str == ':')
> + return -EINVAL;
> +
> + memset(spec, 0, sizeof(*spec));
> + spec->btf = btf;
> +
> + /* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
> + while (*spec_str) {
> + if (*spec_str == ':')
> + ++spec_str;
> + if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
> + return -EINVAL;
> + if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
> + return -E2BIG;
> + spec_str += parsed_len;
> + spec->raw_spec[spec->raw_len++] = access_idx;
> + }
> +
> + if (spec->raw_len == 0)
> + return -EINVAL;
> +
> + /* first spec value is always reloc type array index */
> + t = skip_mods_and_typedefs(btf, type_id, &id);
> + if (!t)
> + return -EINVAL;
> +
> + access_idx = spec->raw_spec[0];
> + spec->spec[0].type_id = id;
> + spec->spec[0].idx = access_idx;
> + spec->len++;
> +
> + sz = btf__resolve_size(btf, id);
> + if (sz < 0)
> + return sz;
> + spec->offset = access_idx * sz;
> +
> + for (i = 1; i < spec->raw_len; i++) {
> + t = skip_mods_and_typedefs(btf, id, &id);
> + if (!t)
> + return -EINVAL;
> +
> + access_idx = spec->raw_spec[i];
> +
> + if (btf_is_composite(t)) {
> + const struct btf_member *m = (void *)(t + 1);
Why (void *) instead of (const struct btf_member *)? There are a few more
in the rest of the patch.
> + __u32 offset;
> +
> + if (access_idx >= BTF_INFO_VLEN(t->info))
> + return -EINVAL;
> +
> + m = &m[access_idx];
> +
> + if (BTF_INFO_KFLAG(t->info)) {
> + if (BTF_MEMBER_BITFIELD_SIZE(m->offset))
> + return -EINVAL;
> + offset = BTF_MEMBER_BIT_OFFSET(m->offset);
> + } else {
> + offset = m->offset;
> + }
> + if (m->offset % 8)
> + return -EINVAL;
> + spec->offset += offset / 8;
> +
> + if (m->name_off) {
> + name = btf__name_by_offset(btf, m->name_off);
> + if (str_is_empty(name))
> + return -EINVAL;
> +
> + spec->spec[spec->len].type_id = id;
> + spec->spec[spec->len].idx = access_idx;
> + spec->spec[spec->len].name = name;
> + spec->len++;
> + }
> +
> + id = m->type;
> + } else if (btf_is_array(t)) {
> + const struct btf_array *a = (void *)(t + 1);
> +
> + t = skip_mods_and_typedefs(btf, a->type, &id);
> + if (!t || access_idx >= a->nelems)
> + return -EINVAL;
> +
> + spec->spec[spec->len].type_id = id;
> + spec->spec[spec->len].idx = access_idx;
> + spec->len++;
> +
> + sz = btf__resolve_size(btf, id);
> + if (sz < 0)
> + return sz;
> + spec->offset += access_idx * sz;
> + } else {
> + pr_warning("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %d\n",
> + type_id, spec_str, i, id, btf_kind(t));
> + return -EINVAL;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/* Given 'some_struct_name___with_flavor' return the length of a name prefix
> + * before last triple underscore. Struct name part after last triple
> + * underscore is ignored by BPF CO-RE relocation during relocation matching.
> + */
> +static size_t bpf_core_essential_name_len(const char *name)
> +{
> + size_t n = strlen(name);
> + int i = n - 3;
> +
> + while (i > 0) {
> + if (name[i] == '_' && name[i + 1] == '_' && name[i + 2] == '_')
> + return i;
> + i--;
> + }
> + return n;
> +}
> +
> +/* dynamically sized list of type IDs */
> +struct ids_vec {
> + __u32 *data;
> + int len;
> +};
> +
> +static void bpf_core_free_cands(struct ids_vec *cand_ids)
> +{
> + free(cand_ids->data);
> + free(cand_ids);
> +}
> +
> +static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
> + __u32 local_type_id,
> + const struct btf *targ_btf)
> +{
> + size_t local_essent_len, targ_essent_len;
> + const char *local_name, *targ_name;
> + const struct btf_type *t;
> + struct ids_vec *cand_ids;
> + __u32 *new_ids;
> + int i, err, n;
> +
> + t = btf__type_by_id(local_btf, local_type_id);
> + if (!t)
> + return ERR_PTR(-EINVAL);
> +
> + local_name = btf__name_by_offset(local_btf, t->name_off);
> + if (str_is_empty(local_name))
> + return ERR_PTR(-EINVAL);
> + local_essent_len = bpf_core_essential_name_len(local_name);
> +
> + cand_ids = calloc(1, sizeof(*cand_ids));
> + if (!cand_ids)
> + return ERR_PTR(-ENOMEM);
> +
> + n = btf__get_nr_types(targ_btf);
> + for (i = 1; i <= n; i++) {
> + t = btf__type_by_id(targ_btf, i);
> + targ_name = btf__name_by_offset(targ_btf, t->name_off);
> + if (str_is_empty(targ_name))
> + continue;
> +
> + targ_essent_len = bpf_core_essential_name_len(targ_name);
> + if (targ_essent_len != local_essent_len)
> + continue;
> +
> + if (strncmp(local_name, targ_name, local_essent_len) == 0) {
> + pr_debug("[%d] (%s): found candidate [%d] (%s)\n",
> + local_type_id, local_name, i, targ_name);
> + new_ids = realloc(cand_ids->data, cand_ids->len + 1);
> + if (!new_ids) {
> + err = -ENOMEM;
> + goto err_out;
> + }
> + cand_ids->data = new_ids;
> + cand_ids->data[cand_ids->len++] = i;
> + }
> + }
> + return cand_ids;
> +err_out:
> + bpf_core_free_cands(cand_ids);
> + return ERR_PTR(err);
> +}
> +
> +/* Check two types for compatibility, skipping const/volatile/restrict and
> + * typedefs, to ensure we are relocating offset to the compatible entities:
> + * - any two STRUCTs/UNIONs are compatible and can be mixed;
> + * - any two FWDs are compatible;
> + * - any two PTRs are always compatible;
> + * - for ENUMs, check sizes, names are ignored;
> + * - for INT, size and bitness should match, signedness is ignored;
> + * - for ARRAY, dimensionality is ignored, element types are checked for
> + * compatibility recursively;
> + * - everything else shouldn't be ever a target of relocation.
> + * These rules are not set in stone and probably will be adjusted as we get
> + * more experience with using BPF CO-RE relocations.
> + */
> +static int bpf_core_fields_are_compat(const struct btf *local_btf,
> + __u32 local_id,
> + const struct btf *targ_btf,
> + __u32 targ_id)
> +{
> + const struct btf_type *local_type, *targ_type;
> + __u16 kind;
> +
> +recur:
> + local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
> + targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
> + if (!local_type || !targ_type)
> + return -EINVAL;
> +
> + if (btf_is_composite(local_type) && btf_is_composite(targ_type))
> + return 1;
> + if (BTF_INFO_KIND(local_type->info) != BTF_INFO_KIND(targ_type->info))
> + return 0;
> +
> + kind = BTF_INFO_KIND(local_type->info);
> + switch (kind) {
> + case BTF_KIND_FWD:
> + case BTF_KIND_PTR:
> + return 1;
> + case BTF_KIND_ENUM:
> + return local_type->size == targ_type->size;
> + case BTF_KIND_INT: {
> + __u32 loc_int = *(__u32 *)(local_type + 1);
> + __u32 targ_int = *(__u32 *)(targ_type + 1);
> +
> + return BTF_INT_OFFSET(loc_int) == 0 &&
> + BTF_INT_OFFSET(targ_int) == 0 &&
> + local_type->size == targ_type->size &&
> + BTF_INT_BITS(loc_int) == BTF_INT_BITS(targ_int);
> + }
> + case BTF_KIND_ARRAY: {
> + const struct btf_array *loc_a, *targ_a;
> +
> + loc_a = (void *)(local_type + 1);
> + targ_a = (void *)(targ_type + 1);
> + local_id = loc_a->type;
> + targ_id = targ_a->type;
> + goto recur;
> + }
> + default:
> + pr_warning("unexpected kind %d relocated, local [%d], target [%d]\n",
> + kind, local_id, targ_id);
> + return 0;
> + }
> +}
> +
> +/*
> + * Given single high-level named field accessor in local type, find
> + * corresponding high-level accessor for a target type. Along the way,
> + * maintain low-level spec for target as well. Also keep updating target
> + * offset.
> + *
> + * Searching is performed through recursive exhaustive enumeration of all
> + * fields of a struct/union. If there are any anonymous (embedded)
> + * structs/unions, they are recursively searched as well. If field with
> + * desired name is found, check compatibility between local and target types,
> + * before returning result.
> + *
> + * 1 is returned, if field is found.
> + * 0 is returned if no compatible field is found.
> + * <0 is returned on error.
> + */
> +static int bpf_core_match_member(const struct btf *local_btf,
> + const struct bpf_core_accessor *local_acc,
> + const struct btf *targ_btf,
> + __u32 targ_id,
> + struct bpf_core_spec *spec,
> + __u32 *next_targ_id)
> +{
> + const struct btf_type *local_type, *targ_type;
> + const struct btf_member *local_member, *m;
> + const char *local_name, *targ_name;
> + __u32 local_id;
> + int i, n, found;
> +
> + targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
> + if (!targ_type)
> + return -EINVAL;
> + if (!btf_is_composite(targ_type))
> + return 0;
> +
> + local_id = local_acc->type_id;
> + local_type = btf__type_by_id(local_btf, local_id);
> + local_member = (void *)(local_type + 1);
> + local_member += local_acc->idx;
> + local_name = btf__name_by_offset(local_btf, local_member->name_off);
> +
> + n = BTF_INFO_VLEN(targ_type->info);
> + m = (void *)(targ_type + 1);
> + for (i = 0; i < n; i++, m++) {
> + __u32 offset;
> +
> + /* bitfield relocations not supported */
> + if (BTF_INFO_KFLAG(targ_type->info)) {
> + if (BTF_MEMBER_BITFIELD_SIZE(m->offset))
> + continue;
> + offset = BTF_MEMBER_BIT_OFFSET(m->offset);
> + } else {
> + offset = m->offset;
> + }
> + if (offset % 8)
> + continue;
> +
> + /* too deep struct/union/array nesting */
> + if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
> + return -E2BIG;
> +
> + /* speculate this member will be the good one */
> + spec->offset += offset / 8;
> + spec->raw_spec[spec->raw_len++] = i;
> +
> + targ_name = btf__name_by_offset(targ_btf, m->name_off);
> + if (str_is_empty(targ_name)) {
> + /* embedded struct/union, we need to go deeper */
> + found = bpf_core_match_member(local_btf, local_acc,
> + targ_btf, m->type,
> + spec, next_targ_id);
> + if (found) /* either found or error */
> + return found;
> + } else if (strcmp(local_name, targ_name) == 0) {
> + /* matching named field */
> + struct bpf_core_accessor *targ_acc;
> +
> + targ_acc = &spec->spec[spec->len++];
> + targ_acc->type_id = targ_id;
> + targ_acc->idx = i;
> + targ_acc->name = targ_name;
> +
> + *next_targ_id = m->type;
> + found = bpf_core_fields_are_compat(local_btf,
> + local_member->type,
> + targ_btf, m->type);
> + if (!found)
> + spec->len--; /* pop accessor */
> + return found;
> + }
> + /* member turned out not to be what we looked for */
> + spec->offset -= offset / 8;
> + spec->raw_len--;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Try to match local spec to a target type and, if successful, produce full
> + * target spec (high-level, low-level + offset).
> + */
> +static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
> + const struct btf *targ_btf, __u32 targ_id,
> + struct bpf_core_spec *targ_spec)
> +{
> + const struct btf_type *targ_type;
> + const struct bpf_core_accessor *local_acc;
> + struct bpf_core_accessor *targ_acc;
> + int i, sz, matched;
> +
> + memset(targ_spec, 0, sizeof(*targ_spec));
> + targ_spec->btf = targ_btf;
> +
> + local_acc = &local_spec->spec[0];
> + targ_acc = &targ_spec->spec[0];
> +
> + for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
> + targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
> + &targ_id);
> + if (!targ_type)
> + return -EINVAL;
> +
> + if (local_acc->name) {
> + matched = bpf_core_match_member(local_spec->btf,
> + local_acc,
> + targ_btf, targ_id,
> + targ_spec, &targ_id);
> + if (matched <= 0)
> + return matched;
> + } else {
> + /* for i=0, targ_id is already treated as array element
> + * type (because it's the original struct), for others
> + * we should find array element type first
> + */
> + if (i > 0) {
> + const struct btf_array *a;
> +
> + if (!btf_is_array(targ_type))
> + return 0;
> +
> + a = (void *)(targ_type + 1);
> + if (local_acc->idx >= a->nelems)
> + return 0;
> + if (!skip_mods_and_typedefs(targ_btf, a->type,
> + &targ_id))
> + return -EINVAL;
> + }
> +
> + /* too deep struct/union/array nesting */
> + if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
> + return -E2BIG;
> +
> + targ_acc->type_id = targ_id;
> + targ_acc->idx = local_acc->idx;
> + targ_acc->name = NULL;
> + targ_spec->len++;
> + targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
> + targ_spec->raw_len++;
> +
> + sz = btf__resolve_size(targ_btf, targ_id);
> + if (sz < 0)
> + return sz;
> + targ_spec->offset += local_acc->idx * sz;
> + }
> + }
> +
> + return 1;
> +}
> +
> +/*
> + * Patch relocatable BPF instruction.
> + * Expected insn->imm value is provided for validation, as well as the new
> + * relocated value.
> + *
> + * Currently three kinds of BPF instructions are supported:
> + * 1. rX = <imm> (assignment with immediate operand);
> + * 2. rX += <imm> (arithmetic operations with immediate operand);
> + * 3. *(rX) = <imm> (indirect memory assignment with immediate operand).
> + *
> + * If actual insn->imm value is wrong, bail out.
> + */
> +static int bpf_core_reloc_insn(struct bpf_program *prog, int insn_off,
> + __u32 orig_off, __u32 new_off)
> +{
> + struct bpf_insn *insn;
> + int insn_idx;
> + __u8 class;
> +
> + if (insn_off % sizeof(struct bpf_insn))
> + return -EINVAL;
> + insn_idx = insn_off / sizeof(struct bpf_insn);
> +
> + insn = &prog->insns[insn_idx];
> + class = BPF_CLASS(insn->code);
> +
> + if (class == BPF_ALU || class == BPF_ALU64) {
> + if (BPF_SRC(insn->code) != BPF_K)
> + return -EINVAL;
> + if (insn->imm != orig_off)
> + return -EINVAL;
> + insn->imm = new_off;
> + pr_debug("prog '%s': patched insn #%d (ALU/ALU64) imm %d -> %d\n",
> + bpf_program__title(prog, false),
> + insn_idx, orig_off, new_off);
> + } else {
> + pr_warning("prog '%s': trying to relocate unrecognized insn #%d, code:%x, src:%x, dst:%x, off:%x, imm:%x\n",
> + bpf_program__title(prog, false),
> + insn_idx, insn->code, insn->src_reg, insn->dst_reg,
> + insn->off, insn->imm);
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +/*
> + * Probe few well-known locations for vmlinux kernel image and try to load BTF
> + * data out of it to use for target BTF.
> + */
> +static struct btf *bpf_core_find_kernel_btf(void)
> +{
> + const char *locations[] = {
> + "/lib/modules/%1$s/vmlinux-%1$s",
> + "/usr/lib/modules/%1$s/kernel/vmlinux",
> + };
> + char path[PATH_MAX + 1];
> + struct utsname buf;
> + struct btf *btf;
> + int i, err;
> +
> + err = uname(&buf);
> + if (err) {
> + pr_warning("failed to uname(): %d\n", err);
> + return ERR_PTR(err);
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(locations); i++) {
> + snprintf(path, PATH_MAX, locations[i], buf.release);
> + pr_debug("attempting to load kernel BTF from '%s'\n", path);
> +
> + if (access(path, R_OK))
> + continue;
> +
> + btf = btf__parse_elf(path, NULL);
> + if (IS_ERR(btf))
> + continue;
> +
> + pr_debug("successfully loaded kernel BTF from '%s'\n", path);
> + return btf;
> + }
> +
> + pr_warning("failed to find valid kernel BTF\n");
> + return ERR_PTR(-ESRCH);
> +}
> +
> +/* Output spec definition in the format:
> + * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
> + * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
> + */
> +static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
> +{
> + const struct btf_type *t;
> + const char *s;
> + __u32 type_id;
> + int i;
> +
> + type_id = spec->spec[0].type_id;
> + t = btf__type_by_id(spec->btf, type_id);
> + s = btf__name_by_offset(spec->btf, t->name_off);
> + libbpf_print(level, "[%u] (%s) + ", type_id, s);
> +
> + for (i = 0; i < spec->raw_len; i++)
> + libbpf_print(level, "%d%s", spec->raw_spec[i],
> + i == spec->raw_len - 1 ? " => " : ":");
> +
> + libbpf_print(level, "%u @ &x", spec->offset);
> +
> + for (i = 0; i < spec->len; i++) {
> + if (spec->spec[i].name)
> + libbpf_print(level, ".%s", spec->spec[i].name);
> + else
> + libbpf_print(level, "[%u]", spec->spec[i].idx);
> + }
> +
> +}
> +
> +static size_t bpf_core_hash_fn(const void *key, void *ctx)
> +{
> + return (size_t)key;
> +}
> +
> +static bool bpf_core_equal_fn(const void *k1, const void *k2, void *ctx)
> +{
> + return k1 == k2;
> +}
> +
> +static void *u32_to_ptr(__u32 x)
> +{
> + return (void *)(uintptr_t)x;
> +}
> +
> +/*
> + * CO-RE relocate single instruction.
> + *
> + * The outline and important points of the algorithm:
> + * 1. For given local type, find corresponding candidate target types.
> + * Candidate type is a type with the same "essential" name, ignoring
> + * everything after last triple underscore (___). E.g., `sample`,
> + * `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
> + * for each other. Names with triple underscore are referred to as
> + * "flavors" and are useful, among other things, to allow to
> + * specify/support incompatible variations of the same kernel struct, which
> + * might differ between different kernel versions and/or build
> + * configurations.
> + *
> + * N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
> + * converter, when deduplicated BTF of a kernel still contains more than
> + * one different types with the same name. In that case, ___2, ___3, etc
> + * are appended starting from second name conflict. But start flavors are
> + * also useful to be defined "locally", in BPF program, to extract same
> + * data from incompatible changes between different kernel
> + * versions/configurations. For instance, to handle field renames between
> + * kernel versions, one can use two flavors of the struct name with the
> + * same common name and use conditional relocations to extract that field,
> + * depending on target kernel version.
> + * 2. For each candidate type, try to match local specification to this
> + * candidate target type. Matching involves finding corresponding
> + * high-level spec accessors, meaning that all named fields should match,
> + * as well as all array accesses should be within the actual bounds. Also,
> + * types should be compatible (see bpf_core_fields_are_compat for details).
> + * 3. It is supported and expected that there might be multiple flavors
> + * matching the spec. As long as all the specs resolve to the same set of
> + * offsets across all candidates, there is not error. If there is any
> + * ambiguity, CO-RE relocation will fail. This is necessary to accomodate
> + * imprefection of BTF deduplication, which can cause slight duplication of
> + * the same BTF type, if some directly or indirectly referenced (by
> + * pointer) type gets resolved to different actual types in different
> + * object files. If such situation occurs, deduplicated BTF will end up
> + * with two (or more) structurally identical types, which differ only in
> + * types they refer to through pointer. This should be OK in most cases and
> + * is not an error.
> + * 4. Candidate types search is performed by linearly scanning through all
> + * types in target BTF. It is anticipated that this is overall more
> + * efficient memory-wise and not significantly worse (if not better)
> + * CPU-wise compared to prebuilding a map from all local type names to
> + * a list of candidate type names. It's also sped up by caching resolved
> + * list of matching candidates per each local "root" type ID, that has at
> + * least one bpf_offset_reloc associated with it. This list is shared
> + * between multiple relocations for the same type ID and is updated as some
> + * of the candidates are pruned due to structural incompatibility.
> + */
> +static int bpf_core_reloc_offset(struct bpf_program *prog,
> + const struct bpf_offset_reloc *relo,
> + int relo_idx,
> + const struct btf *local_btf,
> + const struct btf *targ_btf,
> + struct hashmap *cand_cache)
> +{
> + const char *prog_name = bpf_program__title(prog, false);
> + struct bpf_core_spec local_spec, cand_spec, targ_spec;
> + const void *type_key = u32_to_ptr(relo->type_id);
> + const struct btf_type *local_type, *cand_type;
> + const char *local_name, *cand_name;
> + struct ids_vec *cand_ids;
> + __u32 local_id, cand_id;
> + const char *spec_str;
> + int i, j, err;
> +
> + local_id = relo->type_id;
> + local_type = btf__type_by_id(local_btf, local_id);
> + if (!local_type)
> + return -EINVAL;
> +
> + local_name = btf__name_by_offset(local_btf, local_type->name_off);
> + if (str_is_empty(local_name))
> + return -EINVAL;
> +
> + spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
> + if (str_is_empty(spec_str))
> + return -EINVAL;
> +
> + err = bpf_core_spec_parse(local_btf, local_id, spec_str, &local_spec);
> + if (err) {
> + pr_warning("prog '%s': relo #%d: parsing [%d] (%s) + %s failed: %d\n",
> + prog_name, relo_idx, local_id, local_name, spec_str,
> + err);
> + return -EINVAL;
> + }
> +
> + pr_debug("prog '%s': relo #%d: spec is ", prog_name, relo_idx);
> + bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
> + libbpf_print(LIBBPF_DEBUG, "\n");
> +
> + if (!hashmap__find(cand_cache, type_key, (void **)&cand_ids)) {
> + cand_ids = bpf_core_find_cands(local_btf, local_id, targ_btf);
> + if (IS_ERR(cand_ids)) {
> + pr_warning("prog '%s': relo #%d: target candidate search failed for [%d] (%s): %ld",
> + prog_name, relo_idx, local_id, local_name,
> + PTR_ERR(cand_ids));
> + return PTR_ERR(cand_ids);
> + }
> + err = hashmap__set(cand_cache, type_key, cand_ids, NULL, NULL);
> + if (err) {
> + bpf_core_free_cands(cand_ids);
> + return err;
> + }
> + }
> +
> + for (i = 0, j = 0; i < cand_ids->len; i++) {
> + cand_id = cand_ids->data[i];
> + cand_type = btf__type_by_id(targ_btf, cand_id);
> + cand_name = btf__name_by_offset(targ_btf, cand_type->name_off);
> +
> + err = bpf_core_spec_match(&local_spec, targ_btf,
> + cand_id, &cand_spec);
> + if (err < 0) {
> + pr_warning("prog '%s': relo #%d: failed to match spec ",
> + prog_name, relo_idx);
> + bpf_core_dump_spec(LIBBPF_WARN, &local_spec);
> + libbpf_print(LIBBPF_WARN,
> + " to candidate #%d [%d] (%s): %d\n",
> + i, cand_id, cand_name, err);
> + return err;
> + }
> + if (err == 0) {
> + pr_debug("prog '%s': relo #%d: candidate #%d [%d] (%s) doesn't match spec ",
> + prog_name, relo_idx, i, cand_id, cand_name);
> + bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
> + libbpf_print(LIBBPF_DEBUG, "\n");
> + continue;
> + }
> +
> + pr_debug("prog '%s': relo #%d: candidate #%d matched as spec ",
> + prog_name, relo_idx, i);
> + bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
> + libbpf_print(LIBBPF_DEBUG, "\n");
> +
> + if (j == 0) {
> + targ_spec = cand_spec;
> + } else if (cand_spec.offset != targ_spec.offset) {
> + /* if there are many candidates, they should all
> + * resolve to the same offset
> + */
> + pr_warning("prog '%s': relo #%d: candidate #%d spec ",
> + prog_name, relo_idx, i);
> + bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
> + libbpf_print(LIBBPF_WARN,
> + " conflicts with target spec ");
> + bpf_core_dump_spec(LIBBPF_WARN, &targ_spec);
> + libbpf_print(LIBBPF_WARN, "\n");
> + return -EINVAL;
> + }
> +
> + cand_ids->data[j++] = cand_spec.spec[0].type_id;
> + }
> +
> + cand_ids->len = j;
> + if (cand_ids->len == 0) {
> + pr_warning("prog '%s': relo #%d: no matching targets found for [%d] (%s) + %s\n",
> + prog_name, relo_idx, local_id, local_name, spec_str);
> + return -ESRCH;
> + }
> +
> + err = bpf_core_reloc_insn(prog, relo->insn_off,
> + local_spec.offset, targ_spec.offset);
> + if (err) {
> + pr_warning("prog '%s': relo #%d: failed to patch insn at offset %d: %d\n",
> + prog_name, relo_idx, relo->insn_off, err);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int
> +bpf_core_reloc_offsets(struct bpf_object *obj, const char *targ_btf_path)
> +{
> + const struct btf_ext_info_sec *sec;
> + const struct bpf_offset_reloc *rec;
> + const struct btf_ext_info *seg;
> + struct hashmap_entry *entry;
> + struct hashmap *cand_cache = NULL;
> + struct bpf_program *prog;
> + struct btf *targ_btf;
> + const char *sec_name;
> + int i, err = 0;
> +
> + if (targ_btf_path)
> + targ_btf = btf__parse_elf(targ_btf_path, NULL);
> + else
> + targ_btf = bpf_core_find_kernel_btf();
> + if (IS_ERR(targ_btf)) {
> + pr_warning("failed to get target BTF: %ld\n",
> + PTR_ERR(targ_btf));
> + return PTR_ERR(targ_btf);
> + }
> +
> + cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
> + if (IS_ERR(cand_cache)) {
> + err = PTR_ERR(cand_cache);
> + goto out;
> + }
> +
> + seg = &obj->btf_ext->offset_reloc_info;
> + for_each_btf_ext_sec(seg, sec) {
> + sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
> + if (str_is_empty(sec_name)) {
> + err = -EINVAL;
> + goto out;
> + }
> + prog = bpf_object__find_program_by_title(obj, sec_name);
> + if (!prog) {
> + pr_warning("failed to find program '%s' for CO-RE offset relocation\n",
> + sec_name);
> + err = -EINVAL;
> + goto out;
> + }
> +
> + pr_debug("prog '%s': performing %d CO-RE offset relocs\n",
> + sec_name, sec->num_info);
> +
> + for_each_btf_ext_rec(seg, sec, i, rec) {
> + err = bpf_core_reloc_offset(prog, rec, i, obj->btf,
> + targ_btf, cand_cache);
> + if (err) {
> + pr_warning("prog '%s': relo #%d: failed to relocate: %d\n",
> + sec_name, i, err);
> + goto out;
> + }
> + }
> + }
> +
> +out:
> + btf__free(targ_btf);
> + if (!IS_ERR_OR_NULL(cand_cache)) {
> + hashmap__for_each_entry(cand_cache, entry, i) {
> + bpf_core_free_cands(entry->value);
> + }
> + hashmap__free(cand_cache);
> + }
> + return err;
> +}
> +
> +static int
> +bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
> +{
> + int err = 0;
> +
> + if (obj->btf_ext->offset_reloc_info.len)
> + err = bpf_core_reloc_offsets(obj, targ_btf_path);
> +
> + return err;
> +}
> +
> static int
> bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
> struct reloc_desc *relo)
> @@ -2399,14 +3293,21 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
> return 0;
> }
>
> -
> static int
> -bpf_object__relocate(struct bpf_object *obj)
> +bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
> {
> struct bpf_program *prog;
> size_t i;
> int err;
>
> + if (obj->btf_ext) {
> + err = bpf_object__relocate_core(obj, targ_btf_path);
> + if (err) {
> + pr_warning("failed to perform CO-RE relocations: %d\n",
> + err);
> + return err;
> + }
> + }
> for (i = 0; i < obj->nr_programs; i++) {
> prog = &obj->programs[i];
>
> @@ -2807,7 +3708,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
> obj->loaded = true;
>
> CHECK_ERR(bpf_object__create_maps(obj), err, out);
> - CHECK_ERR(bpf_object__relocate(obj), err, out);
> + CHECK_ERR(bpf_object__relocate(obj, attr->target_btf_path), err, out);
> CHECK_ERR(bpf_object__load_progs(obj, attr->log_level), err, out);
>
> return 0;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8a9d462a6f6d..e8f70977d137 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -92,6 +92,7 @@ LIBBPF_API void bpf_object__close(struct bpf_object *object);
> struct bpf_object_load_attr {
> struct bpf_object *obj;
> int log_level;
> + const char *target_btf_path;
> };
>
> /* Load/unload object into/from kernel */
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-31 0:39 ` Song Liu
@ 2019-07-31 1:00 ` Andrii Nakryiko
2019-07-31 5:19 ` Song Liu
0 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-31 1:00 UTC (permalink / raw)
To: Song Liu
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
On Tue, Jul 30, 2019 at 5:39 PM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
> >
> > This patch implements the core logic for BPF CO-RE offsets relocations.
> > Every instruction that needs to be relocated has corresponding
> > bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> > to match recorded "local" relocation spec against potentially many
> > compatible "target" types, creating corresponding spec. Details of the
> > algorithm are noted in corresponding comments in the code.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> > tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
> > tools/lib/bpf/libbpf.h | 1 +
> > 2 files changed, 909 insertions(+), 7 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
[...]
Please trim irrelevant parts. It doesn't matter with desktop Gmail,
but pretty much everywhere else is very hard to work with.
> > +
> > + for (i = 1; i < spec->raw_len; i++) {
> > + t = skip_mods_and_typedefs(btf, id, &id);
> > + if (!t)
> > + return -EINVAL;
> > +
> > + access_idx = spec->raw_spec[i];
> > +
> > + if (btf_is_composite(t)) {
> > + const struct btf_member *m = (void *)(t + 1);
>
> Why (void *) instead of (const struct btf_member *)? There are a few more
> in the rest of the patch.
>
I just picked the most succinct and non-repetitive form. It's
immediately apparent which type it's implicitly converted to, so I
felt there is no need to repeat it. Also, just (void *) is much
shorter. :)
> > + __u32 offset;
> > +
> > + if (access_idx >= BTF_INFO_VLEN(t->info))
> > + return -EINVAL;
> > +
[...]
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-31 1:00 ` Andrii Nakryiko
@ 2019-07-31 5:19 ` Song Liu
2019-07-31 6:52 ` Andrii Nakryiko
0 siblings, 1 reply; 27+ messages in thread
From: Song Liu @ 2019-07-31 5:19 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
> On Jul 30, 2019, at 6:00 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Jul 30, 2019 at 5:39 PM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>>>
>>> This patch implements the core logic for BPF CO-RE offsets relocations.
>>> Every instruction that needs to be relocated has corresponding
>>> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
>>> to match recorded "local" relocation spec against potentially many
>>> compatible "target" types, creating corresponding spec. Details of the
>>> algorithm are noted in corresponding comments in the code.
>>>
>>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
>>> ---
>>> tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
>>> tools/lib/bpf/libbpf.h | 1 +
>>> 2 files changed, 909 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>
> [...]
>
> Please trim irrelevant parts. It doesn't matter with desktop Gmail,
> but pretty much everywhere else is very hard to work with.
This won't be a problem if the patch is shorter. ;)
>
>>> +
>>> + for (i = 1; i < spec->raw_len; i++) {
>>> + t = skip_mods_and_typedefs(btf, id, &id);
>>> + if (!t)
>>> + return -EINVAL;
>>> +
>>> + access_idx = spec->raw_spec[i];
>>> +
>>> + if (btf_is_composite(t)) {
>>> + const struct btf_member *m = (void *)(t + 1);
>>
>> Why (void *) instead of (const struct btf_member *)? There are a few more
>> in the rest of the patch.
>>
>
> I just picked the most succinct and non-repetitive form. It's
> immediately apparent which type it's implicitly converted to, so I
> felt there is no need to repeat it. Also, just (void *) is much
> shorter. :)
_All_ other code in btf.c converts the pointer to the target type.
In some cases, it is not apparent which type it is converted to,
for example:
+ m = (void *)(targ_type + 1);
I would suggest we do implicit conversion whenever possible.
Thanks,
Song
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-31 5:19 ` Song Liu
@ 2019-07-31 6:52 ` Andrii Nakryiko
2019-07-31 8:29 ` Song Liu
0 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-31 6:52 UTC (permalink / raw)
To: Song Liu
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
On Tue, Jul 30, 2019 at 10:19 PM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Jul 30, 2019, at 6:00 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Jul 30, 2019 at 5:39 PM Song Liu <songliubraving@fb.com> wrote:
> >>
> >>
> >>
> >>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
> >>>
> >>> This patch implements the core logic for BPF CO-RE offsets relocations.
> >>> Every instruction that needs to be relocated has corresponding
> >>> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> >>> to match recorded "local" relocation spec against potentially many
> >>> compatible "target" types, creating corresponding spec. Details of the
> >>> algorithm are noted in corresponding comments in the code.
> >>>
> >>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> >>> ---
> >>> tools/lib/bpf/libbpf.c | 915 ++++++++++++++++++++++++++++++++++++++++-
> >>> tools/lib/bpf/libbpf.h | 1 +
> >>> 2 files changed, 909 insertions(+), 7 deletions(-)
> >>>
> >>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> >
> > [...]
> >
> > Please trim irrelevant parts. It doesn't matter with desktop Gmail,
> > but pretty much everywhere else is very hard to work with.
>
> This won't be a problem if the patch is shorter. ;)
>
> >
> >>> +
> >>> + for (i = 1; i < spec->raw_len; i++) {
> >>> + t = skip_mods_and_typedefs(btf, id, &id);
> >>> + if (!t)
> >>> + return -EINVAL;
> >>> +
> >>> + access_idx = spec->raw_spec[i];
> >>> +
> >>> + if (btf_is_composite(t)) {
> >>> + const struct btf_member *m = (void *)(t + 1);
> >>
> >> Why (void *) instead of (const struct btf_member *)? There are a few more
> >> in the rest of the patch.
> >>
> >
> > I just picked the most succinct and non-repetitive form. It's
> > immediately apparent which type it's implicitly converted to, so I
> > felt there is no need to repeat it. Also, just (void *) is much
> > shorter. :)
>
> _All_ other code in btf.c converts the pointer to the target type.
Most in libbpf.c doesn't, though. Also, I try to preserve pointer
constness for uses that don't modify BTF types (pretty much all of
them in libbpf), so it becomes really verbose, despite extremely short
variable names:
const struct btf_member *m = (const struct btf_member *)(t + 1);
Add one or two levels of nestedness and you are wrapping this line.
> In some cases, it is not apparent which type it is converted to,
> for example:
>
> + m = (void *)(targ_type + 1);
>
> I would suggest we do implicit conversion whenever possible.
Implicit conversion (`m = targ_type + 1;`) is a compilation error,
that won't work.
>
> Thanks,
> Song
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-31 6:52 ` Andrii Nakryiko
@ 2019-07-31 8:29 ` Song Liu
2019-07-31 17:18 ` Andrii Nakryiko
0 siblings, 1 reply; 27+ messages in thread
From: Song Liu @ 2019-07-31 8:29 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
> On Jul 30, 2019, at 11:52 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Jul 30, 2019 at 10:19 PM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 30, 2019, at 6:00 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>>>
>>> On Tue, Jul 30, 2019 at 5:39 PM Song Liu <songliubraving@fb.com> wrote:
>>>>
>>>>
>>>>
>>>>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>>>>>
>>>>> This patch implements the core logic for BPF CO-RE offsets relocations.
>>>>> Every instruction that needs to be relocated has corresponding
>>>>> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
>>>>> to match recorded "local" relocation spec against potentially many
>>>>> compatible "target" types, creating corresponding spec. Details of the
>>>>> algorithm are noted in corresponding comments in the code.
>>>>>
>>>>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
[...]
>>>>
>>>
>>> I just picked the most succinct and non-repetitive form. It's
>>> immediately apparent which type it's implicitly converted to, so I
>>> felt there is no need to repeat it. Also, just (void *) is much
>>> shorter. :)
>>
>> _All_ other code in btf.c converts the pointer to the target type.
>
> Most in libbpf.c doesn't, though. Also, I try to preserve pointer
> constness for uses that don't modify BTF types (pretty much all of
> them in libbpf), so it becomes really verbose, despite extremely short
> variable names:
>
> const struct btf_member *m = (const struct btf_member *)(t + 1);
I don't think being verbose is a big problem here. Overusing
(void *) feels like a bigger problem.
>
> Add one or two levels of nestedness and you are wrapping this line.
>
>> In some cases, it is not apparent which type it is converted to,
>> for example:
>>
>> + m = (void *)(targ_type + 1);
>>
>> I would suggest we do implicit conversion whenever possible.
>
> Implicit conversion (`m = targ_type + 1;`) is a compilation error,
> that won't work.
I misused "implicit" here. I actually meant to say
m = ((const struct btf_member *)(t + 1);
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-31 8:29 ` Song Liu
@ 2019-07-31 17:18 ` Andrii Nakryiko
2019-07-31 17:46 ` Song Liu
0 siblings, 1 reply; 27+ messages in thread
From: Andrii Nakryiko @ 2019-07-31 17:18 UTC (permalink / raw)
To: Song Liu
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
On Wed, Jul 31, 2019 at 1:30 AM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Jul 30, 2019, at 11:52 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Jul 30, 2019 at 10:19 PM Song Liu <songliubraving@fb.com> wrote:
> >>
> >>
> >>
> >>> On Jul 30, 2019, at 6:00 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> >>>
> >>> On Tue, Jul 30, 2019 at 5:39 PM Song Liu <songliubraving@fb.com> wrote:
> >>>>
> >>>>
> >>>>
> >>>>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
> >>>>>
> >>>>> This patch implements the core logic for BPF CO-RE offsets relocations.
> >>>>> Every instruction that needs to be relocated has corresponding
> >>>>> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> >>>>> to match recorded "local" relocation spec against potentially many
> >>>>> compatible "target" types, creating corresponding spec. Details of the
> >>>>> algorithm are noted in corresponding comments in the code.
> >>>>>
> >>>>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
>
> [...]
>
> >>>>
> >>>
> >>> I just picked the most succinct and non-repetitive form. It's
> >>> immediately apparent which type it's implicitly converted to, so I
> >>> felt there is no need to repeat it. Also, just (void *) is much
> >>> shorter. :)
> >>
> >> _All_ other code in btf.c converts the pointer to the target type.
> >
> > Most in libbpf.c doesn't, though. Also, I try to preserve pointer
> > constness for uses that don't modify BTF types (pretty much all of
> > them in libbpf), so it becomes really verbose, despite extremely short
> > variable names:
> >
> > const struct btf_member *m = (const struct btf_member *)(t + 1);
>
> I don't think being verbose is a big problem here. Overusing
Problem is too big and strong word to describe this :). It hurts
readability and will often quite artificially force either wrapping
the line or unnecessarily splitting declaration and assignment. Void *
on the other hand is short and usually is in the same line as target
type declaration, if not, you'll have to find local variable
declaration to double-check type, if you are unsure.
Using (void *) + implicit cast to target pointer type is not
unprecedented in libbpf:
$ rg ' = \((const )?struct \w+ \*\)' tools/lib/bpf/ | wc -l
52
$ rg ' = \((const )?void \*\)' tools/lib/bpf/ | wc -l
35
52 vs 35 is majority overall, but not by a landslide.
> (void *) feels like a bigger problem.
Why do you feel it's a problem? void * conveys that we have a piece of
memory that we will need to reinterpret as some concrete pointer type.
That's what we are doing, skipping btf_type and then interpreting
memory after common btf_type prefix is some other type, depending on
actual BTF kind. I don't think void * is misleading in any way.
In any case, if you still feel strongly about this after all my
arguments, please let me know and I will convert them in this patch
set. It's not like I'm opposed to use duplicate type names (though it
does feel sort of Java-like before it got limited type inference),
it's just in practice it leads to unnecessarily verbose code which
doesn't really improve anything.
>
> >
> > Add one or two levels of nestedness and you are wrapping this line.
> >
> >> In some cases, it is not apparent which type it is converted to,
> >> for example:
> >>
> >> + m = (void *)(targ_type + 1);
> >>
> >> I would suggest we do implicit conversion whenever possible.
> >
> > Implicit conversion (`m = targ_type + 1;`) is a compilation error,
> > that won't work.
>
> I misused "implicit" here. I actually meant to say
>
> m = ((const struct btf_member *)(t + 1);
Ah, so you meant explicit, yep. It's either `void *` or `const struct
something *` then.
>
>
>
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm
2019-07-31 17:18 ` Andrii Nakryiko
@ 2019-07-31 17:46 ` Song Liu
0 siblings, 0 replies; 27+ messages in thread
From: Song Liu @ 2019-07-31 17:46 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Andrii Nakryiko, bpf, netdev, Alexei Starovoitov, daniel,
Yonghong Song, Kernel Team
> On Jul 31, 2019, at 10:18 AM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Wed, Jul 31, 2019 at 1:30 AM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 30, 2019, at 11:52 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>>>
>>> On Tue, Jul 30, 2019 at 10:19 PM Song Liu <songliubraving@fb.com> wrote:
>>>>
>>>>
>>>>
>>>>> On Jul 30, 2019, at 6:00 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>>>>>
>>>>> On Tue, Jul 30, 2019 at 5:39 PM Song Liu <songliubraving@fb.com> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> On Jul 30, 2019, at 12:53 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>>>>>>>
>>>>>>> This patch implements the core logic for BPF CO-RE offsets relocations.
>>>>>>> Every instruction that needs to be relocated has corresponding
>>>>>>> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
>>>>>>> to match recorded "local" relocation spec against potentially many
>>>>>>> compatible "target" types, creating corresponding spec. Details of the
>>>>>>> algorithm are noted in corresponding comments in the code.
>>>>>>>
>>>>>>> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
>>
>> [...]
>>
>>>>>>
>>>>>
>>>>> I just picked the most succinct and non-repetitive form. It's
>>>>> immediately apparent which type it's implicitly converted to, so I
>>>>> felt there is no need to repeat it. Also, just (void *) is much
>>>>> shorter. :)
>>>>
>>>> _All_ other code in btf.c converts the pointer to the target type.
>>>
>>> Most in libbpf.c doesn't, though. Also, I try to preserve pointer
>>> constness for uses that don't modify BTF types (pretty much all of
>>> them in libbpf), so it becomes really verbose, despite extremely short
>>> variable names:
>>>
>>> const struct btf_member *m = (const struct btf_member *)(t + 1);
>>
>> I don't think being verbose is a big problem here. Overusing
>
> Problem is too big and strong word to describe this :). It hurts
> readability and will often quite artificially force either wrapping
> the line or unnecessarily splitting declaration and assignment. Void *
> on the other hand is short and usually is in the same line as target
> type declaration, if not, you'll have to find local variable
> declaration to double-check type, if you are unsure.
>
> Using (void *) + implicit cast to target pointer type is not
> unprecedented in libbpf:
>
> $ rg ' = \((const )?struct \w+ \*\)' tools/lib/bpf/ | wc -l
> 52
> $ rg ' = \((const )?void \*\)' tools/lib/bpf/ | wc -l
> 35
>
> 52 vs 35 is majority overall, but not by a landslide.
>
>> (void *) feels like a bigger problem.
>
> Why do you feel it's a problem? void * conveys that we have a piece of
> memory that we will need to reinterpret as some concrete pointer type.
> That's what we are doing, skipping btf_type and then interpreting
> memory after common btf_type prefix is some other type, depending on
> actual BTF kind. I don't think void * is misleading in any way.
(void *) hides some problem. For example:
struct type_a *ptr_a = NULL;
struct type_b *ptr_b = NULL;
/* we want this */
ptr_a = (struct type_a *)data;
ptr_b = (struct type_b *)(data + offset);
/* typo, should be ptr_b, compiler will complain */
ptr_a = (struct type_b *)(data + offset);
/* typo, should be ptr_b, compiler will ignore */
ptr_a = (void *)(data + offset);
Such typo is not very rare. And it may be really painful to debug.
That being said, I think we have spent too much time on this. I will
let you make the final call. Either way:
Acked-by: Song Liu <songliubraving@fb.com>
^ permalink raw reply [flat|nested] 27+ messages in thread
end of thread, other threads:[~2019-07-31 19:23 UTC | newest]
Thread overview: 27+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-30 19:53 [PATCH v2 bpf-next 00/12] CO-RE offset relocations Andrii Nakryiko
2019-07-30 19:53 ` [PATCH v2 bpf-next 01/12] libbpf: add .BTF.ext offset relocation section loading Andrii Nakryiko
2019-07-30 21:19 ` Song Liu
2019-07-30 19:53 ` [PATCH v2 bpf-next 02/12] libbpf: implement BPF CO-RE offset relocation algorithm Andrii Nakryiko
2019-07-30 23:43 ` Song Liu
2019-07-30 23:55 ` Andrii Nakryiko
2019-07-31 0:16 ` Song Liu
2019-07-31 0:39 ` Song Liu
2019-07-31 1:00 ` Andrii Nakryiko
2019-07-31 5:19 ` Song Liu
2019-07-31 6:52 ` Andrii Nakryiko
2019-07-31 8:29 ` Song Liu
2019-07-31 17:18 ` Andrii Nakryiko
2019-07-31 17:46 ` Song Liu
2019-07-30 19:53 ` [PATCH v2 bpf-next 03/12] selftests/bpf: add BPF_CORE_READ relocatable read macro Andrii Nakryiko
2019-07-30 21:24 ` Song Liu
2019-07-30 21:26 ` Andrii Nakryiko
2019-07-30 21:33 ` Song Liu
2019-07-30 19:54 ` [PATCH v2 bpf-next 04/12] selftests/bpf: add CO-RE relocs testing setup Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 05/12] selftests/bpf: add CO-RE relocs struct flavors tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 06/12] selftests/bpf: add CO-RE relocs nesting tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 07/12] selftests/bpf: add CO-RE relocs array tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 08/12] selftests/bpf: add CO-RE relocs enum/ptr/func_proto tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 09/12] selftests/bpf: add CO-RE relocs modifiers/typedef tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 10/12] selftests/bpf: add CO-RE relocs ptr-as-array tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 11/12] selftests/bpf: add CO-RE relocs ints tests Andrii Nakryiko
2019-07-30 19:54 ` [PATCH v2 bpf-next 12/12] selftests/bpf: add CO-RE relocs misc tests Andrii Nakryiko
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