* [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays
@ 2019-12-15 7:08 Andrii Nakryiko
2019-12-15 7:08 ` [PATCH bpf-next 1/2] libbpf: support flexible arrays in CO-RE Andrii Nakryiko
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Andrii Nakryiko @ 2019-12-15 7:08 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add support for flexible array accesses in a relocatable manner in BPF CO-RE.
It's a typical pattern in C, and kernel in particular, to provide
a fixed-length struct with zero-sized or dimensionless array at the end. In
such cases variable-sized array contents follows immediately after the end of
a struct. This patch set adds support for such access pattern by allowing
accesses to such arrays.
Patch #1 adds libbpf support. Patch #2 adds few test cases for validation.
Andrii Nakryiko (2):
libbpf: support flexible arrays in CO-RE
selftests/bpf: add flexible array relocation tests
tools/lib/bpf/libbpf.c | 34 +++++++++++++---
.../selftests/bpf/prog_tests/core_reloc.c | 4 ++
...f__core_reloc_arrays___equiv_zero_sz_arr.c | 3 ++
..._core_reloc_arrays___err_bad_zero_sz_arr.c | 3 ++
.../btf__core_reloc_arrays___fixed_arr.c | 3 ++
.../selftests/bpf/progs/core_reloc_types.h | 39 +++++++++++++++++++
.../bpf/progs/test_core_reloc_arrays.c | 8 ++--
7 files changed, 85 insertions(+), 9 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___equiv_zero_sz_arr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_zero_sz_arr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___fixed_arr.c
--
2.17.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH bpf-next 1/2] libbpf: support flexible arrays in CO-RE
2019-12-15 7:08 [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays Andrii Nakryiko
@ 2019-12-15 7:08 ` Andrii Nakryiko
2019-12-15 7:08 ` [PATCH bpf-next 2/2] selftests/bpf: add flexible array relocation tests Andrii Nakryiko
2019-12-16 0:56 ` [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays Alexei Starovoitov
2 siblings, 0 replies; 4+ messages in thread
From: Andrii Nakryiko @ 2019-12-15 7:08 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Some data stuctures in kernel are defined with either zero-sized array or
flexible (dimensionless) array at the end of a struct. Actual data of such
array follows in memory immediately after the end of that struct, forming its
variable-sized "body" of elements. Support such access pattern in CO-RE
relocation handling.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/lib/bpf/libbpf.c | 34 +++++++++++++++++++++++++++++-----
1 file changed, 29 insertions(+), 5 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 27d5f7ecba32..51e7a25c6c88 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2537,6 +2537,21 @@ static bool str_is_empty(const char *s)
return !s || !s[0];
}
+static bool is_flex_arr(const struct btf *btf,
+ const struct bpf_core_accessor *acc,
+ const struct btf_array *arr)
+{
+ const struct btf_type *t;
+
+ /* not a flexible array, if not inside a struct or has non-zero size */
+ if (!acc->name || arr->nelems > 0)
+ return false;
+
+ /* has to be the last member of enclosing struct */
+ t = btf__type_by_id(btf, acc->type_id);
+ return acc->idx == btf_vlen(t) - 1;
+}
+
/*
* Turn bpf_field_reloc into a low- and high-level spec representation,
* validating correctness along the way, as well as calculating resulting
@@ -2574,6 +2589,7 @@ static int bpf_core_spec_parse(const struct btf *btf,
struct bpf_core_spec *spec)
{
int access_idx, parsed_len, i;
+ struct bpf_core_accessor *acc;
const struct btf_type *t;
const char *name;
__u32 id;
@@ -2621,6 +2637,7 @@ static int bpf_core_spec_parse(const struct btf *btf,
return -EINVAL;
access_idx = spec->raw_spec[i];
+ acc = &spec->spec[spec->len];
if (btf_is_composite(t)) {
const struct btf_member *m;
@@ -2638,18 +2655,23 @@ static int bpf_core_spec_parse(const struct btf *btf,
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;
+ acc->type_id = id;
+ acc->idx = access_idx;
+ acc->name = name;
spec->len++;
}
id = m->type;
} else if (btf_is_array(t)) {
const struct btf_array *a = btf_array(t);
+ bool flex;
t = skip_mods_and_typedefs(btf, a->type, &id);
- if (!t || access_idx >= a->nelems)
+ if (!t)
+ return -EINVAL;
+
+ flex = is_flex_arr(btf, acc - 1, a);
+ if (!flex && access_idx >= a->nelems)
return -EINVAL;
spec->spec[spec->len].type_id = id;
@@ -2954,12 +2976,14 @@ static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
*/
if (i > 0) {
const struct btf_array *a;
+ bool flex;
if (!btf_is_array(targ_type))
return 0;
a = btf_array(targ_type);
- if (local_acc->idx >= a->nelems)
+ flex = is_flex_arr(targ_btf, targ_acc - 1, a);
+ if (!flex && local_acc->idx >= a->nelems)
return 0;
if (!skip_mods_and_typedefs(targ_btf, a->type,
&targ_id))
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH bpf-next 2/2] selftests/bpf: add flexible array relocation tests
2019-12-15 7:08 [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays Andrii Nakryiko
2019-12-15 7:08 ` [PATCH bpf-next 1/2] libbpf: support flexible arrays in CO-RE Andrii Nakryiko
@ 2019-12-15 7:08 ` Andrii Nakryiko
2019-12-16 0:56 ` [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays Alexei Starovoitov
2 siblings, 0 replies; 4+ messages in thread
From: Andrii Nakryiko @ 2019-12-15 7:08 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add few tests validation CO-RE relocation handling of flexible array accesses.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
.../selftests/bpf/prog_tests/core_reloc.c | 4 ++
...f__core_reloc_arrays___equiv_zero_sz_arr.c | 3 ++
..._core_reloc_arrays___err_bad_zero_sz_arr.c | 3 ++
.../btf__core_reloc_arrays___fixed_arr.c | 3 ++
.../selftests/bpf/progs/core_reloc_types.h | 39 +++++++++++++++++++
.../bpf/progs/test_core_reloc_arrays.c | 8 ++--
6 files changed, 56 insertions(+), 4 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___equiv_zero_sz_arr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_zero_sz_arr.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___fixed_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 05fe85281ff7..31e177adbdf1 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -74,6 +74,7 @@
.b123 = 2, \
.c1c = 3, \
.d00d = 4, \
+ .f10c = 0, \
}, \
.output_len = sizeof(struct core_reloc_arrays_output) \
}
@@ -308,12 +309,15 @@ static struct core_reloc_test_case test_cases[] = {
ARRAYS_CASE(arrays),
ARRAYS_CASE(arrays___diff_arr_dim),
ARRAYS_CASE(arrays___diff_arr_val_sz),
+ ARRAYS_CASE(arrays___equiv_zero_sz_arr),
+ ARRAYS_CASE(arrays___fixed_arr),
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),
+ ARRAYS_ERR_CASE(arrays___err_bad_zero_sz_arr),
/* enum/ptr/int handling scenarios */
PRIMITIVES_CASE(primitives),
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___equiv_zero_sz_arr.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___equiv_zero_sz_arr.c
new file mode 100644
index 000000000000..65eac371b061
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___equiv_zero_sz_arr.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___equiv_zero_sz_arr x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_zero_sz_arr.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_zero_sz_arr.c
new file mode 100644
index 000000000000..ecda2b545ac2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_zero_sz_arr.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_bad_zero_sz_arr x) {}
diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___fixed_arr.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___fixed_arr.c
new file mode 100644
index 000000000000..fe1d01232c22
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___fixed_arr.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___fixed_arr x) {}
diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index 9311489e14b2..6d598cfbdb3e 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -327,6 +327,7 @@ struct core_reloc_arrays_output {
char b123;
int c1c;
int d00d;
+ int f10c;
};
struct core_reloc_arrays_substruct {
@@ -339,6 +340,7 @@ struct core_reloc_arrays {
char b[2][3][4];
struct core_reloc_arrays_substruct c[3];
struct core_reloc_arrays_substruct d[1][2];
+ struct core_reloc_arrays_substruct f[][2];
};
/* bigger array dimensions */
@@ -347,6 +349,7 @@ struct core_reloc_arrays___diff_arr_dim {
char b[3][4][5];
struct core_reloc_arrays_substruct c[4];
struct core_reloc_arrays_substruct d[2][3];
+ struct core_reloc_arrays_substruct f[1][3];
};
/* different size of array's value (struct) */
@@ -363,6 +366,29 @@ struct core_reloc_arrays___diff_arr_val_sz {
int d;
int __padding2;
} d[1][2];
+ struct {
+ int __padding1;
+ int c;
+ int __padding2;
+ } f[][2];
+};
+
+struct core_reloc_arrays___equiv_zero_sz_arr {
+ int a[5];
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+ /* equivalent to flexible array */
+ struct core_reloc_arrays_substruct f[0][2];
+};
+
+struct core_reloc_arrays___fixed_arr {
+ int a[5];
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ struct core_reloc_arrays_substruct d[1][2];
+ /* not a flexible array anymore, but within access bounds */
+ struct core_reloc_arrays_substruct f[1][2];
};
struct core_reloc_arrays___err_too_small {
@@ -370,6 +396,7 @@ struct core_reloc_arrays___err_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_substruct f[][2];
};
struct core_reloc_arrays___err_too_shallow {
@@ -377,6 +404,7 @@ struct core_reloc_arrays___err_too_shallow {
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_substruct f[][2];
};
struct core_reloc_arrays___err_non_array {
@@ -384,6 +412,7 @@ struct core_reloc_arrays___err_non_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_substruct f[][2];
};
struct core_reloc_arrays___err_wrong_val_type {
@@ -391,6 +420,16 @@ struct core_reloc_arrays___err_wrong_val_type {
char b[2][3][4];
int c[3]; /* value is not a struct */
struct core_reloc_arrays_substruct d[1][2];
+ struct core_reloc_arrays_substruct f[][2];
+};
+
+struct core_reloc_arrays___err_bad_zero_sz_arr {
+ /* zero-sized array, but not at the end */
+ struct core_reloc_arrays_substruct f[0][2];
+ int a[5];
+ char b[2][3][4];
+ struct core_reloc_arrays_substruct c[3];
+ 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
index 89951b684282..053b86f6b53f 100644
--- a/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
@@ -18,6 +18,7 @@ struct core_reloc_arrays_output {
char b123;
int c1c;
int d00d;
+ int f01c;
};
struct core_reloc_arrays_substruct {
@@ -30,6 +31,7 @@ struct core_reloc_arrays {
char b[2][3][4];
struct core_reloc_arrays_substruct c[3];
struct core_reloc_arrays_substruct d[1][2];
+ struct core_reloc_arrays_substruct f[][2];
};
#define CORE_READ(dst, src) bpf_core_read(dst, sizeof(*(dst)), src)
@@ -40,18 +42,16 @@ 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 (CORE_READ(&out->a2, &in->a[2]))
return 1;
- /* in->b[1][2][3] */
if (CORE_READ(&out->b123, &in->b[1][2][3]))
return 1;
- /* in->c[1].c */
if (CORE_READ(&out->c1c, &in->c[1].c))
return 1;
- /* in->d[0][0].d */
if (CORE_READ(&out->d00d, &in->d[0][0].d))
return 1;
+ if (CORE_READ(&out->f01c, &in->f[0][1].c))
+ return 1;
return 0;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays
2019-12-15 7:08 [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays Andrii Nakryiko
2019-12-15 7:08 ` [PATCH bpf-next 1/2] libbpf: support flexible arrays in CO-RE Andrii Nakryiko
2019-12-15 7:08 ` [PATCH bpf-next 2/2] selftests/bpf: add flexible array relocation tests Andrii Nakryiko
@ 2019-12-16 0:56 ` Alexei Starovoitov
2 siblings, 0 replies; 4+ messages in thread
From: Alexei Starovoitov @ 2019-12-16 0:56 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, Network Development, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Kernel Team
On Sat, Dec 14, 2019 at 11:09 PM Andrii Nakryiko <andriin@fb.com> wrote:
>
> Add support for flexible array accesses in a relocatable manner in BPF CO-RE.
> It's a typical pattern in C, and kernel in particular, to provide
> a fixed-length struct with zero-sized or dimensionless array at the end. In
> such cases variable-sized array contents follows immediately after the end of
> a struct. This patch set adds support for such access pattern by allowing
> accesses to such arrays.
>
> Patch #1 adds libbpf support. Patch #2 adds few test cases for validation.
Applied. Thanks
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-12-15 7:08 [PATCH bpf-next 0/2] CO-RE relocation support for flexible arrays Andrii Nakryiko
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2019-12-15 7:08 ` [PATCH bpf-next 2/2] selftests/bpf: add flexible array relocation tests Andrii Nakryiko
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