From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: "Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
netdev@vger.kernel.org
Subject: [PATCH bpf-next v5 06/12] libbpf: Support kernel module function calls
Date: Mon, 27 Sep 2021 20:29:35 +0530 [thread overview]
Message-ID: <20210927145941.1383001-7-memxor@gmail.com> (raw)
In-Reply-To: <20210927145941.1383001-1-memxor@gmail.com>
This patch adds libbpf support for kernel module function call support.
The fd_array parameter is used during BPF program load is used to pass
module BTFs referenced by the program. insn->off is set to index into
this array, but starts from 1, because insn->off as 0 is reserved for
btf_vmlinux.
We try to use existing insn->off for a module, since the kernel limits
the maximum distinct module BTFs for kfuncs to 256, and also because
index must never exceed the maximum allowed value that can fit in
insn->off (INT16_MAX). In the future, if kernel interprets signed offset
as unsigned for kfunc calls, this limit can be increased to UINT16_MAX.
Also introduce a btf__find_by_name_kind_own helper to start searching
from module BTF's start id when we know that the BTF ID is not present
in vmlinux BTF (in find_ksym_btf_id).
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
tools/lib/bpf/bpf.c | 1 +
tools/lib/bpf/btf.c | 19 ++++++--
tools/lib/bpf/libbpf.c | 80 +++++++++++++++++++++++----------
tools/lib/bpf/libbpf_internal.h | 3 ++
4 files changed, 76 insertions(+), 27 deletions(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 2401fad090c5..7d1741ceaa32 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -264,6 +264,7 @@ int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr)
attr.line_info_rec_size = load_attr->line_info_rec_size;
attr.line_info_cnt = load_attr->line_info_cnt;
attr.line_info = ptr_to_u64(load_attr->line_info);
+ attr.fd_array = ptr_to_u64(load_attr->fd_array);
if (load_attr->name)
memcpy(attr.prog_name, load_attr->name,
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 6ad63e4d418a..f1d872b3fbf4 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -695,15 +695,16 @@ __s32 btf__find_by_name(const struct btf *btf, const char *type_name)
return libbpf_err(-ENOENT);
}
-__s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
- __u32 kind)
+static __s32 __btf__find_by_name_kind(const struct btf *btf,
+ const char *type_name, __u32 kind,
+ bool own)
{
__u32 i, nr_types = btf__get_nr_types(btf);
if (kind == BTF_KIND_UNKN || !strcmp(type_name, "void"))
return 0;
- for (i = 1; i <= nr_types; i++) {
+ for (i = own ? btf->start_id : 1; i <= nr_types; i++) {
const struct btf_type *t = btf__type_by_id(btf, i);
const char *name;
@@ -717,6 +718,18 @@ __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
return libbpf_err(-ENOENT);
}
+__s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name,
+ __u32 kind)
+{
+ return __btf__find_by_name_kind(btf, type_name, kind, true);
+}
+
+__s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
+ __u32 kind)
+{
+ return __btf__find_by_name_kind(btf, type_name, kind, false);
+}
+
static bool btf_is_modifiable(const struct btf *btf)
{
return (void *)btf->hdr != btf->raw_data;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ef5db34bf913..0f4d203f926e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -420,6 +420,11 @@ struct extern_desc {
/* local btf_id of the ksym extern's type. */
__u32 type_id;
+ /* offset to be patched in for insn->off, this is 0 for
+ * vmlinux BTF, and BTF fd index in obj->fd_array for
+ * module BTF
+ */
+ __s16 offset;
} ksym;
};
};
@@ -431,6 +436,7 @@ struct module_btf {
char *name;
__u32 id;
int fd;
+ int fd_array_idx;
};
struct bpf_object {
@@ -516,6 +522,10 @@ struct bpf_object {
void *priv;
bpf_object_clear_priv_t clear_priv;
+ int *fd_array;
+ size_t fd_array_cap;
+ size_t fd_array_cnt;
+
char path[];
};
#define obj_elf_valid(o) ((o)->efile.elf)
@@ -1145,6 +1155,9 @@ static struct bpf_object *bpf_object__new(const char *path,
obj->kern_version = get_kernel_version();
obj->loaded = false;
+ /* We cannot use index 0 for module BTF fds */
+ obj->fd_array_cnt = 1;
+
INIT_LIST_HEAD(&obj->list);
list_add(&obj->list, &bpf_objects_list);
return obj;
@@ -5357,6 +5370,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
ext = &obj->externs[relo->sym_off];
insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
insn[0].imm = ext->ksym.kernel_btf_id;
+ insn[0].off = ext->ksym.offset;
break;
case RELO_SUBPROG_ADDR:
if (insn[0].src_reg != BPF_PSEUDO_FUNC) {
@@ -6151,6 +6165,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
}
load_attr.log_level = prog->log_level;
load_attr.prog_flags = prog->prog_flags;
+ load_attr.fd_array = prog->obj->fd_array;
if (prog->obj->gen_loader) {
bpf_gen__prog_load(prog->obj->gen_loader, &load_attr,
@@ -6661,13 +6676,14 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
__u16 kind, struct btf **res_btf,
- int *res_btf_fd)
+ struct module_btf **res_mod_btf)
{
- int i, id, btf_fd, err;
+ struct module_btf *mod_btf;
struct btf *btf;
+ int i, id, err;
btf = obj->btf_vmlinux;
- btf_fd = 0;
+ mod_btf = NULL;
id = btf__find_by_name_kind(btf, ksym_name, kind);
if (id == -ENOENT) {
@@ -6676,10 +6692,10 @@ static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
return err;
for (i = 0; i < obj->btf_module_cnt; i++) {
- btf = obj->btf_modules[i].btf;
- /* we assume module BTF FD is always >0 */
- btf_fd = obj->btf_modules[i].fd;
- id = btf__find_by_name_kind(btf, ksym_name, kind);
+ /* we assume module_btf's BTF FD is always >0 */
+ mod_btf = &obj->btf_modules[i];
+ btf = mod_btf->btf;
+ id = btf__find_by_name_kind_own(btf, ksym_name, kind);
if (id != -ENOENT)
break;
}
@@ -6688,7 +6704,7 @@ static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
return -ESRCH;
*res_btf = btf;
- *res_btf_fd = btf_fd;
+ *res_mod_btf = mod_btf;
return id;
}
@@ -6697,11 +6713,12 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
{
const struct btf_type *targ_var, *targ_type;
__u32 targ_type_id, local_type_id;
+ struct module_btf *mod_btf = NULL;
const char *targ_var_name;
- int id, btf_fd = 0, err;
struct btf *btf = NULL;
+ int id, err;
- id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &btf_fd);
+ id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &mod_btf);
if (id == -ESRCH && ext->is_weak) {
return 0;
} else if (id < 0) {
@@ -6736,7 +6753,7 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
}
ext->is_set = true;
- ext->ksym.kernel_btf_obj_fd = btf_fd;
+ ext->ksym.kernel_btf_obj_fd = mod_btf ? mod_btf->fd : 0;
ext->ksym.kernel_btf_id = id;
pr_debug("extern (var ksym) '%s': resolved to [%d] %s %s\n",
ext->name, id, btf_kind_str(targ_var), targ_var_name);
@@ -6748,40 +6765,52 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
struct extern_desc *ext)
{
int local_func_proto_id, kfunc_proto_id, kfunc_id;
+ struct module_btf *mod_btf = NULL;
const struct btf_type *kern_func;
- struct btf *kern_btf = NULL;
- int ret, kern_btf_fd = 0;
+ struct btf *btf = NULL;
+ int ret;
local_func_proto_id = ext->ksym.type_id;
- kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC,
- &kern_btf, &kern_btf_fd);
+ kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, &btf, &mod_btf);
if (kfunc_id < 0) {
pr_warn("extern (func ksym) '%s': not found in kernel BTF\n",
ext->name);
return kfunc_id;
}
- if (kern_btf != obj->btf_vmlinux) {
- pr_warn("extern (func ksym) '%s': function in kernel module is not supported\n",
- ext->name);
- return -ENOTSUP;
- }
-
- kern_func = btf__type_by_id(kern_btf, kfunc_id);
+ kern_func = btf__type_by_id(btf, kfunc_id);
kfunc_proto_id = kern_func->type;
ret = bpf_core_types_are_compat(obj->btf, local_func_proto_id,
- kern_btf, kfunc_proto_id);
+ btf, kfunc_proto_id);
if (ret <= 0) {
pr_warn("extern (func ksym) '%s': func_proto [%d] incompatible with kernel [%d]\n",
ext->name, local_func_proto_id, kfunc_proto_id);
return -EINVAL;
}
+ /* set index for module BTF fd in fd_array, if unset */
+ if (mod_btf && !mod_btf->fd_array_idx) {
+ /* insn->off is s16 */
+ if (obj->fd_array_cnt == INT16_MAX) {
+ pr_warn("extern (func ksym) '%s': module BTF fd index %d too big to fit in bpf_insn offset\n",
+ ext->name, mod_btf->fd_array_idx);
+ return -E2BIG;
+ }
+
+ ret = libbpf_ensure_mem((void **)&obj->fd_array, &obj->fd_array_cap, sizeof(int),
+ obj->fd_array_cnt + 1);
+ if (ret)
+ return ret;
+ mod_btf->fd_array_idx = obj->fd_array_cnt;
+ /* we assume module BTF FD is always >0 */
+ obj->fd_array[obj->fd_array_cnt++] = mod_btf->fd;
+ }
+
ext->is_set = true;
- ext->ksym.kernel_btf_obj_fd = kern_btf_fd;
ext->ksym.kernel_btf_id = kfunc_id;
+ ext->ksym.offset = mod_btf ? mod_btf->fd_array_idx : 0;
pr_debug("extern (func ksym) '%s': resolved to kernel [%d]\n",
ext->name, kfunc_id);
@@ -6941,6 +6970,9 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
err = bpf_gen__finish(obj->gen_loader);
}
+ /* clean up fd_array */
+ zfree(&obj->fd_array);
+
/* clean up module BTFs */
for (i = 0; i < obj->btf_module_cnt; i++) {
close(obj->btf_modules[i].fd);
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index ceb0c98979bc..1969d0ce35cf 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -291,6 +291,7 @@ struct bpf_prog_load_params {
__u32 log_level;
char *log_buf;
size_t log_buf_sz;
+ int *fd_array;
};
int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr);
@@ -401,6 +402,8 @@ int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ct
int btf_type_visit_str_offs(struct btf_type *t, str_off_visit_fn visit, void *ctx);
int btf_ext_visit_type_ids(struct btf_ext *btf_ext, type_id_visit_fn visit, void *ctx);
int btf_ext_visit_str_offs(struct btf_ext *btf_ext, str_off_visit_fn visit, void *ctx);
+__s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name,
+ __u32 kind);
extern enum libbpf_strict_mode libbpf_mode;
--
2.33.0
next prev parent reply other threads:[~2021-09-27 15:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 14:59 [PATCH bpf-next v5 00/12] Support kernel module function calls from eBPF Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 01/12] bpf: Introduce BPF support for kernel module function calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 02/12] bpf: Be conservative while processing invalid kfunc calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 03/12] bpf: btf: Introduce helpers for dynamic BTF set registration Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 04/12] tools: Allow specifying base BTF file in resolve_btfids Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 05/12] bpf: Enable TCP congestion control kfunc from modules Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` Kumar Kartikeya Dwivedi [this message]
2021-09-27 14:59 ` [PATCH bpf-next v5 07/12] libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0 Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 08/12] libbpf: Make gen_loader data aligned Kumar Kartikeya Dwivedi
2021-09-29 20:50 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 09/12] libbpf: Update gen_loader to emit BTF_KIND_FUNC relocations Kumar Kartikeya Dwivedi
2021-09-29 0:01 ` Alexei Starovoitov
2021-09-29 0:10 ` Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 10/12] libbpf: Fix skel_internal.h to set errno on loader retval < 0 Kumar Kartikeya Dwivedi
2021-09-30 3:45 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 11/12] bpf: selftests: Fix fd cleanup in get_branch_snapshot Kumar Kartikeya Dwivedi
2021-09-28 23:58 ` Song Liu
2021-09-29 20:26 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 12/12] bpf: selftests: Add selftests for module kfunc support Kumar Kartikeya Dwivedi
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