Now that feature detection code is in bpf-next tree, integrate __arg_ctx
kernel-side support into kernel_supports() framework.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/lib/bpf/features.c | 58 +++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.c | 65 +--------------------------------
tools/lib/bpf/libbpf_internal.h | 2 +
3 files changed, 61 insertions(+), 64 deletions(-)
diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
index 5a5c766bf615..6b0738ad7063 100644
--- a/tools/lib/bpf/features.c
+++ b/tools/lib/bpf/features.c
@@ -407,6 +407,61 @@ static int probe_kern_btf_enum64(int token_fd)
strs, sizeof(strs), token_fd));
}
+static int probe_kern_arg_ctx_tag(int token_fd)
+{
+ static const char strs[] = "\0a\0b\0arg:ctx\0";
+ const __u32 types[] = {
+ /* [1] INT */
+ BTF_TYPE_INT_ENC(1 /* "a" */, BTF_INT_SIGNED, 0, 32, 4),
+ /* [2] PTR -> VOID */
+ BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 0),
+ /* [3] FUNC_PROTO `int(void *a)` */
+ BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 1),
+ BTF_PARAM_ENC(1 /* "a" */, 2),
+ /* [4] FUNC 'a' -> FUNC_PROTO (main prog) */
+ BTF_TYPE_ENC(1 /* "a" */, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 3),
+ /* [5] FUNC_PROTO `int(void *b __arg_ctx)` */
+ BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 1),
+ BTF_PARAM_ENC(3 /* "b" */, 2),
+ /* [6] FUNC 'b' -> FUNC_PROTO (subprog) */
+ BTF_TYPE_ENC(3 /* "b" */, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 5),
+ /* [7] DECL_TAG 'arg:ctx' -> func 'b' arg 'b' */
+ BTF_TYPE_DECL_TAG_ENC(5 /* "arg:ctx" */, 6, 0),
+ };
+ const struct bpf_insn insns[] = {
+ /* main prog */
+ BPF_CALL_REL(+1),
+ BPF_EXIT_INSN(),
+ /* global subprog */
+ BPF_EMIT_CALL(BPF_FUNC_get_func_ip), /* needs PTR_TO_CTX */
+ BPF_EXIT_INSN(),
+ };
+ const struct bpf_func_info_min func_infos[] = {
+ { 0, 4 }, /* main prog -> FUNC 'a' */
+ { 2, 6 }, /* subprog -> FUNC 'b' */
+ };
+ LIBBPF_OPTS(bpf_prog_load_opts, opts,
+ .token_fd = token_fd,
+ .prog_flags = token_fd ? BPF_F_TOKEN_FD : 0,
+ );
+ int prog_fd, btf_fd, insn_cnt = ARRAY_SIZE(insns);
+
+ btf_fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs), token_fd);
+ if (btf_fd < 0)
+ return 0;
+
+ opts.prog_btf_fd = btf_fd;
+ opts.func_info = &func_infos;
+ opts.func_info_cnt = ARRAY_SIZE(func_infos);
+ opts.func_info_rec_size = sizeof(func_infos[0]);
+
+ prog_fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, "det_arg_ctx",
+ "GPL", insns, insn_cnt, &opts);
+ close(btf_fd);
+
+ return probe_fd(prog_fd);
+}
+
typedef int (*feature_probe_fn)(int /* token_fd */);
static struct kern_feature_cache feature_cache;
@@ -476,6 +531,9 @@ static struct kern_feature_desc {
[FEAT_UPROBE_MULTI_LINK] = {
"BPF multi-uprobe link support", probe_uprobe_multi_link,
},
+ [FEAT_ARG_CTX_TAG] = {
+ "kernel-side __arg_ctx tag", probe_kern_arg_ctx_tag,
+ },
};
bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index fa7094ff3e66..41ab7a21f868 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6462,69 +6462,6 @@ static int clone_func_btf_info(struct btf *btf, int orig_fn_id, struct bpf_progr
return fn_id;
}
-static int probe_kern_arg_ctx_tag(void)
-{
- /* To minimize merge conflicts with BPF token series that refactors
- * feature detection code a lot, we don't integrate
- * probe_kern_arg_ctx_tag() into kernel_supports() feature-detection
- * framework yet, doing our own caching internally.
- * This will be cleaned up a bit later when bpf/bpf-next trees settle.
- */
- static int cached_result = -1;
- static const char strs[] = "\0a\0b\0arg:ctx\0";
- const __u32 types[] = {
- /* [1] INT */
- BTF_TYPE_INT_ENC(1 /* "a" */, BTF_INT_SIGNED, 0, 32, 4),
- /* [2] PTR -> VOID */
- BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 0),
- /* [3] FUNC_PROTO `int(void *a)` */
- BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 1),
- BTF_PARAM_ENC(1 /* "a" */, 2),
- /* [4] FUNC 'a' -> FUNC_PROTO (main prog) */
- BTF_TYPE_ENC(1 /* "a" */, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 3),
- /* [5] FUNC_PROTO `int(void *b __arg_ctx)` */
- BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 1),
- BTF_PARAM_ENC(3 /* "b" */, 2),
- /* [6] FUNC 'b' -> FUNC_PROTO (subprog) */
- BTF_TYPE_ENC(3 /* "b" */, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 5),
- /* [7] DECL_TAG 'arg:ctx' -> func 'b' arg 'b' */
- BTF_TYPE_DECL_TAG_ENC(5 /* "arg:ctx" */, 6, 0),
- };
- const struct bpf_insn insns[] = {
- /* main prog */
- BPF_CALL_REL(+1),
- BPF_EXIT_INSN(),
- /* global subprog */
- BPF_EMIT_CALL(BPF_FUNC_get_func_ip), /* needs PTR_TO_CTX */
- BPF_EXIT_INSN(),
- };
- const struct bpf_func_info_min func_infos[] = {
- { 0, 4 }, /* main prog -> FUNC 'a' */
- { 2, 6 }, /* subprog -> FUNC 'b' */
- };
- LIBBPF_OPTS(bpf_prog_load_opts, opts);
- int prog_fd, btf_fd, insn_cnt = ARRAY_SIZE(insns);
-
- if (cached_result >= 0)
- return cached_result;
-
- btf_fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs), 0);
- if (btf_fd < 0)
- return 0;
-
- opts.prog_btf_fd = btf_fd;
- opts.func_info = &func_infos;
- opts.func_info_cnt = ARRAY_SIZE(func_infos);
- opts.func_info_rec_size = sizeof(func_infos[0]);
-
- prog_fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, "det_arg_ctx",
- "GPL", insns, insn_cnt, &opts);
- close(btf_fd);
-
- cached_result = probe_fd(prog_fd);
- return cached_result;
-}
-
/* Check if main program or global subprog's function prototype has `arg:ctx`
* argument tags, and, if necessary, substitute correct type to match what BPF
* verifier would expect, taking into account specific program type. This
@@ -6549,7 +6486,7 @@ static int bpf_program_fixup_func_info(struct bpf_object *obj, struct bpf_progra
return 0;
/* don't do any fix ups if kernel natively supports __arg_ctx */
- if (probe_kern_arg_ctx_tag() > 0)
+ if (kernel_supports(obj, FEAT_ARG_CTX_TAG))
return 0;
/* some BPF program types just don't have named context structs, so
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 930cc9616527..757dde832d8c 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -358,6 +358,8 @@ enum kern_feature_id {
FEAT_SYSCALL_WRAPPER,
/* BPF multi-uprobe link support */
FEAT_UPROBE_MULTI_LINK,
+ /* Kernel supports arg:ctx tag (__arg_ctx) for global subprogs natively */
+ FEAT_ARG_CTX_TAG,
__FEAT_CNT,
};
--
2.34.1
