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    SubjectRe: [PATCH bpf-next v2 1/9] bpf: tracing: add support to record and check the accessed args
    On Mon, Mar 11, 2024 at 2:34 AM Menglong Dong
    <dongmenglong.8@bytedance.com> wrote:
    >
    > In this commit, we add the 'accessed_args' field to struct bpf_prog_aux,
    > which is used to record the accessed index of the function args in
    > btf_ctx_access().
    >
    > Meanwhile, we add the function btf_check_func_part_match() to compare the
    > accessed function args of two function prototype. This function will be
    > used in the following commit.
    >
    > Signed-off-by: Menglong Dong <dongmenglong.8@bytedance.com>
    > ---
    > include/linux/bpf.h | 4 ++
    > kernel/bpf/btf.c | 108 +++++++++++++++++++++++++++++++++++++++++++-
    > 2 files changed, 110 insertions(+), 2 deletions(-)
    >
    > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
    > index 95e07673cdc1..0f677fdcfcc7 100644
    > --- a/include/linux/bpf.h
    > +++ b/include/linux/bpf.h
    > @@ -1461,6 +1461,7 @@ struct bpf_prog_aux {
    > const struct btf_type *attach_func_proto;
    > /* function name for valid attach_btf_id */
    > const char *attach_func_name;
    > + u64 accessed_args;
    > struct bpf_prog **func;
    > void *jit_data; /* JIT specific data. arch dependent */
    > struct bpf_jit_poke_descriptor *poke_tab;
    > @@ -2565,6 +2566,9 @@ struct bpf_reg_state;
    > int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog);
    > int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
    > struct btf *btf, const struct btf_type *t);
    > +int btf_check_func_part_match(struct btf *btf1, const struct btf_type *t1,
    > + struct btf *btf2, const struct btf_type *t2,
    > + u64 func_args);
    > const char *btf_find_decl_tag_value(const struct btf *btf, const struct btf_type *pt,
    > int comp_idx, const char *tag_key);
    > int btf_find_next_decl_tag(const struct btf *btf, const struct btf_type *pt,
    > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
    > index 170d017e8e4a..c2a0299d4358 100644
    > --- a/kernel/bpf/btf.c
    > +++ b/kernel/bpf/btf.c
    > @@ -6125,19 +6125,24 @@ static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
    > }
    >
    > static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
    > - int off)
    > + int off, int *aligned_idx)
    > {
    > const struct btf_param *args;
    > const struct btf_type *t;
    > u32 offset = 0, nr_args;
    > int i;
    >
    > + if (aligned_idx)
    > + *aligned_idx = -ENOENT;
    > +
    > if (!func_proto)
    > return off / 8;
    >
    > nr_args = btf_type_vlen(func_proto);
    > args = (const struct btf_param *)(func_proto + 1);
    > for (i = 0; i < nr_args; i++) {
    > + if (aligned_idx && offset == off)
    > + *aligned_idx = i;
    > t = btf_type_skip_modifiers(btf, args[i].type, NULL);
    > offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8);
    > if (off < offset)
    > @@ -6207,7 +6212,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
    > tname, off);
    > return false;
    > }
    > - arg = get_ctx_arg_idx(btf, t, off);
    > + arg = get_ctx_arg_idx(btf, t, off, NULL);
    > args = (const struct btf_param *)(t + 1);
    > /* if (t == NULL) Fall back to default BPF prog with
    > * MAX_BPF_FUNC_REG_ARGS u64 arguments.
    > @@ -6217,6 +6222,9 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
    > /* skip first 'void *__data' argument in btf_trace_##name typedef */
    > args++;
    > nr_args--;
    > + prog->aux->accessed_args |= (1 << (arg + 1));
    > + } else {
    > + prog->aux->accessed_args |= (1 << arg);

    What do you need this aligned_idx for ?
    I'd expect that above "accessed_args |= (1 << arg);" is enough.

    > }
    >
    > if (arg > nr_args) {
    > @@ -7024,6 +7032,102 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr
    > return btf_check_func_type_match(log, btf1, t1, btf2, t2);
    > }
    >
    > +static u32 get_ctx_arg_total_size(struct btf *btf, const struct btf_type *t)
    > +{
    > + const struct btf_param *args;
    > + u32 size = 0, nr_args;
    > + int i;
    > +
    > + nr_args = btf_type_vlen(t);
    > + args = (const struct btf_param *)(t + 1);
    > + for (i = 0; i < nr_args; i++) {
    > + t = btf_type_skip_modifiers(btf, args[i].type, NULL);
    > + size += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8);
    > + }
    > +
    > + return size;
    > +}
    > +
    > +/* This function is similar to btf_check_func_type_match(), except that it
    > + * only compare some function args of the function prototype t1 and t2.
    > + */
    > +int btf_check_func_part_match(struct btf *btf1, const struct btf_type *func1,
    > + struct btf *btf2, const struct btf_type *func2,
    > + u64 func_args)

    This is way too much copy paste.
    Please share the code with btf_check_func_type_match.

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