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Follow-up patches will add support for fentry/fexit programs as well. >>> >>> While at it, mark bpf_tracing_func_proto() as static to make it obvious that >>> it's only used from within the kernel/trace/bpf_trace.c. >>> >>> Cc: Peter Zijlstra >>> Signed-off-by: Andrii Nakryiko >>> --- >>> include/linux/bpf.h | 3 --- >>> include/uapi/linux/bpf.h | 16 ++++++++++++++++ >>> kernel/trace/bpf_trace.c | 35 +++++++++++++++++++++++++++++++++- >>> tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++ >>> 4 files changed, 66 insertions(+), 4 deletions(-) >>> >>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >>> index 74b35faf0b73..94ebedc1e13a 100644 >>> --- a/include/linux/bpf.h >>> +++ b/include/linux/bpf.h >>> @@ -2110,9 +2110,6 @@ extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto; >>> extern const struct bpf_func_proto bpf_sk_setsockopt_proto; >>> extern const struct bpf_func_proto bpf_sk_getsockopt_proto; >>> >>> -const struct bpf_func_proto *bpf_tracing_func_proto( >>> - enum bpf_func_id func_id, const struct bpf_prog *prog); >>> - >>> const struct bpf_func_proto *tracing_prog_func_proto( >>> enum bpf_func_id func_id, const struct bpf_prog *prog); >>> >>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h >>> index bc1fd54a8f58..96afeced3467 100644 >>> --- a/include/uapi/linux/bpf.h >>> +++ b/include/uapi/linux/bpf.h >>> @@ -4856,6 +4856,21 @@ union bpf_attr { >>> * Get address of the traced function (for tracing and kprobe programs). >>> * Return >>> * Address of the traced function. >>> + * >>> + * u64 bpf_get_user_ctx(void *ctx) >>> + * Description >>> + * Get user_ctx value provided (optionally) during the program >>> + * attachment. It might be different for each individual >>> + * attachment, even if BPF program itself is the same. >>> + * Expects BPF program context *ctx* as a first argument. >>> + * >>> + * Supported for the following program types: >>> + * - kprobe/uprobe; >>> + * - tracepoint; >>> + * - perf_event. >> >> I think it is possible in the future we may need to support more >> program types with user_ctx, not just u64 but more than 64bit value. >> Should we may make this helper extensible like >> long bpf_get_user_ctx(void *ctx, void *user_ctx, u32 user_ctx_len) >> >> The return value will 0 to be good and a negative indicating an error. >> What do you think? > > I explicitly wanted to keep this user_ctx/bpf_cookie to a small fixed > size. __u64 is perfect because it's small enough to not require > dynamic memory allocation, but big enough to store any kind of index > into an array *or* user-space pointer. So if user needs more storage > than 8 bytes, they will be able to have a bigger array where > user_ctx/bpf_cookie is just an integer index or some sort of key into > hashmap, whichever is more convenient. Okay. returning an index to a map is a good idea. This way, indeed a u64 return value is enough. > > So I'd like to keep it lean and simple. It is already powerful enough > to support any scenario, IMO. > >> >>> + * Return >>> + * Value specified by user at BPF link creation/attachment time >>> + * or 0, if it was not specified. >>> */ >>> #define __BPF_FUNC_MAPPER(FN) \ >>> FN(unspec), \ >>> @@ -5032,6 +5047,7 @@ union bpf_attr { >>> FN(timer_start), \ >>> FN(timer_cancel), \ >>> FN(get_func_ip), \ >>> + FN(get_user_ctx), \ >>> /* */ >>> >>> /* integer value in 'imm' field of BPF_CALL instruction selects which helper >>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c >>> index c9cf6a0d0fb3..b14978b3f6fb 100644 >>> --- a/kernel/trace/bpf_trace.c >>> +++ b/kernel/trace/bpf_trace.c >>> @@ -975,7 +975,34 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = { >>> .arg1_type = ARG_PTR_TO_CTX, >>> }; >>> >>> -const struct bpf_func_proto * >>> +BPF_CALL_1(bpf_get_user_ctx_trace, void *, ctx) >>> +{ >>> + struct bpf_trace_run_ctx *run_ctx; >>> + >>> + run_ctx = container_of(current->bpf_ctx, struct bpf_trace_run_ctx, run_ctx); >>> + return run_ctx->user_ctx; >>> +} >>> + >>> +static const struct bpf_func_proto bpf_get_user_ctx_proto_trace = { >>> + .func = bpf_get_user_ctx_trace, >>> + .gpl_only = false, >>> + .ret_type = RET_INTEGER, >>> + .arg1_type = ARG_PTR_TO_CTX, >>> +}; >>> + >> [...]