From nobody Sun Feb 8 01:29:53 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EBF9AC001DF for ; Mon, 17 Jul 2023 15:25:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231892AbjGQPZU (ORCPT ); Mon, 17 Jul 2023 11:25:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57724 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231861AbjGQPYx (ORCPT ); Mon, 17 Jul 2023 11:24:53 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 57B8E1735; Mon, 17 Jul 2023 08:24:34 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 893F0610F4; Mon, 17 Jul 2023 15:24:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECED0C433C8; Mon, 17 Jul 2023 15:24:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689607452; bh=HNw7NmAJWJoLfuOb7lcwr0tG/Yg91E6W1MXYrCfkES8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BUWZzB8ih/Pn17MNMbs4bLT6F3qq7F/IIIg66MNQnM/DH93rG0K9UG221F0zupoZZ O8oW/qK3mGyNFuNNcZkDuie4iQeVW++xBPymTfa82sLjllXjEsGcNw5l2PsHu/PRvx wF05Fc0Ew3ZII0weMaCacrFY2FKt74DBReB0ND1/u87o8reC3fXiDsXcraOkeRYLGK GqGnDPhFHYD1elbCbub6fi9URBamkp6az5E8dpcjqCzL+r13FIzSxRRUbdxMHXsKyJ QnfxwukYukf9m52v9zeqdsOAM7niAy1zWZ0hxrqZEeaI5gtH3xyW8K9mb1kbkFMScI VYQVMZlWdIX6w== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v2 5/9] tracing/probes: Support BTF field access from $retval Date: Tue, 18 Jul 2023 00:24:07 +0900 Message-Id: <168960744719.34107.443329109565685838.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <168960739768.34107.15145201749042174448.stgit@devnote2> References: <168960739768.34107.15145201749042174448.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Support BTF argument on '$retval' for function return events including kretprobe and fprobe for accessing the return value. This also allows user to access its fields if the return value is a pointer of a data structure. E.g. # echo 'f getname_flags%return +0($retval->name):string' \ > dynamic_events # echo 1 > events/fprobes/getname_flags__exit/enable # ls > /dev/null # head -n 40 trace | tail ls-87 [000] ...1. 8067.616101: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./function_profile_enabled" ls-87 [000] ...1. 8067.616108: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./trace_stat" ls-87 [000] ...1. 8067.616115: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./set_graph_notrace" ls-87 [000] ...1. 8067.616122: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./set_graph_function" ls-87 [000] ...1. 8067.616129: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./set_ftrace_notrace" ls-87 [000] ...1. 8067.616135: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./set_ftrace_filter" ls-87 [000] ...1. 8067.616143: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./touched_functions" ls-87 [000] ...1. 8067.616237: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./enabled_functions" ls-87 [000] ...1. 8067.616245: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./available_filter_functions" ls-87 [000] ...1. 8067.616253: getname_flags__exit: (vf= s_fstatat+0x3c/0x70 <- getname_flags) arg1=3D"./set_ftrace_notrace_pid" Signed-off-by: Masami Hiramatsu (Google) --- Changes in v2: - Use '$retval' instead of 'retval' because it is confusing. --- kernel/trace/trace_probe.c | 98 +++++++++++++++++-----------------------= ---- 1 file changed, 37 insertions(+), 61 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index dd646d35637d..4442ff9c2728 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -536,6 +536,22 @@ static int parse_btf_arg(char *varname, return -EOPNOTSUPP; } =20 + if (ctx->flags & TPARG_FL_RETURN) { + if (strcmp(varname, "$retval") !=3D 0) { + trace_probe_log_err(ctx->offset, NO_BTFARG); + return -ENOENT; + } + /* Check whether the function return type is not void */ + type =3D btf_find_func_proto(btf, ctx->funcname); + if (!IS_ERR_OR_NULL(type) && type->type =3D=3D 0) { + trace_probe_log_err(ctx->offset, NO_RETVAL); + return -ENOENT; + } + code->op =3D FETCH_OP_RETVAL; + tid =3D type->type; + goto found; + } + if (!ctx->params) { params =3D find_btf_func_param(ctx->funcname, &ctx->nr_params, ctx->flags & TPARG_FL_TPOINT); @@ -556,7 +572,6 @@ static int parse_btf_arg(char *varname, code->param =3D i + 1; else code->param =3D i; - tid =3D params[i].type; goto found; } @@ -581,7 +596,7 @@ static int parse_btf_arg(char *varname, return 0; } =20 -static const struct fetch_type *parse_btf_arg_type( +static const struct fetch_type *find_fetch_type_from_btf_type( struct traceprobe_parse_context *ctx) { struct btf *btf =3D traceprobe_get_btf(); @@ -593,26 +608,6 @@ static const struct fetch_type *parse_btf_arg_type( return find_fetch_type(typestr, ctx->flags); } =20 -static const struct fetch_type *parse_btf_retval_type( - struct traceprobe_parse_context *ctx) -{ - struct btf *btf =3D traceprobe_get_btf(); - const char *typestr =3D NULL; - const struct btf_type *type; - s32 tid; - - if (btf && ctx->funcname) { - type =3D btf_find_func_proto(btf, ctx->funcname); - if (!IS_ERR_OR_NULL(type)) { - type =3D btf_type_skip_modifiers(btf, type->type, &tid); - if (!IS_ERR_OR_NULL(type)) - typestr =3D fetch_type_from_btf_type(btf, type, ctx); - } - } - - return find_fetch_type(typestr, ctx->flags); -} - static int parse_btf_bitfield(struct fetch_insn **pcode, struct traceprobe_parse_context *ctx) { @@ -635,20 +630,6 @@ static int parse_btf_bitfield(struct fetch_insn **pcod= e, return 0; } =20 -static bool is_btf_retval_void(const char *funcname) -{ - struct btf *btf =3D traceprobe_get_btf(); - const struct btf_type *t; - - if (!btf) - return false; - - t =3D btf_find_func_proto(btf, funcname); - if (IS_ERR_OR_NULL(t)) - return false; - - return t->type =3D=3D 0; -} #else static struct btf *traceprobe_get_btf(void) { @@ -676,24 +657,23 @@ static int parse_btf_bitfield(struct fetch_insn **pco= de, return -EOPNOTSUPP; } =20 -#define parse_btf_arg_type(ctx) \ - find_fetch_type(NULL, ctx->flags) - -#define parse_btf_retval_type(ctx) \ +#define find_fetch_type_from_btf_type(ctx) \ find_fetch_type(NULL, ctx->flags) =20 -#define is_btf_retval_void(funcname) (false) - #endif =20 #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long)) =20 -static int parse_probe_vars(char *arg, const struct fetch_type *t, - struct fetch_insn *code, +/* Parse $vars. @orig_arg points '$', which syncs to @ctx->offset */ +static int parse_probe_vars(char *orig_arg, const struct fetch_type *t, + struct fetch_insn **pcode, + struct fetch_insn *end, struct traceprobe_parse_context *ctx) { - unsigned long param; + struct fetch_insn *code =3D *pcode; int err =3D TP_ERR_BAD_VAR; + char *arg =3D orig_arg + 1; + unsigned long param; int ret =3D 0; int len; =20 @@ -712,18 +692,17 @@ static int parse_probe_vars(char *arg, const struct f= etch_type *t, goto inval; } =20 - if (strcmp(arg, "retval") =3D=3D 0) { - if (ctx->flags & TPARG_FL_RETURN) { - if ((ctx->flags & TPARG_FL_KERNEL) && - is_btf_retval_void(ctx->funcname)) { - err =3D TP_ERR_NO_RETVAL; - goto inval; - } + if (str_has_prefix(arg, "retval")) { + if (!(ctx->flags & TPARG_FL_RETURN)) { + err =3D TP_ERR_RETVAL_ON_PROBE; + goto inval; + } + if (!(ctx->flags & TPARG_FL_KERNEL) || + !IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS)) { code->op =3D FETCH_OP_RETVAL; return 0; } - err =3D TP_ERR_RETVAL_ON_PROBE; - goto inval; + return parse_btf_arg(orig_arg, pcode, end, ctx); } =20 len =3D str_has_prefix(arg, "stack"); @@ -825,7 +804,7 @@ parse_probe_arg(char *arg, const struct fetch_type *typ= e, =20 switch (arg[0]) { case '$': - ret =3D parse_probe_vars(arg + 1, type, code, ctx); + ret =3D parse_probe_vars(arg, type, pcode, end, ctx); break; =20 case '%': /* named register */ @@ -1122,12 +1101,9 @@ static int traceprobe_parse_probe_arg_body(const cha= r *argv, ssize_t *size, goto fail; =20 /* Update storing type if BTF is available */ - if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && !t) { - if (ctx->last_type) - parg->type =3D parse_btf_arg_type(ctx); - else if (ctx->flags & TPARG_FL_RETURN) - parg->type =3D parse_btf_retval_type(ctx); - } + if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && + !t && ctx->last_type) + parg->type =3D find_fetch_type_from_btf_type(ctx); =20 ret =3D -EINVAL; /* Store operation */