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mx.microsoft.com 1; spf=pass smtp.mailfrom=atomlin.com; dmarc=pass action=none header.from=atomlin.com; dkim=pass header.d=atomlin.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=atomlin.com; Received: from CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:183::5) by LO3P123MB3193.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:b5::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.339.11; Sat, 22 Aug 2026 21:36:20 +0000 Received: from CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM ([fe80::cec4:77ab:262e:d230]) by CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM ([fe80::cec4:77ab:262e:d230%4]) with mapi id 15.21.0339.010; Sat, 22 Aug 2026 21:36:20 +0000 From: Aaron Tomlin To: peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org Cc: mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, james.clark@linaro.org, howardchu95@gmail.com, atomlin@atomlin.com, neelx@suse.com, chjohnst@mail.com, sean@ashe.io, steve@abita.co, rishil1999@outlook.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH perf-tools-next v5 3/4] perf trace: Enhance BTF type formatting to symbolise kernel function pointers Date: Sat, 22 Aug 2026 17:35:57 -0400 Message-ID: <20260822213558.704018-4-atomlin@atomlin.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260822213558.704018-1-atomlin@atomlin.com> References: <20260822213558.704018-1-atomlin@atomlin.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: LO4P123CA0432.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:18b::23) To CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:183::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB6607:EE_|LO3P123MB3193:EE_ X-MS-Office365-Filtering-Correlation-Id: 99015d41-38b3-4980-7f59-08df00955dcf X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|23010399003|366016|10067099003|56012099006|3023799007|6133799003|18002099003|22082099003; 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However, function pointer arguments are currently not recognised during BTF pretty-printing and default to hexadecimal output. Introduce btf_is_func_ptr() to inspect BTF type hierarchies (i.e., traversing pointers, typedefs, and type modifiers) to determine whether a parameter resolves to a function prototype (BTF_KIND_FUNC_PROTO). Generalise BTF type caching via syscall_arg_fmt__cache_btf_type() to handle structs, unions, enums, and function pointers alike. When a field is identified as a kernel function pointer, trace__btf_scnprintf() routes its value to syscall_arg__scnprintf_ksym(), enabling automatic zero-config symbolisation of kernel function pointers whenever BTF is available. Signed-off-by: Aaron Tomlin --- tools/perf/builtin-trace.c | 100 ++++++++++++++++++++++++++++--------- 1 file changed, 77 insertions(+), 23 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 10fbea7ed4db..4f8b4f2cf677 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -122,6 +122,7 @@ struct syscall_arg_fmt { #ifdef HAVE_LIBBPF_SUPPORT const struct btf_type *type; int type_id; /* used in btf_dump */ + bool btf_type_cached; #endif }; @@ -979,21 +980,61 @@ static size_t syscall_arg__scnprintf_getrandom_flags(char *bf, size_t size, #define SCA_GETRANDOM_FLAGS syscall_arg__scnprintf_getrandom_flags #ifdef HAVE_LIBBPF_SUPPORT -static void syscall_arg_fmt__cache_btf_enum(struct syscall_arg_fmt *arg_fmt, struct btf *btf, char *type) +static bool btf_is_func_ptr(const struct btf *btf, const struct btf_type *type) { + while (type) { + if (btf_is_ptr(type) || btf_is_typedef(type) || btf_is_mod(type)) + type = btf__type_by_id(btf, type->type); + else + break; + } + return type && btf_is_func_proto(type); +} + +static void syscall_arg_fmt__cache_btf_type(struct syscall_arg_fmt *arg_fmt, + struct btf *btf, const char *type) +{ + char name[128]; + const char *pos; + size_t len = 0; int id; - type = strstr(type, "enum "); + arg_fmt->btf_type_cached = true; + if (type == NULL) return; - type += 5; // skip "enum " to get the enumeration name + /* Pointers to enums are memory addresses, not scalar enums */ + if (strstr(type, "enum ") && strchr(type, '*')) + return; + + if ((pos = strstr(type, "enum ")) != NULL) + pos += 5; + else if ((pos = strstr(type, "struct ")) != NULL) + pos += 7; + else if ((pos = strstr(type, "union ")) != NULL) + pos += 6; + else + pos = type; + + while (isspace(*pos)) + pos++; + + while ((isalnum(pos[len]) || pos[len] == '_') && len < sizeof(name) - 1) { + name[len] = pos[len]; + len++; + } + name[len] = '\0'; - id = btf__find_by_name(btf, type); + if (len == 0) + return; + + id = btf__find_by_name(btf, name); if (id < 0) return; arg_fmt->type = btf__type_by_id(btf, id); + arg_fmt->type_id = id; } static bool syscall_arg__strtoul_btf_enum(char *bf, size_t size, struct syscall_arg *arg, u64 *val) @@ -1027,10 +1068,8 @@ static bool syscall_arg__strtoul_btf_type(char *bf, size_t size, struct syscall_ if (btf == NULL) return false; - if (arg->fmt->type == NULL) { - // See if this is an enum - syscall_arg_fmt__cache_btf_enum(arg->fmt, btf, type); - } + if (!arg->fmt->btf_type_cached) + syscall_arg_fmt__cache_btf_type(arg->fmt, btf, type); // Now let's see if we have a BTF type resolved bt = arg->fmt->type; @@ -1038,19 +1077,22 @@ static bool syscall_arg__strtoul_btf_type(char *bf, size_t size, struct syscall_ return false; // If it is an enum: - if (btf_is_enum(arg->fmt->type)) + if (btf_is_enum(arg->fmt->type)) { + if (type && strchr(type, '*')) + return false; return syscall_arg__strtoul_btf_enum(bf, size, arg, val); + } return false; } -static size_t btf_enum_scnprintf(const struct btf_type *type, struct btf *btf, char *bf, size_t size, int val) +static size_t btf_enum_scnprintf(const struct btf_type *type, struct btf *btf, char *bf, size_t size, unsigned long val) { struct btf_enum *be = btf_enum(type); const unsigned int nr_entries = btf_vlen(type); for (unsigned int i = 0; i < nr_entries; ++i, ++be) { - if (be->val == val) { + if ((unsigned long)(__u32)be->val == val || (unsigned long)be->val == val) { return scnprintf(bf, size, "%s", btf__name_by_offset(btf, be->name_off)); } @@ -1077,14 +1119,19 @@ static size_t btf_struct_scnprintf(const struct btf_type *type, struct btf *btf, .bf = bf, .size = size, }; - struct augmented_arg *augmented_arg = arg->augmented.args; + struct augmented_arg *augmented_arg; int type_id = arg->fmt->type_id, consumed; struct btf_dump *btf_dump; LIBBPF_OPTS(btf_dump_opts, dump_opts); LIBBPF_OPTS(btf_dump_type_data_opts, dump_data_opts); - if (arg == NULL || arg->augmented.args == NULL) + if (arg == NULL || arg->augmented.args == NULL || arg->augmented.size <= 0 || + arg->fmt == NULL || !arg->fmt->from_user) + return 0; + + augmented_arg = arg->augmented.args; + if (augmented_arg->size <= 0) return 0; dump_data_opts.compact = true; @@ -1095,8 +1142,10 @@ static size_t btf_struct_scnprintf(const struct btf_type *type, struct btf *btf, return 0; /* pretty print the struct data here */ - if (btf_dump__dump_type_data(btf_dump, type_id, arg->augmented.args->value, type->size, &dump_data_opts) == 0) + if (btf_dump__dump_type_data(btf_dump, type_id, augmented_arg->value, type->size, &dump_data_opts) == 0) { + btf_dump__free(btf_dump); return 0; + } consumed = sizeof(*augmented_arg) + augmented_arg->size; arg->augmented.args = ((void *)arg->augmented.args) + consumed; @@ -1108,33 +1157,37 @@ static size_t btf_struct_scnprintf(const struct btf_type *type, struct btf *btf, } static size_t trace__btf_scnprintf(struct trace *trace, struct syscall_arg *arg, char *bf, - size_t size, int val, char *type) + size_t size, unsigned long val, char *type) { struct syscall_arg_fmt *arg_fmt = arg->fmt; if (trace->btf == NULL) return 0; - if (arg_fmt->type == NULL) { - // Check if this is an enum and if we have the BTF type for it. - syscall_arg_fmt__cache_btf_enum(arg_fmt, trace->btf, type); - } + if (!arg_fmt->btf_type_cached) + syscall_arg_fmt__cache_btf_type(arg_fmt, trace->btf, type); // Did we manage to find a BTF type for the syscall/tracepoint argument? if (arg_fmt->type == NULL) return 0; - if (btf_is_enum(arg_fmt->type)) + if (btf_is_enum(arg_fmt->type)) { + if (type && strchr(type, '*')) + return 0; return btf_enum_scnprintf(arg_fmt->type, trace->btf, bf, size, val); - else if (btf_is_struct(arg_fmt->type) || btf_is_union(arg_fmt->type)) + } else if (btf_is_struct(arg_fmt->type) || btf_is_union(arg_fmt->type)) return btf_struct_scnprintf(arg_fmt->type, trace->btf, bf, size, arg); + else if (btf_is_func_ptr(trace->btf, arg_fmt->type)) { + arg->val = val; + return syscall_arg__scnprintf_ksym(bf, size, arg); + } return 0; } #else // HAVE_LIBBPF_SUPPORT static size_t trace__btf_scnprintf(struct trace *trace __maybe_unused, struct syscall_arg *arg __maybe_unused, - char *bf __maybe_unused, size_t size __maybe_unused, int val __maybe_unused, + char *bf __maybe_unused, size_t size __maybe_unused, unsigned long val __maybe_unused, char *type __maybe_unused) { return 0; @@ -2584,7 +2637,8 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, default_scnprintf = sc->arg_fmt[arg.idx].scnprintf; - if (trace->force_btf || default_scnprintf == NULL || default_scnprintf == SCA_PTR) { + if (trace->force_btf || default_scnprintf == NULL || + default_scnprintf == SCA_PTR || default_scnprintf == SCA_KSYM) { btf_printed = trace__btf_scnprintf(trace, &arg, bf + printed, size - printed, val, field->type); if (btf_printed) { -- 2.55.0