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Mon, 10 Jun 2024 06:10:16 -0700 (PDT) Received: from localhost.localdomain ([120.229.49.105]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f6bd7e3e66sm81938285ad.182.2024.06.10.06.10.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jun 2024 06:10:16 -0700 (PDT) From: Howard Chu To: peterz@infradead.org Cc: mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, mic@digikod.net, gnoack@google.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, bpf@vger.kernel.org Subject: [PATCH v1] perf trace: BTF-based enum pretty printing Date: Mon, 10 Jun 2024 21:10:32 +0800 Message-ID: <20240610131032.516323-1-howardchu95@gmail.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This is a feature implemented on the basis of the previous bug fix https://lore.kernel.org/linux-perf-users/d18a9606-ac9f-4ca7-afaf-fcf4c951cb= 90@web.de/T/#t In this patch, I use BTF to turn enum value to the corresponding name. There is only one system call that uses enum value as its argument, that is `landlock_add_rule`. The vmlinux btf is loaded lazily, when user decided to trace the `landlock_add_rule` syscall. But if one decide to run `perf trace` without any arguments, the behaviour is to trace `landlock_add_rule`, so vmlinux btf will be loaded by default. The laziest behaviour is to load vmlinux btf when a `landlock_add_rule` syscall hits. But I think you could lose some samples when loading vmlinux btf at run time, for it can delay the handling of other samples. I might need your precious opinions on this... before: ``` perf $ ./perf trace -e landlock_add_rule 0.000 ( 0.008 ms): ldlck-test/438194 landlock_add_rule(rule_type: 2) = =3D -1 EBADFD (File descriptor in bad = state) 0.010 ( 0.001 ms): ldlck-test/438194 landlock_add_rule(rule_type: 1) = =3D -1 EBADFD (File descriptor in bad = state) ``` after: ``` perf $ ./perf trace -e landlock_add_rule 0.000 ( 0.029 ms): ldlck-test/438194 landlock_add_rule(rule_type: LAND= LOCK_RULE_NET_PORT) =3D -1 EBADFD (File descriptor in bad = state) 0.036 ( 0.004 ms): ldlck-test/438194 landlock_add_rule(rule_type: LAND= LOCK_RULE_PATH_BENEATH) =3D -1 EBADFD (File descriptor in bad = state) ``` P.S. If you don't apply the patch "perf trace: Fix syscall untraceable bug", there will be no output whatsoever when running `perf trace -e landlock_add_rule` Signed-off-by: Howard Chu --- tools/perf/builtin-trace.c | 69 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 66 insertions(+), 3 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 5cbe1748911d..5acb9a910ea1 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -19,6 +19,7 @@ #ifdef HAVE_LIBBPF_SUPPORT #include #include +#include #ifdef HAVE_BPF_SKEL #include "bpf_skel/augmented_raw_syscalls.skel.h" #endif @@ -110,6 +111,7 @@ struct syscall_arg_fmt { const char *name; u16 nr_entries; // for arrays bool show_zero; + bool is_enum; }; =20 struct syscall_fmt { @@ -140,6 +142,7 @@ struct trace { #ifdef HAVE_BPF_SKEL struct augmented_raw_syscalls_bpf *skel; #endif + struct btf *btf; struct record_opts opts; struct evlist *evlist; struct machine *host; @@ -887,6 +890,36 @@ static size_t syscall_arg__scnprintf_getrandom_flags(c= har *bf, size_t size, =20 #define SCA_GETRANDOM_FLAGS syscall_arg__scnprintf_getrandom_flags =20 +static size_t btf_enum_scnprintf(char *bf, size_t size, int val, + struct btf *btf, const char *type) +{ + const struct btf_type *bt; + struct btf_enum *e; + char enum_prefix[][16] =3D {"enum", "const enum"}, *ep; + int id; + + for (size_t i =3D 0; i < ARRAY_SIZE(enum_prefix); i++) { + ep =3D enum_prefix[i]; + if (strlen(type) > strlen(ep) + 1 && strstr(type, ep) =3D=3D type) + type +=3D strlen(ep) + 1; + } + + id =3D btf__find_by_name(btf, type); + if (id < 0) + return 0; + + bt =3D btf__type_by_id(btf, id); + e =3D btf_enum(bt); + + for (int i =3D 0; i < btf_vlen(bt); i++, e++) { + if (e->val =3D=3D val) + return scnprintf(bf, size, "%s", + btf__name_by_offset(btf, e->name_off)); + } + + return 0; +} + #define STRARRAY(name, array) \ { .scnprintf =3D SCA_STRARRAY, \ .strtoul =3D STUL_STRARRAY, \ @@ -1238,6 +1271,7 @@ struct syscall { bool is_exit; bool is_open; bool nonexistent; + bool use_btf; struct tep_format_field *args; const char *name; const struct syscall_fmt *fmt; @@ -1756,6 +1790,7 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *a= rg, struct tep_format_field continue; =20 len =3D strlen(field->name); + arg->is_enum =3D false; =20 if (strcmp(field->type, "const char *") =3D=3D 0 && ((len >=3D 4 && strcmp(field->name + len - 4, "name") =3D=3D 0) || @@ -1782,6 +1817,8 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *a= rg, struct tep_format_field * 7 unsigned long */ arg->scnprintf =3D SCA_FD; + } else if (strstr(field->type, "enum")) { + arg->is_enum =3D true; } else { const struct syscall_arg_fmt *fmt =3D syscall_arg_fmt__find_by_name(field->name); @@ -1798,7 +1835,13 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *= arg, struct tep_format_field =20 static int syscall__set_arg_fmts(struct syscall *sc) { - struct tep_format_field *last_field =3D syscall_arg_fmt__init_array(sc->a= rg_fmt, sc->args); + struct tep_format_field *last_field =3D syscall_arg_fmt__init_array(sc->a= rg_fmt, sc->args), + *field =3D sc->args; + struct syscall_arg_fmt *arg =3D sc->arg_fmt; + + for (; field; field =3D field->next, ++arg) + if (arg->is_enum) + sc->use_btf =3D true; =20 if (last_field) sc->args_size =3D last_field->offset + last_field->size; @@ -1811,6 +1854,7 @@ static int trace__read_syscall_info(struct trace *tra= ce, int id) char tp_name[128]; struct syscall *sc; const char *name =3D syscalltbl__name(trace->sctbl, id); + int err; =20 #ifdef HAVE_SYSCALL_TABLE_SUPPORT if (trace->syscalls.table =3D=3D NULL) { @@ -1883,7 +1927,17 @@ static int trace__read_syscall_info(struct trace *tr= ace, int id) sc->is_exit =3D !strcmp(name, "exit_group") || !strcmp(name, "exit"); sc->is_open =3D !strcmp(name, "open") || !strcmp(name, "openat"); =20 - return syscall__set_arg_fmts(sc); + err =3D syscall__set_arg_fmts(sc); + + /* after calling syscall__set_arg_fmts() we'll know whether use_btf is tr= ue */ + if (sc->use_btf && trace->btf =3D=3D NULL) { + trace->btf =3D btf__load_vmlinux_btf(); + if (verbose > 0) + fprintf(trace->output, trace->btf ? "vmlinux BTF loaded\n" : + "Failed to load vmlinux BTF\n"); + } + + return err; } =20 static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) @@ -2050,7 +2104,7 @@ static size_t syscall__scnprintf_args(struct syscall = *sc, char *bf, size_t size, unsigned char *args, void *augmented_args, int augmented_args_si= ze, struct trace *trace, struct thread *thread) { - size_t printed =3D 0; + size_t printed =3D 0, p; unsigned long val; u8 bit =3D 1; struct syscall_arg arg =3D { @@ -2103,6 +2157,15 @@ static size_t syscall__scnprintf_args(struct syscall= *sc, char *bf, size_t size, if (trace->show_arg_names) printed +=3D scnprintf(bf + printed, size - printed, "%s: ", field->na= me); =20 + if (sc->arg_fmt[arg.idx].is_enum =3D=3D true && trace->btf) { + p =3D btf_enum_scnprintf(bf + printed, size - printed, val, + trace->btf, field->type); + if (p) { + printed +=3D p; + continue; + } + } + printed +=3D syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx], bf + printed, size - printed, &arg, val); } --=20 2.45.2