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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) = -1 EBADFD (File descriptor in bad state) 0.010 ( 0.001 ms): ldlck-test/438194 landlock_add_rule(rule_type: 1) = -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: LANDLOCK_RULE_NET_PORT) = -1 EBADFD (File descriptor in bad state) 0.036 ( 0.004 ms): ldlck-test/438194 landlock_add_rule(rule_type: LANDLOCK_RULE_PATH_BENEATH) = -1 EBADFD (File descriptor in bad state) ``` Committer notes: Made it build with NO_LIBBPF=1, simplified btf_enum_fprintf(), see [1] for the discussion. Signed-off-by: Howard Chu Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Günther Noack Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Mark Rutland Cc: Mickaël Salaün Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lore.kernel.org/lkml/20240613022757.3589783-1-howardchu95@gmail.com Link: https://lore.kernel.org/lkml/ZnXAhFflUl_LV1QY@x1 # [1] Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-trace.c | 110 +++++++++++++++++++++++++++++++++++-- 1 file changed, 106 insertions(+), 4 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index c4fa8191253d..24e751bc0ecd 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 +111,10 @@ struct syscall_arg_fmt { const char *name; u16 nr_entries; // for arrays bool show_zero; + bool is_enum; +#ifdef HAVE_LIBBPF_SUPPORT + const struct btf_type *type; +#endif }; struct syscall_fmt { @@ -139,6 +144,9 @@ struct trace { } syscalls; #ifdef HAVE_BPF_SKEL struct augmented_raw_syscalls_bpf *skel; +#endif +#ifdef HAVE_LIBBPF_SUPPORT + struct btf *btf; #endif struct record_opts opts; struct evlist *evlist; @@ -204,6 +212,20 @@ struct trace { } oe; }; +static void trace__load_vmlinux_btf(struct trace *trace __maybe_unused) +{ +#ifdef HAVE_LIBBPF_SUPPORT + if (trace->btf != NULL) + return; + + trace->btf = btf__load_vmlinux_btf(); + if (verbose > 0) { + fprintf(trace->output, trace->btf ? "vmlinux BTF loaded\n" : + "Failed to load vmlinux BTF\n"); + } +#endif +} + struct tp_field { int offset; union { @@ -887,6 +909,64 @@ 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 int syscall_arg_fmt__cache_btf_enum(struct syscall_arg_fmt *arg_fmt, struct btf *btf, char *type) +{ + int id; + + // Already cached? + if (arg_fmt->type != NULL) + return 0; + + type = strstr(type, "enum "); + if (type == NULL) + return -1; + + type += 5; // skip "enum " to get the enumeration name + + id = btf__find_by_name(btf, type); + if (id < 0) + return -1; + + arg_fmt->type = btf__type_by_id(btf, id); + return arg_fmt->type == NULL ? -1 : 0; +} + +static size_t btf_enum_scnprintf(const struct btf_type *type, struct btf *btf, char *bf, size_t size, int val) +{ + struct btf_enum *be = btf_enum(type); + const int nr_entries = btf_vlen(type); + + for (int i = 0; i < nr_entries; ++i, ++be) { + if (be->val == val) { + return scnprintf(bf, size, "%s", + btf__name_by_offset(btf, be->name_off)); + } + } + + return 0; +} + +static size_t trace__btf_enum_scnprintf(struct trace *trace, struct syscall_arg_fmt *arg_fmt, char *bf, + size_t size, int val, char *type) +{ + if (trace->btf == NULL) + return 0; + + if (syscall_arg_fmt__cache_btf_enum(arg_fmt, trace->btf, type) < 0) + return 0; + + return btf_enum_scnprintf(arg_fmt->type, trace->btf, bf, size, val); +} +#else // HAVE_LIBBPF_SUPPORT +static size_t trace__btf_enum_scnprintf(struct trace *trace __maybe_unused, struct syscall_arg_fmt *arg_fmt __maybe_unused, + char *bf __maybe_unused, size_t size __maybe_unused, int val __maybe_unused, + char *type __maybe_unused) +{ + return 0; +} +#endif // HAVE_LIBBPF_SUPPORT + #define STRARRAY(name, array) \ { .scnprintf = SCA_STRARRAY, \ .strtoul = STUL_STRARRAY, \ @@ -1238,6 +1318,7 @@ 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; @@ -1744,7 +1825,8 @@ static const struct syscall_arg_fmt *syscall_arg_fmt__find_by_name(const char *n } static struct tep_format_field * -syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field *field) +syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field *field, + bool *use_btf) { struct tep_format_field *last_field = NULL; int len; @@ -1756,6 +1838,7 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field continue; len = strlen(field->name); + arg->is_enum = false; if (strcmp(field->type, "const char *") == 0 && ((len >= 4 && strcmp(field->name + len - 4, "name") == 0) || @@ -1782,6 +1865,8 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field * 7 unsigned long */ arg->scnprintf = SCA_FD; + } else if (strstr(field->type, "enum") && use_btf != NULL) { + *use_btf = arg->is_enum = true; } else { const struct syscall_arg_fmt *fmt = syscall_arg_fmt__find_by_name(field->name); @@ -1798,7 +1883,8 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field static int syscall__set_arg_fmts(struct syscall *sc) { - struct tep_format_field *last_field = syscall_arg_fmt__init_array(sc->arg_fmt, sc->args); + struct tep_format_field *last_field = syscall_arg_fmt__init_array(sc->arg_fmt, sc->args, + &sc->use_btf); if (last_field) sc->args_size = last_field->offset + last_field->size; @@ -1811,6 +1897,7 @@ static int trace__read_syscall_info(struct trace *trace, int id) char tp_name[128]; struct syscall *sc; const char *name = syscalltbl__name(trace->sctbl, id); + int err; #ifdef HAVE_SYSCALL_TABLE_SUPPORT if (trace->syscalls.table == NULL) { @@ -1883,7 +1970,13 @@ static int trace__read_syscall_info(struct trace *trace, int id) sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit"); sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat"); - return syscall__set_arg_fmts(sc); + err = syscall__set_arg_fmts(sc); + + /* after calling syscall__set_arg_fmts() we'll know whether use_btf is true */ + if (sc->use_btf) + trace__load_vmlinux_btf(trace); + + return err; } static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) @@ -1891,7 +1984,7 @@ static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) struct syscall_arg_fmt *fmt = evsel__syscall_arg_fmt(evsel); if (fmt != NULL) { - syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields); + syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields, NULL); return 0; } @@ -2103,6 +2196,15 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, if (trace->show_arg_names) printed += scnprintf(bf + printed, size - printed, "%s: ", field->name); + if (sc->arg_fmt[arg.idx].is_enum) { + size_t p = trace__btf_enum_scnprintf(trace, &sc->arg_fmt[arg.idx], bf + printed, + size - printed, val, field->type); + if (p) { + printed += p; + continue; + } + } + printed += syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx], bf + printed, size - printed, &arg, val); } -- 2.45.2