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In 'struct syscall_arg_fmt': ``` struct { void *entry; u16 nr_entries; } btf_entry; ``` This is the new member btf_entry, it saves the 'struct btf_member' pointer , so that we don't have to do btf__find_by_name(), btf__type_by_id(), btf_enum(), and btf_vlen() everytime a landlock_add_rule() syscall entered. Note that entry is of type 'void *', because this btf_entry can also be applied to 'struct btf_member *' for 'BTF_KIND_STRUCT', hopefully in the future. === This is a feature implemented on the basis of the previous bug fix https://lore.kernel.org/linux-perf-users/d18a9606-ac9f-4ca7-afaf-fcf4c951cb90@web.de/T/#t In this patch, BTF is used 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) = -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) ``` Signed-off-by: Howard Chu --- tools/perf/builtin-trace.c | 96 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 92 insertions(+), 4 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 5cbe1748911d..a89379ccac39 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 +111,11 @@ struct syscall_arg_fmt { const char *name; u16 nr_entries; // for arrays bool show_zero; + bool is_enum; + struct { + void *entry; + u16 nr_entries; + } btf_entry; }; struct syscall_fmt { @@ -140,6 +146,7 @@ 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 +894,56 @@ static size_t syscall_arg__scnprintf_getrandom_flags(char *bf, size_t size, #define SCA_GETRANDOM_FLAGS syscall_arg__scnprintf_getrandom_flags +static int btf_enum_find_entry(struct btf *btf, char *type, struct syscall_arg_fmt *arg_fmt) +{ + const struct btf_type *bt; + char enum_prefix[][16] = { "enum", "const enum" }, *ep; + int id; + size_t i; + + for (i = 0; i < ARRAY_SIZE(enum_prefix); i++) { + ep = enum_prefix[i]; + if (strlen(type) > strlen(ep) + 1 && strstarts(type, ep)) + type += strlen(ep) + 1; + } + + id = btf__find_by_name(btf, type); + if (id < 0) + return -1; + + bt = btf__type_by_id(btf, id); + if (bt == NULL) + return -1; + + arg_fmt->btf_entry.entry = btf_enum(bt); + arg_fmt->btf_entry.nr_entries = btf_vlen(bt); + + return 0; +} + +static size_t btf_enum_scnprintf(char *bf, size_t size, int val, struct btf *btf, char *type, + struct syscall_arg_fmt *arg_fmt) +{ + struct btf_enum *be; + int i; + + /* if btf_entry is NULL, find and save it to arg_fmt */ + if (arg_fmt->btf_entry.entry == NULL) + if (btf_enum_find_entry(btf, type, arg_fmt)) + return 0; + + be = (struct btf_enum *)arg_fmt->btf_entry.entry; + + for (i = 0; i < arg_fmt->btf_entry.nr_entries; ++i, ++be) { + if (be->val == val) { + return scnprintf(bf, size, "%s", + btf__name_by_offset(btf, be->name_off)); + } + } + + return 0; +} + #define STRARRAY(name, array) \ { .scnprintf = SCA_STRARRAY, \ .strtoul = STUL_STRARRAY, \ @@ -1238,6 +1295,7 @@ 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; @@ -1699,6 +1757,14 @@ static void trace__symbols__exit(struct trace *trace) symbol__exit(); } +static void trace__load_vmlinux_btf(struct trace *trace) +{ + trace->btf = btf__load_vmlinux_btf(); + if (verbose > 0) + fprintf(trace->output, trace->btf ? "vmlinux BTF loaded\n" : + "Failed to load vmlinux BTF\n"); +} + static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args) { int idx; @@ -1744,7 +1810,8 @@ 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 +1823,7 @@ 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 +1850,8 @@ 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 +1868,8 @@ 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 +1882,7 @@ 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 +1955,13 @@ 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->btf == NULL) + trace__load_vmlinux_btf(trace); + + return err; } static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) @@ -1891,7 +1969,7 @@ 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 +2181,16 @@ 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 && trace->btf) { + size_t p = btf_enum_scnprintf(bf + printed, size - printed, val, + trace->btf, field->type, + &sc->arg_fmt[arg.idx]); + if (p) { + printed += p; + continue; + } + } + printed += syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx], bf + printed, size - printed, &arg, val); }