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@xxxxxx/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) = -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) ``` 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 <howardchu95@xxxxxxxxx> --- 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 <bpf/bpf.h> #include <bpf/libbpf.h> +#include <bpf/btf.h> #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; }; 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(char *bf, size_t size, #define SCA_GETRANDOM_FLAGS syscall_arg__scnprintf_getrandom_flags +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] = {"enum", "const enum"}, *ep; + int id; + + for (size_t i = 0; i < ARRAY_SIZE(enum_prefix); i++) { + ep = enum_prefix[i]; + if (strlen(type) > strlen(ep) + 1 && strstr(type, ep) == type) + type += strlen(ep) + 1; + } + + id = btf__find_by_name(btf, type); + if (id < 0) + return 0; + + bt = btf__type_by_id(btf, id); + e = btf_enum(bt); + + for (int i = 0; i < btf_vlen(bt); i++, e++) { + if (e->val == val) + return scnprintf(bf, size, "%s", + btf__name_by_offset(btf, e->name_off)); + } + + return 0; +} + #define STRARRAY(name, array) \ { .scnprintf = SCA_STRARRAY, \ .strtoul = 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 *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 +1817,8 @@ 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")) { + arg->is_enum = true; } else { const struct syscall_arg_fmt *fmt = 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 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), + *field = sc->args; + struct syscall_arg_fmt *arg = sc->arg_fmt; + + for (; field; field = field->next, ++arg) + if (arg->is_enum) + sc->use_btf = true; if (last_field) sc->args_size = last_field->offset + last_field->size; @@ -1811,6 +1854,7 @@ 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 +1927,17 @@ 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->btf = btf__load_vmlinux_btf(); + if (verbose > 0) + fprintf(trace->output, trace->btf ? "vmlinux BTF loaded\n" : + "Failed to load vmlinux BTF\n"); + } + + return err; } 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_size, struct trace *trace, struct thread *thread) { - size_t printed = 0; + size_t printed = 0, p; unsigned long val; u8 bit = 1; struct syscall_arg arg = { @@ -2103,6 +2157,15 @@ 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 == true && trace->btf) { + p = btf_enum_scnprintf(bf + printed, size - printed, val, + trace->btf, 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
