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, BTF is used to turn enum value to the corresponding enum variable 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 decides to run `perf trace` without any arguments, the behaviour is to trace `landlock_add_rule`, so vmlinux btf will be loaded by default. 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) ``` This patch can be tested using this program, calling landlock_add_rule syscall (created by Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>): #include <linux/landlock.h> /* Definition of LANDLOCK_* constants */ #include <sys/syscall.h> /* Definition of SYS_* constants */ #include <errno.h> #include <string.h> #include <unistd.h> #include <stdint.h> #include <stdio.h> /* Provide own perf_event_open stub because glibc doesn't */ __attribute__((weak)) int landlock_add_rule(int ruleset_fd, enum landlock_rule_type rule_type, const void *rule_attr, uint32_t flags) { return syscall(SYS_landlock_add_rule, ruleset_fd, rule_type, rule_attr, flags); } int main(int argc, char *argv[]) { struct landlock_path_beneath_attr attr = { .allowed_access = 1, }; int err = landlock_add_rule(1, LANDLOCK_RULE_PATH_BENEATH, &attr, 0); printf("landlock_add_rule(1, LANDLOCK_RULE_PATH_BENEATH, { .allowed_access = 1, }, 0) = %d (%s)\n", err, strerror(errno)); attr = (struct landlock_path_beneath_attr){ .parent_fd = 222, }; err = landlock_add_rule(2, LANDLOCK_RULE_NET_PORT, &attr, 0); printf("landlock_add_rule(2, LANDLOCK_RULE_NET_PORT, { .parent_fd = 222, }, 0) = %d (%s)\n", err, strerror(errno)); return err; } Signed-off-by: Howard Chu <howardchu95@xxxxxxxxx> Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Reviewed-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> --- tools/perf/builtin-trace.c | 96 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 91 insertions(+), 5 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index c4fa8191253d..d93f34e9af74 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 +111,11 @@ struct syscall_arg_fmt { const char *name; u16 nr_entries; // for arrays bool show_zero; + bool is_enum; + struct { + void *entries; + 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; @@ -897,6 +904,56 @@ static size_t syscall_arg__scnprintf_getrandom_flags(char *bf, size_t size, .strtoul = STUL_STRARRAY_FLAGS, \ .parm = &strarray__##array, } +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.entries = 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.entries == NULL) + if (btf_enum_find_entry(btf, type, arg_fmt)) + return 0; + + be = (struct btf_enum *)arg_fmt->btf_entry.entries; + + 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; +} + #include "trace/beauty/arch_errno_names.c" #include "trace/beauty/eventfd.c" #include "trace/beauty/futex_op.c" @@ -1699,6 +1756,15 @@ 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 +1810,7 @@ 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; @@ -1782,6 +1848,8 @@ 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); @@ -1796,9 +1864,10 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field return last_field; } -static int syscall__set_arg_fmts(struct syscall *sc) +static int syscall__set_arg_fmts(struct syscall *sc, bool *use_btf) { - 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, + use_btf); if (last_field) sc->args_size = last_field->offset + last_field->size; @@ -1810,7 +1879,9 @@ static int trace__read_syscall_info(struct trace *trace, int id) { char tp_name[128]; struct syscall *sc; + int err; const char *name = syscalltbl__name(trace->sctbl, id); + bool use_btf = false; #ifdef HAVE_SYSCALL_TABLE_SUPPORT if (trace->syscalls.table == NULL) { @@ -1883,7 +1954,12 @@ 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, &use_btf); + + if (use_btf && trace->btf == NULL) + trace__load_vmlinux_btf(trace); + + return err; } static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) @@ -1891,7 +1967,7 @@ 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 +2179,16 @@ 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); } -- 2.45.2
