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Date: Sat, 15 Jun 2024 09:54:00 +0800
From: Howard Chu <howardchu95@...il.com>
To: peterz@...radead.org
Cc: mingo@...hat.com,
acme@...nel.org,
namhyung@...nel.org,
mark.rutland@....com,
alexander.shishkin@...ux.intel.com,
jolsa@...nel.org,
irogers@...gle.com,
adrian.hunter@...el.com,
kan.liang@...ux.intel.com,
mic@...ikod.net,
gnoack@...gle.com,
linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
bpf@...r.kernel.org
Subject: [PATCH v1] perf trace: Augment enum syscall arguments with BTF
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
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@...nel.org>):
#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@...il.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...nel.org>
Suggested-by: Arnaldo Carvalho de Melo <acme@...nel.org>
Reviewed-by: Arnaldo Carvalho de Melo <acme@...nel.org>
---
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
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