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Subject[PATCH 06/13] perf tools: Allow BPF program config probing options
Date
By extending the syntax of BPF object section names, this patch allows
user to config probing options like what they can do in 'perf probe'.

Error message in perf probe is also updated.

Test result:

For following BPF file bpf.c:

SEC("inlines=no\n"
"func=SyS_dup?")
int func(void *ctx)
{
return 1;
}

Cmdline:

# ./perf record -e ./test_probe_glob.c ls /
...
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.013 MB perf.data ]
# ./perf evlist
perf_bpf_probe:func_1
perf_bpf_probe:func

After changing "inlines=no" to "inlines=yes":

Cmdline:

# ./perf record -e ./test_probe_glob.c ls /
...
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.013 MB perf.data ]
# ./perf evlist
perf_bpf_probe:func_3
perf_bpf_probe:func_2
perf_bpf_probe:func_1
perf_bpf_probe:func

Then test 'force':

use following program:

SEC("func=sys_read")
int funca(void *ctx)
{
return 1;
}

SEC("force=no\n"
"func=sys_write")
int funcb(void *ctx)
{
return 1;
}

Error: event "func" already exists.
Hint: Remove existing event by 'perf probe -d'
or force duplicates by 'perf probe -f'
or set 'force=yes' in BPF source.
event syntax error: './test_force.c'
\___ Probe point exist. Try 'perf probe -d "*"' and set 'force=yes'

(add -v to see detail)
...

Then replace 'force=no' to 'force=yes':

# ./perf record -e ./test_force.c ls /
...
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.013 MB perf.data (4 samples) ]
# ./perf evlist
perf_bpf_probe:func_1
perf_bpf_probe:func

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
tools/perf/util/bpf-loader.c | 53 +++++++++++++++++++++++++++++++++++++++++--
tools/perf/util/probe-event.c | 7 ++++--
2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index aeac08c..3694e16 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -7,6 +7,7 @@

#include <bpf/libbpf.h>
#include <linux/err.h>
+#include <linux/string.h>
#include "perf.h"
#include "debug.h"
#include "bpf-loader.h"
@@ -129,6 +130,38 @@ config__module(const char *value, struct perf_probe_event *pev)
return 0;
}

+static int
+config__bool(const char *value,
+ bool *pbool, bool invert)
+{
+ int err;
+ bool bool_value;
+
+ if (!pbool)
+ return -EINVAL;
+
+ err = strtobool(value, &bool_value);
+ if (err)
+ return err;
+
+ *pbool = invert ? !bool_value : bool_value;
+ return 0;
+}
+
+static int
+config__inlines(const char *value,
+ struct perf_probe_event *pev __maybe_unused)
+{
+ return config__bool(value, &probe_conf.no_inlines, true);
+}
+
+static int
+config__force(const char *value,
+ struct perf_probe_event *pev __maybe_unused)
+{
+ return config__bool(value, &probe_conf.force_add, false);
+}
+
static struct {
const char *key;
const char *usage;
@@ -146,7 +179,19 @@ static struct {
.usage = "module=<module name> ",
.desc = "Set kprobe module",
.func = config__module,
- }
+ },
+ {
+ .key = "inlines",
+ .usage = "inlines=[yes|no] ",
+ .desc = "Probe at inline symbol",
+ .func = config__inlines,
+ },
+ {
+ .key = "force",
+ .usage = "force=[yes|no] ",
+ .desc = "Forcibly add events with existing name",
+ .func = config__force,
+ },
};

static int
@@ -240,6 +285,10 @@ config_bpf_program(struct bpf_program *prog)
const char *config_str;
int err;

+ /* Initialize per-program probing setting */
+ probe_conf.no_inlines = false;
+ probe_conf.force_add = false;
+
config_str = bpf_program__title(prog, false);
if (IS_ERR(config_str)) {
pr_debug("bpf: unable to get title for program\n");
@@ -544,7 +593,7 @@ int bpf__strerror_probe(struct bpf_object *obj __maybe_unused,
scnprintf(buf, size, "%s (add -v to see detail)", emsg);
break;
}
- bpf__strerror_entry(EEXIST, "Probe point exist. Try use 'perf probe -d \"*\"'");
+ bpf__strerror_entry(EEXIST, "Probe point exist. Try 'perf probe -d \"*\"' and set 'force=yes'");
bpf__strerror_entry(EACCES, "You need to be root");
bpf__strerror_entry(EPERM, "You need to be root, and /proc/sys/kernel/kptr_restrict should be 0");
bpf__strerror_entry(ENOENT, "You need to check probing points in BPF file");
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 03875f9..93996ec 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2326,8 +2326,11 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
goto out;

if (!allow_suffix) {
- pr_warning("Error: event \"%s\" already exists. "
- "(Use -f to force duplicates.)\n", buf);
+ pr_warning("Error: event \"%s\" already exists.\n"
+ " Hint: Remove existing event by 'perf probe -d'\n"
+ " or force duplicates by 'perf probe -f'\n"
+ " or set 'force=yes' in BPF source.\n",
+ buf);
ret = -EEXIST;
goto out;
}
--
1.8.3.4


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