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Subject[tip:perf/urgent] perf probe: Clear probe_trace_event when add_probe_trace_event() fails
Commit-ID:  092b1f0b5f9f797812da0de927c3aa26acbe8762
Gitweb: http://git.kernel.org/tip/092b1f0b5f9f797812da0de927c3aa26acbe8762
Author: Wang Nan <wangnan0@huawei.com>
AuthorDate: Fri, 13 Nov 2015 12:29:11 +0000
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 13 Nov 2015 12:28:09 -0300

perf probe: Clear probe_trace_event when add_probe_trace_event() fails

When probing with a glob, errors in add_probe_trace_event() won't be
passed to debuginfo__find_trace_events() because it would be modified by
probe_point_search_cb(). It causes a segfault if perf fails to find an
argument for a probe point matched by the glob. For example:

# ./perf probe -v -n 'SyS_dup? oldfd'
probe-definition(0): SyS_dup? oldfd
symbol:SyS_dup? file:(null) line:0 offset:0 return:0 lazy:(null)
parsing arg: oldfd into oldfd
1 arguments
Looking at the vmlinux_path (7 entries long)
Using /lib/modules/4.3.0-rc4+/build/vmlinux for symbols
Open Debuginfo file: /lib/modules/4.3.0-rc4+/build/vmlinux
Try to find probe point from debuginfo.
Matched function: SyS_dup3
found inline addr: 0xffffffff812095c0
Probe point found: SyS_dup3+0
Searching 'oldfd' variable in context.
Converting variable oldfd into trace event.
oldfd type is long int.
found inline addr: 0xffffffff812096d4
Probe point found: SyS_dup2+36
Searching 'oldfd' variable in context.
Failed to find 'oldfd' in this function.
Matched function: SyS_dup3
Probe point found: SyS_dup3+0
Searching 'oldfd' variable in context.
Converting variable oldfd into trace event.
oldfd type is long int.
Matched function: SyS_dup2
Probe point found: SyS_dup2+0
Searching 'oldfd' variable in context.
Converting variable oldfd into trace event.
oldfd type is long int.
Found 4 probe_trace_events.
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: p:probe/SyS_dup3 _text+2135488 oldfd=%di:s64
Segmentation fault (core dumped)
#

This patch ensures that add_probe_trace_event() doesn't touches
tf->ntevs and tf->tevs if those functions fail.

After the patch:

# perf probe 'SyS_dup? oldfd'
Failed to find 'oldfd' in this function.
Added new events:
probe:SyS_dup3 (on SyS_dup? with oldfd)
probe:SyS_dup3_1 (on SyS_dup? with oldfd)
probe:SyS_dup2 (on SyS_dup? with oldfd)

You can now use it in all perf tools, such as:

perf record -e probe:SyS_dup2 -aR sleep 1

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1447417761-156094-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/probe-finder.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 63993d7..05012bb 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1183,7 +1183,7 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
container_of(pf, struct trace_event_finder, pf);
struct perf_probe_point *pp = &pf->pev->point;
struct probe_trace_event *tev;
- struct perf_probe_arg *args;
+ struct perf_probe_arg *args = NULL;
int ret, i;

/* Check number of tevs */
@@ -1198,19 +1198,23 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
ret = convert_to_trace_point(&pf->sp_die, tf->mod, pf->addr,
pp->retprobe, pp->function, &tev->point);
if (ret < 0)
- return ret;
+ goto end;

tev->point.realname = strdup(dwarf_diename(sc_die));
- if (!tev->point.realname)
- return -ENOMEM;
+ if (!tev->point.realname) {
+ ret = -ENOMEM;
+ goto end;
+ }

pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
tev->point.offset);

/* Expand special probe argument if exist */
args = zalloc(sizeof(struct perf_probe_arg) * MAX_PROBE_ARGS);
- if (args == NULL)
- return -ENOMEM;
+ if (args == NULL) {
+ ret = -ENOMEM;
+ goto end;
+ }

ret = expand_probe_args(sc_die, pf, args);
if (ret < 0)
@@ -1234,6 +1238,10 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
}

end:
+ if (ret) {
+ clear_probe_trace_event(tev);
+ tf->ntevs--;
+ }
free(args);
return ret;
}

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