linux/tools
Wang Nan 1c0bd0e891 perf probe: Try to use symbol table if searching debug info failed
A problem can occur in a statically linked perf when vmlinux can be found:

 # perf probe --add sys_epoll_pwait
 probe-definition(0): sys_epoll_pwait
 symbol:sys_epoll_pwait file:(null) line:0 offset:0 return:0 lazy:(null)
 0 arguments
 Looking at the vmlinux_path (7 entries long)
 Using /lib/modules/4.2.0-rc1+/build/vmlinux for symbols
 Open Debuginfo file: /lib/modules/4.2.0-rc1+/build/vmlinux
 Try to find probe point from debuginfo.
 Symbol sys_epoll_pwait address found : ffffffff8122bd40
 Matched function: SyS_epoll_pwait
 Failed to get call frame on 0xffffffff8122bd40
 An error occurred in debuginfo analysis (-2).
   Error: Failed to add events. Reason: No such file or directory (Code: -2)

The reason is caused by libdw that, if libdw is statically linked, it
can't load libebl_{arch}.so reliable.

In this case it is still possible to get the address from
/proc/kalksyms.  However, perf tries that only when libdw returns
-EBADF.

This patch gives it another chance to utilize symbol table, even if
libdw returns an error code other than -EBADF.

After applying this patch:

 # perf probe -nv --add sys_epoll_pwait
 probe-definition(0): sys_epoll_pwait
 symbol:sys_epoll_pwait file:(null) line:0 offset:0 return:0 lazy:(null)
 0 arguments
 Looking at the vmlinux_path (7 entries long)
 Using /lib/modules/4.2.0-rc1+/build/vmlinux for symbols
 Open Debuginfo file: /lib/modules/4.2.0-rc1+/build/vmlinux
 Try to find probe point from debuginfo.
 Symbol sys_epoll_pwait address found : ffffffff8122bd40
 Matched function: SyS_epoll_pwait
 Failed to get call frame on 0xffffffff8122bd40
 An error occurred in debuginfo analysis (-2).
 Trying to use symbols.
 Opening /sys/kernel/debug/tracing/kprobe_events write=1
 Added new event:
 Writing event: p:probe/sys_epoll_pwait _text+2276672
   probe:sys_epoll_pwait (on sys_epoll_pwait)

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

 	perf record -e probe:sys_epoll_pwait -aR sleep 1

Although libdw returns an error (Failed to get call frame), perf tries
symbol table and finally gets correct address.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1440151770-129878-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2015-08-21 12:57:20 -03:00
..
arch tools include: Add basic atomic.h implementation from the kernel sources 2015-05-08 16:11:05 -03:00
build perf tools: Add Intel PT instruction decoder 2015-08-17 11:11:36 -03:00
cgroup
firewire
hv Drivers: hv: fcopy: full handshake support 2015-05-24 12:17:42 -07:00
iio tools:iio:iio_utils: pass strings as const 2015-06-01 08:40:26 +01:00
include tools: Copy rbtree_augmented.h from the kernel 2015-07-05 22:59:05 -03:00
laptop/freefall Move freefall program from Documentation/ to tools/ 2015-06-08 16:42:07 -06:00
lguest tools/lguest: don't use legacy definitions for net device in example launcher. 2015-02-13 17:15:55 +10:30
lib tools lib traceevent: Add checks for returned EVENT_ERROR type 2015-08-21 10:35:09 -03:00
net tools: bpf_jit_disasm: fix segfault on disabled debugging log output 2015-05-27 00:24:10 -04:00
nfsd
perf perf probe: Try to use symbol table if searching debug info failed 2015-08-21 12:57:20 -03:00
power Additional ACPICA material for v4.2-rc1 2015-07-02 17:11:28 -07:00
scripts tools lib traceevent: Add global QUIET_CC_FPIC build output 2013-12-19 16:18:10 -03:00
testing linux-kselftest-4.2-rc5 2015-07-28 10:09:53 -07:00
thermal/tmon tools/thermal: tmon: fixed the 'make install' command 2015-05-09 13:36:58 +08:00
time tools: add script to test udelay 2014-07-23 10:16:38 -07:00
usb tools: ffs-aio-example: use endpoint addresses from descriptors 2015-01-15 09:41:49 -06:00
virtio tools/virtio: add virtio 1.0 in vringh_test 2014-12-15 23:49:22 +02:00
vm tools: Fix tools/vm build 2015-05-12 18:11:06 -03:00
Makefile Staging driver patches for 4.2-rc1 2015-06-26 15:46:08 -07:00