| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAA3XUr1BnS=8RTVyxtVOm4Ahb2DQXUuJJQC1w2SvT5fycjRcEQ@mail.gmail.com>
Date: Mon, 19 Jan 2015 09:50:43 -0800
From: Victor Kamensky <victor.kamensky@...aro.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Jiri Olsa <jolsa@...hat.com>,
Avi Kivity <avi@...udius-systems.com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Anton Blanchard <anton@...ba.org>,
David Ahern <dsahern@...il.com>,
Will Deacon <will.deacon@....com>,
Dave Martin <Dave.Martin@....com>,
open list <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Victor Kamensky <victor.kamensky@...aro.org>,
Jiri Olsa <jolsa@...nel.org>, Waiman Long <Waiman.Long@...com>
Subject: Re: [PATCH 2/2] perf symbols: debuglink should take symfs option into account
Hi Guys,
If it helps to look at below patch, here is a test case
for failure that below patch addresses.
Run on target with root NFS mounted in this case. Current
target is ARM TC2 board.
But I am pretty sure the same sequence will fail on any other
device that is built in cross compiled way, with .gnu_debuglink
split debug symbols and with and perf used with --symfs option:
On target device built split debug executable with .gnu_debuglink
section and collect perf data:
root@...ericarmv7a:~/tests/hang# cat hang.c
void hang(void)
{
while(1);
}
int main (void)
{
hang();
return 0;
}
root@...ericarmv7a:~/tests/hang# gcc -o hang -g hang.c
root@...ericarmv7a:~/tests/hang# cp hang hang.debug
root@...ericarmv7a:~/tests/hang# strip --only-keep-debug hang.debug
root@...ericarmv7a:~/tests/hang# objcopy --add-gnu-debuglink=hang.debug hang
root@...ericarmv7a:~/tests/hang# strip hang
root@...ericarmv7a:~/tests/hang# readelf -S hang | grep gnu_debuglink
[27] .gnu_debuglink PROGBITS 00000000 00060b 000010 00 0 0 1
root@...ericarmv7a:~/tests/hang# readelf -x 27 hang
Hex dump of section '.gnu_debuglink':
0x00000000 68616e67 2e646562 75670000 ee7e9545 hang.debug...~.E
root@...ericarmv7a:~/tests/hang# perf record -e cycles --no-buildid-cache ./hang
^C[ perf record: Woken up 6 times to write data ]
[ perf record: Captured and wrote 1.448 MB perf.data (~63258 samples) ]
root@...ericarmv7a:~/tests/hang# chmod a+r perf.data
On the host trying to decode perf result without proposed fix
using --symfs option to point to target rootfs. Note failure of
decode symbol for hang function.
[kamensky@...eos-lnx2 hang]$ ls -a
. .. hang hang.c hang.debug perf.data
[kamensky@...eos-lnx2 hang]$ $L/tools/perf/perf report --stdio --symfs
/wd2/nfs/rootfs_32_le_tc2_20141218 | head -10
[kernel.kallsyms] with build id
c70bcdc8d97df0dcded9984e3ada2b6ff5a69510 not found, continuing without
symbols
no symbols found in /home/root/tests/hang/hang, maybe install a debug package?
# To display the perf.data header info, please use
--header/--header-only options.
#
# Samples: 37K of event 'cycles'
# Event count (approx.): 9469365389
#
# Overhead Command Shared Object Symbol
# ........ ....... ................. ......................
#
99.97% hang hang [.] 0x00000000000003ec <--
failed to decode symbol
0.01% hang [kernel.kallsyms] [k] 0x00000000c08c5438
[kamensky@...eos-lnx2 hang]$ strace -o /tmp/perf.trace.txt
$L/tools/perf/perf report --stdio --symfs
/wd2/nfs/rootfs_32_le_tc2_20141218 >& /dev/null
[kamensky@...eos-lnx2 hang]$ grep open /tmp/perf.trace.txt | grep hang
open("/home/root/tests/hang/hang", O_RDONLY) = -1 ENOENT (No such file
or directory) <--- filename__read_debuglink tries to open file
open("/wd2/nfs/rootfs_32_le_tc2_20141218//usr/lib/debug/home/root/tests/hang/hang.debug",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("/wd2/nfs/rootfs_32_le_tc2_20141218//usr/lib/debug/home/root/tests/hang/hang",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("/wd2/nfs/rootfs_32_le_tc2_20141218//home/root/tests/hang/hang",
O_RDONLY) = 4
open("/wd2/nfs/rootfs_32_le_tc2_20141218//home/root/tests/hang/.debug/hang",
O_RDONLY) = -1 ENOENT (No such file or directory)
Running version of perf with proposed fix, now perf picks up
right hang.debug symbols file:
[kamensky@...eos-lnx2 hang]$ $L/tools/perf/perf report --stdio --symfs
/wd2/nfs/rootfs_32_le_tc2_20141218 | head -10
[kernel.kallsyms] with build id
c70bcdc8d97df0dcded9984e3ada2b6ff5a69510 not found, continuing without
symbols
# To display the perf.data header info, please use
--header/--header-only options.
#
# Samples: 37K of event 'cycles'
# Event count (approx.): 9469365389
#
# Overhead Command Shared Object Symbol
# ........ ....... ................. ......................
#
99.97% hang hang [.] hang
0.01% hang [kernel.kallsyms] [k] 0x00000000c08c5438
Thanks,
Victor
On 13 January 2015 at 08:59, Victor Kamensky <victor.kamensky@...aro.org> wrote:
> Currently code that tries to read corresponding debug symbol
> file from .gnu_debuglink section (DSO_BINARY_TYPE__DEBUGLINK)
> does not take in account symfs option, so filename__read_debuglink
> function cannot open ELF file, if symfs option is used.
>
> Fix is to add proper handling of symfs as it is done in other
> places: use __symbol__join_symfs function to get real file name
> of target ELF file.
>
> Created malloced copy of target filename in symfs before passing
> it to __symbol__join_symfs function because filename will be
> modified by it if corresponding debuglink is found.
>
> Signed-off-by: Victor Kamensky <victor.kamensky@...aro.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Waiman Long <Waiman.Long@...com>
> Cc: David Ahern <dsahern@...il.com>
> ---
> tools/perf/util/dso.c | 33 ++++++++++++++++++++++-----------
> 1 file changed, 22 insertions(+), 11 deletions(-)
>
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index 45be944..6a2f663 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -42,19 +42,30 @@ int dso__read_binary_type_filename(const struct dso *dso,
> size_t len;
>
> switch (type) {
> - case DSO_BINARY_TYPE__DEBUGLINK: {
> + case DSO_BINARY_TYPE__DEBUGLINK:
> + {
> char *debuglink;
> -
> - strncpy(filename, dso->long_name, size);
> - debuglink = filename + dso->long_name_len;
> - while (debuglink != filename && *debuglink != '/')
> - debuglink--;
> - if (*debuglink == '/')
> - debuglink++;
> - ret = filename__read_debuglink(dso->long_name, debuglink,
> - size - (debuglink - filename));
> - }
> + char *filename_copy;
> +
> + filename_copy = malloc(PATH_MAX);
> + if (filename_copy) {
> + len = __symbol__join_symfs(filename, size,
> + dso->long_name);
> + strncpy(filename_copy, filename, PATH_MAX);
> + debuglink = filename + len;
> + while (debuglink != filename && *debuglink != '/')
> + debuglink--;
> + if (*debuglink == '/')
> + debuglink++;
> + ret = filename__read_debuglink(filename_copy, debuglink,
> + size - (debuglink -
> + filename));
> + free(filename_copy);
> + } else
> + ret = -1;
> break;
> + }
> +
> case DSO_BINARY_TYPE__BUILD_ID_CACHE:
> /* skip the locally configured cache if a symfs is given */
> if (symbol_conf.symfs[0] ||
> --
> 1.9.3
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists