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SubjectRe: Re: perf-probe crash in dwarf_getcfi_elf
(2014/12/30 18:05), Namhyung Kim wrote:
> On Tue, Dec 30, 2014 at 05:47:08PM +0900, Namhyung Kim wrote:
>> On Mon, Dec 29, 2014 at 09:39:18PM -0700, David Ahern wrote:
>>> Hi Namhyung:
>>>
>>> Using perf-probe from top of Linus' tree I get a segfault on both Fedora 16
>>> and 18 (does not crash on Fedora 20). Command used is:
>>>
>>> perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
>>>
>>> git bisect points to:
>>>
>>> commit 03d89412981a7681971bc77edba1669595763030
>>> Author: Namhyung Kim <namhyung@kernel.org>
>>> Date: Mon Apr 7 16:05:48 2014 +0900
>>>
>>> perf probe: Use dwarf_getcfi_elf() instead of dwarf_getcfi()
>>>
>>
>> It seems to be related to below commit in elfutils. We might need to
>> check .eh_frame section has SHT_PROGBITS. Will send a patch soon.
>
>
>>From f56964e74d60a9921214d0e2e5c3d082f5a910c1 Mon Sep 17 00:00:00 2001
> From: Namhyung Kim <namhyung@kernel.org>
> Date: Tue, 30 Dec 2014 17:47:47 +0900
> Subject: [PATCH] perf probe: Fix a segfault on old libdw
>
> David reported that perf can segfault when adding an uprobe event like
> this:
>
> $ perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
>
> (gdb) bt
> #0 parse_eh_frame_hdr (hdr=0x0, hdr_size=2596, hdr_vaddr=71788,
> ehdr=0x7fffffffd390, eh_frame_vaddr=
> 0x7fffffffd378, table_entries=0x8808d8, table_encoding=0x8808e0 "") at
> dwarf_getcfi_elf.c:79
> #1 0x000000385f81615a in getcfi_scn_eh_frame (hdr_vaddr=71788,
> hdr_scn=0x8839b0, shdr=0x7fffffffd2f0, scn=<optimized out>,
> ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:231
> #2 getcfi_shdr (ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:283
> #3 dwarf_getcfi_elf (elf=0x882b30) at dwarf_getcfi_elf.c:309
> #4 0x00000000004d5bac in debuginfo__find_probes (pf=0x7fffffffd4f0,
> dbg=Unhandled dwarf expression opcode 0xfa) at util/probe-finder.c:993
> #5 0x00000000004d634a in debuginfo__find_trace_events (dbg=0x880840,
> pev=<optimized out>, tevs=0x880f88, max_tevs=<optimized out>) at
> util/probe-finder.c:1200
> #6 0x00000000004aed6b in try_to_find_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so",
> max_tevs=128, tevs=0x880f88, pev=0x859b30) at util/probe-event.c:482
> #7 convert_to_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so", max_tevs=128, tevs=0x880f88,
> pev=0x859b30) at util/probe-event.c:2356
> #8 add_perf_probe_events (pevs=<optimized out>, npevs=1, max_tevs=128,
> target=0x881b20 "/lib64/libpthread-2.14.90.so", force_add=false) at
> util/probe-event.c:2391
> #9 0x000000000044014f in __cmd_probe (argc=<optimized out>,
> argv=0x7fffffffe2f0, prefix=Unhandled dwarf expression opcode 0xfa) at
> at builtin-probe.c:488
> #10 0x0000000000440313 in cmd_probe (argc=5, argv=0x7fffffffe2f0,
> prefix=<optimized out>) at builtin-probe.c:506
> #11 0x000000000041d133 in run_builtin (p=0x805680, argc=5,
> argv=0x7fffffffe2f0) at perf.c:341
> #12 0x000000000041c8b2 in handle_internal_command (argv=<optimized out>,
> argc=<optimized out>) at perf.c:400
> #13 run_argv (argv=<optimized out>, argcp=<optimized out>) at perf.c:444
> #14 main (argc=5, argv=0x7fffffffe2f0) at perf.c:559
>
> And I found a related commit (5704c8c4fa71 "getcfi_scn_eh_frame: Don't
> crash and burn when .eh_frame bits aren't there.") in elfutils that
> can lead to a unexpected crash like this. To safely use the function,
> it needs to check the .eh_frame section is a PROGBITS type.
>

Looks good to me :)

> Reported-by: David Ahern <dsahern@gmail.com>
> Cc: Mark Wielaard <mjw@redhat.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you!

> ---
> tools/perf/util/probe-finder.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index c7918f83b300..b5247d777f0e 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -989,8 +989,24 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
> int ret = 0;
>
> #if _ELFUTILS_PREREQ(0, 142)
> + Elf *elf;
> + GElf_Ehdr ehdr;
> + GElf_Shdr shdr;
> +
> /* Get the call frame information from this dwarf */
> - pf->cfi = dwarf_getcfi_elf(dwarf_getelf(dbg->dbg));
> + elf = dwarf_getelf(dbg->dbg);
> + if (elf == NULL)
> + return -EINVAL;
> +
> + if (gelf_getehdr(elf, &ehdr) == NULL)
> + return -EINVAL;
> +
> + if (elf_section_by_name(elf, &ehdr, &shdr, ".eh_frame", NULL) &&
> + shdr.sh_type == SHT_PROGBITS) {
> + pf->cfi = dwarf_getcfi_elf(elf);
> + } else {
> + pf->cfi = dwarf_getcfi(dbg->dbg);
> + }
> #endif
>
> off = 0;
>


--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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