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SubjectRe: perf-probe crash in dwarf_getcfi_elf
On 12/30/14 2:05 AM, Namhyung Kim wrote:
> 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.
>
> Reported-by: David Ahern <dsahern@gmail.com>
> Cc: Mark Wielaard <mjw@redhat.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Solves the crash for me.

Tested-by: David Ahern <dsahern@gmail.com>

Thanks for the quick response, Namhyung.

David


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