perf-probe crash in dwarf_getcfi_elf

[David Ahern]

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@xxxxxxxxxx>
Date:   Mon Apr 7 16:05:48 2014 +0900

    perf probe: Use dwarf_getcfi_elf() instead of dwarf_getcfi()


Backtrace at time of crash is:

(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 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

David
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