Re: [Libunwind-devel] unwind within a signal handler (in linux / arm)

[Harald Servat]

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Al 19/04/12 19:42, En/na Arun Sharma ha escrit:
> On Thu, Apr 19, 2012 at 8:44 AM, Harald Servat <address@hidden> wrote:
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>> Dear all,
>>
>>  I've just downloaded a GIT clone of the libunwind and installed it in
>> a linux/ARM machine.
>>
>>  We use libunwind from an library that monitors an application. This
>> library uses periodical sampling to collect some information (including
>> the callstack). I've found that libunwind segfaults when is issued from
>> the signal handler. I'm attaching the gdb output below.
>>
>>  Has anyone seen this issue before?
> 
> Not very familiar with ARM. But:
> 
> ./configure --enable-debug
> UNW_DEBUG_LEVEL=1 your-program
> 
> and pasting the output should help people figure out what's wrong.
> 

Thank you for the pointers. Now I get

 >_ULarm_dwarf_search_unwind_table: e->fde_offset = 34, segbase = 0,
debug_frame_base = 3f730, fde_addr = 3f764
 >_ULarm_step: dwarf_step()=-10
 >_ULarm_dwarf_search_unwind_table: e->fde_offset = 34, segbase = 0,
debug_frame_base = 3f730, fde_addr = 3f764
 >_ULarm_init_local: (cursor=0xbeb380b0)
 >_ULarm_step: (cursor=0xbeb380b0)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb380b0)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb380b0)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb380b0)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb380b0)
 >_ULarm_dwarf_search_unwind_table: e->fde_offset = 34, segbase = 0,
debug_frame_base = 3f730, fde_addr = 3f764
 >_ULarm_step: dwarf_step()=-10
 >_ULarm_dwarf_search_unwind_table: e->fde_offset = 34, segbase = 0,
debug_frame_base = 3f730, fde_addr = 3f764
 >_ULarm_init_local: (cursor=0xbeb37b70)
 >_ULarm_step: (cursor=0xbeb37b70)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb37b70)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb37b70)
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb37b70)
 >_ULarm_step: (cursor=0xbeb37b70)
 >_ULarm_dwarf_search_unwind_table: e->fde_offset = e748, segbase =
4238d000, debug_frame_base = 71440, fde_addr = 7fb88
 >_ULarm_step: dwarf_step()=1
 >_ULarm_step: (cursor=0xbeb37b70)
 >_ULarm_step: dwarf_step()=-10
Segmentation fault

  It's curious that the e->fde_offset changes from 34 to e748 and
segbase from 0 to 4238d000.

Thank you.
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