Re: [Libunwind-devel] unw_get_proc_info is not signal-safe with debug-frames enabled

[Sergey Korolev]

Doug,

please try this patch also.

пт, 7 сент. 2018 г. в 11:18, Doug Moore <address@hidden>:

Sergey,

Your patch does remove memory allocation from the file, but oddly, I 
still have problems with malloc being invoked.  The second time I 
tested with your patch, I got hung here:

#0  0x0000ffffb5a85d74 in __lll_lock_wait_private () from /lib64/libc.so.6
#1  0x0000ffffb5a0ea38 in malloc () from /lib64/libc.so.6
#2  0x0000ffffb59c15bc in qsort_r () from /lib64/libc.so.6
#3  0x0000ffffb592c8b0 in _ULaarch64_dwarf_find_debug_frame (found=0, 
address@hidden, address@hidden,
    address@hidden, obj_name=0xffffb67dc440 
"/home/dougm/.local/lib/hpctoolkit/ext-libs/libdwarf.so.1", 
start=<optimized out>,
     end=<optimized out>) at dwarf/Gfind_proc_info-lsb.c:380
#4  0x0000ffffb592cab0 in _ULaarch64_dwarf_callback 
(info=0xffffeb099ef8, size=<optimized out>, ptr=0xffffeb09a018) at 
dwarf/Gfind_proc_info-lsb.c:667
#5  0x0000ffffb5abac88 in dl_iterate_phdr () from /lib64/libc.so.6
#6  0x0000ffffb592cff4 in _ULaarch64_dwarf_find_proc_info 
(as=0xffffb5948230 <local_addr_space>, address@hidden, 
address@hidden,
     need_unwind_info=1, arg=0xffffeb09a9a0) at dwarf/Gfind_proc_info-lsb.c:693
#7  0x0000ffffb592a158 in fetch_proc_info (address@hidden, 
ip=281473734119984) at dwarf/Gparser.c:454
#8  0x0000ffffb592ba08 in _ULaarch64_dwarf_reg_states_iterate 
(c=0xffffeb09a1d0, cb=0xffffb6750844 <dwarf_reg_states_callback>, 
token=0xffffeb09a1b8)
     at dwarf/Gparser.c:1034

So, perhaps qsort isn't safe either, as odd as that seems.

Doug

Quoting Sergey Korolev <address@hidden>:

> Doug,
>
> Can you try this patch?
> http://lists.nongnu.org/archive/html/libunwind-devel/2018-06/msg00005.html
>
> пт, 7 сент. 2018 г. в 1:56, Doug Moore <address@hidden>:
>
>> It seems that unw_get_proc_info calls dwarf_make_proc_info, calls
>> fetch_proc_info, calls dwarf_find_proc_info, calls dl_iterate_phdr,
>> calls dwarf_callback, calls dwarf_find_debug_frame, calls calloc, and
>> callloc is not signal safe on the aarch64 device I'm testing on.
>>
>> So would there be a problem with replacing the calloc/realloc memory
>> management of 'tab' in Gfind_proc_info-lsb.c with mmap and munmap and
>> memcpy?
>>
>> Is the memory allocated for 'tab' freed anywhere?  It's not obvious that
>> it is.
>>
>> Thanks,
>>
>> Doug Moore
>>
>> Rice University
>>
>>
>> _______________________________________________
>> Libunwind-devel mailing list
>> address@hidden
>> https://lists.nongnu.org/mailman/listinfo/libunwind-devel
>>

0001-dwarf-do-not-use-qsort-to-sort-the-debug-frame-table.patch
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