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

[Doug Moore]

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