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Re: [Discuss-gnuradio] Segfault with volk on 32 bit AMD

From: Nick Foster
Subject: Re: [Discuss-gnuradio] Segfault with volk on 32 bit AMD
Date: Fri, 16 Mar 2012 11:50:36 -0700

On Fri, Mar 16, 2012 at 11:42 AM, Frederick Stevens <address@hidden> wrote:

Here is the output from gdb:

RUN_VOLK_TESTS: volk_32fc_32f_multiply_32fc_a

Program received signal SIGSEGV, Segmentation fault.
0xb7f2c6e0 in volk_32fc_32f_multiply_32fc_a_generic ()
  from /home/fred/extras/gnuradio/gnuradio/build/volk/lib/libvolk.so.0.0.0

Dump of assembler code for function volk_32fc_32f_multiply_32fc_a_generic:
  0xb7f2c6c0 <+0>:     push   %ebp
  0xb7f2c6c1 <+1>:     mov    %esp,%ebp
  0xb7f2c6c3 <+3>:     push   %edi
  0xb7f2c6c4 <+4>:     push   %esi
  0xb7f2c6c5 <+5>:     mov    0x8(%ebp),%edx
  0xb7f2c6c8 <+8>:     mov    0xc(%ebp),%ecx
  0xb7f2c6cb <+11>:    mov    0x10(%ebp),%edi
  0xb7f2c6ce <+14>:    mov    0x14(%ebp),%esi
  0xb7f2c6d1 <+17>:    test   %esi,%esi
  0xb7f2c6d3 <+19>:    je     0xb7f2c6fc <volk_32fc_32f_multiply_32fc_a_generic+60>
  0xb7f2c6d5 <+21>:    xor    %eax,%eax
  0xb7f2c6d7 <+23>:    mov    %esi,%esi
  0xb7f2c6d9 <+25>:    lea    0x0(%edi,%eiz,1),%edi
=> 0xb7f2c6e0 <+32>:    flds   (%edi,%eax,8)
  0xb7f2c6e3 <+35>:    flds   (%ecx,%eax,8)
  0xb7f2c6e6 <+38>:    fmul   %st(1),%st
  0xb7f2c6e8 <+40>:    fxch   %st(1)
  0xb7f2c6ea <+42>:    fmuls  0x4(%ecx,%eax,8)
  0xb7f2c6ee <+46>:    fxch   %st(1)
  0xb7f2c6f0 <+48>:    fstps  (%edx,%eax,8)
  0xb7f2c6f3 <+51>:    fstps  0x4(%edx,%eax,8)
  0xb7f2c6f7 <+55>:    inc    %eax
  0xb7f2c6f8 <+56>:    cmp    %eax,%esi
  0xb7f2c6fa <+58>:    ja     0xb7f2c6e0 <volk_32fc_32f_multiply_32fc_a_generic+32>
  0xb7f2c6fc <+60>:    pop    %esi
  0xb7f2c6fd <+61>:    pop    %edi
  0xb7f2c6fe <+62>:    pop    %ebp
  0xb7f2c6ff <+63>:    ret
End of assembler dump.

I omitted the first part of the program execution since everything seemed to be working fine.  Hope this helps.  Let me know if you would like me to try something else.



OK, that's weird as hell. That's the generic implementation, which is just a std::complex multiply in a for loop. Can you give me your gcc version?


On 03/16/2012 12:39 PM, Rafael Diniz wrote:
Also using the gdb "disassemble" command you could trace which instruction
raised the fault.

Rafael Diniz

Well, that doesn't make me happy at all. Especially since we just patched
the release yesterday...

Sounds like the AMD chip is handling something wrong (or differently) with
the alignment. All vectors passed using volk_profile are supposed to be
properly byte aligned.

Fred, can you just check for me what happens when you run it under gdb?
Just run "gdb volk_profile" and when it crashes, do a "bt" and post the
results of the backtrace here.


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