[x264-devel] Bus error

[Jason Garrett-Glaser]

On Thu, Mar 5, 2009 at 1:57 PM, Måns Rullgård <mans at mansr.com> wrote:
> Zubair Ali Khan <zkhan at d2tech.com> writes:
>
>> Brad wrote:
>>> On Thursday 05 March 2009 15:51:14 Zubair Ali Khan wrote:
>>>
>>>>  Måns Rullgård wrote:
>>>> Zubair Ali Khan <zkhan at d2tech.com> writes:
>>>>
>>>
>>> Fix your e-mail client. Do not send HTMLized e-mail to the list.
>>>
>>>
>> Hmmm, its thunderbird and on format auto detect. Anyways, I have made
>> it stick to text.
>> Here is the gdb output again.
>> No symbol table is loaded.  Use the "file" command.
>> (gdb) file /home/zkhan/workspace/vid/exe
>> Reading symbols from /home/zkhan/workspace/vid/exe...done.
>> (gdb) target remote 172.16.100.21:10000
>> Remote debugging using 172.16.100.21:10000
>> 0x00008120 in _start ()
>> (gdb) b main
>> During symbol reading, DW_AT_name missing from DW_TAG_base_type.
>> During symbol reading, unsupported tag: 'DW_TAG_const_type'.
>> Breakpoint 1 at 0x8b14: file videncdec.c, line 35.
>> (gdb) c
>> Continuing.
>>
>> Breakpoint 1, main () at videncdec.c:35
>> 35        avcodec_init();
>> (gdb) c
>> Continuing.
>>
>> Program received signal SIGBUS, Bus error.
>> 0x003f6270 in x264_sps_write (s=
>> During symbol reading, incomplete CFI data; unspecified registers
>> (e.g., r0) at 0x3f575c.
>> 0x8abb88, sps=0x8abbc8) at ./common/bs.h:123
>> 123                *(uint32_t*)s->p = endian_fix( s->cur_bits );
>> (gdb) info registers
>> r0             0x0    0
>> r1             0xab0cc042    2869739586
>> r2             0xc000    49152
>> r3             0xc0000    786432
>> r4             0x8abb88    9091976
>> r5             0x3    3
>> r6             0x8abbc8    9092040
>> r7             0x3    3
>> r8             0x5    5
>> r9             0x4026b008    1076277256
>> r10            0x0    0
>> r11            0xbea439dc    3198433756
>> r12            0x401251ff    1074942463
>> sp             0xbea43870    0xbea43870
>> lr             0x3    3
>> pc             0x3f6270    0x3f6270 <x264_sps_write+2840>
>> fps            0x0    0
>> cpsr           0x60000010    1610612752
>> (gdb) bt
>> #0  0x003f6270 in x264_sps_write (s=0x8abb88, sps=0x8abbc8)
>>    at ./common/bs.h:123
>> During symbol reading, DW_AT_type missing from DW_TAG_subrange_type.
>> #1  0x003a8504 in x264_encoder_encode (h=0x8ab6c0, pp_nal=0x8ab6c0,
>>    pi_nal=0x10, pic_in=<value optimized out>, pic_out=0xbea439f8)
>>    at encoder/encoder.c:1579
>> #2  0x00283574 in X264_frame (ctx=<value optimized out>, buf=0x4026b008 "",
>>    bufsize=202752, data=<value optimized out>) at libavcodec/libx264.c:91
>> #3  0x0000d8f0 in avcodec_encode_video (avctx=0x8aafc0,
>>    buf=0xab0cc042 <Address 0xab0cc042 out of bounds>, buf_size=202752,
>>    pict=0x8dfba0) at libavcodec/utils.c:495
>> #4  0x0000955c in H264_encode (obj_ptr=0xbea43a20, out_ptr=0x4026b008,
>>    in_ptr=0x40245008, len=202752) at h264.c:129
>> #5  0x00008c54 in main () at videncdec.c:82
>
> You are apparently using libavcodec from your own application.  Does
> the ffmpeg executable work?
>
>> (gdb) disas $pc-64 $pc+64
>> Dump of assembler code from 0x3f6230 to 0x3f62b0:
>> 0x003f6230 <x264_sps_write+2776>:    rsb    r3, r0, r1
>> 0x003f6234 <x264_sps_write+2780>:    str    r3, [r4, #16]
>> 0x003f6238 <x264_sps_write+2784>:    b    0x3f6668 <x264_sps_write+3856>
>> 0x003f623c <x264_sps_write+2788>:    rsb    r0, r1, r0
>> 0x003f6240 <x264_sps_write+2792>:    ldr    r2, [r4, #12]
>> 0x003f6244 <x264_sps_write+2796>:    lsl    r2, r2, r1
>> 0x003f6248 <x264_sps_write+2800>:    orr    r2, r2, r7, lsr r0
>> 0x003f624c <x264_sps_write+2804>:    ldr    r12, [r4, #4]
>> 0x003f6250 <x264_sps_write+2808>:    lsl    r1, r2, #24
>> 0x003f6254 <x264_sps_write+2812>:    add    r1, r1, r2, lsr #24
>> 0x003f6258 <x264_sps_write+2816>:    lsl    r3, r2, #8
>> 0x003f625c <x264_sps_write+2820>:    and    r3, r3, #16711680    ; 0xff0000
>> 0x003f6260 <x264_sps_write+2824>:    add    r1, r1, r3
>> 0x003f6264 <x264_sps_write+2828>:    lsr    r2, r2, #8
>> 0x003f6268 <x264_sps_write+2832>:    and    r2, r2, #65280    ; 0xff00
>> 0x003f626c <x264_sps_write+2836>:    add    r1, r1, r2
>> 0x003f6270 <x264_sps_write+2840>:    str    r1, [r12]
>
> This is trying to write to an unaligned address, which the CPU does
> support unless disabled.  What does /proc/cpu/alignment contain?
>
> You might be passing avcodec_encode_video() a bad pointer for the
> output buffer.  I suggest double-checking it.

x264 has a known bug with misaligned reads/writes in some cases with
its bitstream writer.  There is a patch a month or two back on the
mailing list; I would apply it, but I will not do so unless someone
can confirm that it actually solves the problem.

Dark Shikari