Bug 500096

Created attachment 343308 [details]
dmesg log

You've got a series of NULL bytes with just 4 bytes of non-null insn at the faulting address:

00000000 <.text>:
   0:	9a ad 7e f0 00 00 00 	lcall  $0x0,$0xf07ead

But this is what's supposed to be there:

    3adc:       55                      push   %ebp
    3add:       89 e5                   mov    %esp,%ebp
    3adf:       57                      push   %edi
    3ae0:       56                      push   %esi
    3ae1:       53                      push   %ebx
    3ae2:       83 ec 08                sub    $0x8,%esp
    3ae5:       e8 fc ff ff ff          call   3ae6 <snd_pcm_info+0xa>
                        3ae6: R_386_PC32        mcount
    3aea:       b9 48 00 00 00          mov    $0x48,%ecx
    3aef:       89 45 ec                mov    %eax,-0x14(%ebp)

I'd guess something has gone wrong with the tracing code given the call to mcount at that address (the fault is actually at the place where the address of mcount sits.)

Hi Chuck,

Sure enough, there's an ftrace BUG() earlier in the dmesg:

ftrace failed to modify [<cfc19c37>] 0xcfc19c37
 actual: 00:48:ac:7e:f0

Has something like this been reported elsewhere?  Thanks.

The stack trace is unreliable because it seems the function prologue of snd_pcm_info() never ran. And it's consistent with snd_pcm_proc_info_read() having made a call directly to the faulting address instead of to the start of the called function. A full kernel dump might be the only way to gather more evidence at this point.

This bug appears to have been reported against 'rawhide' during the Fedora 11 development cycle.
Changing version to '11'.

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