Call to mmap in ALSA lib 1.0.13 fails in src/pcm/pcm_mmap.c line 367

[David Cullen <david.cullen@teligy.com>]

Dear Folks,

I am trying to get ALSA version 1.0.13 working on an AMCC PowerPC
PPC405EP Taihu board with a Sound Blaster Live! 24-bit 7.1 PCI card.
 I am using a patched 2.6.13 kernel that comes with the board.  I
built the kernel with the sound core built in and I used the
cross-compiler tools to build the ALSA driver, library, and utils.
When I run "speaker-test", it crashes in the ALSA library.  The
problem is that the call to mmap in

   alsa-lib-1.0.13/src/pcm/pcm_mmap.c line 367

which looks like

   ptr = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_FILE|MAP_SHARED,
i->u.mmap.fd, i->u.mmap.offset);

returns a pointer that appears to be valid (0x3001E000) but causes a
kernel OOPS when accessed.

Previous calls to mmap in pcm_hw.c on lines 822 and 854 both
succeed, and the pointers returned can be successfully accessed, but
they use the status and control offsets as parameters to mmap.

I haved traced the problem on the target into the ALSA library using
gdb and into the kernel using kgdb and everything looks like it
works properly.  If I disable the semaphore acquisition in do_mmap2,
I can print the contents of the address in kgdb using

   (gdb) print ((char *)vma->vm_start)[0]

after the call to vm_link in do_mmap_pgoff.  However, the board
locks up after the print command.

Anyone have any experience with this type of problem on PowerPC systems?

-- 
Thank you,
David Cullen
Teligy

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