[Bug target/32264] gcc 4.2.0 compiled vanilla kernel 2.4.34.5 crashes when VIA C3 optimized -march=c3

["axel at freakout dot de" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #5 from axel at freakout dot de  2007-06-10 10:05 -------
Subject: Re:  gcc 4.2.0 compiled vanilla kernel
 2.4.34.5 crashes when VIA C3 optimized -march=c3

According to rguenth at gcc dot gnu dot org:
> 
> ------- Comment #4 from rguenth at gcc dot gnu dot org  2007-06-09 10:27 -------
> We need this reduced to a managable testcase that gcc miscompiles.
> 

Sorry - but kernel debugging in the early boot stage goes far
beyond my capabilities. I tried to gather as much information as
i can. The crash can be reproduced just with the kernel itself,
no modules involved.

I've added an archive with two dirs gcc-4.1.2 and gcc-4.2.0 - in
each dir is the compiled kernel vmlinux and the boot image
vmlinuz, with can be loaded by any bootloader (grub, lilo,
syslinux, loadlin, ...).  i also added the corresponding
System.map's.

The kernel were produced from identical (the same) source trees
with gcc 4.1.2 and gcc 4.2.0 on the same machine.  The gcc 4.1.2
compiled kernel boots until panic - no root fs - works ok.  The
gcc 4.2.0 kernel crashes with this output:

======================================================================
Kernel command line: BOOT_IMAGE=vmlinuz4.434
Initializing CPU#0
Detected 797.420 MHz processor.
Console: colour VGA+ 80x25
Unable to handle kernel paging request at virtual address
f000fec4
 printing eip:
c0295690
*pde = 00000000
Oops: 0002
CPU:    0
EIP:    0010:[<c0295690>]   Not tainted
EFLAGS: 00010017
eax: f00fec4    ebx: 00000000   ecx: 00000037   edx: 00000010
esi: 000994c1   edi: c0105000   ebp: 0008e000   esp: c0251fe4
ds: 0018   es: 0020   ss: 0018
Process swapper (pid: 0, stackpage=c0251000)
Stack: 00000020 c0252290 00000010 00000216 c0252630 c0295ae0
c0100191
Call Trace:

Code: 10 00 f3 a5 ea 19 00 00 90 bf f4 3f 8e d8 8e d0 3f a3 c1 8c
 <0>Kernel panic: Attempted to kill the idle task!
In idle task - not syncing
======================================================================

This output is also in the archive dir of gcc-4.2.0/crash.txt

The working kernel (produced from gcc-4.1.2) prints:
======================================================================
Calibrating delay loop... 1592.52 BogoMIPS
======================================================================
at the point where the gcc-4.2.0 produced kernel crashes with the
above messages.

Hope this helps.

Axel


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32264