Re: Another SIGFPE in display code, now in cirrus

[Michael Tokarev <mjt@tls.msk.ru>]

07.05.2010 00:07, Michael Tokarev wrote:
> There was a bug recently fixed in vnc code.  Apparently
> there's something similar in the cirrus emulation as well.
> Here it triggers _always_ (including old versions of kvm)
> when running windows NT and hitting "test" button in its
> display resolution dialog. Here's what gdb is to say:
>
> Program received signal SIGFPE, Arithmetic exception.
> [Switching to Thread 0xf76cab70 (LWP 580)]
> 0x080c5e45 in cirrus_do_copy (s=0x86134dc, dst=960000, src=0, w=2, h=9)
> at hw/cirrus_vga.c:687
> 687 sx = (src % ABS(s->cirrus_blt_srcpitch)) / depth;
> (gdb) p s->cirrus_blt_srcpitch
> $2 = 0
[]
> This qemu-kvm-0.12.3 - actually a debian package of it,
> but there's no patches relevant to video applied.

I just tried current qemu-kvm/master, it crashes at exactly
the same place:

Program received signal SIGFPE, Arithmetic exception.
[Switching to Thread 0xf79dfb70 (LWP 10840)]
0x0821b4ca in cirrus_do_copy (s=0x85dc7ac)
     at hw/cirrus_vga.c:687
687	    sx = (src % ABS(s->cirrus_blt_srcpitch)) / depth;

(gdb) bt
#0  0x0821b4ca in cirrus_do_copy (s=0x85dc7ac) at hw/cirrus_vga.c:687
#1  cirrus_bitblt_videotovideo_copy (s=0x85dc7ac) at hw/cirrus_vga.c:748
#2  cirrus_bitblt_videotovideo (s=0x85dc7ac) at hw/cirrus_vga.c:870
#3  cirrus_bitblt_start (s=0x85dc7ac) at hw/cirrus_vga.c:1011
#4  0x0821d009 in cirrus_vga_mem_writel (opaque=0x85dc7ac, addr=98320,
     val=960000) at hw/cirrus_vga.c:2120
#5  0x0811d147 in cpu_physical_memory_rw (addr=753680, buf=0xf7fdc390 "",
     len=4, is_write=1) at exec.c:3475
#6  0x0807b462 in cpu_physical_memory_write () at cpu-common.h:67
#7  kvm_flush_coalesced_mmio_buffer () at kvm-all.c:808
#8  0x0807cc2e in kvm_run (env=0x84c4650) at qemu-kvm.c:575
#9  0x0807d10c in kvm_cpu_exec (env=0x84c4650) at qemu-kvm.c:1192
#10 0x0807ec0a in kvm_main_loop_cpu (_env=0x84c4650) at qemu-kvm.c:1449
#11 ap_main_loop (_env=0x84c4650) at qemu-kvm.c:1495
#12 0xf7fad3d0 in start_thread () from /lib/libpthread.so.0
#13 0xf7cbf10e in clone () from /lib/libc.so.6

> Anything can be done with it?
>
> Thanks!

/mjt