Daniel Jacobowitz <[EMAIL PROTECTED]> writes:
> It appears to work fairly well.
I can confirm that. I'm currently debugging a segmentation fault in
compiling one source file of firefox. Something that the current ARM
sysemu can do is e.g.
- boot debian/sid NFS root
- compile gcc far enough to produce a cc1plus with debug info
- run gdb inside emacs to debug cc1plus compiling a ff source file
- run cc1plus under gdb with a breakpoint with ignorecount
- be debugged with arm-linux-gdb
IMHO, thats quite impressive :-)
Might as well describe the thing I'm trying to debug. Dunno what the
exact problem is but it is repeatable. The complete test case is a bit
large, but the segfaulting code qestion looks like:
(gdb) disas $pc-16 $pc+16
Dump of assembler code from 0x31bdac to 0x31bdcc:
0x0031bdac <global_alloc+1016>: ldr r1, [r2, #28]
0x0031bdb0 <global_alloc+1020>: add r3, r3, r1
0x0031bdb4 <global_alloc+1024>: str r3, [r4, #8]
0x0031bdb8 <global_alloc+1028>: add r1, r4, #12 ; 0xc
0x0031bdbc <global_alloc+1032>: ldmia r1, {r1, lr}
0x0031bdc0 <global_alloc+1036>: ldr r3, [r0, #16]
0x0031bdc4 <global_alloc+1040>: ldr r2, [r3, #32]
0x0031bdc8 <global_alloc+1044>: add r1, r1, r2
End of assembler dump.
And the registers before SIGSEGV look like:
(gdb) info reg
r0 0x58ff48 5832520
r1 0x4205effc 1107685372
r2 0x41fc7320 1107063584
r3 0x0 0
r4 0x4205eff0 1107685360
r5 0x29e 670
r6 0x42059008 1107660808
r7 0x5d0ab0 6097584
r8 0x3ba8ea 3909866
r9 0x43d9e8 4446696
r10 0x1 1
r11 0x3ecd20 4115744
r12 0xc 12
sp 0xbef3b234 -1091325388
lr 0x2 2
pc 0x31bdbc 3259836
fps 0x1001010 16781328
cpsr 0x10 16
So it looks like we are about to load a couple of longs from
0x4205effc. But when I step:
(gdb) si
Program received signal SIGSEGV, Segmentation fault.
0x0031bdbc in global_alloc (file=0x0) at ../../src/gcc/global.c:490
Looks like the kernel somehow ends up thinking that we are loading
something from zero. Hmm.. the value being loaded to r1 is zero. So
could this be related to crossing a page boundary in the middle of an
instruction? But anyway - I'll try to debug this further..
--
http://www.iki.fi/~ananaza/
_______________________________________________
Qemu-devel mailing list
Qemu-devel@nongnu.org
http://lists.nongnu.org/mailman/listinfo/qemu-devel
