[Qemu-devel] Using gdb to debug early kernel boot?

[Rob Landley]

I'm trying to use gdb -s to debug the early boot of the sh4 kernel, but it's 
not liking me.

It does this:

> qemu-system-sh4 -s -S -M r2d -kernel arch/sh/boot/zImage
... wait for gdb ...
> qemu: fatal: Trying to execute code outside RAM or ROM at 0x88800058
>
> pc=0x88800058 sr=0x400000f0 pr=0x00000000 fpscr=0x00040001
> r0=0x88800058 r1=0xabffffe0 r2=0xdc800000 r3=0x88800000
> r4=0x410ed11e r5=0xd211c711 r6=0x89253020 r7=0xd0193208
> r8=0x2019e1e0 r9=0x6103d30f r10=0x64123128 r11=0x56125511
> r12=0x00000000 r13=0x00000000 r14=0x00000000 r15=0x00000000
> r16=0x00000000 r17=0x400000f0 r18=0x00000000 r19=0x00000000
> r20=0x00000000 r21=0x00000000 r22=0x00000000 r23=0x00000000
> Aborted (core dumped)

(Which is the same behavior without -s -S).  Over in the gdb session, I run 
gdb vmlinux and then:

> (gdb) target remote localhost:1234
> Remote debugging using localhost:1234
> warning: shared library handler failed to enable breakpoint
> 0x00000000 in ?? ()
> (gdb) c
> Continuing.
> Watchdog has expired.  Target detached.
> (gdb)

At which point the qemu instance in the other window has crashed.

Am I doing it wrong?

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.