GNU gdb 4.17
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This GDB was configured as “–host=i486-pc-netbsd –target=i386-linux-gnuaout”…
Setting up the environment for debugging gdb.
Breakpoint 1 at 0x94a4: file panic.c, line 18.
Breakpoint 2 at 0x667b: file init/main.c, line 110.
tcp_open ! localhost:1234
0xfff0 in sys_unlink () at memory.c:430
430 }
(top-gdb)c
Continuing.

Program received signal SIGINT, Interrupt.
panic (s=0x1dd6c “”) at panic.c:23
23 for(;;);
(top-gdb)bt
#0 panic (s=0x1dd6c “”) at panic.c:23
#1 0xd9b3 in mount_root () at memory.c:430
#2 0x12f39 in sys_setup (BIOS=0x1ab38) at hd.c:157
#3 0x7477 in system_call () at sched.c:412
#4 0x1000000 in ?? ()
(top-gdb)

But after a LOT of struggling it certainly looks about right.

Linux 0.11 kernel panic on mounting root

I then went ahead and built GDB 8.0.1, and it’s incredibly slow, and I guess not too compatible with Qemu 0.9 (I had issues with newer builds though) but it does break.

(top-gdb)target remote localhost:1234
Remote debugging using localhost:1234
0x0000fff0 in sys_unlink () at memory.c:83
83 }
(top-gdb)i b
Num Type Disp Enb Address What
1 breakpoint keep y 0x000094a4 in panic at panic.c:18
2 breakpoint keep y 0x000094a4 in panic at panic.c:18
silent
return
(top-gdb)c
Continuing.

Breakpoint 1, panic (s=0xd8cf <sys_mount+227>) at panic.c:18
18 printk(“Kernel panic: %s\n\r”,s);
Reply contains invalid hex digit 79
(top-gdb)i s
Reply contains invalid hex digit 79
(top-gdb)bt
#0 0x0000d9b3 in mount_root () at memory.c:83
#1 0x0001ab60 in hd_info ()
#2 0x00000000 in ?? ()
(top-gdb)i r
eax 0x0 0
ecx 0x51 81
edx 0x1fb4c 129868
ebx 0x0 0
esp 0xffff94 0xffff94
ebp 0xffffa8 0xffffa8
esi 0x1ab60 109408
edi 0x0 0
eip 0xd9b3 0xd9b3 <mount_root+139>
eflags 0x246 [ PF ZF IF ]
cs 0x8 8
ss 0x10 16
ds 0x10 16
es 0x10 16
fs 0x17 23
gs 0x17 23
(top-gdb)

And while it more or less runs there is some issues using the GDB stub from Qemu 0.9.0, although I had a world of pain with newer versions.  And I’ve never done the kernel debug thing before so this is all new to me.

And I guess it goes as no surprise that with GDB 8, they have a.out Linux tagged as obsolete and to be removed.  I guess I need to try a GDB that was current to Qemu 0.90 so it may not have so many packet overruns and unexpected results…