Re: kgdb missing stack frames

On Sun, 18 May 2003, Ian Dowse wrote:

> Support for decoding i386 trap frames in kgdb appears to have been
> lost by revision 1.3 of contrib/gdb/gdb/config/i386/tm-fbsd.h, since
> FRAME_SAVED_PC() is defined there in terms of i386bsd_frame_saved_pc(),
> so fbsd_kern_frame_saved_pc() in gnu/usr.bin/binutils/gdb/kvm-fbsd.c
> never gets called. A simple way to see this is to run
>
> 	gdb -k kernel.debug /dev/mem
>
> and get a backtrace from the idle process:
>
> 	(kgdb) proc 11
> 	(kgdb) bt
> 	#0  mi_switch () at ../../../kern/kern_synch.c:530
> 	#1  0xc01edb92 in ithread_schedule (ithread=0xc1898280, do_switch=1)
> 	    at ../../../kern/kern_intr.c:402
> 	#2  0xc034ad43 in sched_ithd (cookie=0xc1894d80)
> 	    at ../../../i386/isa/ithread.c:77
> 	#3  0xc03380cc in Xintr14 () at {standard input}:382
> 	#4  0xc01ed16c in idle_proc (dummy=0x0) at ../../../kern/kern_idle.c:114
> 	#5  0xc01ecea0 in fork_exit (callout=0xc01ed130 <idle_proc>, arg=0x0,
> 	    frame=0x0) at ../../../kern/kern_fork.c:792
>
> This is what it should look like:
>
> 	(kgdb) proc 11
> 	(kgdb) bt
> 	#0  mi_switch () at ../../../kern/kern_synch.c:530
> 	#1  0xc01edb92 in ithread_schedule (ithread=0xc1898280, do_switch=1)
> 	    at ../../../kern/kern_intr.c:402
> 	#2  0xc034ad43 in sched_ithd (cookie=0xc1898280)
> 	    at ../../../i386/isa/ithread.c:77
> 	#3  0xc033e242 in cpu_idle () at ../../../i386/i386/machdep.c:1074
> 	#4  0xc01ed16c in idle_proc (dummy=0x0) at ../../../kern/kern_idle.c:114
> 	#5  0xc01ecea0 in fork_exit (callout=0xc01ed130 <idle_proc>, arg=0x0,
> 	    frame=0x0) at ../../../kern/kern_fork.c:792
>
> i.e, the cpu_idle() frame now appears instead of Xintr14().

This is no better, since it loses Xintr14()'s frame instead of cpu_idle()'s
frame.

OTOH, it wouldnt hurt in most cases to lose all the frames below
cpu_idle() and above idle_proc(), since they are not really associated
with the process.

Bruce