Re: remote kernel gdb stack frames corrupted after breakpoint or step

    I have committed this  (after getting hit by the problem)


Stephan Uphoff wrote:

>I wrote a patch that should fix the problem for i386.
>
>	http://www.freebsd.org/cgi/query-pr.cgi?pr=71715
>
>Stephan
>
>On Wed, 2004-09-15 at 17:52, Andrew Gallatin wrote:
>  
>
>>Kip McAtee writes:
>> > Greetings-
>> >
>> > I'm building on 5.3-BETA4 (and 6.0 current)
>> > with gdb (and kgdb) 6.1.1.
>> >
>> > I can get into the remote kernel debugger with
>> > sysctl debug.kdb.enter=1
>> >
>> > I can set a breakpoint and continue.
>> > When it hits the breakpoint I get:
>> >
>> > Breakpoint 2, wakeup (ident=0xc0c0f9e8) at ../../../kern/kern_synch.c:253
>> > 253             sleepq_broadcast(ident, SLEEPQ_MSLEEP, -1);
>> > (kgdb) c
>> > Continuing.
>> >
>> > Program received signal SIGSEGV, Segmentation fault.
>> >
>> > Looking at the backtrace implies that the stack frames
>> > are not displayed correctly. I'm setting:
>> >
>>
>>FWIW, I see the same thing when continuing from breakpoints in
>>RELENG_5 via ddb.  I've appended a log from my serial console.
>>
>>Interestingly, dropping into the debugger via break on console works
>>like a charm, its only inserted breakpoints which don't work.
>>I think this started happening after the ddb->kdb conversion.
>>
>>Drew
>>
>>[send halt on serial console]
>>db> break sched_switch
>>db> c
>>[thread 100004]
>>Stopped at      sched_switch+0x1:       movl    %esp,%ebp
>>db> tr
>>sched_switch(1,0,0,0,0) at sched_switch+0x1
>>idle_proc(0,e3f78d48,10e90,10e98,10ea0) at idle_proc+0x143
>>fork_exit(c04fa329,0,e3f78d48) at fork_exit+0x80
>>fork_trampoline() at fork_trampoline+0x8
>>--- trap 0x1, eip = 0, esp = 0xe3f78d7c, ebp = 0 ---
>>db> c
>>
>>
>>kernel trap 12 with interrupts disabled
>>
>>
>>Fatal trap 12: page fault while in kernel mode
>>cpuid = 0; apic id = 00
>>fault virtual address   = 0x0
>>fault code              = supervisor read, page not present
>>instruction pointer     = 0x8:0xc0527256
>>stack pointer           = 0x10:0xe3f78c8c
>>frame pointer           = 0x10:0xe3f78c9c
>>code segment            = base 0x0, limit 0xfffff, type 0x1b
>>                        = DPL 0, pres 1, def32 1, gran 1
>>processor eflags        = resume, IOPL = 0
>>current process         = 12 (idle: cpu0)
>>[thread 100004]
>>Stopped at      sched_switch+0xe:       movl    0(%ebx),%edx
>>db> tr
>>sched_switch(0,10,44096318,47c326eb,ffc00014) at sched_switch+0xe
>>end(74c085d0,b816,a3640000,c,89d0558b) at 0xc1562640
>>db> call cpu_reset
>>cpu_reset called on cpu#0
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>>    
>>
>
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