Date: Mon, 7 Dec 2015 22:10:51 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: jhb@freebsd.org Cc: freebsd-current@freebsd.org Subject: Re: panic: sbuf_vprintf called with a NULL sbuf pointer Message-ID: <201512080610.tB86Apx0000899@gw.catspoiler.org> In-Reply-To: <483094235.OWQWKtkdYD@ralph.baldwin.cx>
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On 2 Dec, John Baldwin wrote:
> On Wednesday, December 02, 2015 01:25:56 PM Don Lewis wrote:
>> > If you want to look at this further, try going to frame 16 and dissassembling the
>> > instructions before the call to see if you can spot which register the first
>> > parameter (saved in %rdi IIRC) comes from.
>>
>> Dump of assembler code for function sbuf_printf:
>> 0xffffffff80a673e0 <+0>: push %rbp
>> 0xffffffff80a673e1 <+1>: mov %rsp,%rbp
>> 0xffffffff80a673e4 <+4>: push %r14
>> 0xffffffff80a673e6 <+6>: push %rbx
>> 0xffffffff80a673e7 <+7>: sub $0x50,%rsp
>> 0xffffffff80a673eb <+11>: mov %rsi,%r14
>> 0xffffffff80a673ee <+14>: mov %rdi,%rbx
>> 0xffffffff80a673f1 <+17>: mov %r9,-0x38(%rbp)
>> 0xffffffff80a673f5 <+21>: mov %r8,-0x40(%rbp)
>> 0xffffffff80a673f9 <+25>: mov %rcx,-0x48(%rbp)
>> 0xffffffff80a673fd <+29>: mov %rdx,-0x50(%rbp)
>> 0xffffffff80a67401 <+33>: lea -0x60(%rbp),%rax
>> 0xffffffff80a67405 <+37>: mov %rax,-0x20(%rbp)
>> 0xffffffff80a67409 <+41>: lea 0x10(%rbp),%rax
>> 0xffffffff80a6740d <+45>: mov %rax,-0x28(%rbp)
>> 0xffffffff80a67411 <+49>: movl $0x30,-0x2c(%rbp)
>> 0xffffffff80a67418 <+56>: movl $0x10,-0x30(%rbp)
>> 0xffffffff80a6741f <+63>: mov $0xffffffff8137bdf8,%rdi
>> 0xffffffff80a67426 <+70>: mov %rbx,%rsi
>> 0xffffffff80a67429 <+73>: callq 0xffffffff80a66c00 <_assert_sbuf_integrity>
>>
>>
>> 0xffffffff80a237b9 <+825>: jmpq 0xffffffff80a236fd <sigexit+637>
>> 0xffffffff80a237be <+830>: mov $0xffffffff80fd8ad3,%rsi
>> 0xffffffff80a237c5 <+837>: xor %eax,%eax
>> 0xffffffff80a237c7 <+839>: mov %r12,%rdi
>> 0xffffffff80a237ca <+842>: mov -0x228(%rbp),%rdx
>> 0xffffffff80a237d1 <+849>: callq 0xffffffff80a673e0 <sbuf_printf>
>> => 0xffffffff80a237d6 <+854>: inc %r14d
>> 0xffffffff80a237d9 <+857>: jmpq 0xffffffff80a236fd <sigexit+637>
>
> So maybe try 'p $r12' in the corefile_open() frame.
#17 0xffffffff80a237d6 in corefile_open (compress=0, comm=<optimized out>,
uid=<optimized out>, pid=<optimized out>, td=<optimized out>,
vpp=<optimized out>, namep=<optimized out>)
at /usr/src/sys/kern/kern_sig.c:3188
3188 sbuf_printf(&sb, "%s", comm);
(kgdb) p $r12
$1 = 0
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