Date: Mon, 23 Feb 2009 10:10:07 -0700 From: Scott Long <scottl@samsco.org> To: John Baldwin <jhb@freebsd.org> Cc: David Christensen <davidch@broadcom.com>, freebsd-current@freebsd.org Subject: Re: Hopefully Simple Question on Debugging Kernel Modules Message-ID: <49A2D86F.1000509@samsco.org> In-Reply-To: <200902231119.54925.jhb@freebsd.org> References: <5D267A3F22FD854F8F48B3D2B5238193394588D54D@IRVEXCHCCR01.corp.ad.broadcom.com> <200902231119.54925.jhb@freebsd.org>
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John Baldwin wrote: > On Friday 20 February 2009 6:40:56 pm David Christensen wrote: >> I'm sure this is a simple question but the answer is alluding my Google >> search capabilities. My driver is being loaded as a kernel module and >> is failing with the following error: >> >> Fatal trap 12: page fault while in kernel mode >> cpuid = 0; apic id = 00 >> fault virtual address = 0xfffffffe40abe9dc >> fault code = supervisor write data, page not present >> instruction pointer = 0x8:0xffffffff920b638f >> stack pointer = 0x10:0xffffffff9212bb10 >> frame pointer = 0x10:0xffffffff9212bbb0 >> code segment = base 0x0, limit 0xfffff, type 0x1b >> = DPL 0, pres 1, long 1, def32 0, gran 1 >> processor eflags = interrupt enabled, resume, IOPL = 0 >> current process = 12 (irq268: bce0) >> [thread pid 12 tid 100166 ] >> Stopped at bce_intr+0x8df: addl $0x1,0x2c854(%r12,%rax,4) >> db> >> >> I simply need to find the offending source line in my driver. Not sure >> how I've managed to get the driver running at all without this but it's >> time to do things the right way. I have KDB/DDB/GDB built into my >> -CURRENT kernel already. It'd be great to find the source line while in >> the kernel debugger but I'm also fine with rebooting the system to >> identify the line number. > > Just use gdb on bce.ko (built with debug symbols): > > gdb /path/to/if_bce.ko > (gdb) l *bce_intr+0x8df > > If you get a crashdump you can run kgdb on it and just walk up to the relevant > stack frame and use 'l' there to get a listing. > One thing that I've never figured out is how debugging symbols are handled in module builds these days. If I go to /sys/modules/bce and do 'make', it generates a .ko and explicitly strips it. I wind up having to re-run the link command by hand so I get symbols. What is the correct way to do this? Note that I'm not interested in answers that involve "go to /usr/src and run make buildkernel" =-) Scott
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