Re: kswapd0 oops -> debug information

Herbert Poetzl
2005-01-02T07:41:22Z

On Sat, Nov 27, 2004 at 05:21:21PM +0000, Nick Warne wrote:
> On Saturday 27 November 2004 17:01, Randy.Dunlap wrote:
>
> > kernel version?
>
> Heh. My great debug attempt, eh?
>
> kernel 2.6.9
>
> > .config file?
> > full oops message, with stack backtrace?
> > The stack backtrace could tell us who a bad caller is.
> > It can just be a caller's problem, not a bug in (this)
> > one isolated function.
>
> http://linicks.net/kdebug/
>
> > Did you read/check linux/REPORTING-BUGS ?
>
> Yes, but wanted to try and learn myself on what was going on, rather than push
> the onus onto other people.
>
> The book I have re the make /dir/file.s states that it will produce assembler
> with _line_ numbers to corresponding C code. That is where I got lost, as it
> doesn't.

hmm, sorry for the late reply, but better late
than not at all ...

if you do

make fs/file.s V=1

you'll see what make actually does to compile
the source code into assembler code ...

make -f scripts/Makefile.build obj=scripts/basic
make -f scripts/Makefile.build obj=scripts
make -f scripts/Makefile.build obj=fs fs/file.s
gcc -Wp,-MD,fs/.file.s.d -nostdinc -iwithprefix include -D__KERNEL__ -Iinclude -Wall -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -O2 -fomit-frame-pointer -g -pipe -msoft-float -mpreferred-stack-boundary=2 -march=i586 -Iinclude/asm-i386/mach-default -DKBUILD_BASENAME=file -DKBUILD_MODNAME=file -S -o fs/file.s fs/file.c

and if that final gcc command does include a -g
(which can be controlled by CONFIG_DEBUG_INFO, or
simply added by hand), then the output will contain
lines like this:

.loc 1 45 0
.loc 1 46 0

which reference the file and line number in the
source code. files are 'declared' with lines:

.file "file.c"
.file 1 "fs/file.c"
.file 2 "include/linux/posix_types.h"

so you can pretty easy find the code in the
source. a different, but sometimes easier approach
is to use 'addr2line' on the kernel binary (if it
was compiled with CONFIG_DEBUG_INFO) to get the
source line from a kernel address ...

addr2line -e vmlinux c0123456

HTH,
Herbert

> Thanks,
>
> Nick.
>
> --
> "When you're chewing on life's gristle,
> Don't grumble, Give a whistle..."
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