Re: [uml-devel] Am I doing something wrong with -skas0?

[Rob Landley <rob@landley.net>]

On Wednesday 13 July 2005 07:15, Jeff Dike wrote:
> On Tue, Jul 12, 2005 at 11:46:40PM -0500, Rob Landley wrote:
> > VFS: Mounted root (hostfs filesystem) readonly.
> > Kernel panic - not syncing: get_skas_faultinfo : failed to wait for
> > SIGUSR1/SIGTRAP, pid = 7944, n = 7944, errno = 0, status = 0xb
>
> A bunch of people are seeing this.  What's supposed to happen when the
> segfault hits is that it's supposed to continue into the segfault handler.
>
> The fact that it is terminating with SIGSEGV immediately after stopping
> with SIGSEGV means that the signal handler couldn't be delivered for some
> reason.
>
> Either the signal stack or handler aren't present, or the stack isn't
> writable.
>
> So, maybe the stubs aren't being set up properly.  Can you gdb the thing,
> put a breakpoint in get_skas_faultinfo, and look at /proc/<pid>/maps, where
> pid is the pid being ptraced?
>
> The last two pages, at 0x7fffe000 and 7ffff000 are the stubs.  The first
> should be mapped in from the temp VM file with permissions r-x, and the
> second should be anonymous with permissions rwx.
>
>     Jeff

It broke with SIGUSR1 in __kernel_vsyscall(), which I assume is close enough.  
(I typed "go" until it reached the end and it never broke in 
get_skas_faultinfo, but then my gdb is a bit shaky so I'm possibly doing 
something wrong.)

Here's the maps:

landley@driftwood:/proc/7972$ cat maps
08048000-08132000 rwxp 00000000 03:05 
2801050    /home/landley/linux-2.6.12.2/linux
08132000-08165000 rw-p 08132000 00:00 0
08800000-0a000000 rw-s 00800000 03:05 4922001    /tmp/vm_file-gYGr1Q (deleted)
b7eb7000-b7eb9000 rw-p b7eb7000 00:00 0
b7eb9000-b7fdb000 r-xp 00000000 03:05 
2371242    /lib/tls/i686/cmov/libc-2.3.2.so
b7fdb000-b7fe4000 rw-p 00121000 03:05 
2371242    /lib/tls/i686/cmov/libc-2.3.2.so
b7fe4000-b7fe6000 rw-p b7fe4000 00:00 0
b7fe6000-b7fe8000 r-xp 00000000 03:05 
2371260    /lib/tls/i686/cmov/libutil-2.3.2.so
b7fe8000-b7fe9000 rw-p 00001000 03:05 
2371260    /lib/tls/i686/cmov/libutil-2.3.2.so
b7fe9000-b7feb000 rw-p b7fe9000 00:00 0
b7feb000-b8000000 r-xp 00000000 03:05 2371080    /lib/ld-2.3.2.so
b8000000-b8001000 rw-p 00015000 03:05 2371080    /lib/ld-2.3.2.so
bffeb000-c0000000 rwxp bffeb000 00:00 0
ffffe000-fffff000 ---p 00000000 00:00 0

Rob


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