Re: linux 2.6.27 kernel panic on x86 - please revert commit3a85e770aa77e4f1a4096275c97b64c10cd7323e

[Ingo Molnar]

* Jeff Chua <jeff.chua.linux@xxxxxxxxx> wrote:

> On Wed, Oct 15, 2008 at 7:23 PM, Ingo Molnar <mingo@xxxxxxx> wrote:
> >
> > * Jeff Chua <jeff.chua.linux@xxxxxxxxx> wrote:
> >
> >> Commit 3a85e770aa77e4f1a4096275c97b64c10cd7323e broke linux boot on
> >> x86 resulting in kernel panic. Here's the console output ...
> >>
> >> Net: Registered protocol family 17
> >> Using IPI No-Shortcut mode
> >> RAMDISK: Compressed image found at block 0
> >> VFS: Mounted root (ext2 filesystem (readonly).
> >> Freeing unsued kernel memory: 312k freed
> >> init[1]: segfault at ffffe01c up b7f0dc28 sp bfc26628 error 5 in ld-2.7.90.so[b7f0b000+1c000]
> >> Kernel panic - not syncing: Attempted to kill init!
> >
> > hm, ffffe01c is weird - VDSO on some ancient distro perhaps? Do you have
> > CONFIG_COMPAT_VDSO=y enabled?
> >
> > if you have CONFIG_COMPAT_VDSO=y enabled but the read access still
> > faults, then the question is, why is ffffe000 not mapped properly? The
> > logic in arch/x86/vdso/vdso32-setup.c and map_compat_vdso() /
> > arch_setup_additional_pages() seems correct and should result in the
> > VDSO being mapped as user-readable.
> 
> Didn't realized that CONFIG_COMPAT_VDSO=y could cause this problem. I 
> had this set long time ago before upgrading to glibc-2.7
> 
> Unsetting CONFIG_COMPAT_VDSO solves the issue.
> 
> Thanks for your help, and sorry for the fault alarm. Did take a while 
> to trace it down to the commit.

hm, setting the option should not break new glibc so this is a 
regression and we've still got a bug to fix.

	Ingo
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