Hi,
For me, kernels built including this commit
b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS)
results in kexec() failing to load the kernel:
kexec: Undefined symbol: __stack_chk_fail
kexec-bzImage64: Loading purgatory failed
Can be seen:
$ readelf -a arch/x86/purgatory/purgatory.ro | grep UND
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
Adding -ffreestanding or -fno-stack-protector to ccflags-y in
arch/x86/purgatory/Makefile
fixes the problem. Not sure which would be preferred.
On 9/3/19 8:50 AM, Andreas Smas wrote:
> Hi,
>
> For me, kernels built including this commit
> b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS)
>
> results in kexec() failing to load the kernel:
>
> kexec: Undefined symbol: __stack_chk_fail
> kexec-bzImage64: Loading purgatory failed
>
> Can be seen:
>
> $ readelf -a arch/x86/purgatory/purgatory.ro | grep UND
> 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> 51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
>
> Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
>
> Adding -ffreestanding or -fno-stack-protector to ccflags-y in
> arch/x86/purgatory/Makefile
> fixes the problem. Not sure which would be preferred.
>
Hi,
Do you have a kernel .config file that causes this?
I can't seem to reproduce it.
Thanks.
--
~Randy
* Randy Dunlap <[email protected]> wrote:
> On 9/3/19 8:50 AM, Andreas Smas wrote:
> > Hi,
> >
> > For me, kernels built including this commit
> > b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS)
> >
> > results in kexec() failing to load the kernel:
> >
> > kexec: Undefined symbol: __stack_chk_fail
> > kexec-bzImage64: Loading purgatory failed
> >
> > Can be seen:
> >
> > $ readelf -a arch/x86/purgatory/purgatory.ro | grep UND
> > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> > 51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
> >
> > Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
> >
> > Adding -ffreestanding or -fno-stack-protector to ccflags-y in
> > arch/x86/purgatory/Makefile
> > fixes the problem. Not sure which would be preferred.
> >
>
> Hi,
> Do you have a kernel .config file that causes this?
> I can't seem to reproduce it.
Does it go away with this fix in x86/urgent:
ca14c996afe7: ("x86/purgatory: Disable the stackleak GCC plugin for the purgatory")
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/urgent
?
Thanks,
Ingo
On 03/09/2019 17.50, Andreas Smas wrote:
> Hi,
>
> For me, kernels built including this commit
> b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS)
>
> results in kexec() failing to load the kernel:
>
> kexec: Undefined symbol: __stack_chk_fail
> kexec-bzImage64: Loading purgatory failed
>
> Can be seen:
>
> $ readelf -a arch/x86/purgatory/purgatory.ro | grep UND
> 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> 51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
>
> Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
Ubuntu's gcc has -fstack-protector enabled by default, so this happens
if one doesn't pass -fno-stack-protector (which I guess is implied by
-ffreestanding) explicitly.
> Adding -ffreestanding or -fno-stack-protector to ccflags-y in
> arch/x86/purgatory/Makefile
> fixes the problem. Not sure which would be preferred.
Probably -fno-stack-protector, guarded by
CONFIG_CC_HAS_STACKPROTECTOR_NONE (because not all gccs understand
-fno-stack-protector), so
ifdef CONFIG_CC_HAS_STACKPROTECTOR_NONE
ccflags-y += -fno-stack-protector
endif
Rasmus
On Sat, Sep 28, 2019 at 12:41:29PM +0000, Ingo Molnar wrote:
>
> * Randy Dunlap <[email protected]> wrote:
>
> > On 9/3/19 8:50 AM, Andreas Smas wrote:
> > > Hi,
> > >
> > > For me, kernels built including this commit
> > > b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS)
> > >
> > > results in kexec() failing to load the kernel:
> > >
> > > kexec: Undefined symbol: __stack_chk_fail
> > > kexec-bzImage64: Loading purgatory failed
> > >
> > > Can be seen:
> > >
> > > $ readelf -a arch/x86/purgatory/purgatory.ro | grep UND
> > > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> > > 51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
> > >
> > > Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
> > >
> > > Adding -ffreestanding or -fno-stack-protector to ccflags-y in
> > > arch/x86/purgatory/Makefile
> > > fixes the problem. Not sure which would be preferred.
> > >
> >
> > Hi,
> > Do you have a kernel .config file that causes this?
> > I can't seem to reproduce it.
>
> Does it go away with this fix in x86/urgent:
>
> ca14c996afe7: ("x86/purgatory: Disable the stackleak GCC plugin for the purgatory")
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/urgent
>
> ?
>
> Thanks,
>
> Ing
This one was fixed by [1] e16c2983fba0f ("x86/purgatory: Change compiler
flags from -mcmodel=kernel to -mcmodel=large to fix kexec relocation
errors") from Steve Wahl, which in addition to changing mcmodel also
added back -ffreestanding (and -fno-zero-initialized-in-bss). It was
merged on the 12th. The stackleak one is a different undefined symbol
error.
[1] https://marc.info/?l=git-commits-head&m=156829711224800
* Arvind Sankar <[email protected]> wrote:
> On Sat, Sep 28, 2019 at 12:41:29PM +0000, Ingo Molnar wrote:
> >
> > * Randy Dunlap <[email protected]> wrote:
> >
> > > On 9/3/19 8:50 AM, Andreas Smas wrote:
> > > > Hi,
> > > >
> > > > For me, kernels built including this commit
> > > > b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS)
> > > >
> > > > results in kexec() failing to load the kernel:
> > > >
> > > > kexec: Undefined symbol: __stack_chk_fail
> > > > kexec-bzImage64: Loading purgatory failed
> > > >
> > > > Can be seen:
> > > >
> > > > $ readelf -a arch/x86/purgatory/purgatory.ro | grep UND
> > > > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> > > > 51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
> > > >
> > > > Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
> > > >
> > > > Adding -ffreestanding or -fno-stack-protector to ccflags-y in
> > > > arch/x86/purgatory/Makefile
> > > > fixes the problem. Not sure which would be preferred.
> > > >
> > >
> > > Hi,
> > > Do you have a kernel .config file that causes this?
> > > I can't seem to reproduce it.
> >
> > Does it go away with this fix in x86/urgent:
> >
> > ca14c996afe7: ("x86/purgatory: Disable the stackleak GCC plugin for the purgatory")
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/urgent
> >
> > ?
> >
> > Thanks,
> >
> > Ing
> This one was fixed by [1] e16c2983fba0f ("x86/purgatory: Change compiler
> flags from -mcmodel=kernel to -mcmodel=large to fix kexec relocation
> errors") from Steve Wahl, which in addition to changing mcmodel also
> added back -ffreestanding (and -fno-zero-initialized-in-bss). It was
> merged on the 12th. The stackleak one is a different undefined symbol
> error.
>
> [1] https://marc.info/?l=git-commits-head&m=156829711224800
Great, so all known kexec bugs should be fixed for now in Linus's latest
kernel, right?
Thanks,
Ingo