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From:   Arvind Sankar <nivedita@alum.mit.edu>
Date:   Sat, 28 Sep 2019 17:14:55 -0400
To:     Ingo Molnar <mingo@kernel.org>
Cc:     linux-kernel@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
        Andreas Smas <andreas@lonelycoder.com>
Subject: Re: x86/purgatory: undefined symbol __stack_chk_fail
Message-ID: <20190928211453.GA2300554@rani.riverdale.lan>
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On Sat, Sep 28, 2019 at 12:41:29PM +0000, Ingo Molnar wrote:
> 
> * Randy Dunlap <rdunlap@infradead.org> 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