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Date: Thu, 1 Oct 2015 08:29:50 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: minipli@ld-linux.so
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
        Michal Marek <mmarek@suse.cz>, Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>, Pedro Alves <palves@redhat.com>,
        Namhyung Kim <namhyung@gmail.com>,
        Bernd Petrovitsch <bernd@petrovitsch.priv.at>,
        Chris J Arges <chris.j.arges@canonical.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v13 13/23] x86/asm/crypto: Create stack frames in
 aesni-intel_asm.S
Message-ID: <20151001132950.GA4269@treble.redhat.com>
References: <cover.1442935712.git.jpoimboe@redhat.com>
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 <20151001061026.GA20908@ld-linux.so>
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On Thu, Oct 01, 2015 at 08:10:26AM +0200, minipli@ld-linux.so wrote:
> On Tue, Sep 22, 2015 at 10:47:04AM -0500, Josh Poimboeuf wrote:
> > aesni-intel_asm.S has several callable non-leaf functions which don't
> > honor CONFIG_FRAME_POINTER, which can result in bad stack traces.
> > 
> > Create stack frames for them when CONFIG_FRAME_POINTER is enabled.
> > 
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
> > Cc: David S. Miller <davem@davemloft.net>
> > ---
> >  arch/x86/crypto/aesni-intel_asm.S | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/arch/x86/crypto/aesni-intel_asm.S b/arch/x86/crypto/aesni-intel_asm.S
> > index 6bd2c6c..289ef12 100644
> > --- a/arch/x86/crypto/aesni-intel_asm.S
> > +++ b/arch/x86/crypto/aesni-intel_asm.S
> > @@ -31,6 +31,7 @@
> >  
> >  #include <linux/linkage.h>
> >  #include <asm/inst.h>
> > +#include <asm/frame.h>
> >  
> >  /*
> >   * The following macros are used to move an (un)aligned 16 byte value to/from
> > @@ -1800,6 +1801,7 @@ ENDPROC(_key_expansion_256b)
> >   *                   unsigned int key_len)
> >   */
> 
> >  ENTRY(aesni_set_key)
> > +	FRAME_BEGIN
> >  #ifndef __x86_64__
> >  	pushl KEYP
> >  	movl 8(%esp), KEYP		# ctx
> 
> This will break 32 bit builds using the aesni-intel.ko module. You need
> to adjust the esp-based offsets for the non-x86_64 case, as FRAME_BEGIN
> may do another push.
> 
> How about adding a FRAME_OFFSET() macro to <asm/frame.h> to wrap the
> offsets?:
> 
> #ifdef CONFIG_FRAME_POINTER
> # define FRAME_OFFSET(x)	((x) + (BITS_PER_LONG / 8))
> #else
> # define FRAME_OFFSET(x)	(x)
> #endif
> 
> And using them like this:
> 
> 	movl FRAME_OFFSET(8)(%esp), KEYP		# ctx

Ah, right.  The 32-bit ABI passes arguments on the stack instead of via
registers.

For now, I'm inclined to just make FRAME_BEGIN and FRAME_END do nothing
on 32-bit.  We're only doing stack validation on x86_64 and I don't know
if anybody cares about frame pointers on 32-bit at this point.

-- 
Josh