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[Xen-devel] Re: [PATCH] xen: Disable stack protector for irq helper

On Sun, Oct 04, 2009 at 04:06:13PM -0700, Jeremy Fitzhardinge wrote:
> On 10/04/09 11:30, Bastian Blank wrote:
> > The stack protector needs additional registers on x86_32, which are not
> > saved in calls to the small paravirt interrupt handlers. This leads to
> > early crashes as registers are overwritten and not saved by the caller
> > as instructed.
> Thanks for the patch, but I don't think its quite right.  
> PV_CALLEE_SAVE_REGS_THUNK() is responsible for generating a wrapper for
> the functions to save/restore all the appropriate registers.  If it is
> failing to do so, then the correct fix is to update

Well, I did not understand this part of the code, but you seem right. So
lets try the following. I have not yet run tested it.

Save all caller-saved registers on x86_32 for the paravirt callee saved

Signed-off-by: Bastian Blank <waldi@xxxxxxxxxx>

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index e19ffe3..e4272f3 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -793,8 +793,8 @@ static __always_inline void __raw_spin_unlock(struct 
raw_spinlock *lock)
 #define PV_RESTORE_REGS "popl %edx; popl %ecx;"
 /* save and restore all caller-save registers, except return value */
-#define PV_SAVE_ALL_CALLER_REGS                "pushl %ecx;"
-#define PV_RESTORE_ALL_CALLER_REGS     "popl  %ecx;"
 #define PV_FLAGS_ARG "0"
In the strict scientific sense we all feed on death -- even vegetarians.
                -- Spock, "Wolf in the Fold", stardate 3615.4

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