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[ARM] 3102/1: ARM EABI: stack pointer must be 64-bit aligned after a CPU exception

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Patch from Nicolas Pitre

The ARM EABI says that the stack pointer has to be 64-bit aligned for
reasons already mentioned in patch #3101 when calling C functions.

We therefore must verify and adjust sp accordingly when taking an
exception from kernel mode since sp might not necessarily be 64-bit
aligned if the exception occurs in the middle of a kernel function.

If the exception occurs while in user mode then no sp fixup is needed as
long as sizeof(struct pt_regs) as well as any additional syscall data
stack space remain multiples of 8.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nicolas Pitre 2006-01-14 16:18:08 +00:00 committed by Russell King
parent da2b1cd619
commit 2dede2d8e9
3 changed files with 23 additions and 3 deletions
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17
arch/arm/kernel/entry-armv.S
View File

@ -105,14 +105,24 @@ common_invalid:
/*
* SVC mode handlers
*/
#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5)
#define SPFIX(code...) code
#else
#define SPFIX(code...)
#endif
.macro svc_entry
sub sp, sp, #S_FRAME_SIZE
SPFIX( tst sp, #4 )
SPFIX( bicne sp, sp, #4 )
stmib sp, {r1 - r12}
ldmia r0, {r1 - r3}
add r5, sp, #S_SP @ here for interlock avoidance
mov r4, #-1 @ "" "" "" ""
add r0, sp, #S_FRAME_SIZE @ "" "" "" ""
SPFIX( addne r0, r0, #4 )
str r1, [sp] @ save the "real" r0 copied
@ from the exception stack
@ -303,7 +313,14 @@ __pabt_svc:
/*
* User mode handlers
*
* EABI note: sp_svc is always 64-bit aligned here, so should S_FRAME_SIZE
*/
#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5) && (S_FRAME_SIZE & 7)
#error "sizeof(struct pt_regs) must be a multiple of 8"
#endif
.macro usr_entry
sub sp, sp, #S_FRAME_SIZE
stmib sp, {r1 - r12}

1
arch/arm/kernel/entry-header.S
View File

@ -19,6 +19,7 @@
@
@ Most of the stack format comes from struct pt_regs, but with
@ the addition of 8 bytes for storing syscall args 5 and 6.
@ This _must_ remain a multiple of 8 for EABI.
@
#define S_OFF 8

8
include/asm-arm/ptrace.h
View File

@ -60,9 +60,11 @@
#ifndef __ASSEMBLY__
/* this struct defines the way the registers are stored on the
stack during a system call. */
/*
* This struct defines the way the registers are stored on the
* stack during a system call. Note that sizeof(struct pt_regs)
* has to be a multiple of 8.
*/
struct pt_regs {
long uregs[18];
};