[ARM] 3102/1: ARM EABI: stack pointer must be 64-bit aligned after a CPU exception
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>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index fb8e7f4..874e6bb 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -105,14 +105,24 @@
/*
* 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 @@
/*
* 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}
