Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 2dede2d8 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
Browse files

[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: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent da2b1cd6

arch/arm/kernel/entry-armv.S

+17 −0
Original line number Diff line number Diff line
@@ -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}

arch/arm/kernel/entry-header.S

+1 −0
Original line number Diff line number Diff line
@@ -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

include/asm-arm/ptrace.h

+5 −3
Original line number Diff line number Diff line
@@ -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];

};