ARM1136: Align stack to 8 bytes

The ARM ABI requires that the stack be aligned to 8 bytes as it is noted in Procedure Call Standard for the ARM Architecture:
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042d/index.html

Unaligned SP also causes the problem with variable-length arrays allocation when VLA address becomes less than stack pointer during aligning of this address, so the further 'push' into the stack overwrites first 4 bytes of VLA.

Signed-off-by Vitaly Kuzmichev <[email protected]>

Signed-off-by George G. Davis <[email protected]>

---
 arch/arm/cpu/arm1136/start.S |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

(quoted diff) +0 -0

b/arch/arm/cpu/arm1136/start.S index 957f438..d0c5717 100644

arch/arm/cpu/arm1136/start.S +1 -0

@@ -185,6 +185,7 @@ stack_setup:
 #endif
 	sub	sp, r0, #12		/* leave 3 words for abort-stack    */
 #endif	/* CONFIG_PRELOADER */
+	bic	sp, sp, #7		/* 8-byte alignment                 */
 
 clear_bss:
 	ldr	r0, _bss_start		/* find start of bss segment	    */

Hi Vitaly,

the exact same problem applies to ARM1176. Maybe you could update your patch and add the same line to /arch/arm/cpu/arm1176/start.S. I am currently not working on an top-of-tree U-Boot, so it would be not so easy for me to create a separate patch for ARM1176.

Regards,
Martin

u-boot-bounces at lists.denx.de wrote on Tuesday, June 15, 2010 12:52 PM:

Quoted 27 lines

The ARM ABI requires that the stack be aligned to 8 bytes as it is noted in Procedure Call Standard for the ARM Architecture:
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042d/index.html

Unaligned SP also causes the problem with variable-length arrays allocation when VLA address becomes less than stack pointer during aligning of this address, so the further 'push' into the stack overwrites first 4 bytes of VLA.

Signed-off-by Vitaly Kuzmichev <[email protected]>

Signed-off-by George G. Davis <[email protected]>

---
 arch/arm/cpu/arm1136/start.S |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

(quoted diff) +0 -0

b/arch/arm/cpu/arm1136/start.S index 957f438..d0c5717 100644

arch/arm/cpu/arm1136/start.S +1 -0

@@ -185,6 +185,7 @@ stack_setup:
 #endif
 	sub	sp, r0, #12		/* leave 3 words for abort-stack    */
 #endif	/* CONFIG_PRELOADER */
+	bic	sp, sp, #7		/* 8-byte alignment                 */
 
 clear_bss:
 	ldr	r0, _bss_start		/* find start of bss segment	    */

80080030:       e281300f        add     r3, r1, #15     ; 0xf
80080034:       e2033f7e        and     r3, r3, #504    ; 0x1f8

80080038: e1a0500d mov r5, sp

8008003c: e04dd003 sub sp, sp, r3

80080040: e1a0300d mov r3, sp

80080044:       e1a0c1a3        lsr     ip, r3, #3
80080048:       e1a0218c        lsl     r2, ip, #3

The ARM ABI requires that the stack be aligned to 8 bytes as it is noted in Procedure Call Standard for the ARM Architecture:
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042d/index.html

Unaligned SP also causes the problem with variable-length arrays allocation when VLA address becomes less than stack pointer during aligning of this address, so the next 'push' in the stack overwrites first 4 bytes of VLA.

Signed-off-by Vitaly Kuzmichev <[email protected]>

The ARM ABI requires that the stack be aligned to 8 bytes as it is noted in Procedure Call Standard for the ARM Architecture:
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042d/index.html

Unaligned SP also causes the problem with variable-length arrays allocation when VLA address becomes less than stack pointer during aligning of this address, so the next 'push' in the stack overwrites first 4 bytes of VLA.

Signed-off-by Vitaly Kuzmichev <[email protected]>

---
 arch/arm/cpu/arm1136/start.S      |    1 +
 arch/arm/cpu/arm1176/start.S      |    1 +
 arch/arm/cpu/arm720t/start.S      |    1 +
 arch/arm/cpu/arm920t/start.S      |    1 +
 arch/arm/cpu/arm925t/start.S      |    1 +
 arch/arm/cpu/arm926ejs/start.S    |    2 +-
 arch/arm/cpu/arm946es/start.S     |    1 +
 arch/arm/cpu/arm_cortexa8/start.S |    2 +-
 arch/arm/cpu/arm_intcm/start.S    |    1 +
 arch/arm/cpu/ixp/start.S          |    1 +
 arch/arm/cpu/lh7a40x/start.S      |    1 +
 arch/arm/cpu/pxa/start.S          |    1 +
 arch/arm/cpu/s3c44b0/start.S      |    1 +
 arch/arm/cpu/sa1100/start.S       |    1 +
 14 files changed, 14 insertions(+), 2 deletions(-)

Dear Vitaly Kuzmichev,

Quoted 25 lines · In message <[email protected]> you wrote:

The ARM ABI requires that the stack be aligned to 8 bytes as it is noted in Procedure Call Standard for the ARM Architecture:
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042d/index.html

Unaligned SP also causes the problem with variable-length arrays allocation when VLA address becomes less than stack pointer during aligning of this address, so the next 'push' in the stack overwrites first 4 bytes of VLA.

Signed-off-by Vitaly Kuzmichev <[email protected]>

---

?arch/arm/cpu/arm1136/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/arm1176/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/arm720t/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/arm920t/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/arm925t/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/arm926ejs/start.S ? ?| ? ?2 +-
?arch/arm/cpu/arm946es/start.S ? ? | ? ?1 +
?arch/arm/cpu/arm_cortexa8/start.S | ? ?2 +-
?arch/arm/cpu/arm_intcm/start.S ? ?| ? ?1 +
?arch/arm/cpu/ixp/start.S ? ? ? ? ?| ? ?1 +
?arch/arm/cpu/lh7a40x/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/pxa/start.S ? ? ? ? ?| ? ?1 +
?arch/arm/cpu/s3c44b0/start.S ? ? ?| ? ?1 +
?arch/arm/cpu/sa1100/start.S ? ? ? | ? ?1 +

Quoted 1 line

?14 files changed, 14 insertions(+), 2 deletions(-)

This is a pretty intrusive patch as it affects all ARM architectures, but the change has been discussed here several times before, and the actual commit looks OK to me, too.

Tested on tx25(mx25), imx27lite(mx27), qong(mx31) and trab(s3c2400)

Tested-by Wolfgang Denk <[email protected]>

Applied to master (i. e. it will be included in -rc3, this release).

ARM custodians: please help testing this!