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arm: Fix stack alignment during interrupt handling

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On a public interface, the stack pointer must be aligned on an 8-byte
boundary.  However, it may temporarily be only aligned on a 4-byte
boundary.  The interrupt handling code must ensure that the stack
pointer is properly aligned before it calls a function.  See also:

https://developer.arm.com/documentation/den0013/d/Interrupt-Handling/External-interrupt-requests/Nested-interrupt-handling

Update #4579.
This commit is contained in:
Sebastian Huber
2022-01-13 13:30:21 +01:00
parent 41a1903dd9
commit 84ba194477
1 changed files with 23 additions and 10 deletions
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33
cpukit/score/cpu/arm/arm_exc_interrupt.S
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@@ -7,7 +7,7 @@
*/
/*
* Copyright (c) 2009, 2016 embedded brains GmbH. All rights reserved.
* Copyright (c) 2009, 2022 embedded brains GmbH. All rights reserved.
*
* embedded brains GmbH
* Dornierstr. 4
@@ -34,6 +34,9 @@
#ifdef ARM_MULTILIB_ARCH_V4
#define STACK_POINTER_ADJUST r7
#define NON_VOLATILE_SCRATCH r9
#define EXCHANGE_LR r4
#define EXCHANGE_SPSR r5
#define EXCHANGE_CPSR r6
@@ -42,9 +45,7 @@
#define EXCHANGE_LIST {EXCHANGE_LR, EXCHANGE_SPSR, EXCHANGE_CPSR, EXCHANGE_INT_SP}
#define EXCHANGE_SIZE 16
#define NON_VOLATILE_SCRATCH r9
#define CONTEXT_LIST {r0, r1, r2, r3, EXCHANGE_LR, EXCHANGE_SPSR, r7, r12}
#define CONTEXT_LIST {r0, r1, r2, r3, EXCHANGE_LR, EXCHANGE_SPSR, NON_VOLATILE_SCRATCH, r12}
#define CONTEXT_SIZE 32
.arm
@@ -67,12 +68,21 @@ _ARMV4_Exception_interrupt:
/*
* Save context. We save the link register separately because it has
* to be restored in SVC mode. The other registers can be restored in
* INT mode. Ensure that stack remains 8 byte aligned. Use register
* necessary for the stack alignment for the stack pointer of the
* interrupted context.
* INT mode. Ensure that the size of the saved registers is an
* integral multiple of 8 bytes. Provide a non-volatile scratch
* register which may be used accross function calls.
*/
push CONTEXT_LIST
push {NON_VOLATILE_SCRATCH, lr}
push {STACK_POINTER_ADJUST, lr}
/*
* On a public interface, the stack pointer must be aligned on an
* 8-byte boundary. However, it may temporarily be only aligned on a
* 4-byte boundary. Make sure the stack pointer is aligned on an
* 8-byte boundary.
*/
and STACK_POINTER_ADJUST, sp, #0x4
sub sp, sp, STACK_POINTER_ADJUST
/* Get per-CPU control of current processor */
GET_SELF_CPU_CONTROL r0
@@ -202,8 +212,11 @@ _ARMV4_Exception_interrupt:
vmsr FPSCR, r2
#endif /* ARM_MULTILIB_VFP */
/* Restore NON_VOLATILE_SCRATCH register and link register */
pop {NON_VOLATILE_SCRATCH, lr}
/* Undo stack pointer adjustment */
add sp, sp, STACK_POINTER_ADJUST
/* Restore STACK_POINTER_ADJUST register and link register */
pop {STACK_POINTER_ADJUST, lr}
/*
* XXX: Remember and restore stack pointer. The data on the stack is