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ARM: 8451/1: v7-M: Set an early stack for __v7m_setup

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On ARM v7-M, when PROCINFO_INITFUNC (__v7m_setup) is called,
a stack is needed before calling the supervisor call (SVC),
which is used by the supervisor call to save the context.

Currently, __v7m_setup() prepares a temporary stack in the .text.init
section, which is is broken if the kernel is executing directly from
read-only memory.

In particular, this is the case for LPC43xx, which allows
to execute the kernel in-place from a serial flash through its SPIFI
controller.

This commit fixes the issue by seting an early stack to its usual location.

Also, __v7m_setup() is currently saving and restoring the previous
stack. That was bogus, because there's no stack previously set,
so this commit removes it.

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Ezequiel Garcia 2015-11-04 17:08:37 +01:00 committed by Russell King
parent 440ee365d3
commit a4124e7296
1 changed files with 5 additions and 9 deletions
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14
arch/arm/mm/proc-v7m.S
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@ -12,6 +12,7 @@
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/memory.h>
#include <asm/v7m.h>
#include "proc-macros.S"
@ -97,19 +98,19 @@ __v7m_setup:
mov r5, #0x00800000
str r5, [r0, V7M_SCB_SHPR3] @ set PendSV priority
@ SVC to run the kernel in this mode
@ SVC to switch to handler mode. Notice that this requires sp to
@ point to writeable memory because the processor saves
@ some registers to the stack.
badr r1, 1f
ldr r5, [r12, #11 * 4] @ read the SVC vector entry
str r1, [r12, #11 * 4] @ write the temporary SVC vector entry
mov r6, lr @ save LR
mov r7, sp @ save SP
ldr sp, =__v7m_setup_stack_top
ldr sp, =init_thread_union + THREAD_START_SP
cpsie i
svc #0
1: cpsid i
str r5, [r12, #11 * 4] @ restore the original SVC vector entry
mov lr, r6 @ restore LR
mov sp, r7 @ restore SP
@ Special-purpose control register
mov r1, #1
@ -123,11 +124,6 @@ __v7m_setup:
ret lr
ENDPROC(__v7m_setup)
.align 2
__v7m_setup_stack:
.space 4 * 8 @ 8 registers
__v7m_setup_stack_top:
define_processor_functions v7m, dabort=nommu_early_abort, pabort=legacy_pabort, nommu=1
.section ".rodata"