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>
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/v7m.h>
#include "proc-macros.S"
#include <asm/v7m.h>
#include "proc-macros.S"
mov r5, #0x00800000
str r5, [r0, V7M_SCB_SHPR3] @ set PendSV priority
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
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
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
@ Special-purpose control register
mov r1, #1
ret lr
ENDPROC(__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"
define_processor_functions v7m, dabort=nommu_early_abort, pabort=legacy_pabort, nommu=1
.section ".rodata"