ARM: 8451/1: v7-M: Set an early stack for __v7m_setup (a4124e72) · Commits · 戴 / test

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>

arch/arm/mm/proc-v7m.S

+5 −9

Original line number	Diff line number	Diff line
		@@ -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"

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