arch/arm/kernel/entry-header.S - maze/linux - Git at Google

 #include <linux/init.h>
 #include <linux/linkage.h>

 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/errno.h>
 #include <asm/thread_info.h>
 #include <asm/v7m.h>

 @ Bad Abort numbers
 @ -----------------
 @
 #define BAD_PREFETCH	0
 #define BAD_DATA	1
 #define BAD_ADDREXCPTN	2
 #define BAD_IRQ		3
 #define BAD_UNDEFINSTR	4

 @
 @ Most of the stack format comes from struct pt_regs, but with
 @ the addition of 8 bytes for storing syscall args 5 and 6.
 @ This _must_ remain a multiple of 8 for EABI.
 @
 #define S_OFF		8

 /*
  * The SWI code relies on the fact that R0 is at the bottom of the stack
  * (due to slow/fast restore user regs).
  */
 #if S_R0 != 0
 #error "Please fix"
 #endif

 	.macro	zero_fp
 #ifdef CONFIG_FRAME_POINTER
 	mov	fp, #0
 #endif
 	.endm

 	.macro	alignment_trap, rtemp
 #ifdef CONFIG_ALIGNMENT_TRAP
 	ldr	\rtemp, .LCcralign
 	ldr	\rtemp, [\rtemp]
 	mcr	p15, 0, \rtemp, c1, c0
 #endif
 	.endm

 #ifdef CONFIG_CPU_V7M
 /*
  * ARMv7-M exception entry/exit macros.
  *
  * xPSR, ReturnAddress(), LR (R14), R12, R3, R2, R1, and R0 are
  * automatically saved on the current stack (32 words) before
  * switching to the exception stack (SP_main).
  *
  * If exception is taken while in user mode, SP_main is
  * empty. Otherwise, SP_main is aligned to 64 bit automatically
  * (CCR.STKALIGN set).
  *
  * Linux assumes that the interrupts are disabled when entering an
  * exception handler and it may BUG if this is not the case. Interrupts
  * are disabled during entry and reenabled in the exit macro.
  *
  * v7m_exception_slow_exit is used when returning from SVC or PendSV.
  * When returning to kernel mode, we don't return from exception.
  */
 	.macro	v7m_exception_entry
 	@ determine the location of the registers saved by the core during
 	@ exception entry. Depending on the mode the cpu was in when the
 	@ exception happend that is either on the main or the process stack.
 	@ Bit 2 of EXC_RETURN stored in the lr register specifies which stack
 	@ was used.
 	tst	lr, #EXC_RET_STACK_MASK
 	mrsne	r12, psp
 	moveq	r12, sp

 	@ we cannot rely on r0-r3 and r12 matching the value saved in the
 	@ exception frame because of tail-chaining. So these have to be
 	@ reloaded.
 	ldmia	r12!, {r0-r3}

 	@ Linux expects to have irqs off. Do it here before taking stack space
 	cpsid	i

 	sub	sp, #S_FRAME_SIZE-S_IP
 	stmdb	sp!, {r0-r11}

 	@ load saved r12, lr, return address and xPSR.
 	@ r0-r7 are used for signals and never touched from now on. Clobbering
 	@ r8-r12 is OK.
 	mov	r9, r12
 	ldmia	r9!, {r8, r10-r12}

 	@ calculate the original stack pointer value.
 	@ r9 currently points to the memory location just above the auto saved
 	@ xPSR.
 	@ The cpu might automatically 8-byte align the stack. Bit 9
 	@ of the saved xPSR specifies if stack aligning took place. In this case
 	@ another 32-bit value is included in the stack.

 	tst	r12, V7M_xPSR_FRAMEPTRALIGN
 	addne	r9, r9, #4

 	@ store saved r12 using str to have a register to hold the base for stm
 	str	r8, [sp, #S_IP]
 	add	r8, sp, #S_SP
 	@ store r13-r15, xPSR
 	stmia	r8!, {r9-r12}
 	@ store old_r0
 	str	r0, [r8]
 	.endm

         /*
 	 * PENDSV and SVCALL are configured to have the same exception
 	 * priorities. As a kernel thread runs at SVCALL execution priority it
 	 * can never be preempted and so we will never have to return to a
 	 * kernel thread here.
          */
 	.macro	v7m_exception_slow_exit ret_r0
 	cpsid	i
 	ldr	lr, =EXC_RET_THREADMODE_PROCESSSTACK

 	@ read original r12, sp, lr, pc and xPSR
 	add	r12, sp, #S_IP
 	ldmia	r12, {r1-r5}

 	@ an exception frame is always 8-byte aligned. To tell the hardware if
 	@ the sp to be restored is aligned or not set bit 9 of the saved xPSR
 	@ accordingly.
 	tst	r2, #4
 	subne	r2, r2, #4
 	orrne	r5, V7M_xPSR_FRAMEPTRALIGN
 	biceq	r5, V7M_xPSR_FRAMEPTRALIGN

 	@ write basic exception frame
 	stmdb	r2!, {r1, r3-r5}
 	ldmia	sp, {r1, r3-r5}
 	.if	\ret_r0
 	stmdb	r2!, {r0, r3-r5}
 	.else
 	stmdb	r2!, {r1, r3-r5}
 	.endif

 	@ restore process sp
 	msr	psp, r2

 	@ restore original r4-r11
 	ldmia	sp!, {r0-r11}

 	@ restore main sp
 	add	sp, sp, #S_FRAME_SIZE-S_IP

 	cpsie	i
 	bx	lr
 	.endm
 #endif	/* CONFIG_CPU_V7M */

 	@
 	@ Store/load the USER SP and LR registers by switching to the SYS
 	@ mode. Useful in Thumb-2 mode where "stm/ldm rd, {sp, lr}^" is not
 	@ available. Should only be called from SVC mode
 	@
 	.macro	store_user_sp_lr, rd, rtemp, offset = 0
 	mrs	\rtemp, cpsr
 	eor	\rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
 	msr	cpsr_c, \rtemp			@ switch to the SYS mode

 	str	sp, [\rd, #\offset]		@ save sp_usr
 	str	lr, [\rd, #\offset + 4]		@ save lr_usr

 	eor	\rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
 	msr	cpsr_c, \rtemp			@ switch back to the SVC mode
 	.endm

 	.macro	load_user_sp_lr, rd, rtemp, offset = 0
 	mrs	\rtemp, cpsr
 	eor	\rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
 	msr	cpsr_c, \rtemp			@ switch to the SYS mode

 	ldr	sp, [\rd, #\offset]		@ load sp_usr
 	ldr	lr, [\rd, #\offset + 4]		@ load lr_usr

 	eor	\rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
 	msr	cpsr_c, \rtemp			@ switch back to the SVC mode
 	.endm

 #ifndef CONFIG_THUMB2_KERNEL
 	.macro	svc_exit, rpsr, irq = 0
 	.if	\irq != 0
 	@ IRQs already off
 #ifdef CONFIG_TRACE_IRQFLAGS
 	@ The parent context IRQs must have been enabled to get here in
 	@ the first place, so there's no point checking the PSR I bit.
 	bl	trace_hardirqs_on
 #endif
 	.else
 	@ IRQs off again before pulling preserved data off the stack
 	disable_irq_notrace
 #ifdef CONFIG_TRACE_IRQFLAGS
 	tst	\rpsr, #PSR_I_BIT
 	bleq	trace_hardirqs_on
 	tst	\rpsr, #PSR_I_BIT
 	blne	trace_hardirqs_off
 #endif
 	.endif
 	msr	spsr_cxsf, \rpsr
 #if defined(CONFIG_CPU_V6)
 	ldr	r0, [sp]
 	strex	r1, r2, [sp]			@ clear the exclusive monitor
 	ldmib	sp, {r1 - pc}^			@ load r1 - pc, cpsr
 #elif defined(CONFIG_CPU_32v6K)
 	clrex					@ clear the exclusive monitor
 	ldmia	sp, {r0 - pc}^			@ load r0 - pc, cpsr
 #else
 	ldmia	sp, {r0 - pc}^			@ load r0 - pc, cpsr
 #endif
 	.endm

 	.macro	restore_user_regs, fast = 0, offset = 0
 	ldr	r1, [sp, #\offset + S_PSR]	@ get calling cpsr
 	ldr	lr, [sp, #\offset + S_PC]!	@ get pc
 	msr	spsr_cxsf, r1			@ save in spsr_svc
 #if defined(CONFIG_CPU_V6)
 	strex	r1, r2, [sp]			@ clear the exclusive monitor
 #elif defined(CONFIG_CPU_32v6K)
 	clrex					@ clear the exclusive monitor
 #endif
 	.if	\fast
 	ldmdb	sp, {r1 - lr}^			@ get calling r1 - lr
 	.else
 	ldmdb	sp, {r0 - lr}^			@ get calling r0 - lr
 	.endif
 	mov	r0, r0				@ ARMv5T and earlier require a nop
 						@ after ldm {}^
 	add	sp, sp, #S_FRAME_SIZE - S_PC
 	movs	pc, lr				@ return & move spsr_svc into cpsr
 	.endm

 	@
 	@ 32-bit wide "mov pc, reg"
 	@
 	.macro	movw_pc, reg
 	mov	pc, \reg
 	.endm
 #else	/* CONFIG_THUMB2_KERNEL */
 	.macro	svc_exit, rpsr, irq = 0
 	.if	\irq != 0
 	@ IRQs already off
 #ifdef CONFIG_TRACE_IRQFLAGS
 	@ The parent context IRQs must have been enabled to get here in
 	@ the first place, so there's no point checking the PSR I bit.
 	bl	trace_hardirqs_on
 #endif
 	.else
 	@ IRQs off again before pulling preserved data off the stack
 	disable_irq_notrace
 #ifdef CONFIG_TRACE_IRQFLAGS
 	tst	\rpsr, #PSR_I_BIT
 	bleq	trace_hardirqs_on
 	tst	\rpsr, #PSR_I_BIT
 	blne	trace_hardirqs_off
 #endif
 	.endif
 	ldr	lr, [sp, #S_SP]			@ top of the stack
 	ldrd	r0, r1, [sp, #S_LR]		@ calling lr and pc
 	clrex					@ clear the exclusive monitor
 	stmdb	lr!, {r0, r1, \rpsr}		@ calling lr and rfe context
 	ldmia	sp, {r0 - r12}
 	mov	sp, lr
 	ldr	lr, [sp], #4
 	rfeia	sp!
 	.endm

 #ifdef CONFIG_CPU_V7M
 	/*
 	 * Note we don't need to do clrex here as clearing the local monitor is
 	 * part of each exception entry and exit sequence.
 	 */
 	.macro	restore_user_regs, fast = 0, offset = 0
 	.if	\offset
 	add	sp, #\offset
 	.endif
 	v7m_exception_slow_exit ret_r0 = \fast
 	.endm
 #else	/* ifdef CONFIG_CPU_V7M */
 	.macro	restore_user_regs, fast = 0, offset = 0
 	clrex					@ clear the exclusive monitor
 	mov	r2, sp
 	load_user_sp_lr r2, r3, \offset + S_SP	@ calling sp, lr
 	ldr	r1, [sp, #\offset + S_PSR]	@ get calling cpsr
 	ldr	lr, [sp, #\offset + S_PC]	@ get pc
 	add	sp, sp, #\offset + S_SP
 	msr	spsr_cxsf, r1			@ save in spsr_svc
 	.if	\fast
 	ldmdb	sp, {r1 - r12}			@ get calling r1 - r12
 	.else
 	ldmdb	sp, {r0 - r12}			@ get calling r0 - r12
 	.endif
 	add	sp, sp, #S_FRAME_SIZE - S_SP
 	movs	pc, lr				@ return & move spsr_svc into cpsr
 	.endm
 #endif	/* ifdef CONFIG_CPU_V7M / else */

 	@
 	@ 32-bit wide "mov pc, reg"
 	@
 	.macro	movw_pc, reg
 	mov	pc, \reg
 	nop
 	.endm
 #endif	/* !CONFIG_THUMB2_KERNEL */

 /*
  * Context tracking subsystem.  Used to instrument transitions
  * between user and kernel mode.
  */
 	.macro ct_user_exit, save = 1
 #ifdef CONFIG_CONTEXT_TRACKING
 	.if	\save
 	stmdb   sp!, {r0-r3, ip, lr}
 	bl	context_tracking_user_exit
 	ldmia	sp!, {r0-r3, ip, lr}
 	.else
 	bl	context_tracking_user_exit
 	.endif
 #endif
 	.endm

 	.macro ct_user_enter, save = 1
 #ifdef CONFIG_CONTEXT_TRACKING
 	.if	\save
 	stmdb   sp!, {r0-r3, ip, lr}
 	bl	context_tracking_user_enter
 	ldmia	sp!, {r0-r3, ip, lr}
 	.else
 	bl	context_tracking_user_enter
 	.endif
 #endif
 	.endm

 /*
  * These are the registers used in the syscall handler, and allow us to
  * have in theory up to 7 arguments to a function - r0 to r6.
  *
  * r7 is reserved for the system call number for thumb mode.
  *
  * Note that tbl == why is intentional.
  *
  * We must set at least "tsk" and "why" when calling ret_with_reschedule.
  */
 scno	.req	r7		@ syscall number
 tbl	.req	r8		@ syscall table pointer
 why	.req	r8		@ Linux syscall (!= 0)
 tsk	.req	r9		@ current thread_info
	#include <linux/init.h>
	#include <linux/linkage.h>

	#include <asm/assembler.h>
	#include <asm/asm-offsets.h>
	#include <asm/errno.h>
	#include <asm/thread_info.h>
	#include <asm/v7m.h>

	@ Bad Abort numbers
	@ -----------------
	@
	#define BAD_PREFETCH 0
	#define BAD_DATA 1
	#define BAD_ADDREXCPTN 2
	#define BAD_IRQ 3
	#define BAD_UNDEFINSTR 4

	@
	@ Most of the stack format comes from struct pt_regs, but with
	@ the addition of 8 bytes for storing syscall args 5 and 6.
	@ This _must_ remain a multiple of 8 for EABI.
	@
	#define S_OFF 8

	/*
	* The SWI code relies on the fact that R0 is at the bottom of the stack
	* (due to slow/fast restore user regs).
	*/
	#if S_R0 != 0
	#error "Please fix"
	#endif

	.macro zero_fp
	#ifdef CONFIG_FRAME_POINTER
	mov fp, #0
	#endif
	.endm

	.macro alignment_trap, rtemp
	#ifdef CONFIG_ALIGNMENT_TRAP
	ldr \rtemp, .LCcralign
	ldr \rtemp, [\rtemp]
	mcr p15, 0, \rtemp, c1, c0
	#endif
	.endm

	#ifdef CONFIG_CPU_V7M
	/*
	* ARMv7-M exception entry/exit macros.
	*
	* xPSR, ReturnAddress(), LR (R14), R12, R3, R2, R1, and R0 are
	* automatically saved on the current stack (32 words) before
	* switching to the exception stack (SP_main).
	*
	* If exception is taken while in user mode, SP_main is
	* empty. Otherwise, SP_main is aligned to 64 bit automatically
	* (CCR.STKALIGN set).
	*
	* Linux assumes that the interrupts are disabled when entering an
	* exception handler and it may BUG if this is not the case. Interrupts
	* are disabled during entry and reenabled in the exit macro.
	*
	* v7m_exception_slow_exit is used when returning from SVC or PendSV.
	* When returning to kernel mode, we don't return from exception.
	*/
	.macro v7m_exception_entry
	@ determine the location of the registers saved by the core during
	@ exception entry. Depending on the mode the cpu was in when the
	@ exception happend that is either on the main or the process stack.
	@ Bit 2 of EXC_RETURN stored in the lr register specifies which stack
	@ was used.
	tst lr, #EXC_RET_STACK_MASK
	mrsne r12, psp
	moveq r12, sp

	@ we cannot rely on r0-r3 and r12 matching the value saved in the
	@ exception frame because of tail-chaining. So these have to be
	@ reloaded.
	ldmia r12!, {r0-r3}

	@ Linux expects to have irqs off. Do it here before taking stack space
	cpsid i

	sub sp, #S_FRAME_SIZE-S_IP
	stmdb sp!, {r0-r11}

	@ load saved r12, lr, return address and xPSR.
	@ r0-r7 are used for signals and never touched from now on. Clobbering
	@ r8-r12 is OK.
	mov r9, r12
	ldmia r9!, {r8, r10-r12}

	@ calculate the original stack pointer value.
	@ r9 currently points to the memory location just above the auto saved
	@ xPSR.
	@ The cpu might automatically 8-byte align the stack. Bit 9
	@ of the saved xPSR specifies if stack aligning took place. In this case
	@ another 32-bit value is included in the stack.

	tst r12, V7M_xPSR_FRAMEPTRALIGN
	addne r9, r9, #4

	@ store saved r12 using str to have a register to hold the base for stm
	str r8, [sp, #S_IP]
	add r8, sp, #S_SP
	@ store r13-r15, xPSR
	stmia r8!, {r9-r12}
	@ store old_r0
	str r0, [r8]
	.endm

	/*
	* PENDSV and SVCALL are configured to have the same exception
	* priorities. As a kernel thread runs at SVCALL execution priority it
	* can never be preempted and so we will never have to return to a
	* kernel thread here.
	*/
	.macro v7m_exception_slow_exit ret_r0
	cpsid i
	ldr lr, =EXC_RET_THREADMODE_PROCESSSTACK

	@ read original r12, sp, lr, pc and xPSR
	add r12, sp, #S_IP
	ldmia r12, {r1-r5}

	@ an exception frame is always 8-byte aligned. To tell the hardware if
	@ the sp to be restored is aligned or not set bit 9 of the saved xPSR
	@ accordingly.
	tst r2, #4
	subne r2, r2, #4
	orrne r5, V7M_xPSR_FRAMEPTRALIGN
	biceq r5, V7M_xPSR_FRAMEPTRALIGN

	@ write basic exception frame
	stmdb r2!, {r1, r3-r5}
	ldmia sp, {r1, r3-r5}
	.if \ret_r0
	stmdb r2!, {r0, r3-r5}
	.else
	stmdb r2!, {r1, r3-r5}
	.endif

	@ restore process sp
	msr psp, r2

	@ restore original r4-r11
	ldmia sp!, {r0-r11}

	@ restore main sp
	add sp, sp, #S_FRAME_SIZE-S_IP

	cpsie i
	bx lr
	.endm
	#endif /* CONFIG_CPU_V7M */

	@
	@ Store/load the USER SP and LR registers by switching to the SYS
	@ mode. Useful in Thumb-2 mode where "stm/ldm rd, {sp, lr}^" is not
	@ available. Should only be called from SVC mode
	@
	.macro store_user_sp_lr, rd, rtemp, offset = 0
	mrs \rtemp, cpsr
	eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
	msr cpsr_c, \rtemp @ switch to the SYS mode

	str sp, [\rd, #\offset] @ save sp_usr
	str lr, [\rd, #\offset + 4] @ save lr_usr

	eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
	msr cpsr_c, \rtemp @ switch back to the SVC mode
	.endm

	.macro load_user_sp_lr, rd, rtemp, offset = 0
	mrs \rtemp, cpsr
	eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
	msr cpsr_c, \rtemp @ switch to the SYS mode

	ldr sp, [\rd, #\offset] @ load sp_usr
	ldr lr, [\rd, #\offset + 4] @ load lr_usr

	eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
	msr cpsr_c, \rtemp @ switch back to the SVC mode
	.endm

	#ifndef CONFIG_THUMB2_KERNEL
	.macro svc_exit, rpsr, irq = 0
	.if \irq != 0
	@ IRQs already off
	#ifdef CONFIG_TRACE_IRQFLAGS
	@ The parent context IRQs must have been enabled to get here in
	@ the first place, so there's no point checking the PSR I bit.
	bl trace_hardirqs_on
	#endif
	.else
	@ IRQs off again before pulling preserved data off the stack
	disable_irq_notrace
	#ifdef CONFIG_TRACE_IRQFLAGS
	tst \rpsr, #PSR_I_BIT
	bleq trace_hardirqs_on
	tst \rpsr, #PSR_I_BIT
	blne trace_hardirqs_off
	#endif
	.endif
	msr spsr_cxsf, \rpsr
	#if defined(CONFIG_CPU_V6)
	ldr r0, [sp]
	strex r1, r2, [sp] @ clear the exclusive monitor
	ldmib sp, {r1 - pc}^ @ load r1 - pc, cpsr
	#elif defined(CONFIG_CPU_32v6K)
	clrex @ clear the exclusive monitor
	ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
	#else
	ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
	#endif
	.endm

	.macro restore_user_regs, fast = 0, offset = 0
	ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr
	ldr lr, [sp, #\offset + S_PC]! @ get pc
	msr spsr_cxsf, r1 @ save in spsr_svc
	#if defined(CONFIG_CPU_V6)
	strex r1, r2, [sp] @ clear the exclusive monitor
	#elif defined(CONFIG_CPU_32v6K)
	clrex @ clear the exclusive monitor
	#endif
	.if \fast
	ldmdb sp, {r1 - lr}^ @ get calling r1 - lr
	.else
	ldmdb sp, {r0 - lr}^ @ get calling r0 - lr
	.endif
	mov r0, r0 @ ARMv5T and earlier require a nop
	@ after ldm {}^
	add sp, sp, #S_FRAME_SIZE - S_PC
	movs pc, lr @ return & move spsr_svc into cpsr
	.endm

	@
	@ 32-bit wide "mov pc, reg"
	@
	.macro movw_pc, reg
	mov pc, \reg
	.endm
	#else /* CONFIG_THUMB2_KERNEL */
	.macro svc_exit, rpsr, irq = 0
	.if \irq != 0
	@ IRQs already off
	#ifdef CONFIG_TRACE_IRQFLAGS
	@ The parent context IRQs must have been enabled to get here in
	@ the first place, so there's no point checking the PSR I bit.
	bl trace_hardirqs_on
	#endif
	.else
	@ IRQs off again before pulling preserved data off the stack
	disable_irq_notrace
	#ifdef CONFIG_TRACE_IRQFLAGS
	tst \rpsr, #PSR_I_BIT
	bleq trace_hardirqs_on
	tst \rpsr, #PSR_I_BIT
	blne trace_hardirqs_off
	#endif
	.endif
	ldr lr, [sp, #S_SP] @ top of the stack
	ldrd r0, r1, [sp, #S_LR] @ calling lr and pc
	clrex @ clear the exclusive monitor
	stmdb lr!, {r0, r1, \rpsr} @ calling lr and rfe context
	ldmia sp, {r0 - r12}
	mov sp, lr
	ldr lr, [sp], #4
	rfeia sp!
	.endm

	#ifdef CONFIG_CPU_V7M
	/*
	* Note we don't need to do clrex here as clearing the local monitor is
	* part of each exception entry and exit sequence.
	*/
	.macro restore_user_regs, fast = 0, offset = 0
	.if \offset
	add sp, #\offset
	.endif
	v7m_exception_slow_exit ret_r0 = \fast
	.endm
	#else /* ifdef CONFIG_CPU_V7M */
	.macro restore_user_regs, fast = 0, offset = 0
	clrex @ clear the exclusive monitor
	mov r2, sp
	load_user_sp_lr r2, r3, \offset + S_SP @ calling sp, lr
	ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr
	ldr lr, [sp, #\offset + S_PC] @ get pc
	add sp, sp, #\offset + S_SP
	msr spsr_cxsf, r1 @ save in spsr_svc
	.if \fast
	ldmdb sp, {r1 - r12} @ get calling r1 - r12
	.else
	ldmdb sp, {r0 - r12} @ get calling r0 - r12
	.endif
	add sp, sp, #S_FRAME_SIZE - S_SP
	movs pc, lr @ return & move spsr_svc into cpsr
	.endm
	#endif /* ifdef CONFIG_CPU_V7M / else */

	@
	@ 32-bit wide "mov pc, reg"
	@
	.macro movw_pc, reg
	mov pc, \reg
	nop
	.endm
	#endif /* !CONFIG_THUMB2_KERNEL */

	/*
	* Context tracking subsystem. Used to instrument transitions
	* between user and kernel mode.
	*/
	.macro ct_user_exit, save = 1
	#ifdef CONFIG_CONTEXT_TRACKING
	.if \save
	stmdb sp!, {r0-r3, ip, lr}
	bl context_tracking_user_exit
	ldmia sp!, {r0-r3, ip, lr}
	.else
	bl context_tracking_user_exit
	.endif
	#endif
	.endm

	.macro ct_user_enter, save = 1
	#ifdef CONFIG_CONTEXT_TRACKING
	.if \save
	stmdb sp!, {r0-r3, ip, lr}
	bl context_tracking_user_enter
	ldmia sp!, {r0-r3, ip, lr}
	.else
	bl context_tracking_user_enter
	.endif
	#endif
	.endm

	/*
	* These are the registers used in the syscall handler, and allow us to
	* have in theory up to 7 arguments to a function - r0 to r6.
	*
	* r7 is reserved for the system call number for thumb mode.
	*
	* Note that tbl == why is intentional.
	*
	* We must set at least "tsk" and "why" when calling ret_with_reschedule.
	*/
	scno .req r7 @ syscall number
	tbl .req r8 @ syscall table pointer
	why .req r8 @ Linux syscall (!= 0)
	tsk .req r9 @ current thread_info