[POWERPC] 40x/Book-E: Save/restore volatile exception registers

On machines with more than one exception level any system register that
might be modified by the "normal" exception level needs to be saved and
restored on taking a higher level exception.  We already are saving
and restoring ESR and DEAR.

For critical level add SRR0/1.
For debug level add CSRR0/1 and SRR0/1.
For machine check level add DSRR0/1, CSRR0/1, and SRR0/1.

On FSL Book-E parts we always save/restore the MAS registers for critical,
debug, and machine check level exceptions.  On 44x we always save/restore
the MMUCR.

Additionally, we save and restore the ksp_limit since we have to adjust it
for each exception level.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Paul Mackerras <paulus@samba.org>

4 files changed, 174 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index ec9228d687b..8655c767035 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -52,6 +52,10 @@
 #include <asm/iseries/alpaca.h>
 #endif
 
+#if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
+#include "head_booke.h"
+#endif
+
 int main(void)
 {
 	DEFINE(THREAD, offsetof(struct task_struct, thread));
@@ -242,6 +246,25 @@ int main(void)
 	DEFINE(_SRR1, STACK_FRAME_OVERHEAD+sizeof(struct pt_regs)+8);
 #endif /* CONFIG_PPC64 */
 
+#if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
+	DEFINE(EXC_LVL_SIZE, STACK_EXC_LVL_FRAME_SIZE);
+	DEFINE(MAS0, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas0));
+	/* we overload MMUCR for 44x on MAS0 since they are mutually exclusive */
+	DEFINE(MMUCR, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas0));
+	DEFINE(MAS1, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas1));
+	DEFINE(MAS2, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas2));
+	DEFINE(MAS3, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas3));
+	DEFINE(MAS6, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas6));
+	DEFINE(MAS7, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, mas7));
+	DEFINE(_SRR0, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, srr0));
+	DEFINE(_SRR1, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, srr1));
+	DEFINE(_CSRR0, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, csrr0));
+	DEFINE(_CSRR1, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, csrr1));
+	DEFINE(_DSRR0, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, dsrr0));
+	DEFINE(_DSRR1, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, dsrr1));
+	DEFINE(SAVED_KSP_LIMIT, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, saved_ksp_limit));
+#endif
+
 	DEFINE(CLONE_VM, CLONE_VM);
 	DEFINE(CLONE_UNTRACED, CLONE_UNTRACED);
 
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index c94aba54b5d..fe21674d4f0 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -46,14 +46,52 @@
 #ifdef CONFIG_BOOKE
 	.globl	mcheck_transfer_to_handler
 mcheck_transfer_to_handler:
-	b	transfer_to_handler_full
+	mfspr	r0,SPRN_DSRR0
+	stw	r0,_DSRR0(r11)
+	mfspr	r0,SPRN_DSRR1
+	stw	r0,_DSRR1(r11)
+	/* fall through */
 
 	.globl	debug_transfer_to_handler
 debug_transfer_to_handler:
-	b	transfer_to_handler_full
+	mfspr	r0,SPRN_CSRR0
+	stw	r0,_CSRR0(r11)
+	mfspr	r0,SPRN_CSRR1
+	stw	r0,_CSRR1(r11)
+	/* fall through */
 
 	.globl	crit_transfer_to_handler
 crit_transfer_to_handler:
+#ifdef CONFIG_FSL_BOOKE
+	mfspr	r0,SPRN_MAS0
+	stw	r0,MAS0(r11)
+	mfspr	r0,SPRN_MAS1
+	stw	r0,MAS1(r11)
+	mfspr	r0,SPRN_MAS2
+	stw	r0,MAS2(r11)
+	mfspr	r0,SPRN_MAS3
+	stw	r0,MAS3(r11)
+	mfspr	r0,SPRN_MAS6
+	stw	r0,MAS6(r11)
+#ifdef CONFIG_PHYS_64BIT
+	mfspr	r0,SPRN_MAS7
+	stw	r0,MAS7(r11)
+#endif /* CONFIG_PHYS_64BIT */
+#endif /* CONFIG_FSL_BOOKE */
+#ifdef CONFIG_44x
+	mfspr	r0,SPRN_MMUCR
+	stw	r0,MMUCR(r11)
+#endif
+	mfspr	r0,SPRN_SRR0
+	stw	r0,_SRR0(r11)
+	mfspr	r0,SPRN_SRR1
+	stw	r0,_SRR1(r11)
+
+	mfspr	r8,SPRN_SPRG3
+	lwz	r0,KSP_LIMIT(r8)
+	stw	r0,SAVED_KSP_LIMIT(r11)
+	rlwimi	r0,r1,0,0,(31-THREAD_SHIFT)
+	stw	r0,KSP_LIMIT(r8)
 	/* fall through */
 #endif
 
@@ -64,6 +102,16 @@ crit_transfer_to_handler:
 	stw	r0,GPR10(r11)
 	lwz	r0,crit_r11@l(0)
 	stw	r0,GPR11(r11)
+	mfspr	r0,SPRN_SRR0
+	stw	r0,crit_srr0@l(0)
+	mfspr	r0,SPRN_SRR1
+	stw	r0,crit_srr1@l(0)
+
+	mfspr	r8,SPRN_SPRG3
+	lwz	r0,KSP_LIMIT(r8)
+	stw	r0,saved_ksp_limit@l(0)
+	rlwimi	r0,r1,0,0,(31-THREAD_SHIFT)
+	stw	r0,KSP_LIMIT(r8)
 	/* fall through */
 #endif
 
@@ -854,17 +902,90 @@ exc_exit_restart_end:
 	exc_lvl_rfi;							\
 	b	.;		/* prevent prefetch past exc_lvl_rfi */
 
+#define	RESTORE_xSRR(exc_lvl_srr0, exc_lvl_srr1)			\
+	lwz	r9,_##exc_lvl_srr0(r1);					\
+	lwz	r10,_##exc_lvl_srr1(r1);				\
+	mtspr	SPRN_##exc_lvl_srr0,r9;					\
+	mtspr	SPRN_##exc_lvl_srr1,r10;
+
+#if defined(CONFIG_FSL_BOOKE)
+#ifdef CONFIG_PHYS_64BIT
+#define	RESTORE_MAS7							\
+	lwz	r11,MAS7(r1);						\
+	mtspr	SPRN_MAS7,r11;
+#else
+#define	RESTORE_MAS7
+#endif /* CONFIG_PHYS_64BIT */
+#define RESTORE_MMU_REGS						\
+	lwz	r9,MAS0(r1);						\
+	lwz	r10,MAS1(r1);						\
+	lwz	r11,MAS2(r1);						\
+	mtspr	SPRN_MAS0,r9;						\
+	lwz	r9,MAS3(r1);						\
+	mtspr	SPRN_MAS1,r10;						\
+	lwz	r10,MAS6(r1);						\
+	mtspr	SPRN_MAS2,r11;						\
+	mtspr	SPRN_MAS3,r9;						\
+	mtspr	SPRN_MAS6,r10;						\
+	RESTORE_MAS7;
+#elif defined(CONFIG_44x)
+#define RESTORE_MMU_REGS						\
+	lwz	r9,MMUCR(r1);						\
+	mtspr	SPRN_MMUCR,r9;
+#else
+#define RESTORE_MMU_REGS
+#endif
+
+#ifdef CONFIG_40x
 	.globl	ret_from_crit_exc
 ret_from_crit_exc:
+	mfspr	r9,SPRN_SPRG3
+	lis	r10,saved_ksp_limit@ha;
+	lwz	r10,saved_ksp_limit@l(r10);
+	tovirt(r9,r9);
+	stw	r10,KSP_LIMIT(r9)
+	lis	r9,crit_srr0@ha;
+	lwz	r9,crit_srr0@l(r9);
+	lis	r10,crit_srr1@ha;
+	lwz	r10,crit_srr1@l(r10);
+	mtspr	SPRN_SRR0,r9;
+	mtspr	SPRN_SRR1,r10;
 	RET_FROM_EXC_LEVEL(SPRN_CSRR0, SPRN_CSRR1, RFCI)
+#endif /* CONFIG_40x */
 
 #ifdef CONFIG_BOOKE
+	.globl	ret_from_crit_exc
+ret_from_crit_exc:
+	mfspr	r9,SPRN_SPRG3
+	lwz	r10,SAVED_KSP_LIMIT(r1)
+	stw	r10,KSP_LIMIT(r9)
+	RESTORE_xSRR(SRR0,SRR1);
+	RESTORE_MMU_REGS;
+	RET_FROM_EXC_LEVEL(SPRN_CSRR0, SPRN_CSRR1, RFCI)
+
 	.globl	ret_from_debug_exc
 ret_from_debug_exc:
+	mfspr	r9,SPRN_SPRG3
+	lwz	r10,SAVED_KSP_LIMIT(r1)
+	stw	r10,KSP_LIMIT(r9)
+	lwz	r9,THREAD_INFO-THREAD(r9)
+	rlwinm	r10,r1,0,0,(31-THREAD_SHIFT)
+	lwz	r10,TI_PREEMPT(r10)
+	stw	r10,TI_PREEMPT(r9)
+	RESTORE_xSRR(SRR0,SRR1);
+	RESTORE_xSRR(CSRR0,CSRR1);
+	RESTORE_MMU_REGS;
 	RET_FROM_EXC_LEVEL(SPRN_DSRR0, SPRN_DSRR1, RFDI)
 
 	.globl	ret_from_mcheck_exc
 ret_from_mcheck_exc:
+	mfspr	r9,SPRN_SPRG3
+	lwz	r10,SAVED_KSP_LIMIT(r1)
+	stw	r10,KSP_LIMIT(r9)
+	RESTORE_xSRR(SRR0,SRR1);
+	RESTORE_xSRR(CSRR0,CSRR1);
+	RESTORE_xSRR(DSRR0,DSRR1);
+	RESTORE_MMU_REGS;
 	RET_FROM_EXC_LEVEL(SPRN_MCSRR0, SPRN_MCSRR1, RFMCI)
 #endif /* CONFIG_BOOKE */
 
diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index f2cf60d38f7..56d8e5d90c5 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -93,6 +93,12 @@ _ENTRY(crit_r10)
 	.space	4
 _ENTRY(crit_r11)
 	.space	4
+_ENTRY(crit_srr0)
+	.space	4
+_ENTRY(crit_srr1)
+	.space	4
+_ENTRY(saved_ksp_limit)
+	.space	4
 
 /*
  * Exception vector entry code. This code runs with address translation
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index b0874d228ea..f277fade193 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -72,7 +72,7 @@
 #define DEBUG_STACK_BASE	dbgirq_ctx
 #define DEBUG_SPRG		SPRN_SPRG6W
 
-#define EXC_LVL_FRAME_OVERHEAD	(THREAD_SIZE - INT_FRAME_SIZE)
+#define EXC_LVL_FRAME_OVERHEAD	(THREAD_SIZE - INT_FRAME_SIZE - EXC_LVL_SIZE)
 
 #ifdef CONFIG_SMP
 #define BOOKE_LOAD_EXC_LEVEL_STACK(level)		\
@@ -376,4 +376,25 @@ label:
 	addi	r3,r1,STACK_FRAME_OVERHEAD;				      \
 	EXC_XFER_EE_LITE(0x800, kernel_fp_unavailable_exception)
 
+#ifndef __ASSEMBLY__
+struct exception_regs {
+	unsigned long mas0;
+	unsigned long mas1;
+	unsigned long mas2;
+	unsigned long mas3;
+	unsigned long mas6;
+	unsigned long mas7;
+	unsigned long srr0;
+	unsigned long srr1;
+	unsigned long csrr0;
+	unsigned long csrr1;
+	unsigned long dsrr0;
+	unsigned long dsrr1;
+	unsigned long saved_ksp_limit;
+};
+
+/* ensure this structure is always sized to a multiple of the stack alignment */
+#define STACK_EXC_LVL_FRAME_SIZE	_ALIGN_UP(sizeof (struct exception_regs), 16)
+
+#endif /* __ASSEMBLY__ */
 #endif /* __HEAD_BOOKE_H__ */