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Subject[RFC PATCH v1 06/41] powerpc/40x: Prepare for enabling MMU in critical exception prolog
Date
In order the enable MMU early in exception prolog, implement
CONFIG_VMAP_STACK principles in critical exception prolog.

There is no intention to use CONFIG_VMAP_STACK on 40x,
but related code will be used to enable MMU early in exception
in a later patch.

Also address (critirq_ctx-PAGE_OFFSET) directly instead of
using tophys() in order to win one instruction.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/kernel/head_40x.S | 40 +++++++++++++++++++++++++++++++---
1 file changed, 37 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 5b337bf49bcb..1468f38c3860 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -89,6 +89,12 @@ _ENTRY(crit_srr0)
.space 4
_ENTRY(crit_srr1)
.space 4
+_ENTRY(crit_r1)
+ .space 4
+_ENTRY(crit_dear)
+ .space 4
+_ENTRY(crit_esr)
+ .space 4
_ENTRY(saved_ksp_limit)
.space 4

@@ -107,32 +113,60 @@ _ENTRY(saved_ksp_limit)
mfspr r11,SPRN_SRR1
stw r10,crit_srr0@l(0)
stw r11,crit_srr1@l(0)
+#ifdef CONFIG_VMAP_STACK
+ mfspr r10,SPRN_DEAR
+ mfspr r11,SPRN_ESR
+ stw r10,crit_dear@l(0)
+ stw r11,crit_esr@l(0)
+#endif
mfcr r10 /* save CR in r10 for now */
mfspr r11,SPRN_SRR3 /* check whether user or kernel */
andi. r11,r11,MSR_PR
- lis r11,critirq_ctx@ha
- tophys(r11,r11)
- lwz r11,critirq_ctx@l(r11)
+ lis r11,(critirq_ctx-PAGE_OFFSET)@ha
+ lwz r11,(critirq_ctx-PAGE_OFFSET)@l(r11)
beq 1f
/* COMING FROM USER MODE */
mfspr r11,SPRN_SPRG_THREAD /* if from user, start at top of */
lwz r11,TASK_STACK-THREAD(r11) /* this thread's kernel stack */
+#ifdef CONFIG_VMAP_STACK
+1: stw r1,crit_r1@l(0)
+ addi r1,r11,THREAD_SIZE-INT_FRAME_SIZE /* Alloc an excpt frm */
+ LOAD_REG_IMMEDIATE(r11,MSR_KERNEL & ~(MSR_IR | MSR_RI))
+ mtmsr r11
+ isync
+ lwz r11,crit_r1@l(0)
+ stw r11,GPR1(r1)
+ stw r11,0(r1)
+ mr r11,r1
+#else
1: addi r11,r11,THREAD_SIZE-INT_FRAME_SIZE /* Alloc an excpt frm */
tophys(r11,r11)
stw r1,GPR1(r11)
stw r1,0(r11)
tovirt(r1,r11)
+#endif
stw r10,_CCR(r11) /* save various registers */
stw r12,GPR12(r11)
stw r9,GPR9(r11)
mflr r10
stw r10,_LINK(r11)
+#ifdef CONFIG_VMAP_STACK
+ lis r9,PAGE_OFFSET@ha
+ lwz r10,crit_r10@l(r9)
+ lwz r12,crit_r11@l(r9)
+#else
lwz r10,crit_r10@l(0)
lwz r12,crit_r11@l(0)
+#endif
stw r10,GPR10(r11)
stw r12,GPR11(r11)
+#ifdef CONFIG_VMAP_STACK
+ lwz r12,crit_dear@l(r9)
+ lwz r9,crit_esr@l(r9)
+#else
mfspr r12,SPRN_DEAR /* save DEAR and ESR in the frame */
mfspr r9,SPRN_ESR /* in them at the point where the */
+#endif
stw r12,_DEAR(r11) /* since they may have had stuff */
stw r9,_ESR(r11) /* exception was taken */
mfspr r12,SPRN_SRR2
--
2.25.0
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