powerpc: Remove use of a second scratch SPRG in STAB code
The STAB code used on Power3 and RS/64 uses a second scratch SPRG to
save a GPR in order to decide whether to go to do_stab_bolted_* or
to handle a normal data access exception.
This prevents our scheme of freeing SPRG3 which is user visible for
user uses since we cannot use SPRG0 which, on RS/64, seems to be
read-only for supervisor mode (like POWER4).
This reworks the STAB exception entry to use the PACA as temporary
storage instead.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 4e9640c..50f2ad3 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -50,18 +50,28 @@
HMT_MEDIUM
mtspr SPRN_SPRG_SCRATCH0,r13
BEGIN_FTR_SECTION
- mtspr SPRN_SPRG_SCRATCH1,r12
- mfspr r13,SPRN_DAR
- mfspr r12,SPRN_DSISR
- srdi r13,r13,60
- rlwimi r13,r12,16,0x20
- mfcr r12
- cmpwi r13,0x2c
+ mfspr r13,SPRN_SPRG_PACA
+ std r9,PACA_EXSLB+EX_R9(r13)
+ std r10,PACA_EXSLB+EX_R10(r13)
+ mfspr r10,SPRN_DAR
+ mfspr r9,SPRN_DSISR
+ srdi r10,r10,60
+ rlwimi r10,r9,16,0x20
+ mfcr r9
+ cmpwi r10,0x2c
beq do_stab_bolted_pSeries
- mtcrf 0x80,r12
- mfspr r12,SPRN_SPRG_SCRATCH1
-END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
+ ld r10,PACA_EXSLB+EX_R10(r13)
+ std r11,PACA_EXGEN+EX_R11(r13)
+ ld r11,PACA_EXSLB+EX_R9(r13)
+ std r12,PACA_EXGEN+EX_R12(r13)
+ mfspr r12,SPRN_SPRG_SCRATCH0
+ std r10,PACA_EXGEN+EX_R10(r13)
+ std r11,PACA_EXGEN+EX_R9(r13)
+ std r12,PACA_EXGEN+EX_R13(r13)
+ EXCEPTION_PROLOG_PSERIES_1(data_access_common)
+FTR_SECTION_ELSE
EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, data_access_common)
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_SLB)
. = 0x380
.globl data_access_slb_pSeries
@@ -224,9 +234,11 @@
.align 7
do_stab_bolted_pSeries:
- mtcrf 0x80,r12
- mfspr r12,SPRN_SPRG_SCRATCH1
- EXCEPTION_PROLOG_PSERIES(PACA_EXSLB, .do_stab_bolted)
+ std r11,PACA_EXSLB+EX_R11(r13)
+ std r12,PACA_EXSLB+EX_R12(r13)
+ mfspr r10,SPRN_SPRG_SCRATCH0
+ std r10,PACA_EXSLB+EX_R13(r13)
+ EXCEPTION_PROLOG_PSERIES_1(.do_stab_bolted)
#ifdef CONFIG_PPC_PSERIES
/*