[PATCH v2] powerpc/powermac: Fix low_sleep_handler with CONFIG_VMAP_STACK

From: Christophe Leroy
Date: Tue Dec 08 2020 - 00:25:09 EST

low_sleep_handler() can't restore the context from standard
stack because the stack can hardly be accessed with MMU OFF.

Store everything in a global storage area instead of storing
a pointer to the stack in that global storage area.

To avoid a complete churn of the function, still use r1 as
the pointer to the storage area during restore.

Reported-by: Giuseppe Sacco <giuseppe@xxxxxxxxx>
Fixes: cd08f109e262 ("powerpc/32s: Enable CONFIG_VMAP_STACK")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
This is only build tested. Giuseppe can you test it ? Thanks.

v2: Changed an erroneous 'addis' to 'addi' ; Using bss instead of data section
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
arch/powerpc/platforms/Kconfig.cputype | 2 +-
arch/powerpc/platforms/powermac/sleep.S | 132 +++++++++++-------------
2 files changed, 60 insertions(+), 74 deletions(-)

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index c194c4ae8bc7..32a9c4c09b98 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -36,7 +36,7 @@ config PPC_BOOK3S_6xx
select PPC_HAVE_PMU_SUPPORT
select PPC_HAVE_KUEP
select PPC_HAVE_KUAP
- select HAVE_ARCH_VMAP_STACK if !ADB_PMU
+ select HAVE_ARCH_VMAP_STACK

config PPC_85xx
bool "Freescale 85xx"
diff --git a/arch/powerpc/platforms/powermac/sleep.S b/arch/powerpc/platforms/powermac/sleep.S
index 7e0f8ba6e54a..d497a60003d2 100644
--- a/arch/powerpc/platforms/powermac/sleep.S
+++ b/arch/powerpc/platforms/powermac/sleep.S
@@ -44,7 +44,8 @@
#define SL_TB 0xa0
#define SL_R2 0xa8
#define SL_CR 0xac
-#define SL_R12 0xb0 /* r12 to r31 */
+#define SL_LR 0xb0
+#define SL_R12 0xb4 /* r12 to r31 */
#define SL_SIZE (SL_R12 + 80)

.section .text
@@ -63,105 +64,107 @@ _GLOBAL(low_sleep_handler)
blr
#else
mflr r0
- stw r0,4(r1)
- stwu r1,-SL_SIZE(r1)
+ lis r11,sleep_storage@ha
+ addi r11,r11,sleep_storage@l
+ stw r0,SL_LR(r11)
mfcr r0
- stw r0,SL_CR(r1)
- stw r2,SL_R2(r1)
- stmw r12,SL_R12(r1)
+ stw r0,SL_CR(r11)
+ stw r1,SL_SP(r11)
+ stw r2,SL_R2(r11)
+ stmw r12,SL_R12(r11)

/* Save MSR & SDR1 */
mfmsr r4
- stw r4,SL_MSR(r1)
+ stw r4,SL_MSR(r11)
mfsdr1 r4
- stw r4,SL_SDR1(r1)
+ stw r4,SL_SDR1(r11)

/* Get a stable timebase and save it */
1: mftbu r4
- stw r4,SL_TB(r1)
+ stw r4,SL_TB(r11)
mftb r5
- stw r5,SL_TB+4(r1)
+ stw r5,SL_TB+4(r11)
mftbu r3
cmpw r3,r4
bne 1b

/* Save SPRGs */
mfsprg r4,0
- stw r4,SL_SPRG0(r1)
+ stw r4,SL_SPRG0(r11)
mfsprg r4,1
- stw r4,SL_SPRG0+4(r1)
+ stw r4,SL_SPRG0+4(r11)
mfsprg r4,2
- stw r4,SL_SPRG0+8(r1)
+ stw r4,SL_SPRG0+8(r11)
mfsprg r4,3
- stw r4,SL_SPRG0+12(r1)
+ stw r4,SL_SPRG0+12(r11)

/* Save BATs */
mfdbatu r4,0
- stw r4,SL_DBAT0(r1)
+ stw r4,SL_DBAT0(r11)
mfdbatl r4,0
- stw r4,SL_DBAT0+4(r1)
+ stw r4,SL_DBAT0+4(r11)
mfdbatu r4,1
- stw r4,SL_DBAT1(r1)
+ stw r4,SL_DBAT1(r11)
mfdbatl r4,1
- stw r4,SL_DBAT1+4(r1)
+ stw r4,SL_DBAT1+4(r11)
mfdbatu r4,2
- stw r4,SL_DBAT2(r1)
+ stw r4,SL_DBAT2(r11)
mfdbatl r4,2
- stw r4,SL_DBAT2+4(r1)
+ stw r4,SL_DBAT2+4(r11)
mfdbatu r4,3
- stw r4,SL_DBAT3(r1)
+ stw r4,SL_DBAT3(r11)
mfdbatl r4,3
- stw r4,SL_DBAT3+4(r1)
+ stw r4,SL_DBAT3+4(r11)
mfibatu r4,0
- stw r4,SL_IBAT0(r1)
+ stw r4,SL_IBAT0(r11)
mfibatl r4,0
- stw r4,SL_IBAT0+4(r1)
+ stw r4,SL_IBAT0+4(r11)
mfibatu r4,1
- stw r4,SL_IBAT1(r1)
+ stw r4,SL_IBAT1(r11)
mfibatl r4,1
- stw r4,SL_IBAT1+4(r1)
+ stw r4,SL_IBAT1+4(r11)
mfibatu r4,2
- stw r4,SL_IBAT2(r1)
+ stw r4,SL_IBAT2(r11)
mfibatl r4,2
- stw r4,SL_IBAT2+4(r1)
+ stw r4,SL_IBAT2+4(r11)
mfibatu r4,3
- stw r4,SL_IBAT3(r1)
+ stw r4,SL_IBAT3(r11)
mfibatl r4,3
- stw r4,SL_IBAT3+4(r1)
+ stw r4,SL_IBAT3+4(r11)

BEGIN_MMU_FTR_SECTION
mfspr r4,SPRN_DBAT4U
- stw r4,SL_DBAT4(r1)
+ stw r4,SL_DBAT4(r11)
mfspr r4,SPRN_DBAT4L
- stw r4,SL_DBAT4+4(r1)
+ stw r4,SL_DBAT4+4(r11)
mfspr r4,SPRN_DBAT5U
- stw r4,SL_DBAT5(r1)
+ stw r4,SL_DBAT5(r11)
mfspr r4,SPRN_DBAT5L
- stw r4,SL_DBAT5+4(r1)
+ stw r4,SL_DBAT5+4(r11)
mfspr r4,SPRN_DBAT6U
- stw r4,SL_DBAT6(r1)
+ stw r4,SL_DBAT6(r11)
mfspr r4,SPRN_DBAT6L
- stw r4,SL_DBAT6+4(r1)
+ stw r4,SL_DBAT6+4(r11)
mfspr r4,SPRN_DBAT7U
- stw r4,SL_DBAT7(r1)
+ stw r4,SL_DBAT7(r11)
mfspr r4,SPRN_DBAT7L
- stw r4,SL_DBAT7+4(r1)
+ stw r4,SL_DBAT7+4(r11)
mfspr r4,SPRN_IBAT4U
- stw r4,SL_IBAT4(r1)
+ stw r4,SL_IBAT4(r11)
mfspr r4,SPRN_IBAT4L
- stw r4,SL_IBAT4+4(r1)
+ stw r4,SL_IBAT4+4(r11)
mfspr r4,SPRN_IBAT5U
- stw r4,SL_IBAT5(r1)
+ stw r4,SL_IBAT5(r11)
mfspr r4,SPRN_IBAT5L
- stw r4,SL_IBAT5+4(r1)
+ stw r4,SL_IBAT5+4(r11)
mfspr r4,SPRN_IBAT6U
- stw r4,SL_IBAT6(r1)
+ stw r4,SL_IBAT6(r11)
mfspr r4,SPRN_IBAT6L
- stw r4,SL_IBAT6+4(r1)
+ stw r4,SL_IBAT6+4(r11)
mfspr r4,SPRN_IBAT7U
- stw r4,SL_IBAT7(r1)
+ stw r4,SL_IBAT7(r11)
mfspr r4,SPRN_IBAT7L
- stw r4,SL_IBAT7+4(r1)
+ stw r4,SL_IBAT7+4(r11)
END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)

/* Backup various CPU config stuffs */
@@ -180,9 +183,9 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)
lis r5,grackle_wake_up@ha
addi r5,r5,grackle_wake_up@l
tophys(r5,r5)
- stw r5,SL_PC(r1)
+ stw r5,SL_PC(r11)
lis r4,KERNELBASE@h
- tophys(r5,r1)
+ tophys(r5,r11)
addi r5,r5,SL_PC
lis r6,MAGIC@ha
addi r6,r6,MAGIC@l
@@ -194,12 +197,6 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)
tophys(r3,r3)
stw r3,0x80(r4)
stw r5,0x84(r4)
- /* Store a pointer to our backup storage into
- * a kernel global
- */
- lis r3,sleep_storage@ha
- addi r3,r3,sleep_storage@l
- stw r5,0(r3)

.globl low_cpu_offline_self
low_cpu_offline_self:
@@ -279,7 +276,7 @@ _GLOBAL(core99_wake_up)
lis r3,sleep_storage@ha
addi r3,r3,sleep_storage@l
tophys(r3,r3)
- lwz r1,0(r3)
+ addi r1,r3,SL_PC

/* Pass thru to older resume code ... */
_ASM_NOKPROBE_SYMBOL(core99_wake_up)
@@ -399,13 +396,6 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)
blt 1b
sync

- /* restore the MSR and turn on the MMU */
- lwz r3,SL_MSR(r1)
- bl turn_on_mmu
-
- /* get back the stack pointer */
- tovirt(r1,r1)
-
/* Restore TB */
li r3,0
mttbl r3
@@ -419,28 +409,24 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)
mtcr r0
lwz r2,SL_R2(r1)
lmw r12,SL_R12(r1)
- addi r1,r1,SL_SIZE
- lwz r0,4(r1)
- mtlr r0
- blr
-_ASM_NOKPROBE_SYMBOL(grackle_wake_up)

-turn_on_mmu:
- mflr r4
- tovirt(r4,r4)
+ /* restore the MSR and SP and turn on the MMU and return */
+ lwz r3,SL_MSR(r1)
+ lwz r4,SL_LR(r1)
+ lwz r1,SL_SP(r1)
mtsrr0 r4
mtsrr1 r3
sync
isync
rfi
-_ASM_NOKPROBE_SYMBOL(turn_on_mmu)
+_ASM_NOKPROBE_SYMBOL(grackle_wake_up)

#endif /* defined(CONFIG_PM) || defined(CONFIG_CPU_FREQ) */

- .section .data
+ .section .bss
.balign L1_CACHE_BYTES
sleep_storage:
- .long 0
+ .space SL_SIZE
.balign L1_CACHE_BYTES, 0

#endif /* CONFIG_PPC_BOOK3S_32 */
--
2.25.0