[RFC PATCH v2 03/10] powerpc/32: prepare for CONFIG_VMAP_STACK
From: Christophe Leroy
Date: Sat Aug 31 2019 - 06:19:01 EST
To support CONFIG_VMAP_STACK, the kernel has to activate Data MMU
Translation for accessing the stack. Before doing that it must save
SRR0, SRR1 and DAR in order to not loose them in case there is a
Data TLB Miss once the translation is reactivated.
This patch defines fields in the thread struct for saving those
registers. It prepares entry_32.S to handle exception entry with
Data MMU Translation enabled and alters EXCEPTION_PROLOG macros to
save SRR0, SRR1 and DAR and reenable Data MMU.
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
arch/powerpc/include/asm/processor.h | 5 +++
arch/powerpc/include/asm/thread_info.h | 5 +++
arch/powerpc/kernel/asm-offsets.c | 5 +++
arch/powerpc/kernel/entry_32.S | 7 +++
arch/powerpc/kernel/head_32.h | 82 ++++++++++++++++++++++++++++++++--
5 files changed, 101 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index a9993e7a443b..867a4e761d7a 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -163,6 +163,11 @@ struct thread_struct {
#if defined(CONFIG_PPC_BOOK3S_32) && defined(CONFIG_PPC_KUAP)
unsigned long kuap; /* opened segments for user access */
#endif
+#ifdef CONFIG_VMAP_STACK
+ unsigned long dar;
+ unsigned long srr0;
+ unsigned long srr1;
+#endif
/* Debug Registers */
struct debug_reg debug;
struct thread_fp_state fp_state;
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 8e1d0195ac36..488d5c4670ff 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -10,10 +10,15 @@
#define _ASM_POWERPC_THREAD_INFO_H
#include <asm/asm-const.h>
+#include <asm/page.h>
#ifdef __KERNEL__
+#if defined(CONFIG_VMAP_STACK) && CONFIG_THREAD_SHIFT < PAGE_SHIFT
+#define THREAD_SHIFT PAGE_SHIFT
+#else
#define THREAD_SHIFT CONFIG_THREAD_SHIFT
+#endif
#define THREAD_SIZE (1 << THREAD_SHIFT)
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 4ccb6b3a7fbd..a2194fe8f890 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -127,6 +127,11 @@ int main(void)
OFFSET(KSP_VSID, thread_struct, ksp_vsid);
#else /* CONFIG_PPC64 */
OFFSET(PGDIR, thread_struct, pgdir);
+#ifdef CONFIG_VMAP_STACK
+ OFFSET(SRR0, thread_struct, srr0);
+ OFFSET(SRR1, thread_struct, srr1);
+ OFFSET(DAR, thread_struct, dar);
+#endif
#ifdef CONFIG_SPE
OFFSET(THREAD_EVR0, thread_struct, evr[0]);
OFFSET(THREAD_ACC, thread_struct, acc);
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 44716157c918..ef296572a513 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -140,6 +140,9 @@ transfer_to_handler:
stw r12,_CTR(r11)
stw r2,_XER(r11)
mfspr r12,SPRN_SPRG_THREAD
+#ifdef CONFIG_VMAP_STACK
+ tovirt(r12, r12)
+#endif
beq 2f /* if from user, fix up THREAD.regs */
addi r2, r12, -THREAD
addi r11,r1,STACK_FRAME_OVERHEAD
@@ -195,7 +198,11 @@ transfer_to_handler:
transfer_to_handler_cont:
3:
mflr r9
+#ifdef CONFIG_VMAP_STACK
+ tovirt(r9, r9)
+#else
tovirt(r2, r2) /* set r2 to current */
+#endif
lwz r11,0(r9) /* virtual address of handler */
lwz r9,4(r9) /* where to go when done */
#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 8e345f8d4b0e..4980babde59e 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -19,19 +19,42 @@
.macro EXCEPTION_PROLOG_0
mtspr SPRN_SPRG_SCRATCH0,r10
mtspr SPRN_SPRG_SCRATCH1,r11
+#ifdef CONFIG_VMAP_STACK
+ mfspr r10, SPRN_SPRG_THREAD
+ mfspr r11, SPRN_SRR0
+ stw r11, SRR0(r10)
+ mfspr r11, SPRN_DAR
+ stw r11, DAR(r10)
+ mfspr r11,SPRN_SRR1 /* check whether user or kernel */
+ stw r11, SRR1(r10)
+#endif
mfcr r10
.endm
.macro EXCEPTION_PROLOG_1
+#ifndef CONFIG_VMAP_STACK
mfspr r11,SPRN_SRR1 /* check whether user or kernel */
+#endif
andi. r11,r11,MSR_PR
+#ifdef CONFIG_VMAP_STACK
+ li r11, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
+ mtmsr r11
+ subi r11, r1, INT_FRAME_SIZE /* use r1 if kernel */
+#else
tophys(r11,r1) /* use tophys(r1) if kernel */
+ subi r11, r11, INT_FRAME_SIZE /* alloc exc. frame */
+#endif
beq 1f
mfspr r11,SPRN_SPRG_THREAD
+#ifdef CONFIG_VMAP_STACK
+ tovirt(r11, r11)
+#endif
lwz r11,TASK_STACK-THREAD(r11)
- addi r11,r11,THREAD_SIZE
+ addi r11, r11, THREAD_SIZE - INT_FRAME_SIZE
+#ifndef CONFIG_VMAP_STACK
tophys(r11,r11)
-1: subi r11,r11,INT_FRAME_SIZE /* alloc exc. frame */
+#endif
+1:
.endm
.macro EXCEPTION_PROLOG_2
@@ -42,17 +65,36 @@
stw r10,GPR10(r11)
mfspr r12,SPRN_SPRG_SCRATCH1
stw r12,GPR11(r11)
+#ifdef CONFIG_VMAP_STACK
+ mfspr r12, SPRN_SPRG_THREAD
+ tovirt(r12, r12)
+#endif
mflr r10
stw r10,_LINK(r11)
+#ifdef CONFIG_VMAP_STACK
+ lwz r10, DAR(r12)
+ stw r10, _DAR(r11)
+ lwz r9, SRR1(r12)
+ lwz r12, SRR0(r12)
+#else
mfspr r12,SPRN_SRR0
mfspr r9,SPRN_SRR1
+#endif
stw r1,GPR1(r11)
stw r1,0(r11)
+#ifdef CONFIG_VMAP_STACK
+ mr r1, r11 /* set new kernel sp */
+#else
tovirt(r1,r11) /* set new kernel sp */
+#endif
#ifdef CONFIG_40x
rlwinm r9,r9,0,14,12 /* clear MSR_WE (necessary?) */
#else
+#ifdef CONFIG_VMAP_STACK
+ li r10,MSR_KERNEL & ~MSR_IR /* can take exceptions */
+#else
li r10,MSR_KERNEL & ~(MSR_IR|MSR_DR) /* can take exceptions */
+#endif
mtmsr r10 /* (except for mach check in rtas) */
#endif
stw r0,GPR0(r11)
@@ -65,24 +107,56 @@
.macro SYSCALL_ENTRY trapno
mfspr r12,SPRN_SPRG_THREAD
+#ifdef CONFIG_VMAP_STACK
+ mfspr r9, SPRN_SRR0
+ mfspr r10, SPRN_DAR
+ mfspr r11,SPRN_SRR1 /* check whether user or kernel */
+ stw r9, SRR0(r12)
+ stw r10, DAR(r12)
+ stw r11, SRR1(r12)
+#endif
mfcr r10
lwz r11,TASK_STACK-THREAD(r12)
- mflr r9
addi r11,r11,THREAD_SIZE - INT_FRAME_SIZE
rlwinm r10,r10,0,4,2 /* Clear SO bit in CR */
+#ifdef CONFIG_VMAP_STACK
+ li r9, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
+ mtmsr r9 /* (except for mach check in rtas) */
+ tovirt(r12, r12)
+#else
tophys(r11,r11)
+#endif
+ mflr r9
stw r10,_CCR(r11) /* save registers */
+#ifdef CONFIG_VMAP_STACK
+ lwz r10, DAR(r12)
+ stw r10, _DAR(r11)
+ lwz r10, SRR0(r12)
+#else
mfspr r10,SPRN_SRR0
+#endif
stw r9,_LINK(r11)
+#ifdef CONFIG_VMAP_STACK
+ lwz r9, SRR1(r12)
+#else
mfspr r9,SPRN_SRR1
+#endif
stw r1,GPR1(r11)
stw r1,0(r11)
+#ifdef CONFIG_VMAP_STACK
+ mr r1, r11
+#else
tovirt(r1,r11) /* set new kernel sp */
+#endif
stw r10,_NIP(r11)
#ifdef CONFIG_40x
rlwinm r9,r9,0,14,12 /* clear MSR_WE (necessary?) */
#else
+#ifdef CONFIG_VMAP_STACK
+ LOAD_REG_IMMEDIATE(r10, MSR_KERNEL & ~MSR_IR) /* can take exceptions */
+#else
LOAD_REG_IMMEDIATE(r10, MSR_KERNEL & ~(MSR_IR|MSR_DR)) /* can take exceptions */
+#endif
mtmsr r10 /* (except for mach check in rtas) */
#endif
lis r10,STACK_FRAME_REGS_MARKER@ha /* exception frame marker */
@@ -121,7 +195,9 @@
#endif
3:
+#ifndef CONFIG_VMAP_STACK
tovirt(r2, r2) /* set r2 to current */
+#endif
lis r11, transfer_to_syscall@h
ori r11, r11, transfer_to_syscall@l
#ifdef CONFIG_TRACE_IRQFLAGS
--
2.13.3