[PATCH v4 06/16] powerpc/32: prepare for CONFIG_VMAP_STACK

From: Christophe Leroy
Date: Tue Nov 26 2019 - 07:36:19 EST

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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 also DAR and DSISR when relevant, in order to not
loose them in case there is a Data TLB Miss once the translation is
reactivated.

This patch adds fields in 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, DAR and DSISR then reenables Data MMU.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
arch/powerpc/include/asm/processor.h | 6 ++
arch/powerpc/include/asm/thread_info.h | 5 ++
arch/powerpc/kernel/asm-offsets.c | 6 ++
arch/powerpc/kernel/entry_32.S | 7 +++
arch/powerpc/kernel/head_32.h | 101 +++++++++++++++++++++++++++++----
5 files changed, 115 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index a9993e7a443b..92c02d15f117 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -163,6 +163,12 @@ 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 srr0;
+ unsigned long srr1;
+ unsigned long dar;
+ unsigned long dsisr;
+#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 484f54dab247..782cbf489ab0 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -127,6 +127,12 @@ 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);
+ OFFSET(DSISR, thread_struct, dsisr);
+#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 317ad9df8ba8..2a26fe19f0b1 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 f19a1ab91fb5..59e775930be8 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -10,31 +10,57 @@
* We assume sprg3 has the physical address of the current
* task's thread_struct.
*/
-.macro EXCEPTION_PROLOG
- EXCEPTION_PROLOG_0
+.macro EXCEPTION_PROLOG ext
+ EXCEPTION_PROLOG_0 \ext
EXCEPTION_PROLOG_1
- EXCEPTION_PROLOG_2
+ EXCEPTION_PROLOG_2 \ext
.endm

-.macro EXCEPTION_PROLOG_0
+.macro EXCEPTION_PROLOG_0 ext
mtspr SPRN_SPRG_SCRATCH0,r10
mtspr SPRN_SPRG_SCRATCH1,r11
+#ifdef CONFIG_VMAP_STACK
+ mfspr r10, SPRN_SPRG_THREAD
+ .ifnb \ext
+ mfspr r11, SPRN_DAR
+ stw r11, DAR(r10)
+ mfspr r11, SPRN_DSISR
+ stw r11, DSISR(r10)
+ .endif
+ mfspr r11, SPRN_SRR0
+ stw r11, SRR0(r10)
+#endif
mfspr r11, SPRN_SRR1 /* check whether user or kernel */
+#ifdef CONFIG_VMAP_STACK
+ stw r11, SRR1(r10)
+#endif
mfcr r10
andi. r11, r11, MSR_PR
.endm

.macro EXCEPTION_PROLOG_1
+#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
+.macro EXCEPTION_PROLOG_2 ext
stw r10,_CCR(r11) /* save registers */
stw r12,GPR12(r11)
stw r9,GPR9(r11)
@@ -44,15 +70,36 @@
stw r12,GPR11(r11)
mflr r10
stw r10,_LINK(r11)
+#ifdef CONFIG_VMAP_STACK
+ mfspr r12, SPRN_SPRG_THREAD
+ tovirt(r12, r12)
+ .ifnb \ext
+ lwz r10, DAR(r12)
+ stw r10, _DAR(r11)
+ lwz r10, DSISR(r12)
+ stw r10, _DSISR(r11)
+ .endif
+ 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 +112,49 @@

.macro SYSCALL_ENTRY trapno
mfspr r12,SPRN_SPRG_THREAD
+#ifdef CONFIG_VMAP_STACK
+ mfspr r9, SPRN_SRR0
+ mfspr r11, SPRN_SRR1
+ stw r9, SRR0(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 */
+ addi r11, r11, THREAD_SIZE - INT_FRAME_SIZE
+#ifdef CONFIG_VMAP_STACK
+ li r9, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
+ tovirt(r12, r12)
+ mtmsr r9
+#else
tophys(r11,r11)
+#endif
+ mflr r9
stw r10,_CCR(r11) /* save registers */
+ stw r9, _LINK(r11)
+#ifdef CONFIG_VMAP_STACK
+ lwz r10, SRR0(r12)
+ lwz r9, SRR1(r12)
+#else
mfspr r10,SPRN_SRR0
- stw r9,_LINK(r11)
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 +193,9 @@
#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
@@ -145,14 +219,21 @@
.endm

.macro save_dar_dsisr_on_stack reg1, reg2, sp
+#ifndef CONFIG_VMAP_STACK
mfspr \reg1, SPRN_DAR
mfspr \reg2, SPRN_DSISR
stw \reg1, _DAR(\sp)
stw \reg2, _DSISR(\sp)
+#endif
.endm

.macro get_and_save_dar_dsisr_on_stack reg1, reg2, sp
+#ifdef CONFIG_VMAP_STACK
+ lwz \reg1, _DAR(\sp)
+ lwz \reg2, _DSISR(\sp)
+#else
save_dar_dsisr_on_stack \reg1, \reg2, \sp
+#endif
.endm

/*
--
2.13.3

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Previous message: Christophe Leroy: "[PATCH v4 05/16] powerpc/32: add a macro to get and/or save DAR and DSISR on stack."
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Next in thread: Christophe Leroy: "[PATCH v4 08/16] powerpc/32: Add early stack overflow detection with VMAP stack."
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