linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct
@ 2020-09-07 13:42 Christophe Leroy
  2020-09-07 13:42 ` [PATCH 2/2] powerpc/32: Fix vmap stack - Properly set r1 before activating MMU Christophe Leroy
  2020-09-17 11:27 ` [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct Michael Ellerman
  0 siblings, 2 replies; 3+ messages in thread
From: Christophe Leroy @ 2020-09-07 13:42 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
  Cc: linux-kernel, linuxppc-dev

We need r1 to be properly set before activating MMU, so
reading task_struct->stack must be done with MMU off.

This means we need an additional register to play with MSR
bits while r11 now points to the stack. For that, move r10
back to CR (As is already done for hash MMU) and use r10.

We still don't have r1 correct yet when we activate MMU.
It is done in following patch.

Fixes: 028474876f47 ("powerpc/32: prepare for CONFIG_VMAP_STACK")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/head_32.S |  6 ------
 arch/powerpc/kernel/head_32.h | 31 ++++++-------------------------
 2 files changed, 6 insertions(+), 31 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index f3ab94d73936..d967266d62e8 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -274,14 +274,8 @@ __secondary_hold_acknowledge:
 	DO_KVM  0x200
 MachineCheck:
 	EXCEPTION_PROLOG_0
-#ifdef CONFIG_VMAP_STACK
-	li	r11, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
-	mtmsr	r11
-	isync
-#endif
 #ifdef CONFIG_PPC_CHRP
 	mfspr	r11, SPRN_SPRG_THREAD
-	tovirt_vmstack r11, r11
 	lwz	r11, RTAS_SP(r11)
 	cmpwi	cr1, r11, 0
 	bne	cr1, 7f
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 9abec6cd099c..21effebb9277 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -39,24 +39,13 @@
 .endm
 
 .macro EXCEPTION_PROLOG_1 for_rtas=0
-#ifdef CONFIG_VMAP_STACK
-	.ifeq	\for_rtas
-	li	r11, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
-	mtmsr	r11
-	isync
-	.endif
 	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
-	tovirt_vmstack r11, r11
 	lwz	r11,TASK_STACK-THREAD(r11)
 	addi	r11, r11, THREAD_SIZE - INT_FRAME_SIZE
-	tophys_novmstack r11, r11
 1:
+	tophys_novmstack r11, r11
 #ifdef CONFIG_VMAP_STACK
 	mtcrf	0x7f, r11
 	bt	32 - THREAD_ALIGN_SHIFT, stack_overflow
@@ -64,12 +53,11 @@
 .endm
 
 .macro EXCEPTION_PROLOG_2 handle_dar_dsisr=0
-#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_PPC_BOOK3S)
-BEGIN_MMU_FTR_SECTION
+#ifdef CONFIG_VMAP_STACK
 	mtcr	r10
-FTR_SECTION_ELSE
-	stw	r10, _CCR(r11)
-ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
+	li	r10, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
+	mtmsr	r10
+	isync
 #else
 	stw	r10,_CCR(r11)		/* save registers */
 #endif
@@ -77,11 +65,9 @@ ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
 	stw	r12,GPR12(r11)
 	stw	r9,GPR9(r11)
 	stw	r10,GPR10(r11)
-#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_PPC_BOOK3S)
-BEGIN_MMU_FTR_SECTION
+#ifdef CONFIG_VMAP_STACK
 	mfcr	r10
 	stw	r10, _CCR(r11)
-END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
 #endif
 	mfspr	r12,SPRN_SPRG_SCRATCH1
 	stw	r12,GPR11(r11)
@@ -97,11 +83,7 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
 	stw	r10, _DSISR(r11)
 	.endif
 	lwz	r9, SRR1(r12)
-#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_PPC_BOOK3S)
-BEGIN_MMU_FTR_SECTION
 	andi.	r10, r9, MSR_PR
-END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
-#endif
 	lwz	r12, SRR0(r12)
 #else
 	mfspr	r12,SPRN_SRR0
@@ -328,7 +310,6 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
 #ifdef CONFIG_VMAP_STACK
 #ifdef CONFIG_SMP
 	mfspr	r11, SPRN_SPRG_THREAD
-	tovirt(r11, r11)
 	lwz	r11, TASK_CPU - THREAD(r11)
 	slwi	r11, r11, 3
 	addis	r11, r11, emergency_ctx@ha
-- 
2.25.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* [PATCH 2/2] powerpc/32: Fix vmap stack - Properly set r1 before activating MMU
  2020-09-07 13:42 [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct Christophe Leroy
@ 2020-09-07 13:42 ` Christophe Leroy
  2020-09-17 11:27 ` [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct Michael Ellerman
  1 sibling, 0 replies; 3+ messages in thread
From: Christophe Leroy @ 2020-09-07 13:42 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
  Cc: linux-kernel, linuxppc-dev

We need r1 to be properly set before activating MMU, otherwise any new
exception taken while saving registers into the stack in exception
prologs will use the user stack, which is wrong and will even lockup
or crash when KUAP is selected.

Do that by switching the meaning of r11 and r1 until we have saved r1
to the stack: copy r1 into r11 and setup the new stack pointer in r1.
To avoid complicating and impacting all generic and specific prolog
code (and more), copy back r1 into r11 once r11 is save onto
the stack.

We could get rid of copying r1 back and forth at the cost of
rewriting everything to use r1 instead of r11 all the way when
CONFIG_VMAP_STACK is set, but the effort is probably not worth it.

Fixes: 028474876f47 ("powerpc/32: prepare for CONFIG_VMAP_STACK")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/head_32.h | 43 +++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 21effebb9277..cc36998c5541 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -39,15 +39,24 @@
 .endm
 
 .macro EXCEPTION_PROLOG_1 for_rtas=0
+#ifdef CONFIG_VMAP_STACK
+	mr	r11, r1
+	subi	r1, r1, INT_FRAME_SIZE		/* use r1 if kernel */
+	beq	1f
+	mfspr	r1,SPRN_SPRG_THREAD
+	lwz	r1,TASK_STACK-THREAD(r1)
+	addi	r1, r1, THREAD_SIZE - INT_FRAME_SIZE
+#else
 	subi	r11, r1, INT_FRAME_SIZE		/* use r1 if kernel */
 	beq	1f
 	mfspr	r11,SPRN_SPRG_THREAD
 	lwz	r11,TASK_STACK-THREAD(r11)
 	addi	r11, r11, THREAD_SIZE - INT_FRAME_SIZE
+#endif
 1:
 	tophys_novmstack r11, r11
 #ifdef CONFIG_VMAP_STACK
-	mtcrf	0x7f, r11
+	mtcrf	0x7f, r1
 	bt	32 - THREAD_ALIGN_SHIFT, stack_overflow
 #endif
 .endm
@@ -62,6 +71,15 @@
 	stw	r10,_CCR(r11)		/* save registers */
 #endif
 	mfspr	r10, SPRN_SPRG_SCRATCH0
+#ifdef CONFIG_VMAP_STACK
+	stw	r11,GPR1(r1)
+	stw	r11,0(r1)
+	mr	r11, r1
+#else
+	stw	r1,GPR1(r11)
+	stw	r1,0(r11)
+	tovirt(r1, r11)		/* set new kernel sp */
+#endif
 	stw	r12,GPR12(r11)
 	stw	r9,GPR9(r11)
 	stw	r10,GPR10(r11)
@@ -89,9 +107,6 @@
 	mfspr	r12,SPRN_SRR0
 	mfspr	r9,SPRN_SRR1
 #endif
-	stw	r1,GPR1(r11)
-	stw	r1,0(r11)
-	tovirt_novmstack r1, r11	/* set new kernel sp */
 #ifdef CONFIG_40x
 	rlwinm	r9,r9,0,14,12		/* clear MSR_WE (necessary?) */
 #else
@@ -309,19 +324,19 @@
 .macro vmap_stack_overflow_exception
 #ifdef CONFIG_VMAP_STACK
 #ifdef CONFIG_SMP
-	mfspr	r11, SPRN_SPRG_THREAD
-	lwz	r11, TASK_CPU - THREAD(r11)
-	slwi	r11, r11, 3
-	addis	r11, r11, emergency_ctx@ha
+	mfspr	r1, SPRN_SPRG_THREAD
+	lwz	r1, TASK_CPU - THREAD(r1)
+	slwi	r1, r1, 3
+	addis	r1, r1, emergency_ctx@ha
 #else
-	lis	r11, emergency_ctx@ha
+	lis	r1, emergency_ctx@ha
 #endif
-	lwz	r11, emergency_ctx@l(r11)
-	cmpwi	cr1, r11, 0
+	lwz	r1, emergency_ctx@l(r1)
+	cmpwi	cr1, r1, 0
 	bne	cr1, 1f
-	lis	r11, init_thread_union@ha
-	addi	r11, r11, init_thread_union@l
-1:	addi	r11, r11, THREAD_SIZE - INT_FRAME_SIZE
+	lis	r1, init_thread_union@ha
+	addi	r1, r1, init_thread_union@l
+1:	addi	r1, r1, THREAD_SIZE - INT_FRAME_SIZE
 	EXCEPTION_PROLOG_2
 	SAVE_NVGPRS(r11)
 	addi	r3, r1, STACK_FRAME_OVERHEAD
-- 
2.25.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct
  2020-09-07 13:42 [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct Christophe Leroy
  2020-09-07 13:42 ` [PATCH 2/2] powerpc/32: Fix vmap stack - Properly set r1 before activating MMU Christophe Leroy
@ 2020-09-17 11:27 ` Michael Ellerman
  1 sibling, 0 replies; 3+ messages in thread
From: Michael Ellerman @ 2020-09-17 11:27 UTC (permalink / raw)
  To: Michael Ellerman, Benjamin Herrenschmidt, Paul Mackerras,
	Christophe Leroy
  Cc: linuxppc-dev, linux-kernel

On Mon, 7 Sep 2020 13:42:09 +0000 (UTC), Christophe Leroy wrote:
> We need r1 to be properly set before activating MMU, so
> reading task_struct->stack must be done with MMU off.
> 
> This means we need an additional register to play with MSR
> bits while r11 now points to the stack. For that, move r10
> back to CR (As is already done for hash MMU) and use r10.
> 
> [...]

Applied to powerpc/next.

[1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct
      https://git.kernel.org/powerpc/c/c118c7303ad528be8ff2aea8cd1ee15452c763f0
[2/2] powerpc/32: Fix vmap stack - Properly set r1 before activating MMU
      https://git.kernel.org/powerpc/c/da7bb43ab9da39bcfed0d146ce94e1f0cbae4ca0

cheers

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-09-17 12:00 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-07 13:42 [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct Christophe Leroy
2020-09-07 13:42 ` [PATCH 2/2] powerpc/32: Fix vmap stack - Properly set r1 before activating MMU Christophe Leroy
2020-09-17 11:27 ` [PATCH 1/2] powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct Michael Ellerman

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).