powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct

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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a027d447022a006c9c4958ac734128e577a3c5c1.1599486108.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 5624db0e09a1c4b1d4f0f6943fd8ddd5960b4736..b0e184f795c0d6582ba6bfbebc2cf3fb699ed651 100644 (file)
--- 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 9abec6cd099c69a19c5b46a4e6ff973dae7182af..21effebb927796b5dfc8a9ca4afe2b63c48081b6 100644 (file)
--- 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 @@ label:
 #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