[PATCH v2] powerpc/32s: Fix DSI and ISI exceptions for CONFIG_VMAP_STACK
Christophe Leroy
christophe.leroy at c-s.fr
Thu Feb 13 21:04:46 AEDT 2020
hash_page() needs to read page tables from kernel memory. When entire
kernel memory is mapped by BATs, which is normally the case when
CONFIG_STRICT_KERNEL_RWX is not set, it works even if the page hosting
the page table is not referenced in the MMU hash table.
However, if the page where the page table resides is not covered by
a BAT, a DSI fault can be encountered from hash_page(), and it loops
forever. This can happen when CONFIG_STRICT_KERNEL_RWX is selected
and the alignment of the different regions is too small to allow
covering the entire memory with BATs. This also happens when
CONFIG_DEBUG_PAGEALLOC is selected or when booting with 'nobats'
flag.
Also, if the page containing the kernel stack is not present in the
MMU hash table, registers cannot be saved and a recursive DSI fault
is encountered.
To allow hash_page() to properly do its job at all time and load the
MMU hash table whenever needed, it must run with data MMU disabled.
This means it must be called before re-enabling data MMU. To allow
this, registers clobbered by hash_page() and create_hpte() have to
be saved in the thread struct together with SRR0, SSR1, DAR and DSISR.
It is also necessary to ensure that DSI prolog doesn't overwrite
regs saved by prolog of the current running exception. That means:
- DSI can only use SPRN_SPRG_SCRATCH0
- Exceptions must free SPRN_SPRG_SCRATCH0 before writing to the stack.
This also fixes the Oops reported by Erhard when create_hpte() is
called by add_hash_page().
Fixes: cd08f109e262 ("powerpc/32s: Enable CONFIG_VMAP_STACK")
Reported-by: Erhard F. <erhard_f at mailbox.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206501
Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
v2: Reworked the DSI to call hash_page() even earlier and without
cloberring what ongoing exception saved in SPRG registers and
thread struct.
Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
arch/powerpc/include/asm/processor.h | 4 +
arch/powerpc/kernel/asm-offsets.c | 12 +++
arch/powerpc/kernel/head_32.S | 138 ++++++++++++++++++++++++++-
arch/powerpc/kernel/head_32.h | 13 ++-
arch/powerpc/mm/book3s32/hash_low.S | 52 +++++-----
arch/powerpc/mm/book3s32/mmu.c | 7 +-
6 files changed, 189 insertions(+), 37 deletions(-)
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 8387698bd5b6..eedcbfb9a6ff 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -168,6 +168,10 @@ struct thread_struct {
unsigned long srr1;
unsigned long dar;
unsigned long dsisr;
+#ifdef CONFIG_PPC_BOOK3S_32
+ unsigned long r0, r3, r4, r5, r6, r8, r9, r11;
+ unsigned long lr, ctr;
+#endif
#endif
/* Debug Registers */
struct debug_reg debug;
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index c25e562f1cd9..fcf24a365fc0 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -132,6 +132,18 @@ int main(void)
OFFSET(SRR1, thread_struct, srr1);
OFFSET(DAR, thread_struct, dar);
OFFSET(DSISR, thread_struct, dsisr);
+#ifdef CONFIG_PPC_BOOK3S_32
+ OFFSET(THR0, thread_struct, r0);
+ OFFSET(THR3, thread_struct, r3);
+ OFFSET(THR4, thread_struct, r4);
+ OFFSET(THR5, thread_struct, r5);
+ OFFSET(THR6, thread_struct, r6);
+ OFFSET(THR8, thread_struct, r8);
+ OFFSET(THR9, thread_struct, r9);
+ OFFSET(THR11, thread_struct, r11);
+ OFFSET(THLR, thread_struct, lr);
+ OFFSET(THCTR, thread_struct, ctr);
+#endif
#endif
#ifdef CONFIG_SPE
OFFSET(THREAD_EVR0, thread_struct, evr[0]);
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 0493fcac6409..5e1f0a796ec6 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -301,6 +301,39 @@ MachineCheck:
. = 0x300
DO_KVM 0x300
DataAccess:
+#ifdef CONFIG_VMAP_STACK
+ mtspr SPRN_SPRG_SCRATCH0,r10
+ mfspr r10, SPRN_SPRG_THREAD
+BEGIN_MMU_FTR_SECTION
+ stw r11, THR11(r10)
+ mfspr r10, SPRN_DSISR
+ mfcr r11
+#ifdef CONFIG_PPC_KUAP
+ andis. r10, r10, (DSISR_BAD_FAULT_32S | DSISR_DABRMATCH | DSISR_PROTFAULT)@h
+#else
+ andis. r10, r10, (DSISR_BAD_FAULT_32S | DSISR_DABRMATCH)@h
+#endif
+ mfspr r10, SPRN_SPRG_THREAD
+ beq hash_page_dsi
+.Lhash_page_dsi_cont:
+ mtcr r11
+ lwz r11, THR11(r10)
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
+ mtspr SPRN_SPRG_SCRATCH1,r11
+ mfspr r11, SPRN_DAR
+ stw r11, DAR(r10)
+ mfspr r11, SPRN_DSISR
+ stw r11, DSISR(r10)
+ mfspr r11, SPRN_SRR0
+ stw r11, SRR0(r10)
+ mfspr r11, SPRN_SRR1 /* check whether user or kernel */
+ stw r11, SRR1(r10)
+ mfcr r10
+ andi. r11, r11, MSR_PR
+
+ EXCEPTION_PROLOG_1
+ b handle_page_fault_tramp_1
+#else /* CONFIG_VMAP_STACK */
EXCEPTION_PROLOG handle_dar_dsisr=1
get_and_save_dar_dsisr_on_stack r4, r5, r11
BEGIN_MMU_FTR_SECTION
@@ -316,11 +349,32 @@ BEGIN_MMU_FTR_SECTION
FTR_SECTION_ELSE
b handle_page_fault_tramp_2
ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
+#endif /* CONFIG_VMAP_STACK */
/* Instruction access exception. */
. = 0x400
DO_KVM 0x400
InstructionAccess:
+#ifdef CONFIG_VMAP_STACK
+ mtspr SPRN_SPRG_SCRATCH0,r10
+ mtspr SPRN_SPRG_SCRATCH1,r11
+ mfspr r10, SPRN_SPRG_THREAD
+ mfspr r11, SPRN_SRR0
+ stw r11, SRR0(r10)
+ mfspr r11, SPRN_SRR1 /* check whether user or kernel */
+ stw r11, SRR1(r10)
+ mfcr r10
+BEGIN_MMU_FTR_SECTION
+ andis. r11, r11, SRR1_ISI_NOPT at h /* no pte found? */
+ bne hash_page_isi
+.Lhash_page_isi_cont:
+ mfspr r11, SPRN_SRR1 /* check whether user or kernel */
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
+ andi. r11, r11, MSR_PR
+
+ EXCEPTION_PROLOG_1
+ EXCEPTION_PROLOG_2
+#else /* CONFIG_VMAP_STACK */
EXCEPTION_PROLOG
andis. r0,r9,SRR1_ISI_NOPT at h /* no pte found? */
beq 1f /* if so, try to put a PTE */
@@ -329,6 +383,7 @@ InstructionAccess:
BEGIN_MMU_FTR_SECTION
bl hash_page
END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
+#endif /* CONFIG_VMAP_STACK */
1: mr r4,r12
andis. r5,r9,DSISR_SRR1_MATCH_32S at h /* Filter relevant SRR1 bits */
stw r4, _DAR(r11)
@@ -344,7 +399,7 @@ Alignment:
EXCEPTION_PROLOG handle_dar_dsisr=1
save_dar_dsisr_on_stack r4, r5, r11
addi r3,r1,STACK_FRAME_OVERHEAD
- EXC_XFER_STD(0x600, alignment_exception)
+ b alignment_exception_tramp
/* Program check exception */
EXCEPTION(0x700, ProgramCheck, program_check_exception, EXC_XFER_STD)
@@ -645,15 +700,96 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
. = 0x3000
+alignment_exception_tramp:
+ EXC_XFER_STD(0x600, alignment_exception)
+
handle_page_fault_tramp_1:
+#ifdef CONFIG_VMAP_STACK
+ EXCEPTION_PROLOG_2 handle_dar_dsisr=1
+#endif
lwz r4, _DAR(r11)
lwz r5, _DSISR(r11)
/* fall through */
handle_page_fault_tramp_2:
EXC_XFER_LITE(0x300, handle_page_fault)
+#ifdef CONFIG_VMAP_STACK
+.macro save_regs_thread thread
+ stw r0, THR0(\thread)
+ stw r3, THR3(\thread)
+ stw r4, THR4(\thread)
+ stw r5, THR5(\thread)
+ stw r6, THR6(\thread)
+ stw r8, THR8(\thread)
+ stw r9, THR9(\thread)
+ mflr r0
+ stw r0, THLR(\thread)
+ mfctr r0
+ stw r0, THCTR(\thread)
+.endm
+
+.macro restore_regs_thread thread
+ lwz r0, THLR(\thread)
+ mtlr r0
+ lwz r0, THCTR(\thread)
+ mtctr r0
+ lwz r0, THR0(\thread)
+ lwz r3, THR3(\thread)
+ lwz r4, THR4(\thread)
+ lwz r5, THR5(\thread)
+ lwz r6, THR6(\thread)
+ lwz r8, THR8(\thread)
+ lwz r9, THR9(\thread)
+.endm
+
+hash_page_dsi:
+ save_regs_thread r10
+ mfdsisr r3
+ mfdar r4
+ mfsrr1 r9
+ rlwinm r3, r3, 32 - 15, _PAGE_RW /* DSISR_STORE -> _PAGE_RW */
+ bl hash_page
+ mfspr r10, SPRN_SPRG_THREAD
+ restore_regs_thread r10
+ b .Lhash_page_dsi_cont
+
+hash_page_isi:
+ mr r11, r10
+ mfspr r10, SPRN_SPRG_THREAD
+ save_regs_thread r10
+ li r3, 0
+ lwz r4, SRR0(r10)
+ lwz r9, SRR1(r10)
+ bl hash_page
+ mfspr r10, SPRN_SPRG_THREAD
+ restore_regs_thread r10
+ mr r10, r11
+ b .Lhash_page_isi_cont
+
+ .globl fast_hash_page_return
+fast_hash_page_return:
+ andis. r10, r9, SRR1_ISI_NOPT at h /* Set on ISI, cleared on DSI */
+ mfspr r10, SPRN_SPRG_THREAD
+ restore_regs_thread r10
+ bne 1f
+
+ /* DSI */
+ mtcr r11
+ lwz r11, THR11(r10)
+ mfspr r10, SPRN_SPRG_SCRATCH0
+ SYNC
+ RFI
+
+1: /* ISI */
+ mtcr r11
+ mfspr r11, SPRN_SPRG_SCRATCH1
+ mfspr r10, SPRN_SPRG_SCRATCH0
+ SYNC
+ RFI
+
stack_overflow:
vmap_stack_overflow_exception
+#endif
AltiVecUnavailable:
EXCEPTION_PROLOG
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index a6a5fbbf8504..82bc0826108a 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -64,11 +64,19 @@
.endm
.macro EXCEPTION_PROLOG_2 handle_dar_dsisr=0
+#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_PPC_BOOK3S)
+ mtcr r10
+#else
stw r10,_CCR(r11) /* save registers */
+#endif
+ mfspr r10,SPRN_SPRG_SCRATCH0
stw r12,GPR12(r11)
stw r9,GPR9(r11)
- mfspr r10,SPRN_SPRG_SCRATCH0
stw r10,GPR10(r11)
+#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_PPC_BOOK3S)
+ mfcr r10
+ stw r10,_CCR(r11) /* save registers */
+#endif
mfspr r12,SPRN_SPRG_SCRATCH1
stw r12,GPR11(r11)
mflr r10
@@ -83,6 +91,9 @@
stw r10, _DSISR(r11)
.endif
lwz r9, SRR1(r12)
+#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_PPC_BOOK3S)
+ andi. r10, r9, MSR_PR
+#endif
lwz r12, SRR0(r12)
#else
mfspr r12,SPRN_SRR0
diff --git a/arch/powerpc/mm/book3s32/hash_low.S b/arch/powerpc/mm/book3s32/hash_low.S
index c11b0a005196..2015c4f96238 100644
--- a/arch/powerpc/mm/book3s32/hash_low.S
+++ b/arch/powerpc/mm/book3s32/hash_low.S
@@ -25,12 +25,6 @@
#include <asm/feature-fixups.h>
#include <asm/code-patching-asm.h>
-#ifdef CONFIG_VMAP_STACK
-#define ADDR_OFFSET 0
-#else
-#define ADDR_OFFSET PAGE_OFFSET
-#endif
-
#ifdef CONFIG_SMP
.section .bss
.align 2
@@ -53,8 +47,8 @@ mmu_hash_lock:
.text
_GLOBAL(hash_page)
#ifdef CONFIG_SMP
- lis r8, (mmu_hash_lock - ADDR_OFFSET)@h
- ori r8, r8, (mmu_hash_lock - ADDR_OFFSET)@l
+ lis r8, (mmu_hash_lock - PAGE_OFFSET)@h
+ ori r8, r8, (mmu_hash_lock - PAGE_OFFSET)@l
lis r0,0x0fff
b 10f
11: lwz r6,0(r8)
@@ -72,12 +66,9 @@ _GLOBAL(hash_page)
cmplw 0,r4,r0
ori r3,r3,_PAGE_USER|_PAGE_PRESENT /* test low addresses as user */
mfspr r5, SPRN_SPRG_PGDIR /* phys page-table root */
-#ifdef CONFIG_VMAP_STACK
- tovirt(r5, r5)
-#endif
blt+ 112f /* assume user more likely */
- lis r5, (swapper_pg_dir - ADDR_OFFSET)@ha /* if kernel address, use */
- addi r5 ,r5 ,(swapper_pg_dir - ADDR_OFFSET)@l /* kernel page table */
+ lis r5, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */
+ addi r5 ,r5 ,(swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */
rlwimi r3,r9,32-12,29,29 /* MSR_PR -> _PAGE_USER */
112:
#ifndef CONFIG_PTE_64BIT
@@ -89,9 +80,6 @@ _GLOBAL(hash_page)
lwzx r8,r8,r5 /* Get L1 entry */
rlwinm. r8,r8,0,0,20 /* extract pt base address */
#endif
-#ifdef CONFIG_VMAP_STACK
- tovirt(r8, r8)
-#endif
#ifdef CONFIG_SMP
beq- hash_page_out /* return if no mapping */
#else
@@ -143,30 +131,36 @@ retry:
bne- retry /* retry if someone got there first */
mfsrin r3,r4 /* get segment reg for segment */
+#ifndef CONFIG_VMAP_STACK
mfctr r0
stw r0,_CTR(r11)
+#endif
bl create_hpte /* add the hash table entry */
#ifdef CONFIG_SMP
eieio
- lis r8, (mmu_hash_lock - ADDR_OFFSET)@ha
+ lis r8, (mmu_hash_lock - PAGE_OFFSET)@ha
li r0,0
- stw r0, (mmu_hash_lock - ADDR_OFFSET)@l(r8)
+ stw r0, (mmu_hash_lock - PAGE_OFFSET)@l(r8)
#endif
+#ifdef CONFIG_VMAP_STACK
+ b fast_hash_page_return
+#else
/* Return from the exception */
lwz r5,_CTR(r11)
mtctr r5
lwz r0,GPR0(r11)
lwz r8,GPR8(r11)
b fast_exception_return
+#endif
#ifdef CONFIG_SMP
hash_page_out:
eieio
- lis r8, (mmu_hash_lock - ADDR_OFFSET)@ha
+ lis r8, (mmu_hash_lock - PAGE_OFFSET)@ha
li r0,0
- stw r0, (mmu_hash_lock - ADDR_OFFSET)@l(r8)
+ stw r0, (mmu_hash_lock - PAGE_OFFSET)@l(r8)
blr
#endif /* CONFIG_SMP */
@@ -341,7 +335,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
patch_site 1f, patch__hash_page_A1
patch_site 2f, patch__hash_page_A2
/* Get the address of the primary PTE group in the hash table (r3) */
-0: lis r0, (Hash_base - ADDR_OFFSET)@h /* base address of hash table */
+0: lis r0, (Hash_base - PAGE_OFFSET)@h /* base address of hash table */
1: rlwimi r0,r3,LG_PTEG_SIZE,HASH_LEFT,HASH_RIGHT /* VSID -> hash */
2: rlwinm r3,r4,20+LG_PTEG_SIZE,HASH_LEFT,HASH_RIGHT /* PI -> hash */
xor r3,r3,r0 /* make primary hash */
@@ -355,10 +349,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
beq+ 10f /* no PTE: go look for an empty slot */
tlbie r4
- lis r4, (htab_hash_searches - ADDR_OFFSET)@ha
- lwz r6, (htab_hash_searches - ADDR_OFFSET)@l(r4)
+ lis r4, (htab_hash_searches - PAGE_OFFSET)@ha
+ lwz r6, (htab_hash_searches - PAGE_OFFSET)@l(r4)
addi r6,r6,1 /* count how many searches we do */
- stw r6, (htab_hash_searches - ADDR_OFFSET)@l(r4)
+ stw r6, (htab_hash_searches - PAGE_OFFSET)@l(r4)
/* Search the primary PTEG for a PTE whose 1st (d)word matches r5 */
mtctr r0
@@ -390,10 +384,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
beq+ found_empty
/* update counter of times that the primary PTEG is full */
- lis r4, (primary_pteg_full - ADDR_OFFSET)@ha
- lwz r6, (primary_pteg_full - ADDR_OFFSET)@l(r4)
+ lis r4, (primary_pteg_full - PAGE_OFFSET)@ha
+ lwz r6, (primary_pteg_full - PAGE_OFFSET)@l(r4)
addi r6,r6,1
- stw r6, (primary_pteg_full - ADDR_OFFSET)@l(r4)
+ stw r6, (primary_pteg_full - PAGE_OFFSET)@l(r4)
patch_site 0f, patch__hash_page_C
/* Search the secondary PTEG for an empty slot */
@@ -427,8 +421,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
* lockup here but that shouldn't happen
*/
-1: lis r4, (next_slot - ADDR_OFFSET)@ha /* get next evict slot */
- lwz r6, (next_slot - ADDR_OFFSET)@l(r4)
+1: lis r4, (next_slot - PAGE_OFFSET)@ha /* get next evict slot */
+ lwz r6, (next_slot - PAGE_OFFSET)@l(r4)
addi r6,r6,HPTE_SIZE /* search for candidate */
andi. r6,r6,7*HPTE_SIZE
stw r6,next_slot at l(r4)
diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index 0a1c65a2c565..b47c75f5386d 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -413,7 +413,7 @@ void __init MMU_init_hw(void)
void __init MMU_init_hw_patch(void)
{
unsigned int hmask = Hash_mask >> (16 - LG_HPTEG_SIZE);
- unsigned int hash;
+ unsigned int hash = (unsigned int)Hash - PAGE_OFFSET;
if (ppc_md.progress)
ppc_md.progress("hash:patch", 0x345);
@@ -425,11 +425,6 @@ void __init MMU_init_hw_patch(void)
/*
* Patch up the instructions in hashtable.S:create_hpte
*/
- if (IS_ENABLED(CONFIG_VMAP_STACK))
- hash = (unsigned int)Hash;
- else
- hash = (unsigned int)Hash - PAGE_OFFSET;
-
modify_instruction_site(&patch__hash_page_A0, 0xffff, hash >> 16);
modify_instruction_site(&patch__hash_page_A1, 0x7c0, hash_mb << 6);
modify_instruction_site(&patch__hash_page_A2, 0x7c0, hash_mb2 << 6);
--
2.25.0
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