[v4 0/6] powerpc: implement machine check safe memcpy

[v4 0/6] powerpc: implement machine check safe memcpy

[Santosh Sivaraj]

During a memcpy from a pmem device, if a machine check exception is
generated we end up in a panic. In case of fsdax read, this should
only result in a -EIO. Avoid MCE by implementing memcpy_mcsafe.

Before this patch series:

```
bash-4.4# mount -o dax /dev/pmem0 /mnt/pmem/
[ 7621.714094] Disabling lock debugging due to kernel taint
[ 7621.714099] MCE: CPU0: machine check (Severe) Host UE Load/Store [Not recovered]
[ 7621.714104] MCE: CPU0: NIP: [c000000000088978] memcpy_power7+0x418/0x7e0
[ 7621.714107] MCE: CPU0: Hardware error
[ 7621.714112] opal: Hardware platform error: Unrecoverable Machine Check exception
[ 7621.714118] CPU: 0 PID: 1368 Comm: mount Tainted: G   M              5.2.0-rc5-00239-g241e39004581 #50
[ 7621.714123] NIP:  c000000000088978 LR: c0000000008e16f8 CTR: 00000000000001de
[ 7621.714129] REGS: c0000000fffbfd70 TRAP: 0200   Tainted: G   M               (5.2.0-rc5-00239-g241e39004581)
[ 7621.714131] MSR:  9000000002209033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 24428840  XER: 00040000
[ 7621.714160] CFAR: c0000000000889a8 DAR: deadbeefdeadbeef DSISR: 00008000 IRQMASK: 0
[ 7621.714171] GPR00: 000000000e000000 c0000000f0b8b1e0 c0000000012cf100 c0000000ed8e1100 
[ 7621.714186] GPR04: c000020000001100 0000000000010000 0000000000000200 03fffffff1272000 
[ 7621.714201] GPR08: 0000000080000000 0000000000000010 0000000000000020 0000000000000030 
[ 7621.714216] GPR12: 0000000000000040 00007fffb8c6d390 0000000000000050 0000000000000060 
[ 7621.714232] GPR16: 0000000000000070 0000000000000000 0000000000000001 c0000000f0b8b960 
[ 7621.714247] GPR20: 0000000000000001 c0000000f0b8b940 0000000000000001 0000000000010000 
[ 7621.714262] GPR24: c000000001382560 c00c0000003b6380 c00c0000003b6380 0000000000010000 
[ 7621.714277] GPR28: 0000000000000000 0000000000010000 c000020000000000 0000000000010000 
[ 7621.714294] NIP [c000000000088978] memcpy_power7+0x418/0x7e0
[ 7621.714298] LR [c0000000008e16f8] pmem_do_bvec+0xf8/0x430
... <snip> ...
```

After this patch series:

```
bash-4.4# mount -o dax /dev/pmem0 /mnt/pmem/
[25302.883978] Buffer I/O error on dev pmem0, logical block 0, async page read
[25303.020816] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[25303.021236] EXT4-fs (pmem0): Can't read superblock on 2nd try
[25303.152515] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[25303.284031] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[25304.084100] UDF-fs: bad mount option "dax" or missing value
mount: /mnt/pmem: wrong fs type, bad option, bad superblock on /dev/pmem0, missing codepage or helper program, or other error.
```

MCE is injected on a pmem address using mambo. The last patch which adds a nop
is only for testing on mambo, where r13 is not restored upon hitting vector 200.

The memcpy code can be optimised by adding VMX optimizations and GAS macros can
be used to enable code reusablity, which I will send as another series.

---
Change-log:

v4:
* Squash return remaining bytes patch to memcpy_mcsafe implemtation patch [christophe]
* Access ok should be checked for copy_to_user_mcsafe() [christophe]

v3:
* Drop patch which enables DR/IR for external modules
* Drop notifier call chain, we don't want to do that in real mode
* Return remaining bytes from memcpy_mcsafe correctly
* We no longer restore r13 for simulator tests, rather use a nop at 
  vector 0x200 [workaround for simulator; not to be merged]

v2:
* Don't set RI bit explicitly [mahesh]
* Re-ordered series to get r13 workaround as the last patch

---
Balbir Singh (2):
  powerpc/mce: Bug fixes for MCE handling in kernel space
  powerpc/memcpy: Add memcpy_mcsafe for pmem

Reza Arbab (2):
  powerpc/mce: Make machine_check_ue_event() static
  powerpc/64s: save r13 in MCE handler (simulator workaroud)

Santosh Sivaraj (2):
  powerpc/mce: Handle UE event for memcpy_mcsafe
  powerpc: add machine check safe copy_to_user

 arch/powerpc/Kconfig                 |   1 +
 arch/powerpc/include/asm/mce.h       |   7 +-
 arch/powerpc/include/asm/string.h    |   2 +
 arch/powerpc/include/asm/uaccess.h   |  14 ++
 arch/powerpc/kernel/exceptions-64s.S |   1 +
 arch/powerpc/kernel/mce.c            |  11 +-
 arch/powerpc/kernel/mce_power.c      |  41 +++--
 arch/powerpc/lib/Makefile            |   2 +-
 arch/powerpc/lib/memcpy_mcsafe_64.S  | 239 +++++++++++++++++++++++++++
 arch/powerpc/platforms/pseries/ras.c |   6 +-
 10 files changed, 304 insertions(+), 20 deletions(-)
 create mode 100644 arch/powerpc/lib/memcpy_mcsafe_64.S

-- 
2.20.1

[v4 1/6] powerpc/mce: Make machine_check_ue_event() static

[Santosh Sivaraj]

From: Reza Arbab <arbab@linux.ibm.com>

The function doesn't get used outside this file, so make it static.

Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/mce.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index b18df633eae9..e78c4f18ea0a 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -33,7 +33,7 @@ static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT],
 					mce_ue_event_queue);
 
 static void machine_check_process_queued_event(struct irq_work *work);
-void machine_check_ue_event(struct machine_check_event *evt);
+static void machine_check_ue_event(struct machine_check_event *evt);
 static void machine_process_ue_event(struct work_struct *work);
 
 static struct irq_work mce_event_process_work = {
@@ -203,7 +203,7 @@ void release_mce_event(void)
 /*
  * Queue up the MCE event which then can be handled later.
  */
-void machine_check_ue_event(struct machine_check_event *evt)
+static void machine_check_ue_event(struct machine_check_event *evt)
 {
 	int index;
 
-- 
2.20.1

[v4 2/6] powerpc/mce: Bug fixes for MCE handling in kernel space

[Santosh Sivaraj]

From: Balbir Singh <bsingharora@gmail.com>

The code currently assumes PAGE_SHIFT as the shift value of
the pfn, this works correctly (mostly) for user space pages,
but the correct thing to do is

1. Extract the shift value returned via the pte-walk API's
2. Use the shift value to access the instruction address.

Note, the final physical address still use PAGE_SHIFT for
computation. handle_ierror() is not modified and handle_derror()
is modified just for extracting the correct instruction
address.

This is largely due to __find_linux_pte() returning pfn's
shifted by pdshift. The code is much more generic and can
handle shift values returned.

Fixes: ba41e1e1ccb9 ("powerpc/mce: Hookup derror (load/store) UE errors")

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[arbab@linux.ibm.com: Fixup pseries_do_memory_failure()]
Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/include/asm/mce.h       |  3 ++-
 arch/powerpc/kernel/mce_power.c      | 26 ++++++++++++++++----------
 arch/powerpc/platforms/pseries/ras.c |  6 ++++--
 3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index a4c6a74ad2fb..94888a7025b3 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -209,7 +209,8 @@ extern void release_mce_event(void);
 extern void machine_check_queue_event(void);
 extern void machine_check_print_event_info(struct machine_check_event *evt,
 					   bool user_mode, bool in_guest);
-unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr);
+unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr,
+			  unsigned int *shift);
 #ifdef CONFIG_PPC_BOOK3S_64
 void flush_and_reload_slb(void);
 #endif /* CONFIG_PPC_BOOK3S_64 */
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index e39536aad30d..04666c0b40a8 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -23,7 +23,8 @@
  * Convert an address related to an mm to a PFN. NOTE: we are in real
  * mode, we could potentially race with page table updates.
  */
-unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
+unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr,
+			  unsigned int *shift)
 {
 	pte_t *ptep;
 	unsigned long flags;
@@ -36,13 +37,15 @@ unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
 
 	local_irq_save(flags);
 	if (mm == current->mm)
-		ptep = find_current_mm_pte(mm->pgd, addr, NULL, NULL);
+		ptep = find_current_mm_pte(mm->pgd, addr, NULL, shift);
 	else
-		ptep = find_init_mm_pte(addr, NULL);
+		ptep = find_init_mm_pte(addr, shift);
 	local_irq_restore(flags);
 	if (!ptep || pte_special(*ptep))
 		return ULONG_MAX;
-	return pte_pfn(*ptep);
+	if (!*shift)
+		*shift = PAGE_SHIFT;
+	return (pte_val(*ptep) & PTE_RPN_MASK) >> *shift;
 }
 
 /* flush SLBs and reload */
@@ -358,15 +361,16 @@ static int mce_find_instr_ea_and_pfn(struct pt_regs *regs, uint64_t *addr,
 	unsigned long pfn, instr_addr;
 	struct instruction_op op;
 	struct pt_regs tmp = *regs;
+	unsigned int shift;
 
-	pfn = addr_to_pfn(regs, regs->nip);
+	pfn = addr_to_pfn(regs, regs->nip, &shift);
 	if (pfn != ULONG_MAX) {
-		instr_addr = (pfn << PAGE_SHIFT) + (regs->nip & ~PAGE_MASK);
+		instr_addr = (pfn << shift) + (regs->nip & ((1 << shift) - 1));
 		instr = *(unsigned int *)(instr_addr);
 		if (!analyse_instr(&op, &tmp, instr)) {
-			pfn = addr_to_pfn(regs, op.ea);
+			pfn = addr_to_pfn(regs, op.ea, &shift);
 			*addr = op.ea;
-			*phys_addr = (pfn << PAGE_SHIFT);
+			*phys_addr = (pfn << shift);
 			return 0;
 		}
 		/*
@@ -442,12 +446,14 @@ static int mce_handle_ierror(struct pt_regs *regs,
 			if (mce_err->sync_error &&
 				table[i].error_type == MCE_ERROR_TYPE_UE) {
 				unsigned long pfn;
+				unsigned int shift;
 
 				if (get_paca()->in_mce < MAX_MCE_DEPTH) {
-					pfn = addr_to_pfn(regs, regs->nip);
+					pfn = addr_to_pfn(regs, regs->nip,
+							  &shift);
 					if (pfn != ULONG_MAX) {
 						*phys_addr =
-							(pfn << PAGE_SHIFT);
+							(pfn << shift);
 					}
 				}
 			}
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index f16fdd0f71f7..5e43283d3300 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -740,12 +740,14 @@ static void pseries_do_memory_failure(struct pt_regs *regs,
 		paddr = be64_to_cpu(mce_log->logical_address);
 	} else if (mce_log->sub_err_type & UE_EFFECTIVE_ADDR_PROVIDED) {
 		unsigned long pfn;
+		unsigned int shift;
 
 		pfn = addr_to_pfn(regs,
-				  be64_to_cpu(mce_log->effective_address));
+				  be64_to_cpu(mce_log->effective_address),
+				  &shift);
 		if (pfn == ULONG_MAX)
 			return;
-		paddr = pfn << PAGE_SHIFT;
+		paddr = pfn << shift;
 	} else {
 		return;
 	}
-- 
2.20.1

[v4 3/6] powerpc/memcpy: Add memcpy_mcsafe for pmem

[Santosh Sivaraj]

From: Balbir Singh <bsingharora@gmail.com>

The pmem infrastructure uses memcpy_mcsafe in the pmem layer so as to
convert machine check exceptions into a return value on failure in case
a machine check exception is encountered during the memcpy. The return
value is the number of bytes remaining to be copied.

This patch largely borrows from the copyuser_power7 logic and does not add
the VMX optimizations, largely to keep the patch simple. If needed those
optimizations can be folded in.

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[arbab@linux.ibm.com: Added symbol export]
[santosh: return remaining bytes instead of -EFAULT]
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/include/asm/string.h   |   2 +
 arch/powerpc/lib/Makefile           |   2 +-
 arch/powerpc/lib/memcpy_mcsafe_64.S | 239 ++++++++++++++++++++++++++++
 3 files changed, 242 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/lib/memcpy_mcsafe_64.S

diff --git a/arch/powerpc/include/asm/string.h b/arch/powerpc/include/asm/string.h
index 9bf6dffb4090..b72692702f35 100644
--- a/arch/powerpc/include/asm/string.h
+++ b/arch/powerpc/include/asm/string.h
@@ -53,7 +53,9 @@ void *__memmove(void *to, const void *from, __kernel_size_t n);
 #ifndef CONFIG_KASAN
 #define __HAVE_ARCH_MEMSET32
 #define __HAVE_ARCH_MEMSET64
+#define __HAVE_ARCH_MEMCPY_MCSAFE
 
+extern int memcpy_mcsafe(void *dst, const void *src, __kernel_size_t sz);
 extern void *__memset16(uint16_t *, uint16_t v, __kernel_size_t);
 extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
 extern void *__memset64(uint64_t *, uint64_t v, __kernel_size_t);
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index c55f9c27bf79..529d6536eb4a 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -39,7 +39,7 @@ obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
 			       memcpy_power7.o
 
 obj64-y	+= copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
-	   memcpy_64.o pmem.o
+	   memcpy_64.o pmem.o memcpy_mcsafe_64.o
 
 obj64-$(CONFIG_SMP)	+= locks.o
 obj64-$(CONFIG_ALTIVEC)	+= vmx-helper.o
diff --git a/arch/powerpc/lib/memcpy_mcsafe_64.S b/arch/powerpc/lib/memcpy_mcsafe_64.S
new file mode 100644
index 000000000000..4d8a3d315992
--- /dev/null
+++ b/arch/powerpc/lib/memcpy_mcsafe_64.S
@@ -0,0 +1,239 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) IBM Corporation, 2011
+ * Derived from copyuser_power7.s by Anton Blanchard <anton@au.ibm.com>
+ * Author - Balbir Singh <bsingharora@gmail.com>
+ */
+#include <asm/ppc_asm.h>
+#include <asm/errno.h>
+#include <asm/export.h>
+
+	.macro err1
+100:
+	EX_TABLE(100b,.Ldo_err1)
+	.endm
+
+	.macro err2
+200:
+	EX_TABLE(200b,.Ldo_err2)
+	.endm
+
+.Ldo_err2:
+	ld	r22,STK_REG(R22)(r1)
+	ld	r21,STK_REG(R21)(r1)
+	ld	r20,STK_REG(R20)(r1)
+	ld	r19,STK_REG(R19)(r1)
+	ld	r18,STK_REG(R18)(r1)
+	ld	r17,STK_REG(R17)(r1)
+	ld	r16,STK_REG(R16)(r1)
+	ld	r15,STK_REG(R15)(r1)
+	ld	r14,STK_REG(R14)(r1)
+	addi	r1,r1,STACKFRAMESIZE
+.Ldo_err1:
+	/* Do a byte by byte copy to get the exact remaining size */
+	mtctr	r7
+100:	EX_TABLE(100b, .Ldone)
+46:
+err1;	lbz	r0,0(r4)
+	addi	r4,r4,1
+err1;	stb	r0,0(r3)
+	addi	r3,r3,1
+	bdnz	46b
+	li	r3,0
+	blr
+
+.Ldone:
+	mfctr	r3
+	blr
+
+
+_GLOBAL(memcpy_mcsafe)
+	mr	r7,r5
+	cmpldi	r5,16
+	blt	.Lshort_copy
+
+.Lcopy:
+	/* Get the source 8B aligned */
+	neg	r6,r4
+	mtocrf	0x01,r6
+	clrldi	r6,r6,(64-3)
+
+	bf	cr7*4+3,1f
+err1;	lbz	r0,0(r4)
+	addi	r4,r4,1
+err1;	stb	r0,0(r3)
+	addi	r3,r3,1
+	subi	r7,r7,1
+
+1:	bf	cr7*4+2,2f
+err1;	lhz	r0,0(r4)
+	addi	r4,r4,2
+err1;	sth	r0,0(r3)
+	addi	r3,r3,2
+	subi	r7,r7,2
+
+2:	bf	cr7*4+1,3f
+err1;	lwz	r0,0(r4)
+	addi	r4,r4,4
+err1;	stw	r0,0(r3)
+	addi	r3,r3,4
+	subi	r7,r7,4
+
+3:	sub	r5,r5,r6
+	cmpldi	r5,128
+	blt	5f
+
+	mflr	r0
+	stdu	r1,-STACKFRAMESIZE(r1)
+	std	r14,STK_REG(R14)(r1)
+	std	r15,STK_REG(R15)(r1)
+	std	r16,STK_REG(R16)(r1)
+	std	r17,STK_REG(R17)(r1)
+	std	r18,STK_REG(R18)(r1)
+	std	r19,STK_REG(R19)(r1)
+	std	r20,STK_REG(R20)(r1)
+	std	r21,STK_REG(R21)(r1)
+	std	r22,STK_REG(R22)(r1)
+	std	r0,STACKFRAMESIZE+16(r1)
+
+	srdi	r6,r5,7
+	mtctr	r6
+
+	/* Now do cacheline (128B) sized loads and stores. */
+	.align	5
+4:
+err2;	ld	r0,0(r4)
+err2;	ld	r6,8(r4)
+err2;	ld	r8,16(r4)
+err2;	ld	r9,24(r4)
+err2;	ld	r10,32(r4)
+err2;	ld	r11,40(r4)
+err2;	ld	r12,48(r4)
+err2;	ld	r14,56(r4)
+err2;	ld	r15,64(r4)
+err2;	ld	r16,72(r4)
+err2;	ld	r17,80(r4)
+err2;	ld	r18,88(r4)
+err2;	ld	r19,96(r4)
+err2;	ld	r20,104(r4)
+err2;	ld	r21,112(r4)
+err2;	ld	r22,120(r4)
+	addi	r4,r4,128
+err2;	std	r0,0(r3)
+err2;	std	r6,8(r3)
+err2;	std	r8,16(r3)
+err2;	std	r9,24(r3)
+err2;	std	r10,32(r3)
+err2;	std	r11,40(r3)
+err2;	std	r12,48(r3)
+err2;	std	r14,56(r3)
+err2;	std	r15,64(r3)
+err2;	std	r16,72(r3)
+err2;	std	r17,80(r3)
+err2;	std	r18,88(r3)
+err2;	std	r19,96(r3)
+err2;	std	r20,104(r3)
+err2;	std	r21,112(r3)
+err2;	std	r22,120(r3)
+	addi	r3,r3,128
+	subi	r7,r7,128
+	bdnz	4b
+
+	clrldi	r5,r5,(64-7)
+
+	/* Up to 127B to go */
+5:	srdi	r6,r5,4
+	mtocrf	0x01,r6
+
+6:	bf	cr7*4+1,7f
+err2;	ld	r0,0(r4)
+err2;	ld	r6,8(r4)
+err2;	ld	r8,16(r4)
+err2;	ld	r9,24(r4)
+err2;	ld	r10,32(r4)
+err2;	ld	r11,40(r4)
+err2;	ld	r12,48(r4)
+err2;	ld	r14,56(r4)
+	addi	r4,r4,64
+err2;	std	r0,0(r3)
+err2;	std	r6,8(r3)
+err2;	std	r8,16(r3)
+err2;	std	r9,24(r3)
+err2;	std	r10,32(r3)
+err2;	std	r11,40(r3)
+err2;	std	r12,48(r3)
+err2;	std	r14,56(r3)
+	addi	r3,r3,64
+	subi	r7,r7,64
+
+7:	ld	r14,STK_REG(R14)(r1)
+	ld	r15,STK_REG(R15)(r1)
+	ld	r16,STK_REG(R16)(r1)
+	ld	r17,STK_REG(R17)(r1)
+	ld	r18,STK_REG(R18)(r1)
+	ld	r19,STK_REG(R19)(r1)
+	ld	r20,STK_REG(R20)(r1)
+	ld	r21,STK_REG(R21)(r1)
+	ld	r22,STK_REG(R22)(r1)
+	addi	r1,r1,STACKFRAMESIZE
+
+	/* Up to 63B to go */
+	bf	cr7*4+2,8f
+err1;	ld	r0,0(r4)
+err1;	ld	r6,8(r4)
+err1;	ld	r8,16(r4)
+err1;	ld	r9,24(r4)
+	addi	r4,r4,32
+err1;	std	r0,0(r3)
+err1;	std	r6,8(r3)
+err1;	std	r8,16(r3)
+err1;	std	r9,24(r3)
+	addi	r3,r3,32
+	subi	r7,r7,32
+
+	/* Up to 31B to go */
+8:	bf	cr7*4+3,9f
+err1;	ld	r0,0(r4)
+err1;	ld	r6,8(r4)
+	addi	r4,r4,16
+err1;	std	r0,0(r3)
+err1;	std	r6,8(r3)
+	addi	r3,r3,16
+	subi	r7,r7,16
+
+9:	clrldi	r5,r5,(64-4)
+
+	/* Up to 15B to go */
+.Lshort_copy:
+	mtocrf	0x01,r5
+	bf	cr7*4+0,12f
+err1;	lwz	r0,0(r4)	/* Less chance of a reject with word ops */
+err1;	lwz	r6,4(r4)
+	addi	r4,r4,8
+err1;	stw	r0,0(r3)
+err1;	stw	r6,4(r3)
+	addi	r3,r3,8
+	subi	r7,r7,8
+
+12:	bf	cr7*4+1,13f
+err1;	lwz	r0,0(r4)
+	addi	r4,r4,4
+err1;	stw	r0,0(r3)
+	addi	r3,r3,4
+	subi	r7,r7,4
+
+13:	bf	cr7*4+2,14f
+err1;	lhz	r0,0(r4)
+	addi	r4,r4,2
+err1;	sth	r0,0(r3)
+	addi	r3,r3,2
+	subi	r7,r7,2
+
+14:	bf	cr7*4+3,15f
+err1;	lbz	r0,0(r4)
+err1;	stb	r0,0(r3)
+
+15:	li	r3,0
+	blr
+
+EXPORT_SYMBOL_GPL(memcpy_mcsafe);
-- 
2.20.1

[v4 4/6] powerpc/mce: Handle UE event for memcpy_mcsafe

[Santosh Sivaraj]

If we take a UE on one of the instructions with a fixup entry, set nip
to continue exucution at the fixup entry. Stop processing the event
further or print it.

Based-on-patch-by: Reza Arbab <arbab@linux.ibm.com>
Cc: Reza Arbab <arbab@linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/include/asm/mce.h  |  4 +++-
 arch/powerpc/kernel/mce.c       |  7 ++++++-
 arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index 94888a7025b3..f74257eb013b 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -122,7 +122,8 @@ struct machine_check_event {
 			enum MCE_UeErrorType ue_error_type:8;
 			u8		effective_address_provided;
 			u8		physical_address_provided;
-			u8		reserved_1[5];
+			u8		ignore_event;
+			u8		reserved_1[4];
 			u64		effective_address;
 			u64		physical_address;
 			u8		reserved_2[8];
@@ -193,6 +194,7 @@ struct mce_error_info {
 	enum MCE_Initiator	initiator:8;
 	enum MCE_ErrorClass	error_class:8;
 	bool			sync_error;
+	bool			ignore_event;
 };
 
 #define MAX_MC_EVT	100
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index e78c4f18ea0a..94f2bb307537 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -144,7 +144,9 @@ void save_mce_event(struct pt_regs *regs, long handled,
 		if (phys_addr != ULONG_MAX) {
 			mce->u.ue_error.physical_address_provided = true;
 			mce->u.ue_error.physical_address = phys_addr;
-			machine_check_ue_event(mce);
+			mce->u.ue_error.ignore_event = mce_err->ignore_event;
+			if (!mce->u.ue_error.ignore_event)
+				machine_check_ue_event(mce);
 		}
 	}
 	return;
@@ -230,6 +232,9 @@ void machine_check_queue_event(void)
 	if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
 		return;
 
+	if (evt.error_type == MCE_ERROR_TYPE_UE && evt.u.ue_error.ignore_event)
+		return;
+
 	index = __this_cpu_inc_return(mce_queue_count) - 1;
 	/* If queue is full, just return for now. */
 	if (index >= MAX_MC_EVT) {
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index 04666c0b40a8..db4aa98a23ac 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/ptrace.h>
+#include <linux/extable.h>
 #include <asm/mmu.h>
 #include <asm/mce.h>
 #include <asm/machdep.h>
@@ -18,6 +19,7 @@
 #include <asm/pte-walk.h>
 #include <asm/sstep.h>
 #include <asm/exception-64s.h>
+#include <asm/extable.h>
 
 /*
  * Convert an address related to an mm to a PFN. NOTE: we are in real
@@ -565,9 +567,18 @@ static int mce_handle_derror(struct pt_regs *regs,
 	return 0;
 }
 
-static long mce_handle_ue_error(struct pt_regs *regs)
+static long mce_handle_ue_error(struct pt_regs *regs,
+				struct mce_error_info *mce_err)
 {
 	long handled = 0;
+	const struct exception_table_entry *entry;
+
+	entry = search_exception_tables(regs->nip);
+	if (entry) {
+		mce_err->ignore_event = true;
+		regs->nip = extable_fixup(entry);
+		return 1;
+	}
 
 	/*
 	 * On specific SCOM read via MMIO we may get a machine check
@@ -600,7 +611,7 @@ static long mce_handle_error(struct pt_regs *regs,
 				&phys_addr);
 
 	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
-		handled = mce_handle_ue_error(regs);
+		handled = mce_handle_ue_error(regs, &mce_err);
 
 	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
 
-- 
2.20.1

[v4 5/6] powerpc: add machine check safe copy_to_user

[Santosh Sivaraj]

Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()

Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/Kconfig               |  1 +
 arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8c1c636308c8..a173b392c272 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -134,6 +134,7 @@ config PPC
 	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE	if PPC64
+	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_HAS_ZONE_DEVICE		if PPC_BOOK3S_64
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 76f34346b642..8899864a5552 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -386,6 +386,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
 	return ret;
 }
 
+static __always_inline unsigned long __must_check
+copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
+{
+	if (likely(check_copy_size(from, n, true))) {
+		if (access_ok(to, n)) {
+			allow_write_to_user(to, n);
+			n = memcpy_mcsafe((void *)to, from, n);
+			prevent_write_to_user(to, n);
+		}
+	}
+
+	return n;
+}
+
 extern unsigned long __clear_user(void __user *addr, unsigned long size);
 
 static inline unsigned long clear_user(void __user *addr, unsigned long size)
-- 
2.20.1

[v4 6/6] powerpc/64s: save r13 in MCE handler (simulator workaroud)

[Santosh Sivaraj]

From: Reza Arbab <arbab@linux.ibm.com>

Testing my memcpy_mcsafe() work in progress with an injected UE, I get
an error like this immediately after the function returns:

BUG: Unable to handle kernel data access at 0x7fff84dec8f8
Faulting instruction address: 0xc0080000009c00b0
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV
Modules linked in: mce(O+) vmx_crypto crc32c_vpmsum
CPU: 0 PID: 1375 Comm: modprobe Tainted: G           O      5.1.0-rc6 #267
NIP:  c0080000009c00b0 LR: c0080000009c00a8 CTR: c000000000095f90
REGS: c0000000ee197790 TRAP: 0300   Tainted: G           O       (5.1.0-rc6)
MSR:  900000000280b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 88002826  XER: 00040000
CFAR: c000000000095f8c DAR: 00007fff84dec8f8 DSISR: 40000000 IRQMASK: 0
GPR00: 000000006c6c6568 c0000000ee197a20 c0080000009c8400 fffffffffffffff2
GPR04: c0080000009c02e0 0000000000000006 0000000000000000 c000000003c834c8
GPR08: 0080000000000000 776a6681b7fb5100 0000000000000000 c0080000009c01c8
GPR12: c000000000095f90 00007fff84debc00 000000004d071440 0000000000000000
GPR16: 0000000100000601 c0080000009e0000 c000000000c98dd8 c000000000c98d98
GPR20: c000000003bba970 c0080000009c04d0 c0080000009c0618 c0000000001e5820
GPR24: 0000000000000000 0000000000000100 0000000000000001 c000000003bba958
GPR28: c0080000009c02e8 c0080000009c0318 c0080000009c02e0 0000000000000000
NIP [c0080000009c00b0] cause_ue+0xa8/0xe8 [mce]
LR [c0080000009c00a8] cause_ue+0xa0/0xe8 [mce]

After debugging we see that the first instruction at vector 200 is skipped by
the simulator, due to which r13 is not saved. Adding a nop at 0x200 fixes the
issue.

(This commit is needed for testing this series. This should not be taken
into the tree)
---
 arch/powerpc/kernel/exceptions-64s.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 73ba246ca11d..8e43abb2a744 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -255,6 +255,7 @@ EXC_REAL_BEGIN(machine_check, 0x200, 0x100)
 	 * some code path might still want to branch into the original
 	 * vector
 	 */
+	nop
 	SET_SCRATCH0(r13)		/* save r13 */
 	EXCEPTION_PROLOG_0(PACA_EXMC)
 BEGIN_FTR_SECTION
-- 
2.20.1

Re: [v4 5/6] powerpc: add machine check safe copy_to_user

[Christophe Leroy]

Le 06/07/2019 à 11:46, Santosh Sivaraj a écrit :
> Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
> 
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> ---
>   arch/powerpc/Kconfig               |  1 +
>   arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
>   2 files changed, 15 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 8c1c636308c8..a173b392c272 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -134,6 +134,7 @@ config PPC
>   	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
>   	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HAS_UACCESS_FLUSHCACHE	if PPC64
> +	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
>   	select ARCH_HAS_UBSAN_SANITIZE_ALL
>   	select ARCH_HAS_ZONE_DEVICE		if PPC_BOOK3S_64
>   	select ARCH_HAVE_NMI_SAFE_CMPXCHG
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 76f34346b642..8899864a5552 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -386,6 +386,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
>   	return ret;
>   }
>   
> +static __always_inline unsigned long __must_check
> +copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
> +{
> +	if (likely(check_copy_size(from, n, true))) {
> +		if (access_ok(to, n)) {

After looking once more, it looks like copy_to_user_mcsafe() is only 
called from copyout_mcsafe(), so maybe this access_ok() check is 
superfluous.

> +			allow_write_to_user(to, n);
> +			n = memcpy_mcsafe((void *)to, from, n);
> +			prevent_write_to_user(to, n);
> +		}
> +	}
> +
> +	return n;

Shouldn't it return 0 when check_copy_size() fails ?

Christophe

> +}
> +
>   extern unsigned long __clear_user(void __user *addr, unsigned long size);
>   
>   static inline unsigned long clear_user(void __user *addr, unsigned long size)
>