[RFC PATCH -next V3 5/6] arm64: add {get, put}_user to machine check safe

[Tong Tiangen]

Add {get, put}_user() to machine check safe.

If get/put fail due to hardware memory error, if get/put fail due to
hardware memory error, only the relevant processes are affected, so killing
the user process and isolate the user page with hardware memory errors is a
more reasonable choice than kernel panic.

Add new extable type EX_TYPE_UACCESS_MC_ERR_ZERO which can be used for
uaccess that can be recovered from hardware memory errors. The difference
from EX_TYPE_UACCESS_MC is that this type also sets additional two target
register which save error code and value needs to be set zero.

Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
---
 arch/arm64/include/asm/asm-extable.h | 14 ++++++++++++++
 arch/arm64/include/asm/uaccess.h     |  4 ++--
 arch/arm64/mm/extable.c              |  3 +++
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
index 8af4e7cc9578..62eafb651773 100644
--- a/arch/arm64/include/asm/asm-extable.h
+++ b/arch/arm64/include/asm/asm-extable.h
@@ -10,6 +10,7 @@
 
 /* _MC indicates that can fixup from machine check errors */
 #define EX_TYPE_UACCESS_MC		5
+#define EX_TYPE_UACCESS_MC_ERR_ZERO	6
 
 #ifdef __ASSEMBLY__
 
@@ -75,6 +76,15 @@
 #define EX_DATA_REG(reg, gpr)						\
 	"((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")"
 
+#define _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(insn, fixup, err, zero)		\
+	__DEFINE_ASM_GPR_NUMS							\
+	__ASM_EXTABLE_RAW(#insn, #fixup,					\
+			  __stringify(EX_TYPE_UACCESS_MC_ERR_ZERO),		\
+			  "("							\
+			    EX_DATA_REG(ERR, err) " | "				\
+			    EX_DATA_REG(ZERO, zero)				\
+			  ")")
+
 #define _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, zero)		\
 	__DEFINE_ASM_GPR_NUMS						\
 	__ASM_EXTABLE_RAW(#insn, #fixup, 				\
@@ -87,6 +97,10 @@
 #define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err)			\
 	_ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, wzr)
 
+
+#define _ASM_EXTABLE_UACCESS_MC_ERR(insn, fixup, err)			\
+	_ASM_EXTABLE_UACCESS_MC_ERR_ZERO(insn, fixup, err, wzr)
+
 #define EX_DATA_REG_DATA_SHIFT	0
 #define EX_DATA_REG_DATA	GENMASK(4, 0)
 #define EX_DATA_REG_ADDR_SHIFT	5
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index e8dce0cc5eaa..e41b47df48b0 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -236,7 +236,7 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 	asm volatile(							\
 	"1:	" load "	" reg "1, [%2]\n"			\
 	"2:\n"								\
-	_ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %w0, %w1)			\
+	_ASM_EXTABLE_UACCESS_MC_ERR_ZERO(1b, 2b, %w0, %w1)		\
 	: "+r" (err), "=&r" (x)						\
 	: "r" (addr))
 
@@ -325,7 +325,7 @@ do {									\
 	asm volatile(							\
 	"1:	" store "	" reg "1, [%2]\n"			\
 	"2:\n"								\
-	_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0)				\
+	_ASM_EXTABLE_UACCESS_MC_ERR(1b, 2b, %w0)			\
 	: "+r" (err)							\
 	: "r" (x), "r" (addr))
 
diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
index 5de256a25464..ca7388f3923b 100644
--- a/arch/arm64/mm/extable.c
+++ b/arch/arm64/mm/extable.c
@@ -79,6 +79,7 @@ bool fixup_exception(struct pt_regs *regs)
 	case EX_TYPE_BPF:
 		return ex_handler_bpf(ex, regs);
 	case EX_TYPE_UACCESS_ERR_ZERO:
+	case EX_TYPE_UACCESS_MC_ERR_ZERO:
 		return ex_handler_uaccess_err_zero(ex, regs);
 	case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
 		return ex_handler_load_unaligned_zeropad(ex, regs);
@@ -98,6 +99,8 @@ bool fixup_exception_mc(struct pt_regs *regs)
 	switch (ex->type) {
 	case EX_TYPE_UACCESS_MC:
 		return ex_handler_fixup(ex, regs);
+	case EX_TYPE_UACCESS_MC_ERR_ZERO:
+		return ex_handler_uaccess_err_zero(ex, regs);
 	}
 
 	return false;
-- 
2.18.0.huawei.25