[RFC][PATCH 20/22] x86,usercopy: Remove .fixup usage

[Peter Zijlstra <peterz@infradead.org>]

Typically usercopy does whole word copies followed by a number of byte
copies to finish the tail. This means that on exception it needs to
compute the remaining length as: words*sizeof(long) + bytes.

Create a new extable handler to do just this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/include/asm/extable_fixup_types.h |    5 +++++
 arch/x86/lib/usercopy_32.c                 |   28 +++++-----------------------
 arch/x86/lib/usercopy_64.c                 |    8 +++-----
 arch/x86/mm/extable.c                      |    9 +++++++++
 4 files changed, 22 insertions(+), 28 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -42,4 +42,9 @@
 #define	EX_TYPE_FAULT_SGX		18
 #define	EX_TYPE_KVM_FASTOP		19
 
+#define	EX_TYPE_UACCESS_LEN		20 /* cx := reg + imm*cx */
+#define	EX_TYPE_UACCESS_LEN1		(EX_TYPE_UACCESS_LEN | EX_TYPE_IMM(1))
+#define	EX_TYPE_UACCESS_LEN4		(EX_TYPE_UACCESS_LEN | EX_TYPE_IMM(4))
+#define	EX_TYPE_UACCESS_LEN8		(EX_TYPE_UACCESS_LEN | EX_TYPE_IMM(8))
+
 #endif
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -43,11 +43,7 @@ do {									\
 		"	movl %2,%0\n"					\
 		"1:	rep; stosb\n"					\
 		"2: " ASM_CLAC "\n"					\
-		".section .fixup,\"ax\"\n"				\
-		"3:	lea 0(%2,%0,4),%0\n"				\
-		"	jmp 2b\n"					\
-		".previous\n"						\
-		_ASM_EXTABLE_UA(0b, 3b)					\
+		_ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UACCESS_LEN4, %2)	\
 		_ASM_EXTABLE_UA(1b, 2b)					\
 		: "=&c"(size), "=&D" (__d0)				\
 		: "r"(size & 3), "0"(size / 4), "1"(addr), "a"(0));	\
@@ -149,10 +145,6 @@ __copy_user_intel(void __user *to, const
 		       "36:    movl %%eax, %0\n"
 		       "37:    rep; movsb\n"
 		       "100:\n"
-		       ".section .fixup,\"ax\"\n"
-		       "101:   lea 0(%%eax,%0,4),%0\n"
-		       "       jmp 100b\n"
-		       ".previous\n"
 		       _ASM_EXTABLE_UA(1b, 100b)
 		       _ASM_EXTABLE_UA(2b, 100b)
 		       _ASM_EXTABLE_UA(3b, 100b)
@@ -190,7 +182,7 @@ __copy_user_intel(void __user *to, const
 		       _ASM_EXTABLE_UA(35b, 100b)
 		       _ASM_EXTABLE_UA(36b, 100b)
 		       _ASM_EXTABLE_UA(37b, 100b)
-		       _ASM_EXTABLE_UA(99b, 101b)
+		       _ASM_EXTABLE_TYPE_REG(99b, 100b, EX_TYPE_UACCESS_LEN4, %eax)
 		       : "=&c"(size), "=&D" (d0), "=&S" (d1)
 		       :  "1"(to), "2"(from), "0"(size)
 		       : "eax", "edx", "memory");
@@ -255,10 +247,6 @@ static unsigned long __copy_user_intel_n
 	       "        movl %%eax,%0\n"
 	       "7:      rep; movsb\n"
 	       "8:\n"
-	       ".section .fixup,\"ax\"\n"
-	       "9:      lea 0(%%eax,%0,4),%0\n"
-	       "        jmp 8b\n"
-	       ".previous\n"
 	       _ASM_EXTABLE_UA(0b, 8b)
 	       _ASM_EXTABLE_UA(1b, 8b)
 	       _ASM_EXTABLE_UA(2b, 8b)
@@ -277,7 +265,7 @@ static unsigned long __copy_user_intel_n
 	       _ASM_EXTABLE_UA(81b, 8b)
 	       _ASM_EXTABLE_UA(14b, 8b)
 	       _ASM_EXTABLE_UA(91b, 8b)
-	       _ASM_EXTABLE_UA(6b, 9b)
+	       _ASM_EXTABLE_TYPE_REG(6b, 8b, EX_TYPE_UACCESS_LEN4, %eax)
 	       _ASM_EXTABLE_UA(7b, 8b)
 	       : "=&c"(size), "=&D" (d0), "=&S" (d1)
 	       :  "1"(to), "2"(from), "0"(size)
@@ -315,14 +303,8 @@ do {									\
 		"	movl %3,%0\n"					\
 		"1:	rep; movsb\n"					\
 		"2:\n"							\
-		".section .fixup,\"ax\"\n"				\
-		"5:	addl %3,%0\n"					\
-		"	jmp 2b\n"					\
-		"3:	lea 0(%3,%0,4),%0\n"				\
-		"	jmp 2b\n"					\
-		".previous\n"						\
-		_ASM_EXTABLE_UA(4b, 5b)					\
-		_ASM_EXTABLE_UA(0b, 3b)					\
+		_ASM_EXTABLE_TYPE_REG(4b, 2b, EX_TYPE_UACCESS_LEN1, %3)	\
+		_ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UACCESS_LEN4, %3)	\
 		_ASM_EXTABLE_UA(1b, 2b)					\
 		: "=&c"(size), "=&D" (__d0), "=&S" (__d1), "=r"(__d2)	\
 		: "3"(size), "0"(size), "1"(to), "2"(from)		\
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -35,12 +35,10 @@ unsigned long __clear_user(void __user *
 		"	incq   %[dst]\n"
 		"	decl %%ecx ; jnz  1b\n"
 		"2:\n"
-		".section .fixup,\"ax\"\n"
-		"3:	lea 0(%[size1],%[size8],8),%[size8]\n"
-		"	jmp 2b\n"
-		".previous\n"
-		_ASM_EXTABLE_UA(0b, 3b)
+
+		_ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UACCESS_LEN8, %[size1])
 		_ASM_EXTABLE_UA(1b, 2b)
+
 		: [size8] "=&c"(size), [dst] "=&D" (__d0)
 		: [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr));
 	clac();
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -163,6 +163,13 @@ static bool ex_handler_kvm_fastop(const
 	return true;
 }
 
+static bool ex_handler_uaccess_len(const struct exception_table_entry *fixup,
+				   struct pt_regs *regs, int trapnr, int reg, int imm)
+{
+	regs->cx = imm * regs->cx + *pt_regs_nr(regs, reg);
+	return ex_handler_uaccess(fixup, regs, trapnr);
+}
+
 #define EX_TYPE_MASK	0x000000FF
 #define EX_REG_MASK	0x00000F00
 #define EX_FLAG_MASK	0x0000F000
@@ -242,6 +249,8 @@ int fixup_exception(struct pt_regs *regs
 		return ex_handler_sgx(e, regs, trapnr);
 	case EX_TYPE_KVM_FASTOP:
 		return ex_handler_kvm_fastop(e, regs);
+	case EX_TYPE_UACCESS_LEN:
+		return ex_handler_uaccess_len(e, regs, trapnr, reg, imm);
 	}
 	BUG();
 }