linux-kernel - [RFC][PATCH 03/22] x86,copy_user

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Message-ID: <20211104165524.685209465@infradead.org>
Date:   Thu, 04 Nov 2021 17:47:32 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        jpoimboe@...hat.com, mark.rutland@....com, dvyukov@...gle.com,
        seanjc@...gle.com, pbonzini@...hat.com, mbenes@...e.cz
Subject: [RFC][PATCH 03/22] x86,copy_user_64: Remove .fixup usage

Place the anonymous .fixup code at the tail of the regular functions.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/lib/copy_user_64.S |   32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -32,14 +32,10 @@
 	decl %ecx
 	jnz 100b
 102:
-	.section .fixup,"ax"
-103:	addl %ecx,%edx			/* ecx is zerorest also */
-	jmp .Lcopy_user_handle_tail
-	.previous
 
-	_ASM_EXTABLE_CPY(100b, 103b)
-	_ASM_EXTABLE_CPY(101b, 103b)
-	.endm
+	_ASM_EXTABLE_CPY(100b, .Lcopy_user_handle_align)
+	_ASM_EXTABLE_CPY(101b, .Lcopy_user_handle_align)
+.endm
 
 /*
  * copy_user_generic_unrolled - memory copy with exception handling.
@@ -107,7 +103,6 @@ SYM_FUNC_START(copy_user_generic_unrolle
 	ASM_CLAC
 	ret
 
-	.section .fixup,"ax"
 30:	shll $6,%ecx
 	addl %ecx,%edx
 	jmp 60f
@@ -115,7 +110,6 @@ SYM_FUNC_START(copy_user_generic_unrolle
 	jmp 60f
 50:	movl %ecx,%edx
 60:	jmp .Lcopy_user_handle_tail /* ecx is zerorest also */
-	.previous
 
 	_ASM_EXTABLE_CPY(1b, 30b)
 	_ASM_EXTABLE_CPY(2b, 30b)
@@ -166,20 +160,16 @@ SYM_FUNC_START(copy_user_generic_string)
 	movl %edx,%ecx
 	shrl $3,%ecx
 	andl $7,%edx
-1:	rep
-	movsq
+1:	rep movsq
 2:	movl %edx,%ecx
-3:	rep
-	movsb
+3:	rep movsb
 	xorl %eax,%eax
 	ASM_CLAC
 	ret
 
-	.section .fixup,"ax"
 11:	leal (%rdx,%rcx,8),%ecx
 12:	movl %ecx,%edx		/* ecx is zerorest also */
 	jmp .Lcopy_user_handle_tail
-	.previous
 
 	_ASM_EXTABLE_CPY(1b, 11b)
 	_ASM_EXTABLE_CPY(3b, 12b)
@@ -203,16 +193,13 @@ SYM_FUNC_START(copy_user_enhanced_fast_s
 	cmpl $64,%edx
 	jb .L_copy_short_string	/* less then 64 bytes, avoid the costly 'rep' */
 	movl %edx,%ecx
-1:	rep
-	movsb
+1:	rep movsb
 	xorl %eax,%eax
 	ASM_CLAC
 	ret
 
-	.section .fixup,"ax"
 12:	movl %ecx,%edx		/* ecx is zerorest also */
 	jmp .Lcopy_user_handle_tail
-	.previous
 
 	_ASM_EXTABLE_CPY(1b, 12b)
 SYM_FUNC_END(copy_user_enhanced_fast_string)
@@ -240,6 +227,11 @@ SYM_CODE_START_LOCAL(.Lcopy_user_handle_
 	ret
 
 	_ASM_EXTABLE_CPY(1b, 2b)
+
+.Lcopy_user_handle_align:
+	addl %ecx,%edx			/* ecx is zerorest also */
+	jmp .Lcopy_user_handle_tail
+
 SYM_CODE_END(.Lcopy_user_handle_tail)
 
 /*
@@ -350,7 +342,6 @@ SYM_FUNC_START(__copy_user_nocache)
 	sfence
 	ret
 
-	.section .fixup,"ax"
 .L_fixup_4x8b_copy:
 	shll $6,%ecx
 	addl %ecx,%edx
@@ -366,7 +357,6 @@ SYM_FUNC_START(__copy_user_nocache)
 .L_fixup_handle_tail:
 	sfence
 	jmp .Lcopy_user_handle_tail
-	.previous
 
 	_ASM_EXTABLE_CPY(1b, .L_fixup_4x8b_copy)
 	_ASM_EXTABLE_CPY(2b, .L_fixup_4x8b_copy)