linux-kernel - [PATCH 13/22] x86,segment: Remove .fixup usage

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Message-ID: <20211105171821.232888632@infradead.org>
Date:   Fri, 05 Nov 2021 18:10:36 +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: [PATCH 13/22] x86,segment: Remove .fixup usage

Create and use EX_TYPE_ZERO_REG to clear the register and retry the
segment load on exception.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/extable_fixup_types.h |    1 +
 arch/x86/include/asm/segment.h             |    9 +--------
 2 files changed, 2 insertions(+), 8 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -36,5 +36,6 @@
 #define	EX_TYPE_IMM_REG			17 /* reg := (long)imm */
 #define	EX_TYPE_EFAULT_REG		(EX_TYPE_IMM_REG | EX_DATA_IMM(-EFAULT))
 #define	EX_TYPE_NEG_REG			(EX_TYPE_IMM_REG | EX_DATA_IMM(-1))
+#define	EX_TYPE_ZERO_REG		(EX_TYPE_IMM_REG | EX_DATA_IMM(0))
 
 #endif
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -307,14 +307,7 @@ do {									\
 									\
 	asm volatile("						\n"	\
 		     "1:	movl %k0,%%" #seg "		\n"	\
-									\
-		     ".section .fixup,\"ax\"			\n"	\
-		     "2:	xorl %k0,%k0			\n"	\
-		     "		jmp 1b				\n"	\
-		     ".previous					\n"	\
-									\
-		     _ASM_EXTABLE(1b, 2b)				\
-									\
+		     _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k0)\
 		     : "+r" (__val) : : "memory");			\
 } while (0)