linux-kernel - [RFC][PATCH 11/22] x86,xen: Remove .fixup usage

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Message-ID: <20211104165525.168368031@infradead.org>
Date:   Thu, 04 Nov 2021 17:47:40 +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 11/22] x86,xen: Remove .fixup usage

Employ the fancy new EX_TYPE_IMM_REG to create EX_TYPE_NEG_REG to
store '-1' into the designated register and use this to remove some
Xen .fixup usage.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/extable_fixup_types.h |    1 +
 arch/x86/include/asm/xen/page.h            |   12 ++----------
 2 files changed, 3 insertions(+), 10 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -35,5 +35,6 @@
 
 #define	EX_TYPE_IMM_REG			17 /* reg := (long)imm */
 #define	EX_TYPE_EFAULT_REG		(EX_TYPE_IMM_REG | EX_TYPE_IMM(-EFAULT))
+#define	EX_TYPE_NEG_REG			(EX_TYPE_IMM_REG | EX_TYPE_IMM(-1))
 
 #endif
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -96,11 +96,7 @@ static inline int xen_safe_write_ulong(u
 
 	asm volatile("1: mov %[val], %[ptr]\n"
 		     "2:\n"
-		     ".section .fixup, \"ax\"\n"
-		     "3: sub $1, %[ret]\n"
-		     "   jmp 2b\n"
-		     ".previous\n"
-		     _ASM_EXTABLE(1b, 3b)
+		     _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_NEG_REG, %[ret])
 		     : [ret] "+r" (ret), [ptr] "=m" (*addr)
 		     : [val] "r" (val));
 
@@ -115,11 +111,7 @@ static inline int xen_safe_read_ulong(co
 
 	asm volatile("1: mov %[ptr], %[rval]\n"
 		     "2:\n"
-		     ".section .fixup, \"ax\"\n"
-		     "3: sub $1, %[ret]\n"
-		     "   jmp 2b\n"
-		     ".previous\n"
-		     _ASM_EXTABLE(1b, 3b)
+		     _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_NEG_REG, %[ret])
 		     : [ret] "+r" (ret), [rval] "+r" (rval)
 		     : [ptr] "m" (*addr));
 	*val = rval;