linux-kernel - [RFC][PATCH 14/22] x86,ftrace: Remove .fixup usage

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Date:   Thu, 04 Nov 2021 17:47:43 +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 14/22] x86,ftrace: Remove .fixup usage

Create and use EX_TYPE_ONE_REG to load 1 into the %[faulted] register
on exception.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/extable_fixup_types.h |    1 +
 arch/x86/kernel/ftrace.c                   |    9 ++-------
 2 files changed, 3 insertions(+), 7 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -37,5 +37,6 @@
 #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))
 #define	EX_TYPE_ZERO_REG		(EX_TYPE_IMM_REG | EX_TYPE_IMM(0))
+#define	EX_TYPE_ONE_REG			(EX_TYPE_IMM_REG | EX_TYPE_IMM(1))
 
 #endif
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -661,13 +661,8 @@ void prepare_ftrace_return(unsigned long
 		"   movl $0, %[faulted]\n"
 		"3:\n"
 
-		".section .fixup, \"ax\"\n"
-		"4: movl $1, %[faulted]\n"
-		"   jmp 3b\n"
-		".previous\n"
-
-		_ASM_EXTABLE(1b, 4b)
-		_ASM_EXTABLE(2b, 4b)
+		_ASM_EXTABLE_TYPE_REG(1b, 3b, EX_TYPE_ONE_REG, %[faulted])
+		_ASM_EXTABLE_TYPE_REG(2b, 3b, EX_TYPE_ONE_REG, %[faulted])
 
 		: [old] "=&r" (old), [faulted] "=r" (faulted)
 		: [parent] "r" (parent), [return_hooker] "r" (return_hooker)