From e74deb11931ff682b59d5b9d387f7115f689698e Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 3 Apr 2019 09:39:48 +0200
Subject: x86/uaccess: Introduce user_access_{save,restore}()

Introduce common helpers for when we need to safely suspend a
uaccess section; for instance to generate a {KA,UB}SAN report.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/smap.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'arch/x86/include/asm/smap.h')

diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h
index db333300bd4b..6cfe43171020 100644
--- a/arch/x86/include/asm/smap.h
+++ b/arch/x86/include/asm/smap.h
@@ -58,6 +58,23 @@ static __always_inline void stac(void)
 	alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP);
 }
 
+static __always_inline unsigned long smap_save(void)
+{
+	unsigned long flags;
+
+	asm volatile (ALTERNATIVE("", "pushf; pop %0; " __stringify(__ASM_CLAC),
+				  X86_FEATURE_SMAP)
+		      : "=rm" (flags) : : "memory", "cc");
+
+	return flags;
+}
+
+static __always_inline void smap_restore(unsigned long flags)
+{
+	asm volatile (ALTERNATIVE("", "push %0; popf", X86_FEATURE_SMAP)
+		      : : "g" (flags) : "memory", "cc");
+}
+
 /* These macros can be used in asm() statements */
 #define ASM_CLAC \
 	ALTERNATIVE("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
@@ -69,6 +86,9 @@ static __always_inline void stac(void)
 static inline void clac(void) { }
 static inline void stac(void) { }
 
+static inline unsigned long smap_save(void) { return 0; }
+static inline void smap_restore(unsigned long flags) { }
+
 #define ASM_CLAC
 #define ASM_STAC
 
-- 
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