linux-kernel - [PATCH 05/15] x86: Add arch specific kasan functions

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Message-ID: <911ad4b9f001bca4c274b60144b1db80eab2015f.1738686764.git.maciej.wieczor-retman@intel.com>
Date: Tue,  4 Feb 2025 18:33:46 +0100
From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
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Subject: [PATCH 05/15] x86: Add arch specific kasan functions

KASAN's software tag-based mode needs multiple macros/functions to
handle tag and pointer interactions - mainly to set and retrieve tags
from the top bits of a pointer.

Mimic functions currently used by arm64 but change the tag's position to
bits [60:57] in the pointer.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
---
 arch/x86/include/asm/kasan.h | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h
index de75306b932e..8829337a75fa 100644
--- a/arch/x86/include/asm/kasan.h
+++ b/arch/x86/include/asm/kasan.h
@@ -3,6 +3,8 @@
 #define _ASM_X86_KASAN_H
 
 #include <linux/const.h>
+#include <linux/kasan-tags.h>
+#include <linux/types.h>
 #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
 #define KASAN_SHADOW_SCALE_SHIFT 3
 
@@ -24,8 +26,33 @@
 						  KASAN_SHADOW_SCALE_SHIFT)))
 
 #ifndef __ASSEMBLY__
+#include <linux/bitops.h>
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+
+#define arch_kasan_set_tag(addr, tag)	__tag_set(addr, tag)
+#define arch_kasan_reset_tag(addr)	__tag_reset(addr)
+#define arch_kasan_get_tag(addr)	__tag_get(addr)
+
+#ifdef CONFIG_KASAN_SW_TAGS
+
+#define __tag_shifted(tag)		FIELD_PREP(GENMASK_ULL(60, 57), tag)
+#define __tag_reset(addr)		(sign_extend64((u64)(addr), 56))
+#define __tag_get(addr)			((u8)FIELD_GET(GENMASK_ULL(60, 57), (u64)addr))
+#else
+#define __tag_shifted(tag)		0UL
+#define __tag_reset(addr)		(addr)
+#define __tag_get(addr)			0
+#endif /* CONFIG_KASAN_SW_TAGS */
 
 #ifdef CONFIG_KASAN
+
+static inline const void *__tag_set(const void *addr, u8 tag)
+{
+	u64 __addr = (u64)addr & ~__tag_shifted(KASAN_TAG_KERNEL);
+	return (const void *)(__addr | __tag_shifted(tag));
+}
+
 void __init kasan_early_init(void);
 void __init kasan_init(void);
 void __init kasan_populate_shadow_for_vaddr(void *va, size_t size, int nid);
@@ -34,8 +61,9 @@ static inline void kasan_early_init(void) { }
 static inline void kasan_init(void) { }
 static inline void kasan_populate_shadow_for_vaddr(void *va, size_t size,
 						   int nid) { }
-#endif
 
-#endif
+#endif /* CONFIG_KASAN */
+
+#endif /* __ASSEMBLY__ */
 
 #endif
-- 
2.47.1