1 files changed, 87 insertions, 0 deletions
diff --git a/arch/x86/include/asm/kmsan.h b/arch/x86/include/asm/kmsan.h
new file mode 100644
index 000000000000..8fa6ac0e2d76
--- /dev/null
+++ b/arch/x86/include/asm/kmsan.h
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * x86 KMSAN support.
+ *
+ * Copyright (C) 2022, Google LLC
+ * Author: Alexander Potapenko <glider@google.com>
+ */
+
+#ifndef _ASM_X86_KMSAN_H
+#define _ASM_X86_KMSAN_H
+
+#ifndef MODULE
+
+#include <asm/cpu_entry_area.h>
+#include <asm/processor.h>
+#include <linux/mmzone.h>
+
+DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_shadow);
+DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_origin);
+
+/*
+ * Functions below are declared in the header to make sure they are inlined.
+ * They all are called from kmsan_get_metadata() for every memory access in
+ * the kernel, so speed is important here.
+ */
+
+/*
+ * Compute metadata addresses for the CPU entry area on x86.
+ */
+static inline void *arch_kmsan_get_meta_or_null(void *addr, bool is_origin)
+{
+	unsigned long addr64 = (unsigned long)addr;
+	char *metadata_array;
+	unsigned long off;
+	int cpu;
+
+	if ((addr64 < CPU_ENTRY_AREA_BASE) ||
+	    (addr64 >= (CPU_ENTRY_AREA_BASE + CPU_ENTRY_AREA_MAP_SIZE)))
+		return NULL;
+	cpu = (addr64 - CPU_ENTRY_AREA_BASE) / CPU_ENTRY_AREA_SIZE;
+	off = addr64 - (unsigned long)get_cpu_entry_area(cpu);
+	if ((off < 0) || (off >= CPU_ENTRY_AREA_SIZE))
+		return NULL;
+	metadata_array = is_origin ? cpu_entry_area_origin :
+				     cpu_entry_area_shadow;
+	return &per_cpu(metadata_array[off], cpu);
+}
+
+/*
+ * Taken from arch/x86/mm/physaddr.h to avoid using an instrumented version.
+ */
+static inline bool kmsan_phys_addr_valid(unsigned long addr)
+{
+	if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
+		return !(addr >> boot_cpu_data.x86_phys_bits);
+	else
+		return true;
+}
+
+/*
+ * Taken from arch/x86/mm/physaddr.c to avoid using an instrumented version.
+ */
+static inline bool kmsan_virt_addr_valid(void *addr)
+{
+	unsigned long x = (unsigned long)addr;
+	unsigned long y = x - __START_KERNEL_map;
+
+	/* use the carry flag to determine if x was < __START_KERNEL_map */
+	if (unlikely(x > y)) {
+		x = y + phys_base;
+
+		if (y >= KERNEL_IMAGE_SIZE)
+			return false;
+	} else {
+		x = y + (__START_KERNEL_map - PAGE_OFFSET);
+
+		/* carry flag will be set if starting x was >= PAGE_OFFSET */
+		if ((x > y) || !kmsan_phys_addr_valid(x))
+			return false;
+	}
+
+	return pfn_valid(x >> PAGE_SHIFT);
+}
+
+#endif /* !MODULE */
+
+#endif /* _ASM_X86_KMSAN_H */