1 files changed, 93 insertions, 9 deletions

diff --git a/arch/x86/lib/iomem.c b/arch/x86/lib/iomem.c
index 66894675f3c8..c20e04764edc 100644
--- a/arch/x86/lib/iomem.c
+++ b/arch/x86/lib/iomem.c
@@ -1,12 +1,16 @@
 #include <linux/string.h>
 #include <linux/module.h>
 #include <linux/io.h>
+#include <linux/kmsan-checks.h>
+
+#define movs(type,to,from) \
+	asm volatile("movs" type:"=&D" (to), "=&S" (from):"0" (to), "1" (from):"memory")
 
 /* Originally from i386/string.h */
-static __always_inline void __iomem_memcpy(void *to, const void *from, size_t n)
+static __always_inline void rep_movs(void *to, const void *from, size_t n)
 {
 	unsigned long d0, d1, d2;
-	asm volatile("rep ; movsl\n\t"
+	asm volatile("rep movsl\n\t"
 		     "testb $2,%b4\n\t"
 		     "je 1f\n\t"
 		     "movsw\n"
@@ -19,24 +23,104 @@ static __always_inline void __iomem_memcpy(void *to, const void *from, size_t n)
 		     : "memory");
 }
 
+static void string_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
+{
+	const void *orig_to = to;
+	const size_t orig_n = n;
+
+	if (unlikely(!n))
+		return;
+
+	/* Align any unaligned source IO */
+	if (unlikely(1 & (unsigned long)from)) {
+		movs("b", to, from);
+		n--;
+	}
+	if (n > 1 && unlikely(2 & (unsigned long)from)) {
+		movs("w", to, from);
+		n-=2;
+	}
+	rep_movs(to, (const void *)from, n);
+	/* KMSAN must treat values read from devices as initialized. */
+	kmsan_unpoison_memory(orig_to, orig_n);
+}
+
+static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
+{
+	if (unlikely(!n))
+		return;
+
+	/* Make sure uninitialized memory isn't copied to devices. */
+	kmsan_check_memory(from, n);
+	/* Align any unaligned destination IO */
+	if (unlikely(1 & (unsigned long)to)) {
+		movs("b", to, from);
+		n--;
+	}
+	if (n > 1 && unlikely(2 & (unsigned long)to)) {
+		movs("w", to, from);
+		n-=2;
+	}
+	rep_movs((void *)to, (const void *) from, n);
+}
+
+static void unrolled_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
+{
+	const volatile char __iomem *in = from;
+	char *out = to;
+	int i;
+
+	for (i = 0; i < n; ++i)
+		out[i] = readb(&in[i]);
+}
+
+static void unrolled_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
+{
+	volatile char __iomem *out = to;
+	const char *in = from;
+	int i;
+
+	for (i = 0; i < n; ++i)
+		writeb(in[i], &out[i]);
+}
+
+static void unrolled_memset_io(volatile void __iomem *a, int b, size_t c)
+{
+	volatile char __iomem *mem = a;
+	int i;
+
+	for (i = 0; i < c; ++i)
+		writeb(b, &mem[i]);
+}
+
 void memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
 {
-	__iomem_memcpy(to, (const void *)from, n);
+	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO))
+		unrolled_memcpy_fromio(to, from, n);
+	else
+		string_memcpy_fromio(to, from, n);
 }
 EXPORT_SYMBOL(memcpy_fromio);
 
 void memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
 {
-	__iomem_memcpy((void *)to, (const void *) from, n);
+	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO))
+		unrolled_memcpy_toio(to, from, n);
+	else
+		string_memcpy_toio(to, from, n);
 }
 EXPORT_SYMBOL(memcpy_toio);
 
 void memset_io(volatile void __iomem *a, int b, size_t c)
 {
-	/*
-	 * TODO: memset can mangle the IO patterns quite a bit.
-	 * perhaps it would be better to use a dumb one:
-	 */
-	memset((void *)a, b, c);
+	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {
+		unrolled_memset_io(a, b, c);
+	} else {
+		/*
+		 * TODO: memset can mangle the IO patterns quite a bit.
+		 * perhaps it would be better to use a dumb one:
+		 */
+		memset((void *)a, b, c);
+	}
 }
 EXPORT_SYMBOL(memset_io);