[PATCH] kmemcheck: support for x86_64

[Vegard Nossum]

Add REX prefix handling to kmemcheck's opcode decoder.

Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxx>
---
 arch/x86/Kconfig.debug      |    2 +-
 arch/x86/kernel/kmemcheck.c |   67 ++++++++++++++++++++++++++++++++++--------
 2 files changed, 55 insertions(+), 14 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index af6c1b3..8f02410 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -244,7 +244,7 @@ endif
 
 config KMEMCHECK
 	bool "kmemcheck: trap use of uninitialized memory"
-	depends on X86_32
+	depends on X86
 	depends on !X86_USE_3DNOW
 	depends on SLUB || SLAB
 	depends on !CC_OPTIMIZE_FOR_SIZE
diff --git a/arch/x86/kernel/kmemcheck.c b/arch/x86/kernel/kmemcheck.c
index 80ef428..bd52609 100644
--- a/arch/x86/kernel/kmemcheck.c
+++ b/arch/x86/kernel/kmemcheck.c
@@ -600,6 +600,12 @@ opcode_is_prefix(uint8_t b)
 		|| b == 0x67;
 }
 
+static bool
+opcode_is_rex_prefix(uint8_t b)
+{
+	return (b & 0xf0) == 0x40;
+}
+
 /* This is a VERY crude opcode decoder. We only need to find the size of the
  * load/store that caused our #PF and this should work for all the opcodes
  * that we care about. Moreover, the ones who invented this instruction set
@@ -616,6 +622,15 @@ opcode_get_size(const uint8_t *op)
 			operand_size_override = 16;
 	}
 
+#ifdef X86_64
+	/* REX prefix */
+	if (opcode_is_rex_prefix(*op)) {
+		if (*op & 0x08)
+			return 64;
+		++op;
+	}
+#endif
+
 	/* escape opcode */
 	if (*op == 0x0f) {
 		++op;
@@ -633,7 +648,10 @@ static const uint8_t *
 opcode_get_primary(const uint8_t *op)
 {
 	/* skip prefixes */
-	for (; opcode_is_prefix(*op); ++op);
+	while (opcode_is_prefix(*op))
+		++op;
+	if (opcode_is_rex_prefix(*op))
+		++op;
 	return op;
 }
 
@@ -644,22 +662,16 @@ opcode_get_primary(const uint8_t *op)
 static bool
 check_page_boundary(struct pt_regs *regs, unsigned long addr, unsigned int size)
 {
-	unsigned long page[4];
-
 	if (size == 8)
 		return false;
-
-	page[0] = (addr + 0) & PAGE_MASK;
-	page[1] = (addr + 1) & PAGE_MASK;
-
-	if (size == 16 && page[0] == page[1])
+	if (size == 16 && (addr & PAGE_MASK) == ((addr + 1) & PAGE_MASK))
 		return false;
-
-	page[2] = (addr + 2) & PAGE_MASK;
-	page[3] = (addr + 3) & PAGE_MASK;
-
-	if (size == 32 && page[0] == page[2] && page[0] == page[3])
+	if (size == 32 && (addr & PAGE_MASK) == ((addr + 3) & PAGE_MASK))
 		return false;
+#ifdef X86_64
+	if (size == 64 && (addr & PAGE_MASK) == ((addr + 7) & PAGE_MASK))
+		return false;
+#endif
 
 	/*
 	 * XXX: The addr/size data is also really interesting if this
@@ -683,6 +695,17 @@ test(void *shadow, unsigned int size)
 	 * code to access neighboring bytes.
 	 */
 	switch (size) {
+#ifdef X86_64
+	case 64:
+		if (x[7] == SHADOW_INITIALIZED)
+			return x[7];
+		if (x[6] == SHADOW_INITIALIZED)
+			return x[6];
+		if (x[5] == SHADOW_INITIALIZED)
+			return x[5];
+		if (x[4] == SHADOW_INITIALIZED)
+			return x[4];
+#endif
 	case 32:
 		if (x[3] == SHADOW_INITIALIZED)
 			return x[3];
@@ -697,6 +720,17 @@ test(void *shadow, unsigned int size)
 	}
 #else
 	switch (size) {
+#ifdef X86_64
+	case 64:
+		if (x[7] != SHADOW_INITIALIZED)
+			return x[7];
+		if (x[6] != SHADOW_INITIALIZED)
+			return x[6];
+		if (x[5] != SHADOW_INITIALIZED)
+			return x[5];
+		if (x[4] != SHADOW_INITIALIZED)
+			return x[4];
+#endif
 	case 32:
 		if (x[3] != SHADOW_INITIALIZED)
 			return x[3];
@@ -722,6 +756,13 @@ set(void *shadow, unsigned int size)
 	x = shadow;
 
 	switch (size) {
+#ifdef X86_64
+	case 64:
+		x[7] = SHADOW_INITIALIZED;
+		x[6] = SHADOW_INITIALIZED;
+		x[5] = SHADOW_INITIALIZED;
+		x[4] = SHADOW_INITIALIZED;
+#endif
 	case 32:
 		x[3] = SHADOW_INITIALIZED;
 		x[2] = SHADOW_INITIALIZED;
-- 
1.5.4.1

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