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Subject[PATCH 4/4] kmemcheck: Switch to using kernel disassembler
Date
kmemcheck used to do it's own basic instruction decoding, which is
just a duplication of the work done in arch/x86/lib/insn.c.

Instead, switch it to using the already existing dissasembler, and
switch the magic opcode numbers into something meaningful.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---
arch/x86/mm/kmemcheck/Makefile | 2 +-
arch/x86/mm/kmemcheck/kmemcheck.c | 105 ++++++++++++++++++------------------
arch/x86/mm/kmemcheck/opcode.c | 106 -------------------------------------
arch/x86/mm/kmemcheck/opcode.h | 9 ----
arch/x86/mm/kmemcheck/selftest.c | 12 +++--
arch/x86/mm/kmemcheck/selftest.h | 1 +
6 files changed, 61 insertions(+), 174 deletions(-)
delete mode 100644 arch/x86/mm/kmemcheck/opcode.c
delete mode 100644 arch/x86/mm/kmemcheck/opcode.h

diff --git a/arch/x86/mm/kmemcheck/Makefile b/arch/x86/mm/kmemcheck/Makefile
index 520b3bc..f1749ad 100644
--- a/arch/x86/mm/kmemcheck/Makefile
+++ b/arch/x86/mm/kmemcheck/Makefile
@@ -1 +1 @@
-obj-y := error.o kmemcheck.o opcode.o pte.o selftest.o shadow.o
+obj-y := error.o kmemcheck.o pte.o selftest.o shadow.o
diff --git a/arch/x86/mm/kmemcheck/kmemcheck.c b/arch/x86/mm/kmemcheck/kmemcheck.c
index dd89a13..571664d 100644
--- a/arch/x86/mm/kmemcheck/kmemcheck.c
+++ b/arch/x86/mm/kmemcheck/kmemcheck.c
@@ -25,9 +25,10 @@
#include <asm/kmemcheck.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
+#include <asm/insn.h>
+#include <asm/inat-tables.h>

#include "error.h"
-#include "opcode.h"
#include "pte.h"
#include "selftest.h"
#include "shadow.h"
@@ -521,13 +522,30 @@ enum kmemcheck_method {
KMEMCHECK_WRITE,
};

+char kmemcheck_get_addr_size(struct insn *insn)
+{
+ switch (insn->opcode.value) {
+ case 0xa4:
+ case 0xbe0f:
+ case 0xb60f:
+ return 1;
+
+ case 0xbf0f:
+ case 0xb70f:
+ return 2;
+ case 0x63:
+ if (!X86_REX_W(insn->rex_prefix.value))
+ break;
+ return 4;
+ }
+
+ return insn->mem_bytes;
+}
+
static void kmemcheck_access(struct pt_regs *regs,
unsigned long fallback_address, enum kmemcheck_method fallback_method)
{
- const uint8_t *insn;
- const uint8_t *insn_primary;
- unsigned int size;
-
+ struct insn insn;
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);

/* Recursive fault -- ouch. */
@@ -539,63 +557,42 @@ static void kmemcheck_access(struct pt_regs *regs,

data->busy = true;

- insn = (const uint8_t *) regs->ip;
- insn_primary = kmemcheck_opcode_get_primary(insn);
-
- kmemcheck_opcode_decode(insn, &size);
+ kernel_insn_init(&insn, (const void *)regs->ip);
+ insn_get_length(&insn);

- switch (insn_primary[0]) {
+ switch (insn.mnemonic) {
#ifdef CONFIG_KMEMCHECK_BITOPS_OK
- /* AND, OR, XOR */
- /*
- * Unfortunately, these instructions have to be excluded from
- * our regular checking since they access only some (and not
- * all) bits. This clears out "bogus" bitfield-access warnings.
- */
- case 0x80:
- case 0x81:
- case 0x82:
- case 0x83:
- switch ((insn_primary[1] >> 3) & 7) {
- /* OR */
- case 1:
- /* AND */
- case 4:
- /* XOR */
- case 6:
- kmemcheck_write(regs, fallback_address, size);
- goto out;
-
- /* ADD */
- case 0:
- /* ADC */
- case 2:
- /* SBB */
- case 3:
- /* SUB */
- case 5:
- /* CMP */
- case 7:
- break;
- }
+ /*
+ * Unfortunately, these instructions have to be excluded from
+ * our regular checking since they access only some (and not
+ * all) bits. This clears out "bogus" bitfield-access warnings.
+ */
+ case INSN_OPC_OR:
+ case INSN_OPC_AND:
+ case INSN_OPC_XOR:
+ kmemcheck_write(regs, fallback_address, insn.mem_bytes);
+ goto out;
+
+ case INSN_OPC_ADD:
+ case INSN_OPC_ADC:
+ case INSN_OPC_SBB:
+ case INSN_OPC_SUB:
+ case INSN_OPC_CMP:
break;
#endif
-
- /* MOVS, MOVSB, MOVSW, MOVSD */
- case 0xa4:
- case 0xa5:
+ case INSN_OPC_MOVS_B:
+ case INSN_OPC_MOVS_W_D_Q:
/*
* These instructions are special because they take two
* addresses, but we only get one page fault.
*/
- kmemcheck_copy(regs, regs->si, regs->di, size);
+ kmemcheck_copy(regs, regs->si, regs->di, insn.mem_bytes);
goto out;

- /* CMPS, CMPSB, CMPSW, CMPSD */
- case 0xa6:
- case 0xa7:
- kmemcheck_read(regs, regs->si, size);
- kmemcheck_read(regs, regs->di, size);
+ case INSN_OPC_CMPS_B:
+ case INSN_OPC_CMPS_W_D:
+ kmemcheck_read(regs, regs->si, insn.mem_bytes);
+ kmemcheck_read(regs, regs->di, insn.mem_bytes);
goto out;
}

@@ -606,10 +603,10 @@ static void kmemcheck_access(struct pt_regs *regs,
*/
switch (fallback_method) {
case KMEMCHECK_READ:
- kmemcheck_read(regs, fallback_address, size);
+ kmemcheck_read(regs, fallback_address, insn.mem_bytes);
goto out;
case KMEMCHECK_WRITE:
- kmemcheck_write(regs, fallback_address, size);
+ kmemcheck_write(regs, fallback_address, insn.mem_bytes);
goto out;
}

diff --git a/arch/x86/mm/kmemcheck/opcode.c b/arch/x86/mm/kmemcheck/opcode.c
deleted file mode 100644
index 324aa3f..0000000
--- a/arch/x86/mm/kmemcheck/opcode.c
+++ /dev/null
@@ -1,106 +0,0 @@
-#include <linux/types.h>
-
-#include "opcode.h"
-
-static bool opcode_is_prefix(uint8_t b)
-{
- return
- /* Group 1 */
- b == 0xf0 || b == 0xf2 || b == 0xf3
- /* Group 2 */
- || b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26
- || b == 0x64 || b == 0x65
- /* Group 3 */
- || b == 0x66
- /* Group 4 */
- || b == 0x67;
-}
-
-#ifdef CONFIG_X86_64
-static bool opcode_is_rex_prefix(uint8_t b)
-{
- return (b & 0xf0) == 0x40;
-}
-#else
-static bool opcode_is_rex_prefix(uint8_t b)
-{
- return false;
-}
-#endif
-
-#define REX_W (1 << 3)
-
-/*
- * 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
- * should be shot.
- */
-void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size)
-{
- /* Default operand size */
- int operand_size_override = 4;
-
- /* prefixes */
- for (; opcode_is_prefix(*op); ++op) {
- if (*op == 0x66)
- operand_size_override = 2;
- }
-
- /* REX prefix */
- if (opcode_is_rex_prefix(*op)) {
- uint8_t rex = *op;
-
- ++op;
- if (rex & REX_W) {
- switch (*op) {
- case 0x63:
- *size = 4;
- return;
- case 0x0f:
- ++op;
-
- switch (*op) {
- case 0xb6:
- case 0xbe:
- *size = 1;
- return;
- case 0xb7:
- case 0xbf:
- *size = 2;
- return;
- }
-
- break;
- }
-
- *size = 8;
- return;
- }
- }
-
- /* escape opcode */
- if (*op == 0x0f) {
- ++op;
-
- /*
- * This is move with zero-extend and sign-extend, respectively;
- * we don't have to think about 0xb6/0xbe, because this is
- * already handled in the conditional below.
- */
- if (*op == 0xb7 || *op == 0xbf)
- operand_size_override = 2;
- }
-
- *size = (*op & 1) ? operand_size_override : 1;
-}
-
-const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op)
-{
- /* skip prefixes */
- while (opcode_is_prefix(*op))
- ++op;
- if (opcode_is_rex_prefix(*op))
- ++op;
- return op;
-}
diff --git a/arch/x86/mm/kmemcheck/opcode.h b/arch/x86/mm/kmemcheck/opcode.h
deleted file mode 100644
index 6956aad..0000000
--- a/arch/x86/mm/kmemcheck/opcode.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#ifndef ARCH__X86__MM__KMEMCHECK__OPCODE_H
-#define ARCH__X86__MM__KMEMCHECK__OPCODE_H
-
-#include <linux/types.h>
-
-void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size);
-const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op);
-
-#endif
diff --git a/arch/x86/mm/kmemcheck/selftest.c b/arch/x86/mm/kmemcheck/selftest.c
index c898d33..8976938 100644
--- a/arch/x86/mm/kmemcheck/selftest.c
+++ b/arch/x86/mm/kmemcheck/selftest.c
@@ -1,7 +1,9 @@
#include <linux/bug.h>
#include <linux/kernel.h>

-#include "opcode.h"
+#include <asm/insn.h>
+#include <asm/inat-tables.h>
+
#include "selftest.h"

struct selftest_opcode {
@@ -46,10 +48,12 @@ static const struct selftest_opcode selftest_opcodes[] = {

static bool selftest_opcode_one(const struct selftest_opcode *op)
{
- unsigned size;
-
- kmemcheck_opcode_decode(op->insn, &size);
+ struct insn insn;
+ char size;

+ kernel_insn_init(&insn, op->insn);
+ insn_get_length(&insn);
+ size = kmemcheck_get_addr_size(&insn);
if (size == op->expected_size)
return true;

diff --git a/arch/x86/mm/kmemcheck/selftest.h b/arch/x86/mm/kmemcheck/selftest.h
index 8fed4fe..4cd1c5e 100644
--- a/arch/x86/mm/kmemcheck/selftest.h
+++ b/arch/x86/mm/kmemcheck/selftest.h
@@ -2,5 +2,6 @@
#define ARCH_X86_MM_KMEMCHECK_SELFTEST_H

bool kmemcheck_selftest(void);
+extern char kmemcheck_get_addr_size(struct insn *insn);

#endif
--
1.7.10.4


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