x86/insn: Simplify for_each_insn_prefix()

Use the new-found freedom of allowing variable declarions inside
for() to simplify the for_each_insn_prefix() iterator to no longer
need an external temporary.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

6 files changed, 13 insertions, 21 deletions

diff --git a/arch/x86/boot/compressed/sev-handle-vc.c b/arch/x86/boot/compressed/sev-handle-vc.c
index 7530ad8b768b..030001b46554 100644
--- a/arch/x86/boot/compressed/sev-handle-vc.c
+++ b/arch/x86/boot/compressed/sev-handle-vc.c
@@ -29,11 +29,10 @@
 bool insn_has_rep_prefix(struct insn *insn)
 {
 	insn_byte_t p;
-	int i;
 
 	insn_get_prefixes(insn);
 
-	for_each_insn_prefix(insn, i, p) {
+	for_each_insn_prefix(insn, p) {
 		if (p == 0xf2 || p == 0xf3)
 			return true;
 	}
diff --git a/arch/x86/include/asm/insn.h b/arch/x86/include/asm/insn.h
index 091f88c8254d..846d21c1a7f8 100644
--- a/arch/x86/include/asm/insn.h
+++ b/arch/x86/include/asm/insn.h
@@ -312,7 +312,6 @@ static inline int insn_offset_immediate(struct insn *insn)
 /**
  * for_each_insn_prefix() -- Iterate prefixes in the instruction
  * @insn: Pointer to struct insn.
- * @idx:  Index storage.
  * @prefix: Prefix byte.
  *
  * Iterate prefix bytes of given @insn. Each prefix byte is stored in @prefix
@@ -321,8 +320,8 @@ static inline int insn_offset_immediate(struct insn *insn)
  * Since prefixes.nbytes can be bigger than 4 if some prefixes
  * are repeated, it cannot be used for looping over the prefixes.
  */
-#define for_each_insn_prefix(insn, idx, prefix)	\
-	for (idx = 0; idx < ARRAY_SIZE(insn->prefixes.bytes) && (prefix = insn->prefixes.bytes[idx]) != 0; idx++)
+#define for_each_insn_prefix(insn, prefix)	\
+	for (int idx = 0; idx < ARRAY_SIZE(insn->prefixes.bytes) && (prefix = insn->prefixes.bytes[idx]) != 0; idx++)
 
 #define POP_SS_OPCODE 0x1f
 #define MOV_SREG_OPCODE 0x8e
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 3863d7709386..c1fac3a9fecc 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -141,7 +141,6 @@ bool can_boost(struct insn *insn, void *addr)
 {
 	kprobe_opcode_t opcode;
 	insn_byte_t prefix;
-	int i;
 
 	if (search_exception_tables((unsigned long)addr))
 		return false;	/* Page fault may occur on this address. */
@@ -154,7 +153,7 @@ bool can_boost(struct insn *insn, void *addr)
 	if (insn->opcode.nbytes != 1)
 		return false;
 
-	for_each_insn_prefix(insn, i, prefix) {
+	for_each_insn_prefix(insn, prefix) {
 		insn_attr_t attr;
 
 		attr = inat_get_opcode_attribute(prefix);
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 6318898eb9d0..a563e90832d7 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -259,9 +259,8 @@ static volatile u32 good_2byte_insns[256 / 32] = {
 static bool is_prefix_bad(struct insn *insn)
 {
 	insn_byte_t p;
-	int i;
 
-	for_each_insn_prefix(insn, i, p) {
+	for_each_insn_prefix(insn, p) {
 		insn_attr_t attr;
 
 		attr = inat_get_opcode_attribute(p);
@@ -1404,7 +1403,6 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
 {
 	u8 opc1 = OPCODE1(insn);
 	insn_byte_t p;
-	int i;
 
 	if (insn_is_nop(insn))
 		goto setup;
@@ -1437,7 +1435,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
 	 * Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix.
 	 * No one uses these insns, reject any branch insns with such prefix.
 	 */
-	for_each_insn_prefix(insn, i, p) {
+	for_each_insn_prefix(insn, p) {
 		if (p == 0x66)
 			return -ENOTSUPP;
 	}
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index c991dac1a38e..e03eeec55cfe 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -63,11 +63,10 @@ static bool is_string_insn(struct insn *insn)
 bool insn_has_rep_prefix(struct insn *insn)
 {
 	insn_byte_t p;
-	int i;
 
 	insn_get_prefixes(insn);
 
-	for_each_insn_prefix(insn, i, p) {
+	for_each_insn_prefix(insn, p) {
 		if (p == 0xf2 || p == 0xf3)
 			return true;
 	}
@@ -92,13 +91,13 @@ bool insn_has_rep_prefix(struct insn *insn)
 static int get_seg_reg_override_idx(struct insn *insn)
 {
 	int idx = INAT_SEG_REG_DEFAULT;
-	int num_overrides = 0, i;
+	int num_overrides = 0;
 	insn_byte_t p;
 
 	insn_get_prefixes(insn);
 
 	/* Look for any segment override prefixes. */
-	for_each_insn_prefix(insn, i, p) {
+	for_each_insn_prefix(insn, p) {
 		insn_attr_t attr;
 
 		attr = inat_get_opcode_attribute(p);
@@ -1701,7 +1700,6 @@ bool insn_is_nop(struct insn *insn)
 	u8 sib = 0, sib_scale, sib_index, sib_base;
 	u8 nrex, rex;
 	u8 p, rep = 0;
-	int i;
 
 	if ((nrex = insn->rex_prefix.nbytes)) {
 		rex = insn->rex_prefix.bytes[nrex-1];
@@ -1741,7 +1739,7 @@ bool insn_is_nop(struct insn *insn)
 		modrm_rm = sib_base;
 	}
 
-	for_each_insn_prefix(insn, i, p) {
+	for_each_insn_prefix(insn, p) {
 		if (p == 0xf3) /* REPE */
 			rep = 1;
 	}
@@ -1789,7 +1787,7 @@ bool insn_is_nop(struct insn *insn)
 		if (sib && (sib_scale != 0 || sib_index != 4)) /* (%reg, %eiz, 1) */
 			return false;
 
-		for_each_insn_prefix(insn, i, p) {
+		for_each_insn_prefix(insn, p) {
 			if (p != 0x3e) /* DS */
 				return false;
 		}
diff --git a/tools/arch/x86/include/asm/insn.h b/tools/arch/x86/include/asm/insn.h
index c683d609934b..8f10f2943370 100644
--- a/tools/arch/x86/include/asm/insn.h
+++ b/tools/arch/x86/include/asm/insn.h
@@ -312,7 +312,6 @@ static inline int insn_offset_immediate(struct insn *insn)
 /**
  * for_each_insn_prefix() -- Iterate prefixes in the instruction
  * @insn: Pointer to struct insn.
- * @idx:  Index storage.
  * @prefix: Prefix byte.
  *
  * Iterate prefix bytes of given @insn. Each prefix byte is stored in @prefix
@@ -321,8 +320,8 @@ static inline int insn_offset_immediate(struct insn *insn)
  * Since prefixes.nbytes can be bigger than 4 if some prefixes
  * are repeated, it cannot be used for looping over the prefixes.
  */
-#define for_each_insn_prefix(insn, idx, prefix)	\
-	for (idx = 0; idx < ARRAY_SIZE(insn->prefixes.bytes) && (prefix = insn->prefixes.bytes[idx]) != 0; idx++)
+#define for_each_insn_prefix(insn, prefix)	\
+	for (int idx = 0; idx < ARRAY_SIZE(insn->prefixes.bytes) && (prefix = insn->prefixes.bytes[idx]) != 0; idx++)
 
 #define POP_SS_OPCODE 0x1f
 #define MOV_SREG_OPCODE 0x8e