x86/insn: Remove superfluous checks from instruction decoding routines

It's pointless checking if a particular part of an instruction is
decoded before calling the routine responsible for decoding it as this
check is duplicated in the routines itself. Streamline the code by
removing the superfluous checks. No functional difference.

Signed-off-by: Nikolay Borisov <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Nikolay Borisov

arch/x86/lib/insn.c

@@ -268,11 +268,9 @@ int insn_get_opcode(struct insn *insn)
 	if (opcode->got)
 		return 0;
 
-	if (!insn->prefixes.got) {
-		ret = insn_get_prefixes(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_prefixes(insn);
+	if (ret)
+		return ret;
 
 	/* Get first opcode */
 	op = get_next(insn_byte_t, insn);
@@ -339,11 +337,9 @@ int insn_get_modrm(struct insn *insn)
 	if (modrm->got)
 		return 0;
 
-	if (!insn->opcode.got) {
-		ret = insn_get_opcode(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_opcode(insn);
+	if (ret)
+		return ret;
 
 	if (inat_has_modrm(insn->attr)) {
 		mod = get_next(insn_byte_t, insn);
@@ -386,11 +382,9 @@ int insn_rip_relative(struct insn *insn)
 	if (!insn->x86_64)
 		return 0;
 
-	if (!modrm->got) {
-		ret = insn_get_modrm(insn);
-		if (ret)
-			return 0;
-	}
+	ret = insn_get_modrm(insn);
+	if (ret)
+		return 0;
 	/*
 	 * For rip-relative instructions, the mod field (top 2 bits)
 	 * is zero and the r/m field (bottom 3 bits) is 0x5.
@@ -417,11 +411,9 @@ int insn_get_sib(struct insn *insn)
 	if (insn->sib.got)
 		return 0;
 
-	if (!insn->modrm.got) {
-		ret = insn_get_modrm(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_modrm(insn);
+	if (ret)
+		return ret;
 
 	if (insn->modrm.nbytes) {
 		modrm = insn->modrm.bytes[0];
@@ -460,11 +452,9 @@ int insn_get_displacement(struct insn *insn)
 	if (insn->displacement.got)
 		return 0;
 
-	if (!insn->sib.got) {
-		ret = insn_get_sib(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_sib(insn);
+	if (ret)
+		return ret;
 
 	if (insn->modrm.nbytes) {
 		/*
@@ -628,11 +618,9 @@ int insn_get_immediate(struct insn *insn)
 	if (insn->immediate.got)
 		return 0;
 
-	if (!insn->displacement.got) {
-		ret = insn_get_displacement(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_displacement(insn);
+	if (ret)
+		return ret;
 
 	if (inat_has_moffset(insn->attr)) {
 		if (!__get_moffset(insn))
@@ -703,11 +691,9 @@ int insn_get_length(struct insn *insn)
 	if (insn->length)
 		return 0;
 
-	if (!insn->immediate.got) {
-		ret = insn_get_immediate(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_immediate(insn);
+	if (ret)
+		return ret;
 
 	insn->length = (unsigned char)((unsigned long)insn->next_byte
 				     - (unsigned long)insn->kaddr);

tools/arch/x86/lib/insn.c

@@ -268,11 +268,9 @@ int insn_get_opcode(struct insn *insn)
 	if (opcode->got)
 		return 0;
 
-	if (!insn->prefixes.got) {
-		ret = insn_get_prefixes(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_prefixes(insn);
+	if (ret)
+		return ret;
 
 	/* Get first opcode */
 	op = get_next(insn_byte_t, insn);
@@ -339,11 +337,9 @@ int insn_get_modrm(struct insn *insn)
 	if (modrm->got)
 		return 0;
 
-	if (!insn->opcode.got) {
-		ret = insn_get_opcode(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_opcode(insn);
+	if (ret)
+		return ret;
 
 	if (inat_has_modrm(insn->attr)) {
 		mod = get_next(insn_byte_t, insn);
@@ -386,11 +382,9 @@ int insn_rip_relative(struct insn *insn)
 	if (!insn->x86_64)
 		return 0;
 
-	if (!modrm->got) {
-		ret = insn_get_modrm(insn);
-		if (ret)
-			return 0;
-	}
+	ret = insn_get_modrm(insn);
+	if (ret)
+		return 0;
 	/*
 	 * For rip-relative instructions, the mod field (top 2 bits)
 	 * is zero and the r/m field (bottom 3 bits) is 0x5.
@@ -417,11 +411,9 @@ int insn_get_sib(struct insn *insn)
 	if (insn->sib.got)
 		return 0;
 
-	if (!insn->modrm.got) {
-		ret = insn_get_modrm(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_modrm(insn);
+	if (ret)
+		return ret;
 
 	if (insn->modrm.nbytes) {
 		modrm = insn->modrm.bytes[0];
@@ -460,11 +452,9 @@ int insn_get_displacement(struct insn *insn)
 	if (insn->displacement.got)
 		return 0;
 
-	if (!insn->sib.got) {
-		ret = insn_get_sib(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_sib(insn);
+	if (ret)
+		return ret;
 
 	if (insn->modrm.nbytes) {
 		/*
@@ -628,11 +618,9 @@ int insn_get_immediate(struct insn *insn)
 	if (insn->immediate.got)
 		return 0;
 
-	if (!insn->displacement.got) {
-		ret = insn_get_displacement(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_displacement(insn);
+	if (ret)
+		return ret;
 
 	if (inat_has_moffset(insn->attr)) {
 		if (!__get_moffset(insn))
@@ -703,11 +691,9 @@ int insn_get_length(struct insn *insn)
 	if (insn->length)
 		return 0;
 
-	if (!insn->immediate.got) {
-		ret = insn_get_immediate(insn);
-		if (ret)
-			return ret;
-	}
+	ret = insn_get_immediate(insn);
+	if (ret)
+		return ret;
 
 	insn->length = (unsigned char)((unsigned long)insn->next_byte
 				     - (unsigned long)insn->kaddr);