Commit 427e1646 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by Ingo Molnar
Browse files

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: default avatarNikolay Borisov <nik.borisov@suse.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240222111636.2214523-2-nik.borisov@suse.com
parent b401b621

arch/x86/lib/insn.c

+21 −35
Original line number Diff line number Diff line
@@ -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;

	}



	/* 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;

	}



	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;

	}

	/*

	 * 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;

	}



	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;

	}



	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;

	}



	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;

	}



	insn->length = (unsigned char)((unsigned long)insn->next_byte

				     - (unsigned long)insn->kaddr);

tools/arch/x86/lib/insn.c

+21 −35
Original line number Diff line number Diff line
@@ -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;

	}



	/* 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;

	}



	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;

	}

	/*

	 * 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;

	}



	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;

	}



	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;

	}



	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;

	}



	insn->length = (unsigned char)((unsigned long)insn->next_byte

				     - (unsigned long)insn->kaddr);