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Commit f5b4edcd authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: x86 emulator: simplify rip relative decoding 



rip relative decoding is relative to the instruction pointer of the next
instruction; by moving address adjustment until after decoding is complete,
we remove the need to determine the instruction size.

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 84411d85

arch/x86/kvm/x86_emulate.c

+5 −18
Original line number Original line Diff line number Diff line
@@ -664,7 +664,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, 
{

{

	struct decode_cache *c = &ctxt->decode;

	struct decode_cache *c = &ctxt->decode;

	u8 sib;

	u8 sib;

	int index_reg = 0, base_reg = 0, scale, rip_relative = 0;

	int index_reg = 0, base_reg = 0, scale;

	int rc = 0;

	int rc = 0;





	if (c->rex_prefix) {

	if (c->rex_prefix) {
@@ -754,7 +754,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, 
				c->modrm_ea += c->regs[index_reg] << scale;

				c->modrm_ea += c->regs[index_reg] << scale;

		} else if ((c->modrm_rm & 7) == 5 && c->modrm_mod == 0) {

		} else if ((c->modrm_rm & 7) == 5 && c->modrm_mod == 0) {

			if (ctxt->mode == X86EMUL_MODE_PROT64)

			if (ctxt->mode == X86EMUL_MODE_PROT64)

				rip_relative = 1;

				c->rip_relative = 1;

		} else

		} else

			c->modrm_ea += c->regs[c->modrm_rm];

			c->modrm_ea += c->regs[c->modrm_rm];

		switch (c->modrm_mod) {

		switch (c->modrm_mod) {
@@ -770,22 +770,6 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, 
			break;

			break;

		}

		}

	}

	}

	if (rip_relative) {

		c->modrm_ea += c->eip;

		switch (c->d & SrcMask) {

		case SrcImmByte:

			c->modrm_ea += 1;

			break;

		case SrcImm:

			if (c->d & ByteOp)

				c->modrm_ea += 1;

			else

				if (c->op_bytes == 8)

					c->modrm_ea += 4;

				else

					c->modrm_ea += c->op_bytes;

		}

	}

done:

done:

	return rc;

	return rc;

}

}
@@ -1044,6 +1028,9 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
		break;

		break;

	}

	}





	if (c->rip_relative)

		c->modrm_ea += c->eip;



done:

done:

	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;

	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;

}

}

include/asm-x86/kvm_x86_emulate.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -134,6 +134,7 @@ struct decode_cache { 
	u8 modrm_reg;

	u8 modrm_reg;

	u8 modrm_rm;

	u8 modrm_rm;

	u8 use_modrm_ea;

	u8 use_modrm_ea;

	bool rip_relative;

	unsigned long modrm_ea;

	unsigned long modrm_ea;

	void *modrm_ptr;

	void *modrm_ptr;

	unsigned long modrm_val;

	unsigned long modrm_val;