From 2fb53ad811e238d5dec8716b99986c3f234e3337 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Sun, 11 Apr 2010 13:05:15 +0300 Subject: [PATCH] KVM: x86 emulator: Don't overwrite decode cache Currently if we an instruction spans a page boundary, when we fetch the second half we overwrite the first half. This prevents us from tracing the full instruction opcodes. Fix by appending the second half to the first. Signed-off-by: Avi Kivity Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/emulate.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 64c9854f0458..083b269a83ea 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -646,21 +646,22 @@ static unsigned long ss_base(struct x86_emulate_ctxt *ctxt) static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops, - unsigned long linear, u8 *dest) + unsigned long eip, u8 *dest) { struct fetch_cache *fc = &ctxt->decode.fetch; int rc; - int size; + int size, cur_size; - if (linear < fc->start || linear >= fc->end) { - size = min(15UL, PAGE_SIZE - offset_in_page(linear)); - rc = ops->fetch(linear, fc->data, size, ctxt->vcpu, NULL); + if (eip == fc->end) { + cur_size = fc->end - fc->start; + size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip)); + rc = ops->fetch(ctxt->cs_base + eip, fc->data + cur_size, + size, ctxt->vcpu, NULL); if (rc != X86EMUL_CONTINUE) return rc; - fc->start = linear; - fc->end = linear + size; + fc->end += size; } - *dest = fc->data[linear - fc->start]; + *dest = fc->data[eip - fc->start]; return X86EMUL_CONTINUE; } @@ -673,7 +674,6 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt, /* x86 instructions are limited to 15 bytes. */ if (eip + size - ctxt->eip > 15) return X86EMUL_UNHANDLEABLE; - eip += ctxt->cs_base; while (size--) { rc = do_fetch_insn_byte(ctxt, ops, eip++, dest++); if (rc != X86EMUL_CONTINUE) @@ -935,6 +935,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) /* Shadow copy of register state. Committed on successful emulation. */ memset(c, 0, sizeof(struct decode_cache)); c->eip = ctxt->eip; + c->fetch.start = c->fetch.end = c->eip; ctxt->cs_base = seg_base(ctxt, VCPU_SREG_CS); memcpy(c->regs, ctxt->vcpu->arch.regs, sizeof c->regs); -- 2.34.1