* [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching. @ 2011-04-13 15:44 Nelson Elhage 2011-04-13 16:06 ` Avi Kivity 2011-04-17 9:44 ` [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching Avi Kivity 0 siblings, 2 replies; 5+ messages in thread From: Nelson Elhage @ 2011-04-13 15:44 UTC (permalink / raw) To: Avi Kivity; +Cc: kvm, linux-kernel, Nelson Elhage Currently, setting a large (i.e. negative) base address for %cs does not work on a 64-bit host. The "JOS" teaching operating system, used by MIT and other universities, relies on such segments while bootstrapping its way to full virtual memory management. Signed-off-by: Nelson Elhage <nelhage@ksplice.com> --- arch/x86/kvm/emulate.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 0ad47b8..54e84b2 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -505,9 +505,12 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt, int size, cur_size; if (eip == fc->end) { + unsigned long linear = eip + ctxt->cs_base; + if (ctxt->mode != X86EMUL_MODE_PROT64) + linear &= (u32)-1; 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, + rc = ops->fetch(linear, fc->data + cur_size, size, ctxt->vcpu, &ctxt->exception); if (rc != X86EMUL_CONTINUE) return rc; -- 1.7.2.43.g36c08.dirty ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching. 2011-04-13 15:44 [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching Nelson Elhage @ 2011-04-13 16:06 ` Avi Kivity 2011-04-15 3:27 ` [PATCH] KVM: emulator: Use linearize() when fetching instructions Nelson Elhage 2011-04-17 9:44 ` [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching Avi Kivity 1 sibling, 1 reply; 5+ messages in thread From: Avi Kivity @ 2011-04-13 16:06 UTC (permalink / raw) To: Nelson Elhage; +Cc: kvm, linux-kernel On 04/13/2011 06:44 PM, Nelson Elhage wrote: > Currently, setting a large (i.e. negative) base address for %cs does not work on > a 64-bit host. The "JOS" teaching operating system, used by MIT and other > universities, relies on such segments while bootstrapping its way to full > virtual memory management. > > Signed-off-by: Nelson Elhage<nelhage@ksplice.com> > --- > arch/x86/kvm/emulate.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 0ad47b8..54e84b2 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -505,9 +505,12 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt, > int size, cur_size; > > if (eip == fc->end) { > + unsigned long linear = eip + ctxt->cs_base; > + if (ctxt->mode != X86EMUL_MODE_PROT64) > + linear&= (u32)-1; > 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, > + rc = ops->fetch(linear, fc->data + cur_size, > size, ctxt->vcpu,&ctxt->exception); > if (rc != X86EMUL_CONTINUE) > return rc; A better fix would be to call linearize() here, which does the necessary truncation as well as segment checks. However, this patch is a lot more backportable, so I think it should be applied, and a conversion to linearize() performed afterwards. -- error compiling committee.c: too many arguments to function ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] KVM: emulator: Use linearize() when fetching instructions. 2011-04-13 16:06 ` Avi Kivity @ 2011-04-15 3:27 ` Nelson Elhage 2011-04-17 12:26 ` Avi Kivity 0 siblings, 1 reply; 5+ messages in thread From: Nelson Elhage @ 2011-04-15 3:27 UTC (permalink / raw) To: Avi Kivity; +Cc: kvm, linux-kernel, Nelson Elhage This means that the truncation behavior in linearize needs to grow an additional slight piece of complexity: when fetching, truncation is dependent on the execution mode, instead of the current address size. Signed-off-by: Nelson Elhage <nelhage@ksplice.com> --- arch/x86/include/asm/kvm_emulate.h | 1 - arch/x86/kvm/emulate.c | 23 ++++++++++++----------- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h index 0818448..9b760c8 100644 --- a/arch/x86/include/asm/kvm_emulate.h +++ b/arch/x86/include/asm/kvm_emulate.h @@ -265,7 +265,6 @@ struct x86_emulate_ctxt { unsigned long eip; /* eip before instruction emulation */ /* Emulated execution mode, represented by an X86EMUL_MODE value. */ int mode; - u32 cs_base; /* interruptibility state, as a result of execution of STI or MOV SS */ int interruptibility; diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index a5f63d4..d3d43a7 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -542,7 +542,7 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt) static int linearize(struct x86_emulate_ctxt *ctxt, struct segmented_address addr, - unsigned size, bool write, + unsigned size, bool write, bool fetch, ulong *linear) { struct decode_cache *c = &ctxt->decode; @@ -602,7 +602,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt, } break; } - if (c->ad_bytes != 8) + if (fetch ? ctxt->mode != X86EMUL_MODE_PROT64 : c->ad_bytes != 8) la &= (u32)-1; *linear = la; return X86EMUL_CONTINUE; @@ -621,7 +621,7 @@ static int segmented_read_std(struct x86_emulate_ctxt *ctxt, int rc; ulong linear; - rc = linearize(ctxt, addr, size, false, &linear); + rc = linearize(ctxt, addr, size, false, false, &linear); if (rc != X86EMUL_CONTINUE) return rc; return ctxt->ops->read_std(linear, data, size, ctxt->vcpu, @@ -637,11 +637,13 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt, int size, cur_size; if (eip == fc->end) { - unsigned long linear = eip + ctxt->cs_base; - if (ctxt->mode != X86EMUL_MODE_PROT64) - linear &= (u32)-1; + unsigned long linear; + struct segmented_address addr = {VCPU_SREG_CS, eip}; cur_size = fc->end - fc->start; size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip)); + rc = linearize(ctxt, addr, size, false, true, &linear); + f (rc != X86EMUL_CONTINUE) + return rc; rc = ops->fetch(linear, fc->data + cur_size, size, ctxt->vcpu, &ctxt->exception); if (rc != X86EMUL_CONTINUE) @@ -1047,7 +1049,7 @@ static int segmented_read(struct x86_emulate_ctxt *ctxt, int rc; ulong linear; - rc = linearize(ctxt, addr, size, false, &linear); + rc = linearize(ctxt, addr, size, false, false, &linear); if (rc != X86EMUL_CONTINUE) return rc; return read_emulated(ctxt, ctxt->ops, linear, data, size); @@ -1061,7 +1063,7 @@ static int segmented_write(struct x86_emulate_ctxt *ctxt, int rc; ulong linear; - rc = linearize(ctxt, addr, size, true, &linear); + rc = linearize(ctxt, addr, size, true, false, &linear); if (rc != X86EMUL_CONTINUE) return rc; return ctxt->ops->write_emulated(linear, data, size, @@ -1076,7 +1078,7 @@ static int segmented_cmpxchg(struct x86_emulate_ctxt *ctxt, int rc; ulong linear; - rc = linearize(ctxt, addr, size, true, &linear); + rc = linearize(ctxt, addr, size, true, false, &linear); if (rc != X86EMUL_CONTINUE) return rc; return ctxt->ops->cmpxchg_emulated(linear, orig_data, data, @@ -2576,7 +2578,7 @@ static int em_invlpg(struct x86_emulate_ctxt *ctxt) int rc; ulong linear; - rc = linearize(ctxt, c->src.addr.mem, 1, false, &linear); + rc = linearize(ctxt, c->src.addr.mem, 1, false, false, &linear); if (rc == X86EMUL_CONTINUE) emulate_invlpg(ctxt->vcpu, linear); /* Disable writeback. */ @@ -3154,7 +3156,6 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) c->fetch.end = c->fetch.start + insn_len; if (insn_len > 0) memcpy(c->fetch.data, insn, insn_len); - ctxt->cs_base = seg_base(ctxt, ops, VCPU_SREG_CS); switch (mode) { case X86EMUL_MODE_REAL: -- 1.7.2.43.g36c08.dirty ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: emulator: Use linearize() when fetching instructions. 2011-04-15 3:27 ` [PATCH] KVM: emulator: Use linearize() when fetching instructions Nelson Elhage @ 2011-04-17 12:26 ` Avi Kivity 0 siblings, 0 replies; 5+ messages in thread From: Avi Kivity @ 2011-04-17 12:26 UTC (permalink / raw) To: Nelson Elhage; +Cc: kvm, linux-kernel On 04/15/2011 06:27 AM, Nelson Elhage wrote: > This means that the truncation behavior in linearize needs to grow an additional > slight piece of complexity: when fetching, truncation is dependent on the > execution mode, instead of the current address size. > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index a5f63d4..d3d43a7 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -542,7 +542,7 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt) > > static int linearize(struct x86_emulate_ctxt *ctxt, > struct segmented_address addr, > - unsigned size, bool write, > + unsigned size, bool write, bool fetch, Calls to functions with strings of bool arguments are confusing. Please make this __linearize, and introduce a new linearize() which doesn't have a fetch argument. > ulong *linear) > { > struct decode_cache *c =&ctxt->decode; > @@ -602,7 +602,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt, > } > break; > } linearize() will currently fault on an unreadable code segment. Need to avoid that on instruction fetches. > - if (c->ad_bytes != 8) > + if (fetch ? ctxt->mode != X86EMUL_MODE_PROT64 : c->ad_bytes != 8) > la&= (u32)-1; > *linear = la; > return X86EMUL_CONTINUE; -- error compiling committee.c: too many arguments to function ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching. 2011-04-13 15:44 [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching Nelson Elhage 2011-04-13 16:06 ` Avi Kivity @ 2011-04-17 9:44 ` Avi Kivity 1 sibling, 0 replies; 5+ messages in thread From: Avi Kivity @ 2011-04-17 9:44 UTC (permalink / raw) To: Nelson Elhage; +Cc: kvm, linux-kernel On 04/13/2011 06:44 PM, Nelson Elhage wrote: > Currently, setting a large (i.e. negative) base address for %cs does not work on > a 64-bit host. The "JOS" teaching operating system, used by MIT and other > universities, relies on such segments while bootstrapping its way to full > virtual memory management. Applied, thanks. -- error compiling committee.c: too many arguments to function ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2011-04-17 12:26 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2011-04-13 15:44 [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching Nelson Elhage 2011-04-13 16:06 ` Avi Kivity 2011-04-15 3:27 ` [PATCH] KVM: emulator: Use linearize() when fetching instructions Nelson Elhage 2011-04-17 12:26 ` Avi Kivity 2011-04-17 9:44 ` [PATCH] KVM: emulator: Handle wraparound in (cs_base + offset) when fetching Avi Kivity
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