* [PATCH] KVM: x86: Fix CR3 and LDT sel should not be saved in TSS
@ 2014-04-07 15:37 Nadav Amit
2014-04-16 19:20 ` Marcelo Tosatti
0 siblings, 1 reply; 3+ messages in thread
From: Nadav Amit @ 2014-04-07 15:37 UTC (permalink / raw)
To: gleb, pbonzini; +Cc: tglx, mingo, hpa, x86, kvm, linux-kernel, Nadav Amit
According to Intel specifications, only general purpose registers and segment
selectors should are saved in the old TSS during 32-bit task-switch.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
---
arch/x86/kvm/emulate.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 205b17e..0dec502 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2496,7 +2496,7 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt,
static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
struct tss_segment_32 *tss)
{
- tss->cr3 = ctxt->ops->get_cr(ctxt, 3);
+ /* CR3 and ldt selector are not saved intentionally */
tss->eip = ctxt->_eip;
tss->eflags = ctxt->eflags;
tss->eax = reg_read(ctxt, VCPU_REGS_RAX);
@@ -2514,7 +2514,6 @@ static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
tss->ds = get_segment_selector(ctxt, VCPU_SREG_DS);
tss->fs = get_segment_selector(ctxt, VCPU_SREG_FS);
tss->gs = get_segment_selector(ctxt, VCPU_SREG_GS);
- tss->ldt_selector = get_segment_selector(ctxt, VCPU_SREG_LDTR);
}
static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
@@ -2604,6 +2603,8 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
struct tss_segment_32 tss_seg;
int ret;
u32 new_tss_base = get_desc_base(new_desc);
+ u32 eip_offset = offsetof(struct tss_segment_32, eip);
+ u32 ldt_sel_offset = offsetof(struct tss_segment_32, ldt_selector);
ret = ops->read_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg,
&ctxt->exception);
@@ -2613,8 +2614,9 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
save_state_to_tss32(ctxt, &tss_seg);
- ret = ops->write_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg,
- &ctxt->exception);
+ /* Only GP registers and segment selectors are saved */
+ ret = ops->write_std(ctxt, old_tss_base + eip_offset, &tss_seg.eip,
+ ldt_sel_offset - eip_offset, &ctxt->exception);
if (ret != X86EMUL_CONTINUE)
/* FIXME: need to provide precise fault address */
return ret;
--
1.7.10.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: x86: Fix CR3 and LDT sel should not be saved in TSS
2014-04-07 15:37 [PATCH] KVM: x86: Fix CR3 and LDT sel should not be saved in TSS Nadav Amit
@ 2014-04-16 19:20 ` Marcelo Tosatti
2014-04-28 10:49 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Marcelo Tosatti @ 2014-04-16 19:20 UTC (permalink / raw)
To: Nadav Amit; +Cc: gleb, pbonzini, tglx, mingo, hpa, x86, kvm, linux-kernel
On Mon, Apr 07, 2014 at 06:37:47PM +0300, Nadav Amit wrote:
> According to Intel specifications, only general purpose registers and segment
> selectors should are saved in the old TSS during 32-bit task-switch.
should be
> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
> ---
> arch/x86/kvm/emulate.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 205b17e..0dec502 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2496,7 +2496,7 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt,
> static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
> struct tss_segment_32 *tss)
> {
> - tss->cr3 = ctxt->ops->get_cr(ctxt, 3);
> + /* CR3 and ldt selector are not saved intentionally */
> tss->eip = ctxt->_eip;
> tss->eflags = ctxt->eflags;
> tss->eax = reg_read(ctxt, VCPU_REGS_RAX);
> @@ -2514,7 +2514,6 @@ static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
> tss->ds = get_segment_selector(ctxt, VCPU_SREG_DS);
> tss->fs = get_segment_selector(ctxt, VCPU_SREG_FS);
> tss->gs = get_segment_selector(ctxt, VCPU_SREG_GS);
> - tss->ldt_selector = get_segment_selector(ctxt, VCPU_SREG_LDTR);
> }
>
> static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
Only this hunk is enough ?
> @@ -2604,6 +2603,8 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
> struct tss_segment_32 tss_seg;
> int ret;
> u32 new_tss_base = get_desc_base(new_desc);
> + u32 eip_offset = offsetof(struct tss_segment_32, eip);
> + u32 ldt_sel_offset = offsetof(struct tss_segment_32, ldt_selector);
>
> ret = ops->read_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg,
> &ctxt->exception);
> @@ -2613,8 +2614,9 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
>
> save_state_to_tss32(ctxt, &tss_seg);
>
> - ret = ops->write_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg,
> - &ctxt->exception);
> + /* Only GP registers and segment selectors are saved */
> + ret = ops->write_std(ctxt, old_tss_base + eip_offset, &tss_seg.eip,
> + ldt_sel_offset - eip_offset, &ctxt->exception);
> if (ret != X86EMUL_CONTINUE)
> /* FIXME: need to provide precise fault address */
> return ret;
> --
> 1.7.10.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: x86: Fix CR3 and LDT sel should not be saved in TSS
2014-04-16 19:20 ` Marcelo Tosatti
@ 2014-04-28 10:49 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2014-04-28 10:49 UTC (permalink / raw)
To: Marcelo Tosatti, Nadav Amit
Cc: gleb, tglx, mingo, hpa, x86, kvm, linux-kernel
Il 16/04/2014 21:20, Marcelo Tosatti ha scritto:
> On Mon, Apr 07, 2014 at 06:37:47PM +0300, Nadav Amit wrote:
>> According to Intel specifications, only general purpose registers and segment
>> selectors should are saved in the old TSS during 32-bit task-switch.
>
> should be
>
>> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
>> ---
>> arch/x86/kvm/emulate.c | 10 ++++++----
>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>> index 205b17e..0dec502 100644
>> --- a/arch/x86/kvm/emulate.c
>> +++ b/arch/x86/kvm/emulate.c
>> @@ -2496,7 +2496,7 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt,
>> static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
>> struct tss_segment_32 *tss)
>> {
>> - tss->cr3 = ctxt->ops->get_cr(ctxt, 3);
>> + /* CR3 and ldt selector are not saved intentionally */
>> tss->eip = ctxt->_eip;
>> tss->eflags = ctxt->eflags;
>> tss->eax = reg_read(ctxt, VCPU_REGS_RAX);
>> @@ -2514,7 +2514,6 @@ static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
>> tss->ds = get_segment_selector(ctxt, VCPU_SREG_DS);
>> tss->fs = get_segment_selector(ctxt, VCPU_SREG_FS);
>> tss->gs = get_segment_selector(ctxt, VCPU_SREG_GS);
>> - tss->ldt_selector = get_segment_selector(ctxt, VCPU_SREG_LDTR);
>> }
>>
>> static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
>
> Only this hunk is enough ?
I guess there could be a corner case where the beginning or tail of the
TSS is in a read-only page but EIP...LDT is all writable.
Paolo
>> @@ -2604,6 +2603,8 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
>> struct tss_segment_32 tss_seg;
>> int ret;
>> u32 new_tss_base = get_desc_base(new_desc);
>> + u32 eip_offset = offsetof(struct tss_segment_32, eip);
>> + u32 ldt_sel_offset = offsetof(struct tss_segment_32, ldt_selector);
>>
>> ret = ops->read_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg,
>> &ctxt->exception);
>> @@ -2613,8 +2614,9 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
>>
>> save_state_to_tss32(ctxt, &tss_seg);
>>
>> - ret = ops->write_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg,
>> - &ctxt->exception);
>> + /* Only GP registers and segment selectors are saved */
>> + ret = ops->write_std(ctxt, old_tss_base + eip_offset, &tss_seg.eip,
>> + ldt_sel_offset - eip_offset, &ctxt->exception);
>> if (ret != X86EMUL_CONTINUE)
>> /* FIXME: need to provide precise fault address */
>> return ret;
>> --
>> 1.7.10.4
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-04-07 15:37 [PATCH] KVM: x86: Fix CR3 and LDT sel should not be saved in TSS Nadav Amit
2014-04-16 19:20 ` Marcelo Tosatti
2014-04-28 10:49 ` Paolo Bonzini
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