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SubjectRe: [PATCH 1/5] KVM: x86: Emulator does not calculate address correctly
Il 07/05/2014 14:32, Nadav Amit ha scritto:
> In long-mode, when the address size is 4 bytes, the linear address is not
> truncated as the emulator mistakenly does. Instead, the offset within the
> segment (the ea field) should be truncated according to the address size.
>
> As Intel SDM says: "In 64-bit mode, the effective address components are added
> and the effective address is truncated ... before adding the full 64-bit
> segment base."
>
> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
> ---
> arch/x86/kvm/emulate.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index e8a5840..743e8e3 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -631,7 +631,8 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
> u16 sel;
> unsigned cpl;
>
> - la = seg_base(ctxt, addr.seg) + addr.ea;
> + la = seg_base(ctxt, addr.seg) +
> + (ctxt->ad_bytes == 8 ? addr.ea : (u32)addr.ea);

I think you need "fetch || ctxt->ad_bytes == 8" here.

Paolo

> switch (ctxt->mode) {
> case X86EMUL_MODE_PROT64:
> if (((signed long)la << 16) >> 16 != la)
> @@ -678,7 +679,7 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
> }
> break;
> }
> - if (fetch ? ctxt->mode != X86EMUL_MODE_PROT64 : ctxt->ad_bytes != 8)
> + if (ctxt->mode != X86EMUL_MODE_PROT64)
> la &= (u32)-1;
> if (insn_aligned(ctxt, size) && ((la & (size - 1)) != 0))
> return emulate_gp(ctxt, 0);
>



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