Messages in this thread | | | Date | Sun, 8 Jan 2012 10:26:57 +0900 | From | Takuya Yoshikawa <> | Subject | Re: [PATCH] KVM: fix mov immediate emulation for 64-bit operands |
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Hi,
Nadav Amit <nadav.amit@gmail.com> wrote: > On Jan 7, 2012, at 10:25 PM, H. Peter Anvin wrote: > > > On 01/07/2012 12:21 PM, Nadav Amit wrote: > >> MOV immediate instruction (opcodes 0xB8-0xBF) may take 64-bit operand. > >> The previous emulation implementation assumes the operand is no longer than 32. > >> > >> Signed-off-by: Nadav Amit <nadav.amit@gmail.com> > > > > There are exactly two such instructions: MOV immediate (B8-BF) and MOV > > moff (A0-A3); you may want to check the latter too. > > > > -hpa > > > > These instructions (A0-A3) seem to be already covered by the decode_abs function.
Like these how about introducing a new flag and change the following entries in the decode table to indicate possible 64bit immediate:
/* 0xB8 - 0xBF */ X8(I(DstReg | SrcImm | Mov, em_mov)),
Checking the opcode byte at the operand decoding stage, like below, does not look nice: (IMO so better ask Avi)
+ if (size == 8 && ((ctxt->b & 0xF8) != 0xB8 || ctxt->twobyte)) size = 4;
I am now cleaning up x86_decode_insn() to make each decoding stage clearer.
Takuya
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