x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX
Before this patch, users need to do this to fetch vex.vvvv: if (insn->vex_prefix.nbytes == 2) { vex_vvvv = ((insn->vex_prefix.bytes[1] >> 3) & 0xf) ^ 0xf; } if (insn->vex_prefix.nbytes == 3) { vex_vvvv = ((insn->vex_prefix.bytes[2] >> 3) & 0xf) ^ 0xf; } Make it so that insn->vex_prefix.bytes[2] always contains vex.wvvvvLpp bits. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Frank Ch. Eigler <fche@redhat.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1423767879-31691-1-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -164,6 +164,12 @@ found:
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/* VEX.W overrides opnd_size */
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insn->opnd_bytes = 8;
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} else {
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/*
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* For VEX2, fake VEX3-like byte#2.
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* Makes it easier to decode vex.W, vex.vvvv,
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* vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
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*/
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insn->vex_prefix.bytes[2] = b2 & 0x7f;
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insn->vex_prefix.nbytes = 2;
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insn->next_byte += 2;
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}
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