Commit 8a764a87 authored Feb 12, 2015 by Denys Vlasenko Committed by Ingo Molnar Feb 18, 2015

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>

parent e07e0d4c

arch/x86/lib/insn.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -164,6 +164,12 @@ found:
		/* VEX.W overrides opnd_size */
		insn->opnd_bytes = 8;
		} else {
		/*
		* For VEX2, fake VEX3-like byte#2.
		* Makes it easier to decode vex.W, vex.vvvv,
		* vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
		*/
		insn->vex_prefix.bytes[2] = b2 & 0x7f;
		insn->vex_prefix.nbytes = 2;
		insn->next_byte += 2;
		}

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