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Subject[PATCH 4/6] kvm, emulator: Add initial three-byte insns support
Date
From: Borislav Petkov <bp@suse.de>

Add initial support for handling three-byte instructions in the
emulator.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kvm/emulate.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 67277bcb377a..72093d76c769 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3880,6 +3880,25 @@ static const struct opcode twobyte_table[256] = {
N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N
};

+static const struct gprefix third_opcode_byte_0xf0 = {
+ N, N, N, N
+};
+
+static const struct gprefix third_opcode_byte_0xf1 = {
+ N, N, N, N
+};
+
+/*
+ * Insns below are selected by the prefix which indexed by the third opcode
+ * byte.
+ */
+static const struct opcode opcode_map_0f_38[256] = {
+ /* 0x00 - 0x7f */
+ X16(N), X16(N), X16(N), X16(N), X16(N), X16(N), X16(N), X16(N),
+ /* 0x80 - 0xff */
+ X16(N), X16(N), X16(N), X16(N), X16(N), X16(N), X16(N), X16(N)
+};
+
#undef D
#undef N
#undef G
@@ -4200,6 +4219,13 @@ done_prefixes:
ctxt->opcode_len = 2;
ctxt->b = insn_fetch(u8, ctxt);
opcode = twobyte_table[ctxt->b];
+
+ /* 0F_38 opcode map */
+ if (ctxt->b == 0x38) {
+ ctxt->opcode_len = 3;
+ ctxt->b = insn_fetch(u8, ctxt);
+ opcode = opcode_map_0f_38[ctxt->b];
+ }
}
ctxt->d = opcode.flags;

@@ -4531,6 +4557,8 @@ special_insn:

if (ctxt->opcode_len == 2)
goto twobyte_insn;
+ else if (ctxt->opcode_len == 3)
+ goto threebyte_insn;

switch (ctxt->b) {
case 0x63: /* movsxd */
@@ -4715,6 +4743,8 @@ twobyte_insn:
goto cannot_emulate;
}

+threebyte_insn:
+
if (rc != X86EMUL_CONTINUE)
goto done;

--
1.8.4


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