This patch adds support to the TLS fixup code for x87 opcodes. These
can be treated like 2-byte opcodes with a weird encoding.
The patch includes some extra changes because, now that we have >2 opcode
tables and 9 different lead bytes in a two-byte opcode, a simple boolean
code will not be enough to differentiate one- and two-byte opcodes.
Besides this, the patch is trivial since the segment fixup code cares
about the operands of the instruction, not about its semantics.
---
 arch/x86/x86_32/seg_fixup.c | 58 ++++++++++++++++++++++++++++++++++++------
 1 files changed, 49 insertions(+), 9 deletions(-)
diff --git a/xen/arch/x86/x86_32/seg_fixup.c b/xen/arch/x86/x86_32/seg_fixup.c
--- a/xen/arch/x86/x86_32/seg_fixup.c
+++ b/xen/arch/x86/x86_32/seg_fixup.c
@@ -42,7 +42,7 @@
 #define O OPCODE_BYTE
 #define M HAS_MODRM
 
-static const unsigned char insn_decode[256] = {
+static const u8 insn_decode[256] = {
 /* 0x00 - 0x0F */
 O|M, O|M, O|M, O|M, X, X, X, X,
 O|M, O|M, O|M, O|M, X, X, X, X,
@@ -93,7 +93,18 @@
 X, X, X, X, X, X, O|M, O|M
 };
 
-static const unsigned char twobyte_decode[256] = {
+static const u8 float_decode[64] = {
+ O|M, O|M, O|M, O|M, O|M, O|M, O|M, O|M, /* 0xD8 */
+ O|M, X, O|M, O|M, O|M, O|M, O|M, O|M, /* 0xD9 */
+ O|M, O|M, O|M, O|M, O|M, O|M, O|M, O|M, /* 0xDA */
+ O|M, X, O|M, O|M, X, O|M, X, O|M, /* 0xDB */
+ O|M, O|M, O|M, O|M, O|M, O|M, O|M, O|M, /* 0xDC */
+ O|M, O|M, O|M, O|M, O|M, X, O|M, O|M, /* 0xDD */
+ O|M, O|M, O|M, O|M, O|M, O|M, O|M, O|M, /* 0xDE */
+ O|M, X, O|M, O|M, O|M, O|M, O|M, O|M, /* 0xDF */
+};
+
+static const u8 twobyte_decode[256] = {
 /* 0x00 - 0x0F */
 X, X, X, X, X, X, X, X,
 X, X, X, X, X, X, X, X,
@@ -321,7 +332,9 @@
 s32 disp32 = 0;
 u8 *eip; /* ptr to instruction start */
 u8 *pb, b; /* ptr into instr. / current instr. byte */
- int gs_override = 0, scale = 0, twobyte = 0;
+ int opcode = -1;
+ int gs_override = 0, scale = 0;
+ const u8 *table = insn_decode;
 
 /* WARNING: We only work for ring-3 segments. */
 if ( unlikely(vm86_mode(regs)) || unlikely(!ring_3(regs)) )
@@ -352,8 +365,11 @@
 goto fail;
 }
 
- if ( twobyte )
- break;
+ if (opcode != -1)
+ {
+ opcode = (opcode << 8) | b;
+ break;
+ }
 
 switch ( b )
 {
@@ -374,8 +390,29 @@
 gs_override = 1;
 break;
 case 0x0f: /* Not really a prefix byte */
- twobyte = 1;
+ table = twobyte_decode;
+ opcode = b;
 break;
+ case 0xd8: /* Math coprocessor instructions. */
+ case 0xd9:
+ case 0xda:
+ case 0xdb:
+ case 0xdc:
+ case 0xdd:
+ case 0xde:
+ case 0xdf:
+ /* Float opcodes have a secondary opcode in the modrm byte. */
+ table = float_decode;
+ if ( get_user(modrm, pb + 1) )
+ {
+ dprintk(XENLOG_DEBUG, "Fault while extracting modrm byte\n");
+ goto page_fault;
+ }
+
+ opcode = (b << 8) | modrm;
+ b = ((b & 7) << 3) + ((modrm >> 3) & 7);
+ goto done_prefix;
+
 default: /* Not a prefix byte */
 goto done_prefix;
 }
@@ -388,13 +425,16 @@
 goto fail;
 }
 
- decode = (!twobyte ? insn_decode : twobyte_decode)[b];
+ decode = table[b];
 pb++;
 
 if ( !(decode & OPCODE_BYTE) )
 {
- dprintk(XENLOG_DEBUG, "Unsupported %sopcode %02x\n",
- twobyte ? "two byte " : "", b);
+ if (opcode == -1)
+ dprintk(XENLOG_DEBUG, "Unsupported opcode %02x\n", b);
+ else
+ dprintk(XENLOG_DEBUG, "Unsupported opcode %02x %02x\n",
+ opcode >> 8, opcode & 255);
 goto fail;
 }
 
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