[v2,05/16] x86emul: add XOP decoding

Commit Message

Jan Beulich Sept. 28, 2016, 8:09 a.m. UTC

This way we can at least size (and e.g. skip) them if needed, and we
also won't raise the wrong fault due to not having read all relevant
bytes.

Signed-off-by: Jan Beulich <[e-mail]>
---
v2: Add a comment.
x86emul: add XOP decoding

This way we can at least size (and e.g. skip) them if needed, and we
also won't raise the wrong fault due to not having read all relevant
bytes.

Signed-off-by: Jan Beulich <[e-mail]>
---
v2: Add a comment.

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -279,6 +279,12 @@ static const opcode_desc_t twobyte_table
     ModRM, ModRM, ModRM, ModRM, ModRM, ModRM, ModRM, ModRM
 };
 
+static const opcode_desc_t xop_table[] = {
+    DstReg|SrcImmByte|ModRM,
+    DstReg|SrcMem|ModRM,
+    DstReg|SrcImm|ModRM,
+};
+
 #define REX_PREFIX 0x40
 #define REX_B 0x01
 #define REX_X 0x02
@@ -1591,6 +1597,13 @@ struct x86_emulate_state {
         ext_0f   = vex_0f,
         ext_0f38 = vex_0f38,
         ext_0f3a = vex_0f3a,
+        /*
+         * For XOP use values such that the respective instruction field
+         * can be used without adjustment.
+         */
+        ext_8f08 = 8,
+        ext_8f09,
+        ext_8f0a,
     } ext;
     uint8_t opcode;
     uint8_t modrm, modrm_mod, modrm_reg, modrm_rm;
@@ -1813,7 +1822,7 @@ x86_decode(
         modrm = insn_fetch_type(uint8_t);
         modrm_mod = (modrm & 0xc0) >> 6;
 
-        if ( !ext && ((b & ~1) == 0xc4) )
+        if ( !ext && ((b & ~1) == 0xc4 || (b == 0x8f && (modrm & 0x18))) )
             switch ( def_ad_bytes )
             {
             default:
@@ -1827,11 +1836,11 @@ x86_decode(
                     break;
                 /* fall through */
             case 8:
-                /* VEX */
+                /* VEX / XOP */
                 generate_exception_if(rex_prefix || vex.pfx, EXC_UD, -1);
 
                 vex.raw[0] = modrm;
-                if ( b & 1 )
+                if ( b == 0xc5 )
                 {
                     vex.raw[1] = modrm;
                     vex.opcx = vex_0f;
@@ -1859,18 +1868,30 @@ x86_decode(
                     rex_prefix |= REX_R;
 
                 b = insn_fetch_type(uint8_t);
-                switch ( ext = vex.opcx )
+                ext = vex.opcx;
+                if ( b != 0x8f )
+                {
+                    switch ( ext )
+                    {
+                    case vex_0f:
+                        d = twobyte_table[b];
+                        break;
+                    case vex_0f38:
+                        d = twobyte_table[0x38];
+                        break;
+                    case vex_0f3a:
+                        d = twobyte_table[0x3a];
+                        break;
+                    default:
+                        rc = X86EMUL_UNHANDLEABLE;
+                        goto done;
+                    }
+                }
+                else if ( ext < ext_8f08 +
+                                sizeof(xop_table) / sizeof(*xop_table) )
+                    d = xop_table[ext - ext_8f08];
+                else
                 {
-                case vex_0f:
-                    d = twobyte_table[b];
-                    break;
-                case vex_0f38:
-                    d = twobyte_table[0x38];
-                    break;
-                case vex_0f3a:
-                    d = twobyte_table[0x3a];
-                    break;
-                default:
                     rc = X86EMUL_UNHANDLEABLE;
                     goto done;
                 }
@@ -1932,6 +1953,9 @@ x86_decode(
 
         case ext_0f:
         case ext_0f3a:
+        case ext_8f08:
+        case ext_8f09:
+        case ext_8f0a:
             break;
 
         case ext_0f38:
@@ -2121,6 +2145,9 @@ x86_decode(
 
     case ext_0f38:
     case ext_0f3a:
+    case ext_8f08:
+    case ext_8f09:
+    case ext_8f0a:
         break;
 
     default:
@@ -2337,6 +2364,9 @@ x86_emulate(
     default:
         ASSERT_UNREACHABLE();
     case ext_0f3a:
+    case ext_8f08:
+    case ext_8f09:
+    case ext_8f0a:
         goto cannot_emulate;
     }

Comments

Andrew Cooper Sept. 29, 2016, 9:07 a.m. UTC | #1

On 28/09/16 09:09, Jan Beulich wrote:
> This way we can at least size (and e.g. skip) them if needed, and we
> also won't raise the wrong fault due to not having read all relevant
> bytes.
>
> Signed-off-by: Jan Beulich <[e-mail]>

Reviewed-by: Andrew Cooper <[e-mail]>.  I think... The
prefix decoding is getting very complicated, but I can't suggest an
easier way.

~Andrew

Patch

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -279,6 +279,12 @@  static const opcode_desc_t twobyte_table
     ModRM, ModRM, ModRM, ModRM, ModRM, ModRM, ModRM, ModRM
 };
 
+static const opcode_desc_t xop_table[] = {
+    DstReg|SrcImmByte|ModRM,
+    DstReg|SrcMem|ModRM,
+    DstReg|SrcImm|ModRM,
+};
+
 #define REX_PREFIX 0x40
 #define REX_B 0x01
 #define REX_X 0x02
@@ -1591,6 +1597,13 @@  struct x86_emulate_state {
         ext_0f   = vex_0f,
         ext_0f38 = vex_0f38,
         ext_0f3a = vex_0f3a,
+        /*
+         * For XOP use values such that the respective instruction field
+         * can be used without adjustment.
+         */
+        ext_8f08 = 8,
+        ext_8f09,
+        ext_8f0a,
     } ext;
     uint8_t opcode;
     uint8_t modrm, modrm_mod, modrm_reg, modrm_rm;
@@ -1813,7 +1822,7 @@  x86_decode(
         modrm = insn_fetch_type(uint8_t);
         modrm_mod = (modrm & 0xc0) >> 6;
 
-        if ( !ext && ((b & ~1) == 0xc4) )
+        if ( !ext && ((b & ~1) == 0xc4 || (b == 0x8f && (modrm & 0x18))) )
             switch ( def_ad_bytes )
             {
             default:
@@ -1827,11 +1836,11 @@  x86_decode(
                     break;
                 /* fall through */
             case 8:
-                /* VEX */
+                /* VEX / XOP */
                 generate_exception_if(rex_prefix || vex.pfx, EXC_UD, -1);
 
                 vex.raw[0] = modrm;
-                if ( b & 1 )
+                if ( b == 0xc5 )
                 {
                     vex.raw[1] = modrm;
                     vex.opcx = vex_0f;
@@ -1859,18 +1868,30 @@  x86_decode(
                     rex_prefix |= REX_R;
 
                 b = insn_fetch_type(uint8_t);
-                switch ( ext = vex.opcx )
+                ext = vex.opcx;
+                if ( b != 0x8f )
+                {
+                    switch ( ext )
+                    {
+                    case vex_0f:
+                        d = twobyte_table[b];
+                        break;
+                    case vex_0f38:
+                        d = twobyte_table[0x38];
+                        break;
+                    case vex_0f3a:
+                        d = twobyte_table[0x3a];
+                        break;
+                    default:
+                        rc = X86EMUL_UNHANDLEABLE;
+                        goto done;
+                    }
+                }
+                else if ( ext < ext_8f08 +
+                                sizeof(xop_table) / sizeof(*xop_table) )
+                    d = xop_table[ext - ext_8f08];
+                else
                 {
-                case vex_0f:
-                    d = twobyte_table[b];
-                    break;
-                case vex_0f38:
-                    d = twobyte_table[0x38];
-                    break;
-                case vex_0f3a:
-                    d = twobyte_table[0x3a];
-                    break;
-                default:
                     rc = X86EMUL_UNHANDLEABLE;
                     goto done;
                 }
@@ -1932,6 +1953,9 @@  x86_decode(
 
         case ext_0f:
         case ext_0f3a:
+        case ext_8f08:
+        case ext_8f09:
+        case ext_8f0a:
             break;
 
         case ext_0f38:
@@ -2121,6 +2145,9 @@  x86_decode(
 
     case ext_0f38:
     case ext_0f3a:
+    case ext_8f08:
+    case ext_8f09:
+    case ext_8f0a:
         break;
 
     default:
@@ -2337,6 +2364,9 @@  x86_emulate(
     default:
         ASSERT_UNREACHABLE();
     case ext_0f3a:
+    case ext_8f08:
+    case ext_8f09:
+    case ext_8f0a:
         goto cannot_emulate;
     }