[Xen-changelog] [xen master] x86emul: improve LOCK handling

[patchbot@xxxxxxx]

commit dee231b5a8e0408c12479940cd9874b3869bd5c9
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Aug 17 15:36:55 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Aug 17 15:36:55 2016 +0200

    x86emul: improve LOCK handling
    
    Certain opcodes would so far not have got #UD when a LOCK prefix was
    present. Adjust this by
    - moving the too early generic check into destination operand decoding,
      where DstNone and DstReg already have respective handling
    - switching source and destination of TEST r,r/m, for it to be taken
      care of by aforementioned generic checks
    - explicitly dealing with all forms of CMP, SHLD, SHRD, as well as
      TEST $imm,r/m
    
    To make the handling of opcodes F6 and F7 more obvious, reduce the
    amount of state set in the table, and adjust the respective switch()
    statement accordingly.
    
    Also eliminate the latent bug of the check in DstNone handling not
    considering the opcode extension set.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index cef7bee..f27c6d5 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -111,7 +111,7 @@ static uint8_t opcode_table[256] = {
     /* 0x80 - 0x87 */
     ByteOp|DstMem|SrcImm|ModRM, DstMem|SrcImm|ModRM,
     ByteOp|DstMem|SrcImm|ModRM, DstMem|SrcImmByte|ModRM,
-    ByteOp|DstMem|SrcReg|ModRM, DstMem|SrcReg|ModRM,
+    ByteOp|DstReg|SrcMem|ModRM, DstReg|SrcMem|ModRM,
     ByteOp|DstMem|SrcReg|ModRM, DstMem|SrcReg|ModRM,
     /* 0x88 - 0x8F */
     ByteOp|DstMem|SrcReg|ModRM|Mov, DstMem|SrcReg|ModRM|Mov,
@@ -172,8 +172,7 @@ static uint8_t opcode_table[256] = {
     DstEax|SrcImplicit, DstEax|SrcImplicit, ImplicitOps, ImplicitOps,
     /* 0xF0 - 0xF7 */
     0, ImplicitOps, 0, 0,
-    ImplicitOps, ImplicitOps,
-    ByteOp|DstMem|SrcNone|ModRM, DstMem|SrcNone|ModRM,
+    ImplicitOps, ImplicitOps, ByteOp|ModRM, ModRM,
     /* 0xF8 - 0xFF */
     ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
     ImplicitOps, ImplicitOps, ByteOp|DstMem|SrcNone|ModRM, DstMem|SrcNone|ModRM
@@ -1660,9 +1659,6 @@ x86_emulate(
         }
     }
 
-    /* Lock prefix is allowed only on RMW instructions. */
-    generate_exception_if((d & Mov) && lock_prefix, EXC_UD, -1);
-
     /* ModRM and SIB bytes. */
     if ( d & ModRM )
     {
@@ -1738,7 +1734,11 @@ x86_emulate(
                 switch ( modrm_reg & 7 )
                 {
                 case 0 ... 1: /* test */
-                    d = (d & ~SrcMask) | SrcImm;
+                    d |= DstMem | SrcImm;
+                    break;
+                case 2: /* not */
+                case 3: /* neg */
+                    d |= DstMem;
                     break;
                 case 4: /* mul */
                 case 5: /* imul */
@@ -1748,7 +1748,7 @@ x86_emulate(
                      * DstEax isn't really precise for all cases; updates to
                      * rDX get handled in an open coded manner.
                      */
-                    d = (d & (ByteOp | ModRM)) | DstEax | SrcMem;
+                    d |= DstEax | SrcMem;
                     break;
                 }
                 break;
@@ -1996,8 +1996,9 @@ x86_emulate(
          */
         generate_exception_if(
             lock_prefix &&
-            ((b < 0x20) || (b > 0x23)) && /* MOV CRn/DRn */
-            (b != 0xc7),                  /* CMPXCHG{8,16}B */
+            (ext != ext_0f ||
+             (((b < 0x20) || (b > 0x23)) && /* MOV CRn/DRn */
+              (b != 0xc7))),                /* CMPXCHG{8,16}B */
             EXC_UD, -1);
         dst.type = OP_NONE;
         break;
@@ -2075,6 +2076,8 @@ x86_emulate(
                 goto done;
             dst.orig_val = dst.val;
         }
+        else /* Lock prefix is allowed only on RMW instructions. */
+            generate_exception_if(lock_prefix, EXC_UD, -1);
         break;
     }
 
@@ -2124,6 +2127,7 @@ x86_emulate(
         break;
 
     case 0x38 ... 0x3d: cmp: /* cmp */
+        generate_exception_if(lock_prefix, EXC_UD, -1);
         emulate_2op_SrcV("cmp", src, dst, _regs.eflags);
         dst.type = OP_NONE;
         break;
@@ -3548,6 +3552,7 @@ x86_emulate(
             unsigned long u[2], v;
 
         case 0 ... 1: /* test */
+            generate_exception_if(lock_prefix, EXC_UD, -1);
             goto test;
         case 2: /* not */
             dst.val = ~dst.val;
@@ -4495,6 +4500,7 @@ x86_emulate(
     case 0xad: /* shrd %%cl,r,r/m */ {
         uint8_t shift, width = dst.bytes << 3;
 
+        generate_exception_if(lock_prefix, EXC_UD, -1);
         if ( b & 1 )
             shift = _regs.ecx;
         else
--
generated by git-patchbot for /home/xen/git/xen.git#master

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