[Xen-changelog] [xen master] x86/emul: Simplfy L{ES, DS, SS, FS, GS} handling

[patchbot@xxxxxxx]

commit caf520b2c61a35cdb196e850443038d367c10238
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Dec 14 11:05:18 2016 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Dec 16 13:49:24 2016 +0000

    x86/emul: Simplfy L{ES,DS,SS,FS,GS} handling
    
    %ss, %fs and %gs can be calculated by directly masking the opcode.  %es and
    %ds cant, but the calculation isn't hard.
    
    Use seg rather than dst.val for storing the calculated segment, which is
    appropriately typed.  Drop the sel local variable entirely and use dst.val
    instead.  The mode_64bit() check can be repositioned and simplified to drop
    the ext check.  Replace opencoding of X86EMUL_OKAY.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index 6313b57..f69dece 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -3398,24 +3398,20 @@ x86_emulate(
         _regs.eip = dst.val;
         break;
 
-    case 0xc4: /* les */ {
-        unsigned long sel;
-        dst.val = x86_seg_es;
-    les: /* dst.val identifies the segment */
-        generate_exception_if(mode_64bit() && !ext, EXC_UD);
+    case 0xc4: /* les */
+    case 0xc5: /* lds */
+        generate_exception_if(mode_64bit(), EXC_UD);
+        seg = (b & 1) * 3; /* es = 0, ds = 3 */
+    les:
         generate_exception_if(src.type != OP_MEM, EXC_UD);
         if ( (rc = read_ulong(src.mem.seg, src.mem.off + src.bytes,
-                              &sel, 2, ctxt, ops)) != 0 )
+                              &dst.val, 2, ctxt, ops)) != X86EMUL_OKAY )
             goto done;
-        if ( (rc = load_seg(dst.val, sel, 0, NULL, ctxt, ops)) != 0 )
+        ASSERT(is_x86_user_segment(seg));
+        if ( (rc = load_seg(seg, dst.val, 0, NULL, ctxt, ops)) != X86EMUL_OKAY 
)
             goto done;
         dst.val = src.val;
         break;
-    }
-
-    case 0xc5: /* lds */
-        dst.val = x86_seg_ds;
-        goto les;
 
     case 0xc8: /* enter imm16,imm8 */ {
         uint8_t depth = imm2 & 31;
@@ -5274,21 +5270,15 @@ x86_emulate(
         break;
 
     case X86EMUL_OPC(0x0f, 0xb2): /* lss */
-        dst.val = x86_seg_ss;
+    case X86EMUL_OPC(0x0f, 0xb4): /* lfs */
+    case X86EMUL_OPC(0x0f, 0xb5): /* lgs */
+        seg = b & 7;
         goto les;
 
     case X86EMUL_OPC(0x0f, 0xb3): btr: /* btr */
         emulate_2op_SrcV_nobyte("btr", src, dst, _regs.eflags);
         break;
 
-    case X86EMUL_OPC(0x0f, 0xb4): /* lfs */
-        dst.val = x86_seg_fs;
-        goto les;
-
-    case X86EMUL_OPC(0x0f, 0xb5): /* lgs */
-        dst.val = x86_seg_gs;
-        goto les;
-
     case X86EMUL_OPC(0x0f, 0xb6): /* movzx rm8,r{16,32,64} */
         /* Recompute DstReg as we may have decoded AH/BH/CH/DH. */
         dst.reg   = decode_register(modrm_reg, &_regs, 0);
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog