[Xen-changelog] [xen stable-4.6] x86emul: CMOVcc always writes its destination

[patchbot@xxxxxxx]

commit e1c3fc3549b987653b06fbc82cd076128119183f
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Jan 18 10:22:14 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jan 18 10:22:14 2017 +0100

    x86emul: CMOVcc always writes its destination
    
    This would be benign if there wasn't the zero-extending side effect of
    32-bit operations in 64-bit mode.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: cc53a74291ea5dd5b2c9a327dc386c0e5f859237
    master date: 2016-11-25 14:31:50 +0100
---
 tools/tests/x86_emulator/test_x86_emulator.c | 15 +++++++++++++++
 xen/arch/x86/x86_emulate/x86_emulate.c       |  5 ++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/tools/tests/x86_emulator/test_x86_emulator.c 
b/tools/tests/x86_emulator/test_x86_emulator.c
index c63ac42..c4d0f35 100644
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -632,6 +632,21 @@ int main(int argc, char **argv)
     printf("okay\n");
 #else
     printf("skipped\n");
+
+    printf("%-40s", "Testing cmovz %ecx,%eax...");
+    instr[0] = 0x0f; instr[1] = 0x44; instr[2] = 0xc1;
+    regs.eflags = 0x200;
+    regs.eip    = (unsigned long)&instr[0];
+    regs.rax    = 0x1111111122222222;
+    regs.rcx    = 0x3333333344444444;
+    rc = x86_emulate(&ctxt, &emulops);
+    if ( (rc != X86EMUL_OKAY) ||
+         (regs.rax != 0x0000000022222222) ||
+         (regs.rcx != 0x3333333344444444) ||
+         (regs.eflags != 0x200) ||
+         (regs.eip != (unsigned long)&instr[3]) )
+        goto fail;
+    printf("okay\n");
 #endif
 
 #define decl_insn(which) extern const unsigned char which[], which##_len[]
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index 5c085cf..9860f35 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4296,9 +4296,8 @@ x86_emulate(
     }
 
     case 0x40 ... 0x4f: /* cmovcc */
-        dst.val = src.val;
-        if ( !test_cc(b, _regs.eflags) )
-            dst.type = OP_NONE;
+        if ( test_cc(b, _regs.eflags) )
+            dst.val = src.val;
         break;
 
     case 0x34: /* sysenter */ {
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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