From: Keir Fraser <keir.fraser@citrix.com>
Date: Wed, 5 Dec 2007 10:34:15 +0000 (+0000)
Subject: x86_emulate: EFLAGS.PF only reflects least-significant byte of result,
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~14671
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks:///%22http:/www.example.com/cgi/%22https:/%22bookmarks:/?a=commitdiff_plain;h=184fc7781500b64586c94c50de6e61539046dbcd;p=xen.git

x86_emulate: EFLAGS.PF only reflects least-significant byte of result,
so even_parity() can return to its original prototype.
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
---

diff --git a/xen/arch/x86/x86_emulate.c b/xen/arch/x86/x86_emulate.c
index 20f6cec5b5..66ea5a8454 100644
--- a/xen/arch/x86/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate.c
@@ -508,11 +508,14 @@ do {                                                    \
     }                                                                   \
 })
 
-/* Given longword has even parity (even number of 1s)? */
-static int even_parity(unsigned long v)
+/*
+ * Given byte has even parity (even number of 1s)? SDM Vol. 1 Sec. 3.4.3.1,
+ * "Status Flags": EFLAGS.PF reflects parity of least-sig. byte of result only.
+ */
+static int even_parity(uint8_t v)
 {
-    asm ( "test %0,%0; setp %b0" : "=a" (v) : "0" (v) );
-    return (uint8_t)v;
+    asm ( "test %b0,%b0; setp %b0" : "=a" (v) : "0" (v) );
+    return v;
 }
 
 /* Update address held in a register, based on addressing mode. */
@@ -1915,7 +1918,7 @@ x86_emulate(
         _regs.eflags &= ~(EFLG_SF|EFLG_ZF|EFLG_PF);
         _regs.eflags |= ((uint8_t)_regs.eax == 0) ? EFLG_ZF : 0;
         _regs.eflags |= (( int8_t)_regs.eax <  0) ? EFLG_SF : 0;
-        _regs.eflags |= even_parity((uint8_t)_regs.eax) ? EFLG_PF : 0;
+        _regs.eflags |= even_parity(_regs.eax) ? EFLG_PF : 0;
         break;
     }
 
@@ -1939,7 +1942,7 @@ x86_emulate(
         _regs.eflags &= ~(EFLG_SF|EFLG_ZF|EFLG_PF);
         _regs.eflags |= ((uint8_t)_regs.eax == 0) ? EFLG_ZF : 0;
         _regs.eflags |= (( int8_t)_regs.eax <  0) ? EFLG_SF : 0;
-        _regs.eflags |= even_parity((uint8_t)_regs.eax) ? EFLG_PF : 0;
+        _regs.eflags |= even_parity(_regs.eax) ? EFLG_PF : 0;
         break;
     }
 
@@ -2405,7 +2408,7 @@ x86_emulate(
         _regs.eflags &= ~(EFLG_SF|EFLG_ZF|EFLG_PF);
         _regs.eflags |= ((uint8_t)_regs.eax == 0) ? EFLG_ZF : 0;
         _regs.eflags |= (( int8_t)_regs.eax <  0) ? EFLG_SF : 0;
-        _regs.eflags |= even_parity((uint8_t)_regs.eax) ? EFLG_PF : 0;
+        _regs.eflags |= even_parity(_regs.eax) ? EFLG_PF : 0;
         break;
     }
 
@@ -2417,7 +2420,7 @@ x86_emulate(
         _regs.eflags &= ~(EFLG_SF|EFLG_ZF|EFLG_PF);
         _regs.eflags |= ((uint8_t)_regs.eax == 0) ? EFLG_ZF : 0;
         _regs.eflags |= (( int8_t)_regs.eax <  0) ? EFLG_SF : 0;
-        _regs.eflags |= even_parity((uint8_t)_regs.eax) ? EFLG_PF : 0;
+        _regs.eflags |= even_parity(_regs.eax) ? EFLG_PF : 0;
         break;
     }