[Xen-changelog] [xen-3.0-testing] Fix negation of unsigned quantities in the Xen x86 emulator.

[Xen patchbot-3.0-testing <patchbot-3.0-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 53bb8c0d9639251b61b203b55f9e6b046f8d99d6
# Parent  78a72d42cfc19c06097a92b8d0f824d823813c79
Fix negation of unsigned quantities in the Xen x86 emulator.
This fixes the problems left behind by c/s 10171. Again pointed
out by Jan Beulich; and again different from his suggested patch.
Hopefully this one will be less embarrassing.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
xen-unstable changeset:   10241:2dd8e7c4472897a86cac635b6982fa55f1ab6e07
xen-unstable date:        Thu Jun 01 16:31:37 2006 +0100
---
 xen/arch/x86/traps.c       |    4 ++--
 xen/arch/x86/x86_emulate.c |   15 ++++++++-------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff -r 78a72d42cfc1 -r 53bb8c0d9639 xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c      Thu Jun 01 11:05:13 2006 +0100
+++ b/xen/arch/x86/traps.c      Thu Jun 01 16:33:38 2006 +0100
@@ -873,7 +873,7 @@ static int emulate_privileged_op(struct 
                     PAGE_FAULT(regs->edi, USER_WRITE_FAULT);
                 break;
             }
-            regs->edi += (regs->eflags & EF_DF) ? -(int)op_bytes : op_bytes;
+            regs->edi += (int)((regs->eflags & EF_DF) ? -op_bytes : op_bytes);
             break;
 
         case 0x6e: /* OUTSB */
@@ -899,7 +899,7 @@ static int emulate_privileged_op(struct 
                 outl_user((u32)data, (u16)regs->edx, v, regs);
                 break;
             }
-            regs->esi += (regs->eflags & EF_DF) ? -(int)op_bytes : op_bytes;
+            regs->esi += (int)((regs->eflags & EF_DF) ? -op_bytes : op_bytes);
             break;
         }
 
diff -r 78a72d42cfc1 -r 53bb8c0d9639 xen/arch/x86/x86_emulate.c
--- a/xen/arch/x86/x86_emulate.c        Thu Jun 01 11:05:13 2006 +0100
+++ b/xen/arch/x86/x86_emulate.c        Thu Jun 01 16:33:38 2006 +0100
@@ -379,11 +379,12 @@ do{ __asm__ __volatile__ (              
       ((reg) & ((1UL << (ad_bytes << 3)) - 1))))
 #define register_address_increment(reg, inc)                            \
 do {                                                                    \
+    int _inc = (inc); /* signed type ensures sign extension to long */  \
     if ( ad_bytes == sizeof(unsigned long) )                            \
-        (reg) += (inc);                                                 \
+        (reg) += _inc;                                                  \
     else                                                                \
         (reg) = ((reg) & ~((1UL << (ad_bytes << 3)) - 1)) |             \
-                (((reg) + (inc)) & ((1UL << (ad_bytes << 3)) - 1));     \
+                (((reg) + _inc) & ((1UL << (ad_bytes << 3)) - 1));      \
 } while (0)
 
 void *
@@ -857,7 +858,7 @@ x86_emulate_memop(
                                          &dst.val, 8)) != 0 )
                     goto done;
             }
-            register_address_increment(_regs.esp, -(int)dst.bytes);
+            register_address_increment(_regs.esp, -dst.bytes);
             if ( (rc = ops->write_std(register_address(_regs.ss, _regs.esp),
                                       dst.val, dst.bytes)) != 0 )
                 goto done;
@@ -939,9 +940,9 @@ x86_emulate_memop(
                 goto done;
         }
         register_address_increment(
-            _regs.esi, (_regs.eflags & EFLG_DF) ? -(int)dst.bytes : dst.bytes);
+            _regs.esi, (_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
         register_address_increment(
-            _regs.edi, (_regs.eflags & EFLG_DF) ? -(int)dst.bytes : dst.bytes);
+            _regs.edi, (_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
         break;
     case 0xa6 ... 0xa7: /* cmps */
         DPRINTF("Urk! I don't handle CMPS.\n");
@@ -952,7 +953,7 @@ x86_emulate_memop(
         dst.ptr   = (unsigned long *)cr2;
         dst.val   = _regs.eax;
         register_address_increment(
-            _regs.edi, (_regs.eflags & EFLG_DF) ? -(int)dst.bytes : dst.bytes);
+            _regs.edi, (_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
         break;
     case 0xac ... 0xad: /* lods */
         dst.type  = OP_REG;
@@ -961,7 +962,7 @@ x86_emulate_memop(
         if ( (rc = ops->read_emulated(cr2, &dst.val, dst.bytes)) != 0 )
             goto done;
         register_address_increment(
-            _regs.esi, (_regs.eflags & EFLG_DF) ? -(int)dst.bytes : dst.bytes);
+            _regs.esi, (_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
         break;
     case 0xae ... 0xaf: /* scas */
         DPRINTF("Urk! I don't handle SCAS.\n");

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