On 23/07/2013 01:36, Tim Angus wrote:
> On Mon, 22 Jul 2013 14:36:18 -0500 Harley wrote:
>> It looks like the culprit is the range check (MASK_REG in the new vm)
>> for OP_STORE4. Commenting out MASK_REG under that case seems to make
>> UrbanTerror 4.2 load up. I haven't actually tried a real game though.
>
> This is probably indicative of a bug in Urban Terror. We have hacks in
> sound backends to work around UrT's misuse of the API, but in that case
> it's not harmful. Removing a range check would mean compromising
> security for the sake of UrT. Hmmm.
I've given this some more consideration. Violating the alignment is
bad style for performance reason, but not really dangerous or buggy.
So I propose keeping the boundary check, but getting rid of the
alignment check. Patches are attached.
--
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
diff -r de1eebcbab05 code/qcommon/vm_x86.c
--- code/qcommon/vm_x86.c Mon Jul 15 20:43:44 2013 +0200
+++ code/qcommon/vm_x86.c Tue Jul 23 10:41:43 2013 +0200
@@ -783,7 +783,7 @@
return qtrue;
case OP_STORE4:
- EmitMovEAXStack(vm, (vm->dataMask & ~3));
+ EmitMovEAXStack(vm, vm->dataMask);
#if idx64
EmitRexString(0x41, "C7 04 01"); // mov dword
ptr [r9 + eax], 0x12345678
Emit4(Constant4());
@@ -798,7 +798,7 @@
return qtrue;
case OP_STORE2:
- EmitMovEAXStack(vm, (vm->dataMask & ~1));
+ EmitMovEAXStack(vm, vm->dataMask);
#if idx64
Emit1(0x66); // mov word ptr
[r9 + eax], 0x1234
EmitRexString(0x41, "C7 04 01");
@@ -1369,7 +1369,7 @@
case OP_STORE4:
EmitMovEAXStack(vm, 0);
EmitString("8B 54 9F FC"); // mov
edx, dword ptr -4[edi + ebx * 4]
- MASK_REG("E2", vm->dataMask & ~3); // and
edx, 0x12345678
+ MASK_REG("E2", vm->dataMask); // and
edx, 0x12345678
#if idx64
EmitRexString(0x41, "89 04 11"); // mov
dword ptr [r9 + edx], eax
#else
@@ -1381,7 +1381,7 @@
case OP_STORE2:
EmitMovEAXStack(vm, 0);
EmitString("8B 54 9F FC"); // mov
edx, dword ptr -4[edi + ebx * 4]
- MASK_REG("E2", vm->dataMask & ~1); // and
edx, 0x12345678
+ MASK_REG("E2", vm->dataMask); // and
edx, 0x12345678
#if idx64
Emit1(0x66); // mov
word ptr [r9 + edx], eax
EmitRexString(0x41, "89 04 11");
diff -r de1eebcbab05 code/qcommon/vm_interpreted.c
--- code/qcommon/vm_interpreted.c Mon Jul 15 20:43:44 2013 +0200
+++ code/qcommon/vm_interpreted.c Tue Jul 23 10:41:47 2013 +0200
@@ -436,21 +436,21 @@
return 0;
}
#endif
- r0 = opStack[opStackOfs] = *(int *) &image[r0 &
dataMask & ~3 ];
+ r0 = opStack[opStackOfs] = *(int *) &image[r0 &
dataMask ];
goto nextInstruction2;
case OP_LOAD2:
- r0 = opStack[opStackOfs] = *(unsigned short *)&image[
r0&dataMask&~1 ];
+ r0 = opStack[opStackOfs] = *(unsigned short *)&image[
r0&dataMask ];
goto nextInstruction2;
case OP_LOAD1:
r0 = opStack[opStackOfs] = image[ r0&dataMask ];
goto nextInstruction2;
case OP_STORE4:
- *(int *)&image[ r1&(dataMask & ~3) ] = r0;
+ *(int *)&image[ r1&dataMask ] = r0;
opStackOfs -= 2;
goto nextInstruction;
case OP_STORE2:
- *(short *)&image[ r1&(dataMask & ~1) ] = r0;
+ *(short *)&image[ r1&dataMask ] = r0;
opStackOfs -= 2;
goto nextInstruction;
case OP_STORE1:
@@ -460,7 +460,7 @@
case OP_ARG:
// single byte offset from programStack
- *(int *)&image[ (codeImage[programCounter] +
programStack)&dataMask&~3 ] = r0;
+ *(int *)&image[ (codeImage[programCounter] +
programStack)&dataMask ] = r0;
opStackOfs--;
programCounter += 1;
goto nextInstruction;
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