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Fix return values in nested system calls from QVMs

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When the engine is compiled with Clang it appears that the return value
is being written to the WRONG address, either due to the vm_ variables being
changed (unexpectedly) elsewhere, or as a result of bad assembly assumptions;
having a stack variable pointing to where to write the return value seems
to do the trick.

This fixes the case where, for a trap_Register()-like call, weird numbers
are being returned when, during the process, an error message is printed
(which in Tremulous results in a QVM call and (nested) system call).
This commit is contained in:
/dev/humancontroller 2015-03-23 20:16:11 -05:00 committed by Zack Middleton
parent 33efe82de9
commit 1ce8ba0cdb
1 changed files with 4 additions and 3 deletions
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7
code/qcommon/vm_x86.c
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@ -412,23 +412,24 @@ static void DoSyscall(void)
if(vm_syscallNum < 0) if(vm_syscallNum < 0)
{ {
int *data; int *data, *ret;
#if idx64 #if idx64
int index; int index;
intptr_t args[MAX_VMSYSCALL_ARGS]; intptr_t args[MAX_VMSYSCALL_ARGS];
#endif #endif
data = (int *) (savedVM->dataBase + vm_programStack + 4); data = (int *) (savedVM->dataBase + vm_programStack + 4);
ret = &vm_opStackBase[vm_opStackOfs + 1];
#if idx64 #if idx64
args[0] = ~vm_syscallNum; args[0] = ~vm_syscallNum;
for(index = 1; index < ARRAY_LEN(args); index++) for(index = 1; index < ARRAY_LEN(args); index++)
args[index] = data[index]; args[index] = data[index];
vm_opStackBase[vm_opStackOfs + 1] = savedVM->systemCall(args); *ret = savedVM->systemCall(args);
#else #else
data[0] = ~vm_syscallNum; data[0] = ~vm_syscallNum;
vm_opStackBase[vm_opStackOfs + 1] = savedVM->systemCall((intptr_t *) data); *ret = savedVM->systemCall((intptr_t *) data);
#endif #endif
} }
else else