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[PATCH] Fix possible infinite loop in hires_ms::timeGetTime_ns()
- From: Christian Franke <Christian dot Franke at t-online dot de>
- To: cygwin-patches at cygwin dot com
- Date: Tue, 20 Mar 2012 18:48:10 +0100
- Subject: [PATCH] Fix possible infinite loop in hires_ms::timeGetTime_ns()
ntdll.h:SharedUserData misses a volatile qualifier. This (at least) may
result in an infinite loop in hires_ms::timeGetTime_ns(). Fortunately
this could only happen if LowPart wraps around during the function call.
Generated code:
$ objdump -d -C times.o
...
1160 <hires_ms::timeGetTime_ns()>:
1160: 55 push %ebp
1161: 8b 15 0c 00 fe 7f mov 0x7ffe000c,%edx
1167: 3b 15 10 00 fe 7f cmp 0x7ffe0010,%edx
116d: 89 e5 mov %esp,%ebp
116f: a1 08 00 fe 7f mov 0x7ffe0008,%eax
1174: 75 02 jne 1178 <hires_ms::timeGetTime_ns()+0x18>
1176: 5d pop %ebp
1177: c3 ret
1178: eb fe jmp 1178 <hires_ms::timeGetTime_ns()+0x18>
...
This function results in the same code:
LONGLONG hires_ms::timeGetTime_ns ()
{
LARGE_INTEGER t;
t.HighPart = SharedUserData.InterruptTime.High1Time;
t.LowPart = SharedUserData.InterruptTime.LowPart;
if (t.HighPart == SharedUserData.InterruptTime.High2Time)
return t.QuadPart;
for (;;)
;
}
Christian
2012-03-20 Christian Franke <franke@computer.org>
* ntdll.h (SharedUserData): Add volatile qualifier. This fixes
a possible infinite loop in hires_ms::timeGetTime_ns ().
diff --git a/winsup/cygwin/ntdll.h b/winsup/cygwin/ntdll.h
index d921867..7eee720 100644
--- a/winsup/cygwin/ntdll.h
+++ b/winsup/cygwin/ntdll.h
@@ -1106,9 +1106,10 @@ typedef VOID (APIENTRY *PTIMER_APC_ROUTINE)(PVOID, ULONG, ULONG);
#ifdef __cplusplus
/* This is the mapping of the KUSER_SHARED_DATA structure into the 32 bit
- user address space. We need it here to access the current DismountCount. */
-static KUSER_SHARED_DATA &SharedUserData
- = *(volatile PKUSER_SHARED_DATA) 0x7ffe0000;
+ user address space. We need it here to access the current DismountCount
+ and InterruptTime. */
+static volatile KUSER_SHARED_DATA &SharedUserData
+ = *(volatile KUSER_SHARED_DATA *) 0x7ffe0000;
extern "C"
{