About the application
It runs on Windows XP Professional SP2.
It's built with Microsoft Visual C++ 6.0 with Service Pack 6.
It's MFC based.
It uses several external dlls (e.g. Xerces, ZLib or ACE).
It has high performance requirements.
It does a lot of network and hard disk I/O, but it's also cpu intensive.
It has an exception handling mechanism which generates a minidump when an unhandled exception occurs.
UPDATE: It is a highly multithreaded application and we are using mutexes to protect concurrent access (of course, we might be failing at some place...)
Facts about the crash
It only happens on multiprocessor/multicore machines and under heavy loads of work.
It happens at random (neither we nor our client have found a pattern yet) after some some hours running.
We cannot reproduce the crash on our testing lab. It only happens on some production systems (but always in multicore machines)
It always ends up crashing at the same point, although the complete stack is not always the same. Let me add the stack of the crashing thread (obtained using WinDbg, sorry we don't have symbols)
Exception code: c0000005 ACCESS_VIOLATION
Address : 006a85b9
Access Type : write
Access Address : 2e020fff
Fault address: 006a85b9 01:002a75b9 C:\MyDir\MyApplication.exe
ChildEBP RetAddr Args to Child
WARNING: Stack unwind information not available. Following frames may be wrong.
030af6c8 7c9206eb 77bfc3c9 01a80000 00224bc3 MyApplication+0x2a85b9
030af960 7c91e9c0 7c92901b 00000ab4 00000000 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo])
030af98c 7c9205c8 00000001 00000000 00000000 ntdll!ZwWaitForSingleObject+0xc (FPO: [3,0,0])
030af9c0 7c920551 01a80898 7c92056d 313adfb0 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4])
030afa8c 4ba3ae96 000307da 00130005 00040012 ntdll!RtlFreeHeap+0x1e9 (FPO: [Non-Fpo])
030afacc 77bfc2e3 0214e384 3087c8d8 02151030 0x4ba3ae96
030afb00 7c91e306 7c80bfc1 00000948 00000001 msvcrt!free+0xc8 (FPO: [Non-Fpo])
030afb20 0042965b 030afcc0 0214d780 02151218 ntdll!ZwReleaseSemaphore+0xc (FPO: [3,0,0])
030afb7c 7c9206eb 02e6c471 02ea0000 00000008 MyApplication+0x2965b
030afe60 7c9205c8 02151248 030aff38 7c920551 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo])
030afe74 7c92056d 0210bfb8 02151250 02151250 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4])
030aff38 77bfc2de 01a80000 00000000 77bfc2e3 ntdll!RtlFreeHeap+0x647 (FPO: [Non-Fpo])
7c92056d c5ffffff ce7c94be ff7c94be 00ffffff msvcrt!free+0xc3 (FPO: [Non-Fpo])
7c920575 ff7c94be 00ffffff 12000000 907c94be 0xc5ffffff
7c920579 00ffffff 12000000 907c94be 90909090 0xff7c94be
*** WARNING: Unable to verify checksum for xerces-c_2_7.dll
*** ERROR: Symbol file could not be found. Defaulted to export symbols for xerces-c_2_7.dll -
7c92057d 12000000 907c94be 90909090 8b55ff8b MyApplication+0xbfffff
7c920581 907c94be 90909090 8b55ff8b 08458bec xerces_c_2_7
7c920585 90909090 8b55ff8b 08458bec 04408b66 0x907c94be
7c920589 8b55ff8b 08458bec 04408b66 0004c25d 0x90909090
7c92058d 08458bec 04408b66 0004c25d 90909090 0x8b55ff8b
The address MyApplication+0x2a85b9 corresponds to a call to erase() of a std::list.
What I have tried so far
Reviewing all the code related to the point where the crash ends happening.
Trying to enable pageheap on our testing lab though nothing useful has been found by now.
We have substituted the std::list for a C array and then it crashes in other part of the code (although it is related code, it's not in the code where the old list resided). Coincidentally, now it crashes in another erase, though this time of a std::multiset. Let me copy the stack contained in the dump:
ntdll.dll!_RtlpCoalesceFreeBlocks#16() + 0x124e bytes
ntdll.dll!_RtlFreeHeap#12() + 0x91f bytes
msvcrt.dll!_free() + 0xc3 bytes
MyApplication.exe!006a4fda()
[Frames below may be incorrect and/or missing, no symbols loaded for MyApplication.exe]
MyApplication.exe!0069f305()
ntdll.dll!_NtFreeVirtualMemory#16() + 0xc bytes
ntdll.dll!_RtlpSecMemFreeVirtualMemory#16() + 0x1b bytes
ntdll.dll!_ZwWaitForSingleObject#12() + 0xc bytes
ntdll.dll!_RtlpFreeToHeapLookaside#8() + 0x26 bytes
ntdll.dll!_RtlFreeHeap#12() + 0x114 bytes
msvcrt.dll!_free() + 0xc3 bytes
c5ffffff()
(12-Apr-2010) I've tried to enable heap free checking (using gflags) but it slows down the application a lot...
Possible solutions (that I'm aware of) which cannot be applied
"Migrate the application to a newer compiler": We are working on this but It's not a solution at the moment.
"Enable pageheap (normal or full)": We can't enable pageheap on production machines as this affects performance heavily.
I think that's all I remember now, if I have forgotten something I'll add it asap. If you can give me some hint or propose some possible solution, don't hesitate to answer!
You can try peppering your code with calls to the debug heap checking routines to see if you can locate the corruption closer to the source (you're using the debug CRT to track down this problem, right?):
http://msdn.microsoft.com/en-us/library/aa271695(VS.60).aspx
Use Application Verifier from debugging tools for windows. Sometimes it helps.
Try to set up VS to download OS debug symbols and make sure that OMIT FRAME POINTERS is off in your application. Perhaps stack trace will be informative.
Highly multithreaded
Long time ago I discovered that there is a limit for thread count per process in WinXP. My test snippet could create only few thoursands of thread. The problem was resolved by thread pool.
EDIT:
For my purposes there was enough just to check “Application Verifier” checkbox in gflags.exe. Unfortunately, I have no experience with other options.
As for thread limit, test snippet was simple:
unsigned __stdcall ThreadProc(LPVOID)
{
_tprintf(_T("Thread started\n"));
return 0;
}
int _tmain(int argc, _TCHAR* argv[])
{
while (TRUE)
{
unsigned threadId = 0;
_tprintf(_T("Start thread\n"));
_beginthreadex( NULL, 0, &ThreadProc, NULL, 0, &threadId);
}
return 0;
}
I didn’t wait long this time, but handle count in Task Manager was increasing very fast. My real world application got this effect only in 12 hours. But must say the issue was not in crashing, new threads just not created.
Can you post what exceptions you are getting?
If this is some memory corruption bug, then the crash occurs sometime after the memory corruption, so that will be challenging to track down the root cause. You should:
Travel (or remotely logon) to the production system, install Visual Studio, have .pdb and .map files ready (and windows' symbols as well), attach debugger to the release-build and wait for the crash. Though if you set it up correctly, you can use the minidump file on your dev machine, where you would already have your app and window's symbols setup. Then you can see which free call is throwing, and try to figure out which object is being freed to see if that object is corrupted somehow and nearby objects in memory.
Somehow find a way to reproduce the bug in your office, can you create high enough volumes to duplicate what the customer is doing?
Your posted callstacks don't look particularly illuminating.
Since you are using VS 6 with SP6, then its STL is OK.
Can you tell if the app on the production system is leaking any resources? Running perfmon can help with this.
Another thing, you're not calling new/delete like very frequently from different threads are you? I've found that if you do this fast enough, you'll crash your app rather quickly (did this on XP). I had to replace new/delete calls in my app with VirtualAlloc (windows Virtual Memory API), that worked great for me. Of course, STL could be allocating from the heap as well.
Use a performance profiler that can hook into CPU events, such as VTune. Set it up in sampling mode and tell it to wait for events related to cache line sharing. These are identified by a HITM event from the SNOOP phase.
If you run this on a multi processor machine with a realistic workload then it will find places in your code where there is active contention between threads for a single piece of data. You will need to analyze the profiler hot spots found this way and try to find something that is not being wrapped in an appropriate mutex.
I'm not an expert on CPU architecture or anything, but my understanding is that when the CPUs are about to access a piece of data the system will check if any other CPUs are accessing the same piece of data, this is done by watching the memory fetches and writes coming out of each CPU, a process called snooping. Snooping makes sure that if TWO or more CPUs have the same data in each of their caches that the duplicated copies of the data are removed when one of them is modified. A HIT-Modified event means that the system detected this situation and had to flush one of the CPUs cache lines.
See this document for more information on using VTune like this
http://software.intel.com/en-us/articles/using-intel-vtune-performance-analyzer-events-ratios-optimizing-applications/
I don't have a copy of VTune in front of me right now so maybe this won't work but it seems like the lowest impact way of getting some data. VTune in sampling mode should not cause a lot of problems with performance.
The key here is that this only happens on multiprocessor machines (Cores are the same as processors)
What happens when a threaded program runs on a single processor is that two threads never execute at the same time. The OS has to time-slice each processor to simulate threads.
In a multiprocessor system multiple threads can operate at the same time.
You are probably accessing shared resources from different threads at the same time now.
These resources can be be connections to external systems and even global variables and data structures even Singleton classes.
Unfortunately you now have one of the hardest problems to find.
If you can find the memory being corrupted then you need to find who else is using it on a different thread and then synchronize the memory (Semaphore or CriticalSection).
Unfortunately there is no easy way to find the problem.
You might be able to set the processor affinity temporarily to only run on one processor until you find the problem. See link
http://msdn.microsoft.com/en-us/library/ms684251(VS.85).aspx
Here is a method to set affinity on
For Windows XP/Vista/7, access Affinity by opening the Windows Task Manager (CTL+ALT+DEL, or right-click on Task Bar), select "Processes" tab, right-click the application process you wish to isolate, then select "Set Affinity." Inside the Processor Affinity dialog, un-check the CPU/cores you do not need to use. This effectively isolates that application to the selected CPUs/cores preventing cashe spanning and reducing process-switching and simplifies your ability to supervise CPU/core allocation for multiple programs.
As your second stack trace shows, your application is corrupting the heap. The header of a heap block is written over and thus the crash occurs in the heap manager when coalescing free blocks, or when going through the free list (in the first stack trace).
The code you identified that is currently freeing memory may be a victim of another code overflowing or underflowing a memory block.
The easiest way to debug this kind of crash is to use the debugging help from windows, through pageheap or appverifier, but depending on the application it may slow down too much, or grow the memory usage too high to be usable, which seems to be the case. You may try to use light pageheap, which will have less impact.
You need to identify what part of the application is overflowing. One way to do this is to look at the information contained in the overflown block. If you have a crash in RtlpCoalesceFreeBlocks, I think I remember one of the registers (#esi) is pointing to the start of the corrupted block (I am not on a windows system at the time of this writing and can not check that). Or if you have a dump, using windbg command !heap -a will dump all memory and display corrupted blocks (better log into a file, since the full heap listing can be long). Once corrupted blocks are known, their content may help to identify the code.
Another help can be to enable the stack backtraces (using gflags). This can be done in production as it is lighter than pageheap. It will add some information to heap blocks and may move the crash to another place in your application, but the stack traces will help to identify what code allocated the blocks that are overflowing.
I would focus on getting the issue to happen on a build for which you have proper debugging symbols, at least for your main application. You seem to gloss over this with "sorry we don't have symbols", but when symbols are applied, the stacktraces may show you more information.
What exactly does this mean: "We can't generate symbols because we're linking with a library which doesn't link if we're using them."? This seems odd.
Related
I am having some issues with my virtualHBA driver on Windows Server 2016. A ran the HLK crashdump support test. 3 times out of 10 the test passed. In those 3 failing tests, the crashdump hangs at 0% while taking Complete dump, or Kernel dump or minidump.
By kernel debugging my code, I found that the call to ExAllocatePoolWithTag() for buffer allocation never actually returns.
Below is the statement which never returns.
pDeviceExtension->pcmdbuf=(struct mycmdrsp *)ExAllocatePoolWithTag(NonPagedPoolCacheAligned,pcmdqSignalSize,((ULONG)'TA1'));
I searched on the web regarding this. However, all of the found pages are focusing on this function returning NULL which in my case never returns.
Any help on how to move forward would be highly appreciated.
Thanks in advance.
You can't allocate memory in crash dump mode. You're running at HIGH_LEVEL with interrupts disabled and so you're calling this API at the wrong IRQL.
The typical solution for a hardware adapter is to set the RequestedDumpBufferSize in the PORT_CONFIGURATION_INFORMATION structure during the normal HwFindAdapter call. Then when you're called again in crash dump mode you use the CrashDumpRegion field to get your dump buffer allocation. You then need to write your own "crash dump mode only" allocator to allocate buffers out of this memory region.
It's a huge pain, especially given that it's difficult/impossible to know how much memory you're ultimately going to need. I usually calculate some minimal configuration overhead (i.e. 1 channel, 8 I/O requests at a time, etc.) and then add in a registry configurable slush. The only benefit is that the environment is stripped down so you don't need to be in your all singing, all dancing configuration.
I know that Windows has an option to clear the page file when it shuts down.
Does Windows do anything special with the actual physical/virtual memory when it goes in or out of scope?
For instance, let's say I run application A, which writes a recognizable string to a variable in memory, and then I close the application. Then I run application B. It allocates a large chunk of memory, leaves the contents uninitialized, and searches it for the known string written by application A.
Is there ANY possibility that application B will pick up the string written by application A? Or does Windows scrub the memory before making it available?
Windows does "scrub" the freed memory returned by a process before allocating it to other processes. There is a kernel thread specifically for this task alone.
The zero page thread runs at the lowest priority and is responsible for zeroing out free pages before moving them to the zeroed page list[1].
Rather than worrying about retaining sensitive data in the paging file, you should be worried about continuing to retain it in memory (after use) in the first place. Clearing the page-file on shutdown is not the default behavior. Also a system crash dump will contain any sensitive info that you may have in "plain-text" in RAM.
Windows does NOT "scrub" the memory as long as it is allocated to a process (obviously). Rather it is left to the program(mer) to do so. For this very purpose one can use the SecureZeroMemory() function.
This function is defined as the RtlSecureZeroMemory() function ( see WinBase.h). The implementation of RtlSecureZeroMemory() is provided inline and can be used on any version of Windows ( see WinNT.h)
Use this function instead of ZeroMemory() when you want to ensure that your data will be overwritten promptly, as some C++ compilers can optimize a call to ZeroMemory() by removing it entirely.
WCHAR szPassword[MAX_PATH];
/* Obtain the password */
if (GetPasswordFromUser(szPassword, MAX_PATH))
{
UsePassword(szPassword);
}
/* Before continuing, clear the password from memory */
SecureZeroMemory(szPassword, sizeof(szPassword));
Don't forget to read this interesting article by Raymond Chen.
I am debugging a kernel memory corruption issue. From the resources i have i am able to find that an address(physical) 03a08000(keeps varying everytime), virtual - c3a08000 is being overwritten.
Now i want to know the process that has allocated this memory. How can i do this?
In short my question is, How can i find the name(process ID or any information) of a process that has allocated a given physical address?
Please let me know in case i am not clear on my question.
Edit : Forgot to mention that i have the complete memory dump(Complete 2 gb ram) with me
By the PageMap tools we can map the all the processes in the memory.The PageMap tools consists of two separate command-line utilities:
page-collect.c — Collects the memory “snapshot”; runs on the target platform.
page-analyze.cpp — Analyzes the memory “snapshot” and generates reports; runs on any platform.
EDIT------
To Debug the crash dump it can be done with gdb and other tools. To analyse as quick overview crash dump and other. Complete tutorial on crash dump.
RE-EDIT...................................
I am not too sure about your question but when we are analysing crash dump; it starts as
linux:/var/crash/20111222 # crash System.map-2.6.32.49-0.3-default \
vmlinux-2.6.32.49-0.3-default.gz vmcore
Then we can list all process by ps which also shows the PID & Physical Address both.
There is a command called showmap inside crash tool. This will tell the exact pid and all the memory that is used by that process aswell.
This is the exact information i was looking for.
Kmem shows still better statistics about the details of the related process.
crash > kmem <address>
I'm continue my work on the FGPA driver.
Now I'm adding OpenCL support. So I have a following test.
It's just add NUM_OF_EXEC times write and read requests of same buffers and after that waits for completion.
Each write/read request serialized in driver and sequentially executed as DMA transaction. DMA related code can be viewed here.
So the driver takes a transaction, execute it (rsp_setup_dma and fpga_push_data_to_device), waits for interrupt from FPGA (fpga_int_handler), release resources (fpga_finish_dma_write) and begin a new one. When NUM_OF_EXEC equals to 1, all seems to work, but if I increase it, problem appears. At some point get_user_pages (at rsp_setup_dma) returns -EFAULT. Debugging the kernel, I found out, that allocated vma doesn't have VM_GROWSDOWN flag set (at find_extend_vma in mmap.c). But at this point I stuck, because neither I'm sure that I understand why this flag is needed, neither I have an idea why it is not set. Why can get_user_pages fail with the above symptomps? How can I debug this?
On some architectures the stack grows up and on others the stack grows down. See hppa and hppa64 for the weirdos that created the need for such a flag.
So whenever you have to deal with setting up the stack for a kernel thread or process you'll have to provide the direction in which the stack grows as well.
Using some software in Windows XP that works as a Windows service and doing a restart from the logon screen I see an infamous error message
The instruction at "00x..." referenced memory at "00x...". The memory
could not be read.
I reported the problem to the developers, but looking at the message once again, I noticed that the addresses are the same. So
The instruction at "00xdf3251" referenced memory at "00xdf3251". The memory
could not be read.
Whether this is a bug in the program or not, but what is the state of the memory/access rights or something else that prevents an instruction from reading the memory it is placed. Is it something specific to services?
I would guess there was an attempt to execute an instruction at the address 0xdf3251 and that location wasn't backed up by a readable and executable page of memory (perhaps, completely unmapped).
If that's the case, the exception (page fault, in fact) originates from that instruction and the exception handler has its address on the stack (the location to return to, in case the exception can be somehow resolved and the faulting instruction restarted when the handler returns). And that's the first address you're seeing.
The CR2 register that the page fault handler reads, which is the second address you're seeing, also has the same address because it has to contain the address of an inaccessible memory location irrespective of whether the page fault has been caused by:
complete absence of mapping (there's no page mapped at all)
lack of write permission (the page is read-only)
lack of execute permission (the page has the no-execute bit set) OR
lack of kernel privilege (the page is marked as accessible only in the kernel)
and irrespective of whether it was during a data access or while fetching an instruction (the latter being our case).
That's how you can get the instruction and memory access addresses equal.
Most likely the code had a bug resulting in a memory corruption and some pointer (or a return address on the stack) was overwritten with a bogus value pointing to an inaccessible memory location. And then one way or the other the CPU was directed to continue execution there (most likely using one of these instructions: jmp, call, ret). There's also a chance of having a race condition somewhere.
This kind of crash is most typically caused by stack corruption. A very common kind is a stack buffer overflow. Write too much data in an array stored on the stack and it overwrites a function's return address with the data. When the function then returns, it jumps to the bogus return address and the program falls over because there's no code at the address. They'll have a hard time fixing the bug since there's no easy way to find out where the corruption occurred.
This is a rather infamous kind of bug, it is a major attack vector for malware. Since it can commandeer a program to jump to arbitrary code with data. You ought to have a sitdown with these devs and point this out, it is a major security risk. The cure is easy enough, they should update their tools. Countermeasures against buffer overflow are built into the compilers these days.