Pin allows a tool to insert arbitrary code (written in C or C++) in arbitrary places in the executable. The code is added dynamically while the executable is running. This also makes it possible to attach Pin to an already running process.
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These two components are instrumentation and analysis code. Both components live in a single executable, a Pintool. Pintools can be thought of as plugins that can modify the code generation process inside Pin.
Since a Pintool works like a plugin, it must run in the same address space as Pin and the executable to be instrumented. Hence the Pintool has access to all of the executable's data. It also shares file descriptors and other process information with the executable.
Pintools do not need to add explicit locking to instrumentation routines because Pin calls these routines while holding an internal lock called the VM lock. However, Pin does execute analysis and replacement functions in parallel, so Pintools may need to add locking to these routines if they access global data.
Since Pin, the tool, and the application may each acquire and release locks, Pintool developers must take care to avoid deadlocks with either the application or Pin. Deadlocks generally occur when two threads acquire the same locks in a different order. For example, thread A acquires lock L1 and then acquires lock L2, while thread B acquires lock L2 and then acquires lock L1. This will lead to a deadlock if thread A holds lock L1 and waits for L2 while thread B holds lock L2 and waits for L1. To avoid such deadlocks, Pin imposes a hierarchy on the order in which locks must be acquired. Pin generally acquires its own internal locks before the tool acquires any lock (e.g. via PIN_GetLock()). Additionally, we assume that the application may acquire locks at the top of this hierarchy (i.e. before Pin acquires its internal locks). The following diagram illustrates the hierarchy:
With a small change, we can turn the instruction counting example into a Pintool that prints the address of every instruction that is executed. This tool is useful for understanding the control flow of a program for debugging, or in processor design when simulating an instruction cache.
Pin provides support for buffering data for processing. If all that your analysis callback does is to store its arguments into a buffer, then you should be able to use the buffering API instead, with some performance benefit. PIN_DefineTraceBuffer() defines the buffer that will be used. The buffer is allocated by each thread when it starts up, and deallocated when the thread exits. INS_InsertFillBuffer() writes the requested data directly to the given buffer. The callback delineated in the PIN_DefineTraceBuffer() call is used to process the buffer when the buffer is nearly full, and when the thread exits. Pin does not serialize the calls to this callback, so it is the tool writers responsibilty to make sure this function is thread safe. This example records the PC of all instructions that access memory, and the effective address accessed by the instruction. Note that IARG_REG_REFERENCE, IARG_REG_CONST_REFERENCE, IARG_CONTEXT, IARG_CONST_CONTEXT and IARG_PARTIAL_CONTEXT can NOT be used in the Fast Buffering APIs
Pin's advanced debugging extensions allow you to debug an application, even while it runs under Pin in JIT mode. Moreover, your Pintool can add support for new debugger commands, without making any changes to GDB, LLDB or Visual Studio. This allows you to interactively control your Pintool from within a live debugger session. Finally, Pintools can add powerful new debugger features that are enabled via instrumentation. For example, a Pintool can use instrumentation to look for an interesting condition (like a memory buffer overwrite) and then stop at a live debugger session when that condition occurs.
The previous section illustrated how you can enable the normal debugger features while running an application under Pin. Now, let's see how your Pintool can add new custom debugger commands, even without changing the debugger itself. Custom debugger commands are useful because they allow you to control your Pintool interactively from within a live debugger session. For example, you can ask your Pintool to print out information that it has collected, or you can interactively enable instrumentation only for certain phases of the application.
The previous section illustrated how you can enable the normal debugger features while running an application under Pin. Now, let's see how your Pintool can add new custom debugger commands, even without changing Visual Studio. Custom debugger commands are useful because they allow you to control your Pintool interactively from within a live debugger session. For example, you can ask your Pintool to print out information that it has collected, or you can interactively enable instrumentation only for certain phases of the application.
The -injection switch is UNIX-only and controls the way Pin is injected into the application process. The default, dynamic, is recommended for all users. It uses parent injection unless it is unsupported (Linux 2.4 kernels). Child injection creates the application process as a child of the pin process so you will see both a pin process and the application process running. In parent injection, the pin process exits after injecting the application and is less likely to cause a problem. Using parent injection on an unsupported platform may lead to nondeterministic errors.
When running an application under the control of Pin and a Pintool there are two different programs residing in the address space. The application, and the Pin instrumentation engine together with your Pintool. The Pintool is normally a shared object loaded by Pin. This section describes how to use gdb to find bugs in a Pintool. You cannot run Pin directly from gdb since Pin uses the debugging API to start the application. Instead, you must invoke Pin from the command line with the -pause_tool switch, and use gdb to attach to the Pin process from another window. The -pause_tool n switch makes Pin print out the process identifier (pid) and pause for n seconds.
When running an application under the control of Pin and a Pintool there are two different programs residing in the address space. The application, and the Pin instrumentation engine together with your Pintool. The Pintool is a dynamically loaded library (.dll) loaded by Pin. This section describes how to use the Visual Studio Debugger to find bugs in a Pintool. You cannot run Pin directly from the debugger since Pin uses the debugging API to start the application. Instead, you must invoke Pin from the command line with the -pause_tool switch, and use Visual Studio to attach to the Pin process from another window. The -pause_tool n switch makes Pin print out the process identifier (pid) and pause for n seconds. You have n seconds (20 in our example) to attach the application with the debugger. Note, application resumes once the timeout expires. Attaching debugger later will not have the desired effect.
WinDbg Debugger is the only available option to debug Pintool when it is necessary to attach to an instrumented process after Pin initialization. It also could be used instead of Visual Studio Debugger in scenario described above. The debugger is available at -us/library/windows/hardware/ff551063(v=vs.85).aspx
Pin improves instrumentation performance by automatically inlining analysis routines that have no control-flow changes. Of course, many analysis routines do have control-flow changes. One particularly common case is that an analysis routine has a single "if-then" test, where a small amount of analysis code plus the test is always executed but the "then" part is executed only once a while. To inline this common case, Pin provides a set of conditional instrumentation APIs for the tool writer to rewrite their analysis routines into a form that does not have control-flow changes. The following example from source/tools/ManualExamples/isampling.cpp illustrates how such rewriting can be done:
In the above example, the original analysis routine IpSample() has a conditional control-flow change. It is rewritten into two analysis routines: CountDown() and PrintIp(). CountDown() is the simpler one of the two, which doesn't have control-flow change. It also performs the original conditional test and returns the test result. We use the conditional instrumentaton APIs INS_InsertIfCall() and INS_InsertThenCall() to tell Pin that tbe analysis routine specified by an INS_InsertThenCall() (i.e. PrintIp() in this example) is executed only if the result of the analysis routine specified by the previous INS_InsertIfCall() (i.e. CountDown() in this example) is non-zero. Now CountDown(), the common case, can be inlined by Pin, and only once a while does Pin need to execute PrintIp(), the non-inlined case.
You can use source generators as an additional step in your script compilation process. You can use source generators to add new code while you compile your existing code. Like analyzers, you can use existing source generators or create your own.
If your service is processing long requests, you canincrease the request timeout. If yourservice doesn't return a response within the time specified, the request endsand the service returns an HTTP 504 error, as documented in thecontainer runtime contract.
Before going into the depths of debugging in Wine, here's a small overview of process and thread handling in Wine. It has to be clear that there are two different beasts: processes/threads from the Unix point of view and processes/threads from a Windows point of view.
Wine implements most of the Windows debugging API. The first part of the debugging APIs (in KERNEL32.DLL) allows a W-process, called the debugger, to control the execution of another W-process, the debuggee. To control means stopping/resuming execution, enabling/disabling single stepping, setting breakpoints, reading/writing debuggee memory... Another part of the debugging APIs resides in DBGHELP.DLL (and its ancestor IMAGEHLP.DLL) and lets a debugger look into symbols and types from any module (if the module has been compiled with the proper options). 2ff7e9595c
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