International Business Machines Corporation

Prasanna S Panchamukhi

Balbir Singh

Maneesh Soni

Ananth Narayan Mavinakayanahalli

Vaddagiri Srivatsa

A method of debugging a function upon function exit includes pausing program execution at the time of initializing the function, wherein the function initialization includes saving a set of registers on the stack, recording the value of the stack pointer, configuring a watchpoint register based on the recorded value, wherein the watchpoint register is configured to trap memory references of the function based on the recorded value of the stack pointer, and executing the function. Program execution will pause when it is exiting the function because of stack references made by the function epilogue to restore registers saved on the stack and the configured watchpoint registers.

Debugging program function

A first section of executable computer code of a computer program is dynamically patched by performing the following. A breakpoint is inserted at the first section of executable computer code. During execution of the computer program, an instruction counter is incremented on an instruction-by-instruction basis through the computer program. The instruction counter indicates a current instruction of the computer program being executed. The breakpoint where the instruction counter points to the first section of executable computer code is encountered, which results in a breakpoint handler being called. The breakpoint handler changes the instruction pointer to instead point to a second section of executable computer code. The second section of executable computer code is a patched version of the first section of executable computer code. Upon the breakpoint handler returning, the second section of executable computer code is executed in lieu of the first section of executable computer code.

Dynamically patching computer code using breakpoints

A system and method for instrumentation of software, the software comprising a set of instructions (program or code) which are executable on a processor of a system, for example a computer system. A location in the instruction to insert a probe is first identified. The instruction is replaced with the probe by copying the instruction to a predefined location. The instruction is executed in the kernel space. A first exception is generated upon encountering the probe and calling a first exception handler, and the first exception handler is configured to call an instrumentation routine. A second exception is generated when the instrumentation routine encounters an error and calling a second exception handler, recovering from the exceptions and returning to a sane state to continue normal execution of the instruction.

Recovery from nested exceptions in an instrumentation routine

A method of instrumentation, preferably a computer implemented method for instrumentation, in a program which contains an original program. The original instruction is copied into a user address space which has an unused stack space. When a breakpoint is encountered the original instruction is executed out-of-line in the unused stack space by single stepping. Using this debugging in a multithreaded environment is advantageous as all threads will switch into the unused stack space and execute the breakpoint.

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Bengaluru, India

Prasanna S Panchamukhi