Get instruction pointer on segmentation fault or crash (for x86 JIT compiler project)?

I'm implementing the backend for a JavaScript JIT compiler that produces x86 code. Sometimes, as the result of bugs, I get segmentat开发者_JAVA百科ion faults. It can be quite difficult to trace back what caused them. Hence, I've been wondering if there would be some "easy" way to trap segmentation faults and other such crashes, and get the address of the instruction that caused the fault. This way, I could map the address back to compiled x86 assembly, or even back to source code.

This needs to work on Linux, but ideally on any POSIX compliant system. In the worst case, if I can't catch the seg fault and get the IP in my running JIT, I'd like to be able to trap it outside (kernel log?), and perhaps just have the compiler dump a big file with mappings of addresses to instructions, which I could match with a Python script or something.

Any ideas/suggestions are appreciated. Feel free to share your own debugging tips if you've ever worked on a compiler project of your own.

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If you use sigaction, you can define a signal handler that takes 3 arguments:

void (*sa_sigaction)(int signum, siginfo_t *info, void *ucontext)

The third argument passed to the signal handler is a pointer to an OS and architecture specific data structure. On linux, its a ucontext_t which is defined in the <sys/ucontext.h> header file. Within that, uc_mcontext is an mcontext_t (machine context) which for x86 contains all the registers at the time of the signal in gregs. So you can access

ucontext->uc_mcontext.gregs[REG_EIP]  (32 bit mode)
ucontext->uc_mcontext.gregs[REG_RIP]  (64 bit mode)

to get the instruction pointer of the faulting instruction.