How to identify read or write operations of page fault when using sigaction handler on SIGSEGV?(LINUX)

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http://stackoverflow.com – I use sigaction to handle page fault exception, and the handler function is defind like this: void sigaction_handler(int signum, siginfo_t *info, void *_context) So it's easy to get page fault address by reading info->si_addr. The question is, how to know whether this operation is memory READ or WRITE ? I found the type of _context parameter is ucontext_t defined in /usr/include/sys/ucontext.h There is a cr2 field defined in mcontext_t, but unforunately, it is only avaliable when x86_64 is not defind, thus I could not used cr2 to identify read/write operations. On anotherway, there is a (HowTos)