Leaving this here as comments on that blog seem broken. TL;DR: access(2) is a bit more lightweight than write(2) for this purpose. Consider the following (from

Leaving this here as comments on that blog seem broken. TL;DR: access(2) is a bit more lightweight than write(2) for this purpose. Consider the following (from memory, untested): word_t peek(word_t addr, int success) { word_t ret; errno = 0; access(addr, F_OK); if (success) success = (errno != EFAULT); if (errno != EFAULT) ret = *addr; return ret; } I first learnt about this trick in http://www.gcu-squad.org/2005/08/non-ce-n-est-pas-sale%21/ http://www.gcu-squad.org/2005/08/non-ce-n-est-pas-sale%21/