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copied!<p>This is <em>very</em> similar to a homework I once did. Basically I had a list of "pages" and a list of "frames", with associated information. Using <code>SIGSEGV</code> I would catch faults and alter the memory protection bits as necessary. I'll include parts that you may find useful.</p> <h3>Create mapping. Initially it has no permissions.</h3> <pre><code>int w_create_mapping(size_t size, void **addr) { *addr = mmap(NULL, size * w_get_page_size(), PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0 ); if (*addr == MAP_FAILED) { perror("mmap"); return FALSE; } return TRUE; } </code></pre> <h3>Install signal handler</h3> <pre><code>int w_set_exception_handler(w_exception_handler_t handler) { static struct sigaction sa; sa.sa_sigaction = handler; sigemptyset(&sa.sa_mask); sigaddset(&sa.sa_mask, SIGSEGV); sa.sa_flags = SA_SIGINFO; if (sigaction(SIGSEGV, &sa, &previous_action) < 0) return FALSE; return TRUE; } </code></pre> <h3>Exception handler</h3> <pre><code>static void fault_handler(int signum, siginfo_t *info, void *context) { void *address; /* the address that faulted */ /* Memory location which caused fault */ address = info->si_addr; if (FALSE == page_fault(address)) { _exit(1); } } </code></pre> <h3>Increasing protection</h3> <pre><code>int w_protect_mapping(void *addr, size_t num_pages, w_prot_t protection) { int prot; switch (protection) { case PROTECTION_NONE: prot = PROT_NONE; break; case PROTECTION_READ: prot = PROT_READ; break; case PROTECTION_WRITE: prot = PROT_READ | PROT_WRITE; break; } if (mprotect(addr, num_pages * w_get_page_size(), prot) < 0) return FALSE; return TRUE; } </code></pre> <p>I can't publicly make it all available since the team is likely to use that same homework again.</p>

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