void relro_post()
{
mprotect_cb(relro_start, relro_end - relro_start, PROT_READ);
// mprotect_cb is a pointer allocated in .bss, so we need to restore it to
// a NULL value.
mprotect_cb = NULL;
}
void relro_pre()
{
// By the time the injected code runs, the relro segment is read-only. But
// we want to apply relocations in it, so we set it r/w first. We'll restore
// it to read-only in relro_post.
mprotect_cb(relro_start, relro_end - relro_start, PROT_READ | PROT_WRITE);
}
static inline __attribute__((always_inline)) void do_relocations_with_relro(
void) {
long page_size = sysconf_cb(_SC_PAGESIZE);
uintptr_t aligned_relro_start = ((uintptr_t)relro_start) & ~(page_size - 1);
// The relro segment may not end at a page boundary. If that's the case, the
// remainder of the page needs to stay read-write, so the last page is never
// set read-only. Thus the aligned relro end is page-rounded down.
uintptr_t aligned_relro_end = ((uintptr_t)relro_end) & ~(page_size - 1);
// By the time the injected code runs, the relro segment is read-only. But
// we want to apply relocations in it, so we set it r/w first. We'll restore
// it to read-only in relro_post.
mprotect_cb((void*)aligned_relro_start,
aligned_relro_end - aligned_relro_start, PROT_READ | PROT_WRITE);
do_relocations();
mprotect_cb((void*)aligned_relro_start,
aligned_relro_end - aligned_relro_start, PROT_READ);
// mprotect_cb and sysconf_cb are allocated in .bss, so we need to restore
// them to a NULL value.
mprotect_cb = NULL;
sysconf_cb = NULL;
}