// Updates contents so that any read accesses past the last byte will
// cause a SIGSEGV. It accomplishes this by changing access to the page that
// begins immediately after the end of the contents (as allocators and mmap()
// all operate on page boundaries, this is a reasonable assumption).
// This function will also initialize buf, which caller must free().
void createProtectedBuf(StringPiece& contents, char** buf) {
ASSERT_LE(contents.size(), kPageSize);
const size_t kSuccess = 0;
char* tmp;
if (kSuccess != posix_memalign((void**)buf, kPageSize, 2 * kPageSize)) {
ASSERT_FALSE(true);
}
mprotect(*buf + kPageSize, kPageSize, PROT_NONE);
size_t newBegin = kPageSize - contents.size();
memcpy(*buf + newBegin, contents.data(), contents.size());
contents.reset(*buf + newBegin, contents.size());
}
// Updates contents so that any read accesses past the last byte will
// cause a SIGSEGV. It accomplishes this by changing access to the page that
// begins immediately after the end of the contents (as allocators and mmap()
// all operate on page boundaries, this is a reasonable assumption).
// This function will also initialize buf, which caller must free().
void createProtectedBuf(StringPiece& contents, char** buf) {
ASSERT_LE(contents.size(), kPageSize);
const size_t kSuccess = 0;
char* pageAlignedBuf = (char*)aligned_malloc(2 * kPageSize, kPageSize);
if (pageAlignedBuf == nullptr) {
ASSERT_FALSE(true);
}
// Protect the page after the first full page-aligned region of the
// malloc'ed buffer
mprotect(pageAlignedBuf + kPageSize, kPageSize, PROT_NONE);
size_t newBegin = kPageSize - contents.size();
memcpy(pageAlignedBuf + newBegin, contents.data(), contents.size());
contents.reset(pageAlignedBuf + newBegin, contents.size());
*buf = pageAlignedBuf;
}