[libc-commits] [libc] [libc][mincore] use correct page_size for test (PR #73984)

[Schrodinger ZHU Yifan via libc-commits]

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@@ -29,33 +29,46 @@ TEST(LlvmLibcMincoreTest, UnMappedMemory) {
   EXPECT_THAT(res, Fails(ENOMEM, -1));
 }
 
+// It is always possible to find an aligned boundary if we allocate page sized
+// memory.
+static char *aligned_addr(void *addr, size_t alignment) {
+  char *byte_addr = static_cast<char *>(addr);
+  uintptr_t addr_val = reinterpret_cast<uintptr_t>(addr);
+  uintptr_t offset =
+      addr_val % alignment == 0 ? 0 : alignment - (addr_val % alignment);
+  return byte_addr + offset;
+}
+
 TEST(LlvmLibcMincoreTest, InvalidVec) {
   size_t page_size = static_cast<size_t>(LIBC_NAMESPACE::sysconf(_SC_PAGESIZE));
-  void *addr = LIBC_NAMESPACE::mmap(nullptr, 4 * page_size, PROT_READ,
+  void *addr = LIBC_NAMESPACE::mmap(nullptr, 5 * page_size, PROT_READ,
                                     MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   EXPECT_NE(addr, MAP_FAILED);
-  EXPECT_EQ(reinterpret_cast<unsigned long>(addr) % page_size, 0ul);
+  // Since we allocated 5 pages, we can find an aligned boundary after which
+  // there are at least 4 pages
+  char *aligned = aligned_addr(addr, page_size);
   libc_errno = 0;
-  int res = LIBC_NAMESPACE::mincore(addr, 1, nullptr);
+  int res = LIBC_NAMESPACE::mincore(aligned, 1, nullptr);
   EXPECT_THAT(res, Fails(EFAULT, -1));
   void *area = LIBC_NAMESPACE::mmap(nullptr, page_size, PROT_READ | PROT_WRITE,
                                     MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   EXPECT_NE(area, MAP_FAILED);
   unsigned char *ptr = static_cast<unsigned char *>(area) + page_size - 3;
-  res = LIBC_NAMESPACE::mincore(addr, 4 * page_size, ptr);
+  res = LIBC_NAMESPACE::mincore(aligned, 4 * page_size, ptr);
   EXPECT_THAT(res, Fails(EFAULT, -1));
-  EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, page_size), Succeeds());
-  EXPECT_THAT(LIBC_NAMESPACE::munmap(area, 2), Succeeds());
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SchrodingerZhu wrote:

This is a bug that was not captured before.

https://github.com/llvm/llvm-project/pull/73984