base/allocator: Intercept getcwd and realpath on Android

This is a follow-up of https://crrev.com/c/2418513.
We need to intercept getcwd and realpath, which allocate memory
internally.  The reason is the same as 2418513.

Bug: 1111332
Change-Id: I50c43056609b69020dc84bf181ec6247067cb982
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2438093
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Benoit L <lizeb@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816125}

base/allocator/BUILD.gn

@@ -306,8 +306,14 @@ config("wrap_malloc_symbols") {
     "-Wl,-wrap,realloc",
     "-Wl,-wrap,valloc",
 
+    # <stdlib.h> functions
+    "-Wl,-wrap,realpath",
+
     # <string.h> functions
     "-Wl,-wrap,strdup",
     "-Wl,-wrap,strndup",
+
+    # <unistd.h> functions
+    "-Wl,-wrap,getcwd",
   ]
 }

base/allocator/allocator_shim_override_linker_wrapped_symbols.h

@@ -54,6 +54,26 @@ SHIM_ALWAYS_EXPORT void* __wrap_valloc(size_t size) {
   return ShimValloc(size, nullptr);
 }
 
+const size_t kPathMaxSize = 8192;
+static_assert(kPathMaxSize >= PATH_MAX, "");
+
+extern char* __wrap_strdup(const char* str);
+
+// Override <stdlib.h>
+
+extern char* __real_realpath(const char* path, char* resolved_path);
+
+SHIM_ALWAYS_EXPORT char* __wrap_realpath(const char* path,
+                                         char* resolved_path) {
+  if (resolved_path)
+    return __real_realpath(path, resolved_path);
+
+  char buffer[kPathMaxSize];
+  if (!__real_realpath(path, buffer))
+    return nullptr;
+  return __wrap_strdup(buffer);
+}
+
 // Override <string.h> functions
 
 SHIM_ALWAYS_EXPORT char* __wrap_strdup(const char* str) {
@@ -74,4 +94,20 @@ SHIM_ALWAYS_EXPORT char* __wrap_strndup(const char* str, size_t n) {
   return buffer;
 }
 
+// Override <unistd.h>
+
+extern char* __real_getcwd(char* buffer, size_t size);
+
+SHIM_ALWAYS_EXPORT char* __wrap_getcwd(char* buffer, size_t size) {
+  if (buffer)
+    return __real_getcwd(buffer, size);
+
+  if (!size)
+    size = kPathMaxSize;
+  char local_buffer[size];
+  if (!__real_getcwd(local_buffer, size))
+    return nullptr;
+  return __wrap_strdup(local_buffer);
+}
+
 }  // extern "C"

base/allocator/allocator_shim_unittest.cc

@@ -637,6 +637,15 @@ TEST_F(AllocatorShimTest, InterceptCLibraryFunctions) {
 
   InsertAllocatorDispatch(&g_mock_dispatch);
 
+  // <stdlib.h>
+  counts_before = counts_after;
+  ptr = realpath(".", nullptr);
+  EXPECT_NE(nullptr, ptr);
+  free(ptr);
+  counts_after = total_counts(allocs_intercepted_by_size);
+  EXPECT_GT(counts_after, counts_before);
+
+  // <string.h>
   counts_before = counts_after;
   ptr = strdup("hello, world");
   EXPECT_NE(nullptr, ptr);
@@ -651,6 +660,14 @@ TEST_F(AllocatorShimTest, InterceptCLibraryFunctions) {
   counts_after = total_counts(allocs_intercepted_by_size);
   EXPECT_GT(counts_after, counts_before);
 
+  // <unistd.h>
+  counts_before = counts_after;
+  ptr = getcwd(nullptr, 0);
+  EXPECT_NE(nullptr, ptr);
+  free(ptr);
+  counts_after = total_counts(allocs_intercepted_by_size);
+  EXPECT_GT(counts_after, counts_before);
+
   RemoveAllocatorDispatchForTesting(&g_mock_dispatch);
 }
 #endif  // defined(OS_ANDROID)