Chrome on Android now supports loading the shared library directly from the APK file.

This patch makes two changes to breakpad to enable crash reporting to work correctly when the library is inside another file (an archive):

- Do not filter mappings which map an executable at a non-zero offset.
- If such an executable is mapped look in the ELF information for the
shared object name and use that name in the minidump.

Note this change doesn't care about the archive format and isn't Android
specific (though loading the shared library this way is currently only done on Android).

BUG=390618
R=thestig@chromium.org

Review URL: https://breakpad.appspot.com/7684002

Patch from Anton Carver <anton@chromium.org>.

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1355 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 18 insertions, 10 deletions

diff --git a/src/common/linux/memory_mapped_file.cc b/src/common/linux/memory_mapped_file.cc
index 0f0fcb2b..064326bb 100644
--- a/src/common/linux/memory_mapped_file.cc
+++ b/src/common/linux/memory_mapped_file.cc
@@ -46,15 +46,15 @@ namespace google_breakpad {
 
 MemoryMappedFile::MemoryMappedFile() {}
 
-MemoryMappedFile::MemoryMappedFile(const char* path) {
-  Map(path);
+MemoryMappedFile::MemoryMappedFile(const char* path, size_t offset) {
+  Map(path, offset);
 }
 
 MemoryMappedFile::~MemoryMappedFile() {
   Unmap();
 }
 
-bool MemoryMappedFile::Map(const char* path) {
+bool MemoryMappedFile::Map(const char* path, size_t offset) {
   Unmap();
 
   int fd = sys_open(path, O_RDONLY, 0);
@@ -73,25 +73,33 @@ bool MemoryMappedFile::Map(const char* path) {
     return false;
   }
 
-  // If the file size is zero, simply use an empty MemoryRange and return
-  // true. Don't bother to call mmap() even though mmap() can handle an
-  // empty file on some platforms.
-  if (st.st_size == 0) {
+  // Strangely file size can be negative, but we check above that it is not.
+  size_t file_len = static_cast<size_t>(st.st_size);
+  // If the file does not extend beyond the offset, simply use an empty
+  // MemoryRange and return true. Don't bother to call mmap()
+  // even though mmap() can handle an empty file on some platforms.
+  if (offset >= file_len) {
     sys_close(fd);
     return true;
   }
 
 #if defined(__x86_64__) || defined(__aarch64__)
-  void* data = sys_mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+  void* data = sys_mmap(NULL, file_len, PROT_READ, MAP_PRIVATE, fd, offset);
 #else
-  void* data = sys_mmap2(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+  if ((offset & 4095) != 0) {
+    // Not page aligned.
+    sys_close(fd);
+    return false;
+  }
+  void* data = sys_mmap2(
+      NULL, file_len, PROT_READ, MAP_PRIVATE, fd, offset >> 12);
 #endif
   sys_close(fd);
   if (data == MAP_FAILED) {
     return false;
   }
 
-  content_.Set(data, st.st_size);
+  content_.Set(data, file_len - offset);
   return true;
 }