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

src/common/linux/elf_core_dump_unittest.cc

@@ -70,7 +70,7 @@ TEST(ElfCoreDumpTest, TestElfHeader) {
   ElfCoreDump core;
 
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header) - 1));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
   EXPECT_EQ(NULL, core.GetHeader());
@@ -80,49 +80,49 @@ TEST(ElfCoreDumpTest, TestElfHeader) {
   EXPECT_FALSE(core.GetFirstNote().IsValid());
 
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_ident[0] = ELFMAG0;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_ident[1] = ELFMAG1;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_ident[2] = ELFMAG2;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_ident[3] = ELFMAG3;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_ident[4] = ElfCoreDump::kClass;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_version = EV_CURRENT;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_FALSE(core.IsValid());
 
   header.e_type = ET_CORE;
   ASSERT_TRUE(WriteFile(core_file, &header, sizeof(header)));
-  ASSERT_TRUE(mapped_core_file.Map(core_file));
+  ASSERT_TRUE(mapped_core_file.Map(core_file, 0));
   core.SetContent(mapped_core_file.content());
   EXPECT_TRUE(core.IsValid());
 }
@@ -156,7 +156,8 @@ TEST(ElfCoreDumpTest, ValidCoreFile) {
 #endif
 
   MemoryMappedFile mapped_core_file;
-  ASSERT_TRUE(mapped_core_file.Map(crash_generator.GetCoreFilePath().c_str()));
+  ASSERT_TRUE(
+      mapped_core_file.Map(crash_generator.GetCoreFilePath().c_str(), 0));
 
   ElfCoreDump core;
   core.SetContent(mapped_core_file.content());

src/common/linux/file_id.cc

@@ -149,7 +149,7 @@ bool FileID::ElfFileIdentifierFromMappedFile(const void* base,
 }
 
 bool FileID::ElfFileIdentifier(uint8_t identifier[kMDGUIDSize]) {
-  MemoryMappedFile mapped_file(path_.c_str());
+  MemoryMappedFile mapped_file(path_.c_str(), 0);
   if (!mapped_file.data())  // Should probably check if size >= ElfW(Ehdr)?
     return false;
 

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;
 }
 

src/common/linux/memory_mapped_file.h

@@ -33,6 +33,7 @@
 #ifndef COMMON_LINUX_MEMORY_MAPPED_FILE_H_
 #define COMMON_LINUX_MEMORY_MAPPED_FILE_H_
 
+#include <stddef.h>
 #include "common/basictypes.h"
 #include "common/memory_range.h"
 
@@ -47,7 +48,7 @@ class MemoryMappedFile {
 
   // Constructor that calls Map() to map a file at |path| into memory.
   // If Map() fails, the object behaves as if it is default constructed.
-  explicit MemoryMappedFile(const char* path);
+  MemoryMappedFile(const char* path, size_t offset);
 
   ~MemoryMappedFile();
 
@@ -56,7 +57,7 @@ class MemoryMappedFile {
   // success. Mapping an empty file will succeed but with data() and size()
   // returning NULL and 0, respectively. An existing mapping is unmapped
   // before a new mapping is created.
-  bool Map(const char* path);
+  bool Map(const char* path, size_t offset);
 
   // Unmaps the memory for the mapped file. It's a no-op if no file is
   // mapped.

src/common/linux/memory_mapped_file_unittest.cc

@@ -71,12 +71,12 @@ TEST_F(MemoryMappedFileTest, UnmapWithoutMap) {
 
 TEST_F(MemoryMappedFileTest, MapNonexistentFile) {
   {
-    MemoryMappedFile mapped_file("nonexistent-file");
+    MemoryMappedFile mapped_file("nonexistent-file", 0);
     ExpectNoMappedData(mapped_file);
   }
   {
     MemoryMappedFile mapped_file;
-    EXPECT_FALSE(mapped_file.Map("nonexistent-file"));
+    EXPECT_FALSE(mapped_file.Map("nonexistent-file", 0));
     ExpectNoMappedData(mapped_file);
   }
 }
@@ -87,12 +87,12 @@ TEST_F(MemoryMappedFileTest, MapEmptyFile) {
   ASSERT_TRUE(WriteFile(test_file.c_str(), NULL, 0));
 
   {
-    MemoryMappedFile mapped_file(test_file.c_str());
+    MemoryMappedFile mapped_file(test_file.c_str(), 0);
     ExpectNoMappedData(mapped_file);
   }
   {
     MemoryMappedFile mapped_file;
-    EXPECT_TRUE(mapped_file.Map(test_file.c_str()));
+    EXPECT_TRUE(mapped_file.Map(test_file.c_str(), 0));
     ExpectNoMappedData(mapped_file);
   }
 }
@@ -109,7 +109,7 @@ TEST_F(MemoryMappedFileTest, MapNonEmptyFile) {
   ASSERT_TRUE(WriteFile(test_file.c_str(), data, data_size));
 
   {
-    MemoryMappedFile mapped_file(test_file.c_str());
+    MemoryMappedFile mapped_file(test_file.c_str(), 0);
     EXPECT_FALSE(mapped_file.content().IsEmpty());
     EXPECT_TRUE(mapped_file.data() != NULL);
     EXPECT_EQ(data_size, mapped_file.size());
@@ -117,7 +117,7 @@ TEST_F(MemoryMappedFileTest, MapNonEmptyFile) {
   }
   {
     MemoryMappedFile mapped_file;
-    EXPECT_TRUE(mapped_file.Map(test_file.c_str()));
+    EXPECT_TRUE(mapped_file.Map(test_file.c_str(), 0));
     EXPECT_FALSE(mapped_file.content().IsEmpty());
     EXPECT_TRUE(mapped_file.data() != NULL);
     EXPECT_EQ(data_size, mapped_file.size());
@@ -145,13 +145,13 @@ TEST_F(MemoryMappedFileTest, RemapAfterMap) {
   ASSERT_TRUE(WriteFile(test_file2.c_str(), data2, data2_size));
 
   {
-    MemoryMappedFile mapped_file(test_file1.c_str());
+    MemoryMappedFile mapped_file(test_file1.c_str(), 0);
     EXPECT_FALSE(mapped_file.content().IsEmpty());
     EXPECT_TRUE(mapped_file.data() != NULL);
     EXPECT_EQ(data1_size, mapped_file.size());
     EXPECT_EQ(0, memcmp(data1, mapped_file.data(), data1_size));
 
-    mapped_file.Map(test_file2.c_str());
+    mapped_file.Map(test_file2.c_str(), 0);
     EXPECT_FALSE(mapped_file.content().IsEmpty());
     EXPECT_TRUE(mapped_file.data() != NULL);
     EXPECT_EQ(data2_size, mapped_file.size());
@@ -159,16 +159,50 @@ TEST_F(MemoryMappedFileTest, RemapAfterMap) {
   }
   {
     MemoryMappedFile mapped_file;
-    EXPECT_TRUE(mapped_file.Map(test_file1.c_str()));
+    EXPECT_TRUE(mapped_file.Map(test_file1.c_str(), 0));
     EXPECT_FALSE(mapped_file.content().IsEmpty());
     EXPECT_TRUE(mapped_file.data() != NULL);
     EXPECT_EQ(data1_size, mapped_file.size());
     EXPECT_EQ(0, memcmp(data1, mapped_file.data(), data1_size));
 
-    mapped_file.Map(test_file2.c_str());
+    mapped_file.Map(test_file2.c_str(), 0);
     EXPECT_FALSE(mapped_file.content().IsEmpty());
     EXPECT_TRUE(mapped_file.data() != NULL);
     EXPECT_EQ(data2_size, mapped_file.size());
     EXPECT_EQ(0, memcmp(data2, mapped_file.data(), data2_size));
   }
 }
+
+TEST_F(MemoryMappedFileTest, MapWithOffset) {
+  // Put more data in the test file this time. Offsets can only be
+  // done on page boundaries, so we need a two page file to test this.
+  const int page_size = 4096;
+  char data1[2 * page_size];
+  size_t data1_size = sizeof(data1);
+  for (size_t i = 0; i < data1_size; ++i) {
+    data1[i] = i & 0x7f;
+  }
+
+  AutoTempDir temp_dir;
+  string test_file1 = temp_dir.path() + "/test_file1";
+  ASSERT_TRUE(WriteFile(test_file1.c_str(), data1, data1_size));
+  {
+    MemoryMappedFile mapped_file(test_file1.c_str(), page_size);
+    EXPECT_FALSE(mapped_file.content().IsEmpty());
+    EXPECT_TRUE(mapped_file.data() != NULL);
+    EXPECT_EQ(data1_size - page_size, mapped_file.size());
+    EXPECT_EQ(
+        0,
+        memcmp(data1 + page_size, mapped_file.data(), data1_size - page_size));
+  }
+  {
+    MemoryMappedFile mapped_file;
+    mapped_file.Map(test_file1.c_str(), page_size);
+    EXPECT_FALSE(mapped_file.content().IsEmpty());
+    EXPECT_TRUE(mapped_file.data() != NULL);
+    EXPECT_EQ(data1_size - page_size, mapped_file.size());
+    EXPECT_EQ(
+        0,
+        memcmp(data1 + page_size, mapped_file.data(), data1_size - page_size));
+  }
+}