Linux FileID should work with ELFCLASS32 and ELFCLASS64 regardless of what's

native.

BUG=399
TEST=none
Review URL: http://breakpad.appspot.com/178001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@677 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/common/linux/file_id.cc

@@ -56,37 +56,44 @@ FileID::FileID(const char* path) {
   strncpy(path_, path, sizeof(path_));
 }
 
-// These two functions are also used inside the crashed process, so be safe
+struct ElfClass32 {
+  typedef Elf32_Ehdr Ehdr;
+  typedef Elf32_Shdr Shdr;
+  static const int kClass = ELFCLASS32;
+};
+
+struct ElfClass64 {
+  typedef Elf64_Ehdr Ehdr;
+  typedef Elf64_Shdr Shdr;
+  static const int kClass = ELFCLASS64;
+};
+
+// These three functions are also used inside the crashed process, so be safe
 // and use the syscall/libc wrappers instead of direct syscalls or libc.
-  static bool FindElfTextSection(const void *elf_mapped_base,
+template<typename ElfClass>
+static void FindElfClassTextSection(const char *elf_base,
                                     const void **text_start,
                                     int *text_size) {
-  assert(elf_mapped_base);
+  typedef typename ElfClass::Ehdr Ehdr;
+  typedef typename ElfClass::Shdr Shdr;
+
+  assert(elf_base);
   assert(text_start);
   assert(text_size);
 
-  const char* elf_base =
+  assert(my_strncmp(elf_base, ELFMAG, SELFMAG) == 0);
-    static_cast<const char*>(elf_mapped_base);
+
-  const ElfW(Ehdr)* elf_header =
-    reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
-  if (my_strncmp(elf_base, ELFMAG, SELFMAG) != 0)
-    return false;
-#if __ELF_NATIVE_CLASS == 32
-#define ELFCLASS ELFCLASS32
-#else
-#define ELFCLASS ELFCLASS64
-#endif
-  //TODO: support dumping 32-bit binaries from a 64-bit dump_syms?
-  if (elf_header->e_ident[EI_CLASS] != ELFCLASS)
-    return false;
-  *text_start = NULL;
-  *text_size = 0;
-  const ElfW(Shdr)* sections =
-    reinterpret_cast<const ElfW(Shdr)*>(elf_base + elf_header->e_shoff);
   const char* text_section_name = ".text";
   int name_len = my_strlen(text_section_name);
-  const ElfW(Shdr)* string_section = sections + elf_header->e_shstrndx;
+
-  const ElfW(Shdr)* text_section = NULL;
+  const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
+  assert(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
+
+  const Shdr* sections =
+      reinterpret_cast<const Shdr*>(elf_base + elf_header->e_shoff);
+  const Shdr* string_section = sections + elf_header->e_shstrndx;
+
+  const Shdr* text_section = NULL;
   for (int i = 0; i < elf_header->e_shnum; ++i) {
     if (sections[i].sh_type == SHT_PROGBITS) {
       const char* section_name = (char*)(elf_base +
@@ -102,6 +109,30 @@ FileID::FileID(const char* path) {
     *text_start = elf_base + text_section->sh_offset;
     *text_size = text_section->sh_size;
   }
+}
+
+static bool FindElfTextSection(const void *elf_mapped_base,
+                               const void **text_start,
+                               int *text_size) {
+  assert(elf_mapped_base);
+  assert(text_start);
+  assert(text_size);
+
+  const char* elf_base =
+    static_cast<const char*>(elf_mapped_base);
+  const ElfW(Ehdr)* elf_header =
+    reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
+  if (my_strncmp(elf_base, ELFMAG, SELFMAG) != 0)
+    return false;
+
+  if (elf_header->e_ident[EI_CLASS] == ELFCLASS32) {
+    FindElfClassTextSection<ElfClass32>(elf_base, text_start, text_size);
+  } else if (elf_header->e_ident[EI_CLASS] == ELFCLASS64) {
+    FindElfClassTextSection<ElfClass64>(elf_base, text_start, text_size);
+  } else {
+    return false;
+  }
+
   return true;
 }
 

src/common/linux/file_id_unittest.cc

@@ -29,6 +29,7 @@
 
 // Unit tests for FileID
 
+#include <elf.h>
 #include <stdlib.h>
 
 #include "common/linux/file_id.h"
@@ -74,3 +75,69 @@ TEST(FileIDTest, FileIDStrip) {
   EXPECT_STREQ(identifier_string1, identifier_string2);
   unlink(templ);
 }
+
+struct ElfClass32 {
+  typedef Elf32_Ehdr Ehdr;
+  typedef Elf32_Shdr Shdr;
+  static const int kClass = ELFCLASS32;
+};
+
+struct ElfClass64 {
+  typedef Elf64_Ehdr Ehdr;
+  typedef Elf64_Shdr Shdr;
+  static const int kClass = ELFCLASS64;
+};
+
+template<typename ElfClass>
+struct ElfishElf {
+  typedef typename ElfClass::Ehdr Ehdr;
+  typedef typename ElfClass::Shdr Shdr;
+
+  Ehdr elf_header;
+  Shdr text_header;
+  Shdr string_header;
+  char text_section[128];
+  char string_section[8];
+
+  static void Populate(ElfishElf* elf) {
+    memset(elf, 0, sizeof(ElfishElf));
+    memcpy(elf, ELFMAG, SELFMAG);
+    elf->elf_header.e_ident[EI_CLASS] = ElfClass::kClass;
+    elf->elf_header.e_shoff = offsetof(ElfishElf, text_header);
+    elf->elf_header.e_shnum = 2;
+    elf->elf_header.e_shstrndx = 1;
+    elf->text_header.sh_name = 0;
+    elf->text_header.sh_type = SHT_PROGBITS;
+    elf->text_header.sh_offset = offsetof(ElfishElf, text_section);
+    elf->text_header.sh_size = sizeof(text_section);
+    for (size_t i = 0; i < sizeof(text_section); ++i) {
+      elf->text_section[i] = i * 3;
+    }
+    elf->string_header.sh_offset = offsetof(ElfishElf, string_section);
+    strcpy(elf->string_section, ".text");
+  }
+};
+
+TEST(FileIDTest, ElfClass) {
+  uint8_t identifier[sizeof(MDGUID)];
+  const char expected_identifier_string[] =
+      "80808080-8080-0000-0000-008080808080";
+  char identifier_string[sizeof(expected_identifier_string)];
+
+  ElfishElf<ElfClass32> elf32;
+  ElfishElf<ElfClass32>::Populate(&elf32);
+  EXPECT_TRUE(FileID::ElfFileIdentifierFromMappedFile(&elf32, identifier));
+  FileID::ConvertIdentifierToString(identifier, identifier_string,
+                                    sizeof(identifier_string));
+  EXPECT_STREQ(expected_identifier_string, identifier_string);
+
+  memset(identifier, 0, sizeof(identifier));
+  memset(identifier_string, 0, sizeof(identifier_string));
+
+  ElfishElf<ElfClass64> elf64;
+  ElfishElf<ElfClass64>::Populate(&elf64);
+  EXPECT_TRUE(FileID::ElfFileIdentifierFromMappedFile(&elf64, identifier));
+  FileID::ConvertIdentifierToString(identifier, identifier_string,
+                                    sizeof(identifier_string));
+  EXPECT_STREQ(expected_identifier_string, identifier_string);
+}