Change MDCVInfoELF into something usable.

src/google_breakpad/common/minidump_format.h

 /* Copyright (c) 2006, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 431 matching lines @@
   uint32_t  age;               /* Identifies incremental changes to PDB file */
   uint8_t   pdb_file_name[1];  /* Pathname or filename of PDB file,
                                 * 0-terminated 8-bit character data (UTF-8?) */
 } MDCVInfoPDB70;
 
 static const size_t MDCVInfoPDB70_minsize = offsetof(MDCVInfoPDB70,
                                                      pdb_file_name[0]);
 
 #define MD_CVINFOPDB70_SIGNATURE 0x53445352  /* cvSignature = 'SDSR' */
 
+/*
+ * Modern ELF toolchains insert a "build id" into the ELF headers that
+ * usually contains a hash of some ELF headers + sections to uniquely
+ * identify a binary.
+ * https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Developer_Guide/compiling-build-id.html
+ */
 typedef struct {
-  uint32_t data1[2];
-  uint32_t data2;
-  uint32_t data3;
-  uint32_t data4;
-  uint32_t data5[3];
-  uint8_t  extra[2];
+  uint32_t cv_signature;
+  uint8_t  build_id[1];  /* bytes of build id */

[Mark Mentovai, 2016/02/09 15:55:04]

How many?

[Ted Mielczarek, 2016/02/09 18:01:52]

There isn't really a spec for it, but it allows for an arbitrary number of
bytes. The binutils default is a 160-bit sha-1 hash of the rest of the binary,
so 20 bytes, but ld will let you use a uuid, md5, or an arbitrary hex string:
https://sourceware.org/binutils/docs-2.26/ld/Options.html#index-g_t_002d_002d...

Since the CV record is already variable-length, supporting arbitrary sizes here
isn't particularly hard. For the client-side patch I have to use this, I just
clamp it to a max of 20 bytes since that covers the common case and avoids
having to allocate memory in the minidump writer.

Should I just mention that it's variable-length, but usually 20 bytes?

 } MDCVInfoELF;
 
+static const size_t MDCVInfoELF_minsize = offsetof(MDCVInfoELF,
+                                                   build_id[0]);
+
+#define MD_CVINFOELF_SIGNATURE 0x4270454c  /* cvSignature = 'BpEL' */
+
 /* In addition to the two CodeView record formats above, used for linking
  * to external pdb files, it is possible for debugging data to be carried
  * directly in the CodeView record itself.  These signature values will
  * be found in the first 4 bytes of the CodeView record.  Additional values
  * not commonly experienced in the wild are given by "Microsoft Symbol and
  * Type Information", http://www.x86.org/ftp/manuals/tools/sym.pdf, section
  * 7.2.  An in-depth description of the CodeView 4.1 format is given by
  * "Undocumented Windows 2000 Secrets", Windows 2000 Debugging Support/
  * Microsoft Symbol File Internals/CodeView Subsections,
  * http://www.rawol.com/features/undocumented/sbs-w2k-1-windows-2000-debugging-support.pdf
@@ skipping 493 matching lines @@
   uint64_t  ldbase;
   uint64_t  dynamic;
 } MDRawDebug64;
 
 #if defined(_MSC_VER)
 #pragma warning(pop)
 #endif  /* _MSC_VER */
 
 
 #endif  /* GOOGLE_BREAKPAD_COMMON_MINIDUMP_FORMAT_H__ */