[microdump] Fix hw architecture indication in build fingerprint line

src/client/linux/microdump_writer/microdump_writer.cc

 // Copyright (c) 2014, 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 148 matching lines @@
 
   void DumpOSInformation() {
     const uint8_t n_cpus = static_cast<uint8_t>(sysconf(_SC_NPROCESSORS_CONF));
 
 #if defined(__ANDROID__)
     const char kOSId[] = "A";
 #else
     const char kOSId[] = "L";
 #endif
 
-// We cannot depend on uts.machine. On multiarch devices it always returns the
-// primary arch, not the one that match the executable being run.
+// Dump the runtime architecture. On multiarch devices it might not match the
+// hw architecture (the one returned by uname()), for instance in the case of
+// a 32-bit app running on a aarch64 device.
 #if defined(__aarch64__)
     const char kArch[] = "arm64";
 #elif defined(__ARMEL__)
     const char kArch[] = "arm";
 #elif defined(__x86_64__)
     const char kArch[] = "x86_64";
 #elif defined(__i386__)
     const char kArch[] = "x86";
 #elif defined(__mips__)
     const char kArch[] = "mips";
 #else
 #error "This code has not been ported to your platform yet"
 #endif
 
     LogAppend("O ");
     LogAppend(kOSId);
     LogAppend(" ");
     LogAppend(kArch);
     LogAppend(" ");
     LogAppend(n_cpus);
     LogAppend(" ");
+
+    // Dump the HW architecture (e.g., armv7l, aarch64).
+    struct utsname uts;
+    const bool has_uts_info = (uname(&uts) == 0);
+    const char* hwArch = has_uts_info ? uts.machine : "unknown_hw_arch";
+    LogAppend(hwArch);
+    LogAppend(" ");
+
     // If the client has attached a build fingerprint to the MinidumpDescriptor
     // use that one. Otherwise try to get some basic info from uname().
     if (build_fingerprint_) {
       LogAppend(build_fingerprint_);
+    } else if (has_uts_info) {
+      LogAppend(uts.release);
+      LogAppend(" ");
+      LogAppend(uts.version);
     } else {
-      struct utsname uts;
-      if (uname(&uts) == 0) {
-        LogAppend(uts.machine);
-        LogAppend(" ");
-        LogAppend(uts.release);
-        LogAppend(" ");
-        LogAppend(uts.version);
-      } else {
-        LogAppend("no build fingerprint available");
-      }
+      LogAppend("no build fingerprint available");
     }
     LogCommitLine();
   }
 
   bool DumpThreadStack(uint32_t thread_id,
                        uintptr_t stack_pointer,
                        int max_stack_len,
                        uint8_t** stack_copy) {
     *stack_copy = NULL;
     const void* stack;
@@ skipping 197 matching lines @@
     dumper.set_crash_thread(context->tid);
   }
   MicrodumpWriter writer(context, mappings, build_fingerprint, product_info,
                          &dumper);
   if (!writer.Init())
     return false;
   return writer.Dump();
 }
 
 }  // namespace google_breakpad