[scudo] Support syslog logging on Android and in dieWithMessage

[cryptoad]

Summary

This is controlled by the common option log_to_syslog, which is enabled by
default on Android.

There is a side effect to this as syslog can use malloc or the like. This
is not ideal as this could be called in a failure path while the heap is
corrupted, but it's pretty much compulsory to have that for Android.

The plan is to change WriteOneLineToSyslog to use async_safe_write_log if
available, which doesn't do dynamic memory allocation (added to the Bionic libc
somewhat recently).

[cryptoad]

lib/scudo/scudo_allocator.cpp

209

I forgot to say that this was removed because the background thread will be coming back, but in another form.

[cryptoad]

The plan still didn't work on a freshly flashed device. There are still issues with logging with the init process.

lib/scudo/scudo_allocator.cpp

 
 static bool ScudoInitIsRunning = false;
 
 void initScudo() {
   SanitizerToolName = "Scudo";
   CHECK(!ScudoInitIsRunning && "Scudo init calls itself!");
   ScudoInitIsRunning = true;
 
+  CacheBinaryName();
+
   // Check if hardware CRC32 is supported in the binary and by the platform, if
   // so, opt for the CRC32 hardware version of the checksum.
   if (computeHardwareCRC32 && testCPUFeature(CRC32CPUFeature))
     atomic_store_relaxed(&HashAlgorithm, CRC32Hardware);
 
   initFlags();
-
   AllocatorOptions Options;
   Options.setFrom(getFlags(), common_flags());
   initScudoInternal(Options);
 
-  // TODO(kostyak): determine if MaybeStartBackgroudThread could be of some use.
+  AndroidLogInit();
 
   ScudoInitIsRunning = false;
 }
 
 struct QuarantineCallback {
   explicit QuarantineCallback(AllocatorCache *Cache)
     : Cache_(Cache) {}
 

lib/scudo/scudo_utils.cpp

 void NORETURN dieWithMessage(const char *Format, ...) {
   // Our messages are tiny, 256 characters is more than enough.
   char Message[256];
   va_list Args;
   va_start(Args, Format);
   __sanitizer::VSNPrintf(Message, sizeof(Message), Format, Args);
   va_end(Args);
   RawWrite(Message);
+  LogMessageOnPrintf(Message);
   Die();
 }
 
 #if defined(__x86_64__) || defined(__i386__)
 // i386 and x86_64 specific code to detect CRC32 hardware support via CPUID.
 // CRC32 requires the SSE 4.2 instruction set.
 typedef struct {
   u32 Eax;