[ASan][MIPS] Fix some tests failing on MIPS64

[slthakur]

Summary

Tests fixed:

AddressSanitizer-mips64-linux :: TestCases/null_deref.cc: symbol for pc was wrong.
AddressSanitizer-mips64-linux :: TestCases/Linux/quarantine_size_mb.cc : The flag quarantine_size_mb should not be compared for >=0 as it is defined as u32 type.

[samsonov]

lib/asan/asan_flags.cc

157

No. This quarantinze_size_mb is defined in asan_flags.inc and has type int.

lib/sanitizer_common/sanitizer_linux.cc

1001

This change is OK. Feel free to commit it in a separate change.

lib/asan/asan_flags.cc

#endif
   CHECK_GE(f->redzone, 16);
   CHECK_GE(f->max_redzone, f->redzone);
   CHECK_LE(f->max_redzone, 2048);
   CHECK(IsPowerOfTwo(f->redzone));
   CHECK(IsPowerOfTwo(f->max_redzone));
 
   // quarantine_size is deprecated but we still honor it.
   // quarantine_size can not be used together with quarantine_size_mb.
-  if (f->quarantine_size >= 0 && f->quarantine_size_mb >= 0) {
+  if (f->quarantine_size >= 0 && f->quarantine_size_mb != u32(-1)) {
     Report("%s: please use either 'quarantine_size' (deprecated) or "
            "quarantine_size_mb, but not both\n", SanitizerToolName);
     Die();
   }
   if (f->quarantine_size >= 0)
     f->quarantine_size_mb = f->quarantine_size >> 20;
   if (f->quarantine_size_mb < 0) {
     const int kDefaultQuarantineSizeMb =

lib/sanitizer_common/sanitizer_linux.cc

 # else
   *pc = ucontext->uc_mcontext.gregs[REG_PC];
   *sp = ucontext->uc_mcontext.gregs[REG_O6];
   stk_ptr = (uptr *) *sp;
   *bp = stk_ptr[15];
 # endif
 #elif defined(__mips__)
   ucontext_t *ucontext = (ucontext_t*)context;
-  *pc = ucontext->uc_mcontext.gregs[31];
+  *pc = ucontext->uc_mcontext.pc;
   *bp = ucontext->uc_mcontext.gregs[30];
   *sp = ucontext->uc_mcontext.gregs[29];
 #else
 # error "Unsupported arch"
 #endif
 }
 
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX