[sanitizer] More dead code removal

[cryptoad]

Summary

The following functions are only used in tests: SetEnv,
SanitizerSetThreadName, SanitizerGetThreadName. I don't think they are
going to be used in the future, and I propose to get rid of them, and associated
tests and include.

[vitalybuka]

lib/sanitizer_common/sanitizer_common.h

272

this one is used by external code, check __sanitizer::SetEnv google3

[cryptoad]

Readding SetEnv.

[dvyukov]

I am not following. Isn't it a test for prctl interceptor? Why are we removing useful tests?
Perhaps it's not the most critical functionality. And perhaps SanitizerSetThreadName needs to be moved to the test itself. But still it's a test.

[cryptoad]

In D45838#1073197, @dvyukov wrote:

I am not following. Isn't it a test for prctl interceptor? Why are we removing useful tests?
Perhaps it's not the most critical functionality. And perhaps SanitizerSetThreadName needs to be moved to the test itself. But still it's a test.

Here is my understanding, please let me know if I am wrong:

• Unless mistaken, sanitizer_common_test.cc doesn't involve interceptors, just the tests for the common functions.
• Sanitizer{S,G}etThreadName use prctl and not internal_prctl which might cause problems if they were to be used with interceptors.
• The test removed only tests that actual prctl PR_{G,S}ET_NAME behaves somewhat appropriately, which is probably not that useful.

I tried to verify all this and ran the test manually with a breakpoint on libc's prctl:

[ RUN      ] SanitizerCommon.SanitizerSetThreadName

Breakpoint 1, 0x00007ffff6c592c0 in prctl () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007ffff6c592c0 in prctl () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x000000000054fbd7 in __sanitizer::SanitizerSetThreadName(char const*) () at sanitizer_linux_libcdep.cc:167
#2  0x0000000000495db4 in TestBody () at sanitizer_common_test.cc:100

I think TryToSetThreadName in asan_test.cc leverages an intercepted prctl for this purpose.

[dvyukov]

Tests are not linked with interceptors?

[cryptoad]

In D45838#1073685, @dvyukov wrote:

Tests are not linked with interceptors?

I didn't find anything that suggested that this particular one was, but someone else can probably chime in on that.
sanitizer::SanitizerSetThreadName is present in other binaries (Asan-x86-64-calls-Tests for example) and calls interceptor_prctl there, but is not called by anything.

[dvyukov]

In D45838#1073696, @cryptoad wrote:

In D45838#1073685, @dvyukov wrote:

Tests are not linked with interceptors?

I didn't find anything that suggested that this particular one was, but someone else can probably chime in on that.
sanitizer::SanitizerSetThreadName is present in other binaries (Asan-x86-64-calls-Tests for example) and calls interceptor_prctl there, but is not called by anything.

Humm... should this test go into Asan-x86-64-calls-Tests then?

[cryptoad]

asan_test.cc leverages an intercepted prctl with the ThreadedTestFunc test which calls:

static bool TryToSetThreadName(const char *name) {
#if defined(__linux__) && defined(PR_SET_NAME)
  return 0 == prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0);
#else
  return false;
#endif
}

and checks the names to be right in the death message.

[dvyukov]

Then I don't understand what happens here anymore. Go and drop it.

lib/sanitizer_common/sanitizer_common.h

 uptr ReadLongProcessName(/*out*/ char *buf, uptr buf_len);
 const char *GetProcessName();
 void UpdateProcessName();
 void CacheBinaryName();
 void DisableCoreDumperIfNecessary();
 void DumpProcessMap();
 void PrintModuleMap();
 const char *GetEnv(const char *name);
 bool SetEnv(const char *name, const char *value);
 
 u32 GetUid();
 void ReExec();
 char **GetArgv();
 void PrintCmdline();
 bool StackSizeIsUnlimited();
 uptr GetStackSizeLimitInBytes();
 void SetStackSizeLimitInBytes(uptr limit);

 void NORETURN Abort();
 void NORETURN Die();
 void NORETURN
 CheckFailed(const char *file, int line, const char *cond, u64 v1, u64 v2);
 void NORETURN ReportMmapFailureAndDie(uptr size, const char *mem_type,
                                       const char *mmap_type, error_t err,
                                       bool raw_report = false);
 
-// Set the name of the current thread to 'name', return true on succees.
-// The name may be truncated to a system-dependent limit.
-bool SanitizerSetThreadName(const char *name);
-// Get the name of the current thread (no more than max_len bytes),
-// return true on succees. name should have space for at least max_len+1 bytes.
-bool SanitizerGetThreadName(char *name, int max_len);
-
 // Specific tools may override behavior of "Die" and "CheckFailed" functions
 // to do tool-specific job.
 typedef void (*DieCallbackType)(void);
 
 // It's possible to add several callbacks that would be run when "Die" is
 // called. The callbacks will be run in the opposite order. The tools are
 // strongly recommended to setup all callbacks during initialization, when there
 // is only a single thread.

lib/sanitizer_common/sanitizer_linux_libcdep.cc

 #include <sys/sysctl.h>
 #include <sys/tls.h>
 #endif
 
 #if SANITIZER_SOLARIS
 #include <thread.h>
 #endif
 
-#if SANITIZER_LINUX
-#include <sys/prctl.h>
-#endif
-
 #if SANITIZER_ANDROID
 #include <android/api-level.h>
 #if !defined(CPU_COUNT) && !defined(__aarch64__)
 #include <dirent.h>
 #include <fcntl.h>
 struct __sanitizer::linux_dirent {
   long           d_ino;
   off_t          d_off;
bool SetEnv(const char *name, const char *value) {
   typedef int(*setenv_ft)(const char *name, const char *value, int overwrite);
   setenv_ft setenv_f;
   CHECK_EQ(sizeof(setenv_f), sizeof(f));
   internal_memcpy(&setenv_f, &f, sizeof(f));
   return setenv_f(name, value, 1) == 0;
 }
 #endif
 
-bool SanitizerSetThreadName(const char *name) {
-#ifdef PR_SET_NAME
-  return 0 == prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0);  // NOLINT
-#else
-  return false;
-#endif
-}
-
-bool SanitizerGetThreadName(char *name, int max_len) {
-#ifdef PR_GET_NAME
-  char buff[17];
-  if (prctl(PR_GET_NAME, (unsigned long)buff, 0, 0, 0))  // NOLINT
-    return false;
-  internal_strncpy(name, buff, max_len);
-  name[max_len] = 0;
-  return true;
-#else
-  return false;
-#endif
-}
-
 #if !SANITIZER_FREEBSD && !SANITIZER_ANDROID && !SANITIZER_GO &&               \
     !SANITIZER_NETBSD && !SANITIZER_OPENBSD && !SANITIZER_SOLARIS
 static uptr g_tls_size;
 
 #ifdef __i386__
 # define DL_INTERNAL_FUNCTION __attribute__((regparm(3), stdcall))
 #else
 # define DL_INTERNAL_FUNCTION

lib/sanitizer_common/tests/sanitizer_common_test.cc

for (uptr alignment = 1; alignment <= 32; alignment *= 2) {
         EXPECT_EQ(0U, res % (alignment * PageSize));
         internal_memset((void*)res, 1, size * PageSize);
         UnmapOrDie((void*)res, size * PageSize);
       }
     }
   }
 }
 
-#if SANITIZER_LINUX
-TEST(SanitizerCommon, SanitizerSetThreadName) {
-  const char *names[] = {
-    "0123456789012",
-    "01234567890123",
-    "012345678901234",  // Larger names will be truncated on linux.
-  };
-
-  for (size_t i = 0; i < ARRAY_SIZE(names); i++) {
-    EXPECT_TRUE(SanitizerSetThreadName(names[i]));
-    char buff[100];
-    EXPECT_TRUE(SanitizerGetThreadName(buff, sizeof(buff) - 1));
-    EXPECT_EQ(0, internal_strcmp(buff, names[i]));
-  }
-}
-#endif
-
 TEST(SanitizerCommon, InternalMmapVector) {
   InternalMmapVector<uptr> vector(1);
   for (uptr i = 0; i < 100; i++) {
     EXPECT_EQ(i, vector.size());
     vector.push_back(i);
   }
   for (uptr i = 0; i < 100; i++) {
     EXPECT_EQ(i, vector[i]);