[sanitizer] Use confstr to check libc version in InitTlsSize

[Lekensteyn]

With the three whitespace issues fixed up, LGTM.
(I am also observing that the version check in ThreadDescriptorSize is Linux-only (minus Android), such that the cpp guards !SANITIZER_FREEBSD && !SANITIZER_ANDROID && ... will be broad enough.)

Tested with -m32 -fsanitize=address glibc 2.27.0 (with #define CHECK_GET_TLS_STATIC_INFO_VERSION 1) and glibc 2.23.0.

compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cc

210

style nitpicks: remove the double spaces after ? in the lines above and in sizeof(kGLibC) - 1.

[vitalybuka]

clang-format

compiler-rt/lib/msan/msan.cc

 
 void __msan_init() {
   CHECK(!msan_init_is_running);
   if (msan_inited) return;
   msan_init_is_running = 1;
   SanitizerToolName = "MemorySanitizer";
 
   AvoidCVE_2016_2143();
-  InitTlsSize();
 
   CacheBinaryName();
   CheckASLR();
   InitializeFlags();
 
   // Install tool-specific callbacks in sanitizer_common.
   SetCheckFailedCallback(MsanCheckFailed);
 
   __sanitizer_set_report_path(common_flags()->log_path);
 
   InitializeInterceptors();
+  InitTlsSize();
   InstallDeadlySignalHandlers(MsanOnDeadlySignal);
   InstallAtExitHandler(); // Needs __cxa_atexit interceptor.
 
   DisableCoreDumperIfNecessary();
   if (StackSizeIsUnlimited()) {
     VPrintf(1, "Unlimited stack, doing reexec\n");
     // A reasonably large stack size. It is bigger than the usual 8Mb, because,
     // well, the program could have been run with unlimited stack for a reason.

compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cc

 template <typename T>
 void CallGetTls(void* ptr, size_t* size, size_t* align) {
   typename T::get_tls_func get_tls;
   CHECK_EQ(sizeof(get_tls), sizeof(ptr));
   internal_memcpy(&get_tls, &ptr, sizeof(ptr));
   CHECK_NE(get_tls, 0);
   get_tls(size, align);
 }
+
+bool GetLibcVersion(int *major, int *minor, int *patch) {
+#ifdef _CS_GNU_LIBC_VERSION
+  char buf[64];
+  uptr len = confstr(_CS_GNU_LIBC_VERSION, buf, sizeof(buf));
+  if (len >= sizeof(buf))
+    return false;
+  buf[len] = 0;
+  static const char kGLibC[] = "glibc ";
+  if (internal_strncmp(buf, kGLibC, sizeof(kGLibC) - 1) != 0)
+    return false;
+  const char *p = buf + sizeof(kGLibC) - 1;
+  *major = internal_simple_strtoll(p, &p, 10);
+  *minor = (*p == '.') ? internal_simple_strtoll(p + 1, &p, 10) : 0;
+  *patch = (*p == '.') ? internal_simple_strtoll(p + 1, &p, 10) : 0;
+  return true;
+#else
+  return false;
+#endif
+}
+
+bool CmpLibcVersion(int major, int minor, int patch) {
+  int ma;
+  int mi;
+  int pa;
+  if (!GetLibcVersion(&ma, &mi, &pa))
+    return false;
+  if (ma > major)
+    return true;
+  if (ma < major)
+    return false;
+  if (mi > minor)
+    return true;
+  if (mi < minor)
+    return false;
+  return pa >= patch;
+}
+
 }  // namespace
 
 void InitTlsSize() {
   // all current supported platforms have 16 bytes stack alignment
   const size_t kStackAlign = 16;
   void *get_tls_static_info_ptr = dlsym(RTLD_NEXT, "_dl_get_tls_static_info");
   size_t tls_size = 0;
   size_t tls_align = 0;
   // On i?86, _dl_get_tls_static_info used to be internal_function, i.e.
   // __attribute__((regparm(3), stdcall)) before glibc 2.27 and is normal
   // function in 2.27 and later.
-  if (CHECK_GET_TLS_STATIC_INFO_VERSION &&
-      !dlvsym(RTLD_NEXT, "glob", "GLIBC_2.27"))
+  if (CHECK_GET_TLS_STATIC_INFO_VERSION && !CmpLibcVersion(2, 27, 0))
     CallGetTls<GetTlsStaticInfoRegparmCall>(get_tls_static_info_ptr,
                                             &tls_size, &tls_align);
   else
     CallGetTls<GetTlsStaticInfoCall>(get_tls_static_info_ptr,
                                      &tls_size, &tls_align);
   if (tls_align < kStackAlign)
     tls_align = kStackAlign;
   g_tls_size = RoundUpTo(tls_size, tls_align);

 // sizeof(struct pthread) from glibc.
 static atomic_uintptr_t thread_descriptor_size;
 
 uptr ThreadDescriptorSize() {
   uptr val = atomic_load_relaxed(&thread_descriptor_size);
   if (val)
     return val;
 #if defined(__x86_64__) || defined(__i386__) || defined(__arm__)
-#ifdef _CS_GNU_LIBC_VERSION
-  char buf[64];
-  uptr len = confstr(_CS_GNU_LIBC_VERSION, buf, sizeof(buf));
-  if (len < sizeof(buf) && internal_strncmp(buf, "glibc 2.", 8) == 0) {
-    const char *end;
-    int minor = internal_simple_strtoll(buf + 8, &end, 10);
-    if (end != buf + 8 && (*end == '\0' || *end == '.' || *end == '-')) {
-      int patch = 0;
-      if (*end == '.')
-        // strtoll will return 0 if no valid conversion could be performed
-        patch = internal_simple_strtoll(end + 1, nullptr, 10);
-
-      /* sizeof(struct pthread) values from various glibc versions.  */
-      if (SANITIZER_X32)
-        val = 1728;  // Assume only one particular version for x32.
-      // For ARM sizeof(struct pthread) changed in Glibc 2.23.
-      else if (SANITIZER_ARM)
-        val = minor <= 22 ? 1120 : 1216;
-      else if (minor <= 3)
-        val = FIRST_32_SECOND_64(1104, 1696);
-      else if (minor == 4)
-        val = FIRST_32_SECOND_64(1120, 1728);
-      else if (minor == 5)
-        val = FIRST_32_SECOND_64(1136, 1728);
-      else if (minor <= 9)
-        val = FIRST_32_SECOND_64(1136, 1712);
-      else if (minor == 10)
-        val = FIRST_32_SECOND_64(1168, 1776);
-      else if (minor == 11 || (minor == 12 && patch == 1))
-        val = FIRST_32_SECOND_64(1168, 2288);
-      else if (minor <= 13)
-        val = FIRST_32_SECOND_64(1168, 2304);
-      else
-        val = FIRST_32_SECOND_64(1216, 2304);
-    }
-  }
-#endif
+  int major;
+  int minor;
+  int patch;
+  if (GetLibcVersion(&major, &minor, &patch) && major == 2) {
+      val = 1728; // Assume only one particular version for x32.
 #elif defined(__mips__)
   // TODO(sagarthakur): add more values as per different glibc versions.
   val = FIRST_32_SECOND_64(1152, 1776);
 #elif defined(__aarch64__)
   // The sizeof (struct pthread) is the same from GLIBC 2.17 to 2.22.
   val = 1776;
 #elif defined(__powerpc64__)
   val = 1776; // from glibc.ppc64le 2.20-8.fc21