[sanitizer] Force TLS allocation on s390

When running with an old glibc, CollectStaticTlsBlocks() calls
__tls_get_addr() in order to force TLS allocation. This function is not
available on s390 and the code simply does nothing in this case,
so all the resulting static TLS blocks end up being incorrect.

Fix by calling __tls_get_offset() on s390.

Reviewed By: dvyukov

Differential Revision: https://reviews.llvm.org/D105629

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
index f1d9e62..7ce9e25 100644 (file)
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
@@ -317,21 +317,44 @@ struct TlsBlock {
 };
 }  // namespace
 
+#ifdef __s390__
+extern "C" uptr __tls_get_offset(void *arg);
+
+static uptr TlsGetOffset(uptr ti_module, uptr ti_offset) {
+  // The __tls_get_offset ABI requires %r12 to point to GOT and %r2 to be an
+  // offset of a struct tls_index inside GOT. We don't possess either of the
+  // two, so violate the letter of the "ELF Handling For Thread-Local
+  // Storage" document and assume that the implementation just dereferences
+  // %r2 + %r12.
+  uptr tls_index[2] = {ti_module, ti_offset};
+  register uptr r2 asm("2") = 0;
+  register void *r12 asm("12") = tls_index;
+  asm("basr %%r14, %[__tls_get_offset]"
+      : "+r"(r2)
+      : [__tls_get_offset] "r"(__tls_get_offset), "r"(r12)
+      : "memory", "cc", "0", "1", "3", "4", "5", "14");
+  return r2;
+}
+#else
 extern "C" void *__tls_get_addr(size_t *);
+#endif
 
 static int CollectStaticTlsBlocks(struct dl_phdr_info *info, size_t size,
                                   void *data) {
   if (!info->dlpi_tls_modid)
     return 0;
   uptr begin = (uptr)info->dlpi_tls_data;
-#ifndef __s390__
   if (!g_use_dlpi_tls_data) {
     // Call __tls_get_addr as a fallback. This forces TLS allocation on glibc
     // and FreeBSD.
+#ifdef __s390__
+    begin = (uptr)__builtin_thread_pointer() +
+            TlsGetOffset(info->dlpi_tls_modid, 0);
+#else
     size_t mod_and_off[2] = {info->dlpi_tls_modid, 0};
     begin = (uptr)__tls_get_addr(mod_and_off);
-  }
 #endif
+  }
   for (unsigned i = 0; i != info->dlpi_phnum; ++i)
     if (info->dlpi_phdr[i].p_type == PT_TLS) {
       static_cast<InternalMmapVector<TlsBlock> *>(data)->push_back(