[libc] Setup TLS in x86_64 loader.

The new code added is still very x86_64 specific. AArch64 support will
be added very soon and refactoring of the loader code will be done as
part of the patches adding it.

Reviewed By: asteinhauser

Differential Revision: https://reviews.llvm.org/D82700

3 files changed, 60 insertions, 3 deletions

diff --git a/libc/test/loader/CMakeLists.txt b/libc/test/loader/CMakeLists.txt
index a38d3884ded6..5123bed8aaa9 100644
--- a/libc/test/loader/CMakeLists.txt
+++ b/libc/test/loader/CMakeLists.txt
@@ -37,9 +37,12 @@ function(add_loader_test target_name)
       ${LIBC_BUILD_DIR}/include
   )
 
-  get_fq_deps_list(fq_deps_list ${ADD_LOADER_TEST_DEPENDS})
-  get_object_files_for_test(link_object_files has_skipped_entrypoint_list ${fq_deps_list})
-  target_link_libraries(${fq_target_name} ${link_object_files})
+  if(ADD_LOADER_TEST_DEPENDS)
+    get_fq_deps_list(fq_deps_list ${ADD_LOADER_TEST_DEPENDS})
+    add_dependencies(${fq_target_name} ${fq_deps_list})
+    get_object_files_for_test(link_object_files has_skipped_entrypoint_list ${fq_deps_list})
+    target_link_libraries(${fq_target_name} ${link_object_files})
+  endif()
 
   target_link_options(
     ${fq_target_name}
diff --git a/libc/test/loader/linux/CMakeLists.txt b/libc/test/loader/linux/CMakeLists.txt
index 1f47b2ce3f06..b7899fa4c5c1 100644
--- a/libc/test/loader/linux/CMakeLists.txt
+++ b/libc/test/loader/linux/CMakeLists.txt
@@ -35,3 +35,17 @@ add_loader_test(
   DEPENDS
     libc.loader.linux.crt1
 )
+
+add_loader_test(
+  loader_tls_test
+  SRC
+    tls_test.cpp
+  DEPENDS
+    libc.config.linux.app_h
+    libc.include.errno
+    libc.include.sys_mman
+    libc.loader.linux.crt1
+    libc.src.assert.__assert_fail
+    libc.src.errno.__errno_location
+    libc.src.sys.mman.mmap
+)
diff --git a/libc/test/loader/linux/tls_test.cpp b/libc/test/loader/linux/tls_test.cpp
new file mode 100644
index 000000000000..144d894a2caf
--- /dev/null
+++ b/libc/test/loader/linux/tls_test.cpp
@@ -0,0 +1,40 @@
+//===-- Loader test to check if tls size is read correctly ----------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "include/errno.h"
+#include "include/sys/mman.h"
+
+#undef NDEBUG
+#include "src/assert/assert.h"
+
+#include "src/errno/llvmlibc_errno.h"
+#include "src/sys/mman/mmap.h"
+
+constexpr int threadLocalDataSize = 101;
+_Thread_local int a[threadLocalDataSize] = {123};
+
+int main(int argc, char **argv, char **envp) {
+  assert(a[0] == 123);
+
+  for (int i = 1; i < threadLocalDataSize; ++i)
+    a[i] = i;
+  for (int i = 1; i < threadLocalDataSize; ++i)
+    assert(a[i] == i);
+
+  // Call mmap with bad params so that an error value is
+  // set in errno. Since errno is implemented using a thread
+  // local var, this helps us test setting of errno and
+  // reading it back.
+  assert(llvmlibc_errno == 0);
+  void *addr = __llvm_libc::mmap(nullptr, 0, PROT_READ,
+                                 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  assert(addr == MAP_FAILED);
+  assert(llvmlibc_errno == EINVAL);
+
+  return 0;
+}