platform_bionic/tests/elftls_test.cpp

/*
 * Copyright (C) 2019 The Android Open Source Project
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#include <gtest/gtest.h>

#include <thread>

// Specify the LE access model explicitly. This file is compiled into the
// bionic-unit-tests executable, but the compiler sees an -fpic object file
// output into a static library, so it defaults to dynamic TLS accesses.

// This variable will be zero-initialized (.tbss)
__attribute__((tls_model("local-exec"))) static __thread int tlsvar_le_zero;

// This variable will have an initializer (.tdata)
__attribute__((tls_model("local-exec"))) static __thread int tlsvar_le_init = 10;

// Access libtest_elftls_shared_var's TLS variable using an IE access.
__attribute__((tls_model("initial-exec"))) extern "C" __thread int elftls_shared_var;

TEST(elftls, basic_le) {
  // Check the variables on the main thread.
  ASSERT_EQ(11, ++tlsvar_le_init);
  ASSERT_EQ(1, ++tlsvar_le_zero);

  // Check variables on a new thread.
  std::thread([] {
    ASSERT_EQ(11, ++tlsvar_le_init);
    ASSERT_EQ(1, ++tlsvar_le_zero);
  }).join();
}

TEST(elftls, shared_ie) {
  ASSERT_EQ(21, ++elftls_shared_var);
  std::thread([] {
    ASSERT_EQ(21, ++elftls_shared_var);
  }).join();
}

extern "C" int bump_static_tls_var_1();
extern "C" int bump_static_tls_var_2();

TEST(elftls, tprel_addend) {
  ASSERT_EQ(4, bump_static_tls_var_1());
  ASSERT_EQ(8, bump_static_tls_var_2());
  std::thread([] {
    ASSERT_EQ(4, bump_static_tls_var_1());
    ASSERT_EQ(8, bump_static_tls_var_2());
  }).join();
}

// Because this C++ source file is built with -fpic, the compiler will access
// this variable using a GD model. Typically, the static linker will relax the
// GD to LE, but the arm32 linker doesn't do TLS relaxations, so we can test
// calling __tls_get_addr in a static executable. The static linker knows that
// the main executable's TlsIndex::module_id is 1 and writes that into the GOT.
__thread int tlsvar_general = 30;

TEST(elftls, general) {
  ASSERT_EQ(31, ++tlsvar_general);
  std::thread([] {
    ASSERT_EQ(31, ++tlsvar_general);
  }).join();
}