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// relro_test.cc -- test -z relro for gold
// Copyright (C) 2008-2020 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#include <cassert>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <exception>
#include <stdint.h>
#include <unistd.h>
// This tests we were linked with a script. If we were linked with a
// script, relro currently does not work.
extern char using_script[] __attribute__ ((weak));
// This code is put into a shared library linked with -z relro.
// i1 and i2 are not relro variables.
int i1 = 1;
static int i2 = 2;
// P1 is a global relro variable.
int* const p1 __attribute__ ((aligned(64))) = &i1;
// P2 is a local relro variable.
int* const p2 __attribute__ ((aligned(64))) = &i2;
// Add a TLS variable to make sure -z relro works correctly with TLS.
__thread int i3 = 1;
// Test symbol addresses.
bool
t1()
{
if (using_script)
return true;
void* i1addr = static_cast<void*>(&i1);
void* i2addr = static_cast<void*>(&i2);
const void* p1addr = static_cast<const void*>(&p1);
const void* p2addr = static_cast<const void*>(&p2);
// The relro variables should precede the non-relro variables in the
// memory image.
assert(i1addr > p1addr);
assert(i1addr > p2addr);
assert(i2addr > p1addr);
assert(i2addr > p2addr);
// The relro variables should not be on the same page as the
// non-relro variables.
const size_t page_size = getpagesize();
uintptr_t i1page = reinterpret_cast<uintptr_t>(i1addr) & ~ (page_size - 1);
uintptr_t i2page = reinterpret_cast<uintptr_t>(i2addr) & ~ (page_size - 1);
uintptr_t p1page = reinterpret_cast<uintptr_t>(p1addr) & ~ (page_size - 1);
uintptr_t p2page = reinterpret_cast<uintptr_t>(p2addr) & ~ (page_size - 1);
assert(i1page != p1page);
assert(i1page != p2page);
assert(i2page != p1page);
assert(i2page != p2page);
assert(i3 == 1);
return true;
}
// Tell terminate handler that we are throwing from a signal handler.
static bool throwing;
// A signal handler for SIGSEGV.
extern "C"
void
sigsegv_handler(int)
{
throwing = true;
throw 0;
}
// The original terminate handler.
std::terminate_handler orig_terminate;
// Throwing an exception out of a signal handler doesn't always work
// reliably. When that happens the program will call terminate. We
// set a terminate handler to indicate that the test probably passed.
void
terminate_handler()
{
if (!throwing)
{
orig_terminate();
::exit(EXIT_FAILURE);
}
fprintf(stderr,
"relro_test: terminate called due to failure to throw through signal handler\n");
fprintf(stderr, "relro_test: assuming test succeeded\n");
::exit(EXIT_SUCCESS);
}
// Use a separate function to throw the exception, so that we don't
// need to use -fnon-call-exceptions.
void f2() __attribute__ ((noinline));
void
f2()
{
int** pp1 = const_cast<int**>(&p1);
*pp1 = &i2;
// We shouldn't get here--the assignment to *pp1 should write to
// memory which the dynamic linker marked as read-only, giving us a
// SIGSEGV, causing sigsegv_handler to be invoked, to throw past us.
assert(0);
}
// Changing a relro variable should give us a SIGSEGV.
bool
t2()
{
if (using_script)
return true;
signal(SIGSEGV, sigsegv_handler);
orig_terminate = std::set_terminate(terminate_handler);
try
{
f2();
return false;
}
catch (int i)
{
assert(i == 0);
return true;
}
}
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