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/* Implementation of the test verification functions for memory access
checks.
Copyright (C) 2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <support/xsignal.h>
#include "check_mem_access.h"
static sigjmp_buf sigsegv_jmp_buf;
static void
__sigsegv_handler (int signum)
{
siglongjmp (sigsegv_jmp_buf, signum);
}
bool check_mem_access (const void *addr, bool write)
{
/* This is obviously not thread-safe. */
static bool handler_set_up;
if (!handler_set_up)
{
struct sigaction sa = {
.sa_handler = __sigsegv_handler,
.sa_flags = SA_NODEFER,
};
sigemptyset (&sa.sa_mask);
xsigaction (SIGSEGV, &sa, NULL);
/* Some system generates SIGBUS accessing the guard area when it is
setup with madvise. */
xsigaction (SIGBUS, &sa, NULL);
handler_set_up = true;
}
int r = sigsetjmp (sigsegv_jmp_buf, 0);
if (r == 0)
{
if (write)
*(volatile char *)addr = 'x';
else
*(volatile char *)addr;
return true;
}
if (r == SIGSEGV || r == SIGBUS)
return false;
return true;
}
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