qemu/tests/tcg/multiarch/prot-none.c

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/*
* Test that GDB can access PROT_NONE pages.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
void break_here(void *q)
{
}
int main(void)
{
long pagesize = sysconf(_SC_PAGESIZE);
void *p, *q;
int err;
p = mmap(NULL, pagesize * 2, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
assert(p != MAP_FAILED);
q = p + pagesize - 1;
strcpy(q, "42");
err = mprotect(p, pagesize * 2, PROT_NONE);
assert(err == 0);
break_here(q);
err = mprotect(p, pagesize * 2, PROT_READ);
assert(err == 0);
if (getenv("PROT_NONE_PY")) {
assert(strcmp(q, "24") == 0);
}
return EXIT_SUCCESS;
}