/* Tests for memory protection keys.
Copyright (C) 2017-2018 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
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <inttypes.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <support/check.h>
#include <support/support.h>
#include <support/test-driver.h>
#include <support/xsignal.h>
#include <support/xthread.h>
#include <support/xunistd.h>
#include <sys/mman.h>
/* Used to force threads to wait until the main thread has set up the
keys as intended. */
static pthread_barrier_t barrier;
/* The keys used for testing. These have been allocated with access
rights set based on their array index. */
enum { key_count = 3 };
static int keys[key_count];
static volatile int *pages[key_count];
/* Used to report results from the signal handler. */
static volatile void *sigsegv_addr;
static volatile int sigsegv_code;
static volatile int sigsegv_pkey;
static sigjmp_buf sigsegv_jmp;
/* Used to handle expected read or write faults. */
static void
sigsegv_handler (int signum, siginfo_t *info, void *context)
{
sigsegv_addr = info->si_addr;
sigsegv_code = info->si_code;
sigsegv_pkey = info->si_pkey;
siglongjmp (sigsegv_jmp, 2);
}
static const struct sigaction sigsegv_sigaction =
{
.sa_flags = SA_RESETHAND | SA_SIGINFO,
.sa_sigaction = &sigsegv_handler,
};
/* Check if PAGE is readable (if !WRITE) or writable (if WRITE). */
static bool
check_page_access (int page, bool write)
{
/* This is needed to work around bug 22396: On x86-64, siglongjmp
does not restore the protection key access rights for the current
thread. We restore only the access rights for the keys under
test. (This is not a general solution to this problem, but it
allows testing to proceed after a fault.) */
unsigned saved_rights[key_count];
for (int i = 0; i < key_count; ++i)
saved_rights[i] = pkey_get (keys[i]);
volatile int *addr = pages[page];
if (test_verbose > 0)
{
printf ("info: checking access at %p (page %d) for %s\n",
addr, page, write ? "writing" : "reading");
}
int result = sigsetjmp (sigsegv_jmp, 1);
if (result == 0)
{
xsigaction (SIGSEGV, &sigsegv_sigaction, NULL);
if (write)
*addr = 3;
else
(void) *addr;
xsignal (SIGSEGV, SIG_DFL);
if (test_verbose > 0)
puts (" --> access allowed");
return true;
}
else
{
xsignal (SIGSEGV, SIG_DFL);
if (test_verbose > 0)
puts (" --> access denied");
TEST_COMPARE (result, 2);
TEST_COMPARE ((uintptr_t) sigsegv_addr, (uintptr_t) addr);
TEST_COMPARE (sigsegv_code, SEGV_PKUERR);
TEST_COMPARE (sigsegv_pkey, keys[page]);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_set (keys[i], saved_rights[i]), 0);
return false;
}
}
static volatile sig_atomic_t sigusr1_handler_ran;
/* Used to check the behavior in signal handlers. In x86 all access are
revoked during signal handling. In PowerPC the key permissions are
inherited by the interrupted thread. This test accept both approaches. */
static void
sigusr1_handler (int signum)
{
TEST_COMPARE (signum, SIGUSR1);
for (int i = 0; i < key_count; ++i)
TEST_VERIFY (pkey_get (keys[i]) == PKEY_DISABLE_ACCESS
|| pkey_get (keys[i]) == i);
sigusr1_handler_ran = 1;
}
/* Used to report results from other threads. */
struct thread_result
{
int access_rights[key_count];
pthread_t next_thread;
};
/* Return the thread's access rights for the keys under test. */
static void *
get_thread_func (void *closure)
{
struct thread_result *result = xmalloc (sizeof (*result));
for (int i = 0; i < key_count; ++i)
result->access_rights[i] = pkey_get (keys[i]);
memset (&result->next_thread, 0, sizeof (result->next_thread));
return result;
}
/* Wait for initialization and then check that the current thread does
not have access through the keys under test. */
static void *
delayed_thread_func (void *closure)
{
bool check_access = *(bool *) closure;
pthread_barrier_wait (&barrier);
struct thread_result *result = get_thread_func (NULL);
if (check_access)
{
/* Also check directly. This code should not run with other
threads in parallel because of the SIGSEGV handler which is
installed by check_page_access. */
for (int i = 0; i < key_count; ++i)
{
TEST_VERIFY (!check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
}
result->next_thread = xpthread_create (NULL, get_thread_func, NULL);
return result;
}
static int
do_test (void)
{
long pagesize = xsysconf (_SC_PAGESIZE);
/* pkey_mprotect with key -1 should work even when there is no
protection key support. */
{
int *page = xmmap (NULL, pagesize, PROT_NONE,
MAP_ANONYMOUS | MAP_PRIVATE, -1);
TEST_COMPARE (pkey_mprotect (page, pagesize, PROT_READ | PROT_WRITE, -1),
0);
volatile int *vpage = page;
*vpage = 5;
TEST_COMPARE (*vpage, 5);
xmunmap (page, pagesize);
}
xpthread_barrier_init (&barrier, NULL, 2);
bool delayed_thread_check_access = true;
pthread_t delayed_thread = xpthread_create
(NULL, &delayed_thread_func, &delayed_thread_check_access);
keys[0] = pkey_alloc (0, 0);
if (keys[0] < 0)
{
if (errno == ENOSYS)
FAIL_UNSUPPORTED
("kernel does not support memory protection keys");
if (errno == EINVAL)
FAIL_UNSUPPORTED
("CPU does not support memory protection keys: %m");
FAIL_EXIT1 ("pkey_alloc: %m");
}
TEST_COMPARE (pkey_get (keys[0]), 0);
for (int i = 1; i < key_count; ++i)
{
keys[i] = pkey_alloc (0, i);
if (keys[i] < 0)
FAIL_EXIT1 ("pkey_alloc (0, %d): %m", i);
/* pkey_alloc is supposed to change the current thread's access
rights for the new key. */
TEST_COMPARE (pkey_get (keys[i]), i);
}
/* Check that all the keys have the expected access rights for the
current thread. */
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_get (keys[i]), i);
/* Allocate a test page for each key. */
for (int i = 0; i < key_count; ++i)
{
pages[i] = xmmap (NULL, pagesize, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1);
TEST_COMPARE (pkey_mprotect ((void *) pages[i], pagesize,
PROT_READ | PROT_WRITE, keys[i]), 0);
}
/* Check that the initial thread does not have access to the new
keys. */
{
pthread_barrier_wait (&barrier);
struct thread_result *result = xpthread_join (delayed_thread);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (result->access_rights[i],
PKEY_DISABLE_ACCESS);
struct thread_result *result2 = xpthread_join (result->next_thread);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (result->access_rights[i],
PKEY_DISABLE_ACCESS);
free (result);
free (result2);
}
/* Check that the current thread access rights are inherited by new
threads. */
{
pthread_t get_thread = xpthread_create (NULL, get_thread_func, NULL);
struct thread_result *result = xpthread_join (get_thread);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (result->access_rights[i], i);
free (result);
}
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_get (keys[i]), i);
/* Check that in a signal handler, there is no access. */
xsignal (SIGUSR1, &sigusr1_handler);
xraise (SIGUSR1);
xsignal (SIGUSR1, SIG_DFL);
TEST_COMPARE (sigusr1_handler_ran, 1);
/* The first key results in a writable page. */
TEST_VERIFY (check_page_access (0, false));
TEST_VERIFY (check_page_access (0, true));
/* The other keys do not. */
for (int i = 1; i < key_count; ++i)
{
if (test_verbose)
printf ("info: checking access for key %d, bits 0x%x\n",
i, pkey_get (keys[i]));
for (int j = 0; j < key_count; ++j)
TEST_COMPARE (pkey_get (keys[j]), j);
if (i & PKEY_DISABLE_ACCESS)
{
TEST_VERIFY (!check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
else
{
TEST_VERIFY (i & PKEY_DISABLE_WRITE);
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
}
/* But if we set the current thread's access rights, we gain
access. */
for (int do_write = 0; do_write < 2; ++do_write)
for (int allowed_key = 0; allowed_key < key_count; ++allowed_key)
{
for (int i = 0; i < key_count; ++i)
if (i == allowed_key)
{
if (do_write)
TEST_COMPARE (pkey_set (keys[i], 0), 0);
else
TEST_COMPARE (pkey_set (keys[i], PKEY_DISABLE_WRITE), 0);
}
else
TEST_COMPARE (pkey_set (keys[i], PKEY_DISABLE_ACCESS), 0);
if (test_verbose)
printf ("info: key %d is allowed access for %s\n",
allowed_key, do_write ? "writing" : "reading");
for (int i = 0; i < key_count; ++i)
if (i == allowed_key)
{
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (check_page_access (i, true) == do_write);
}
else
{
TEST_VERIFY (!check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
}
/* Restore access to all keys, and launch a thread which should
inherit that access. */
for (int i = 0; i < key_count; ++i)
{
TEST_COMPARE (pkey_set (keys[i], 0), 0);
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (check_page_access (i, true));
}
delayed_thread_check_access = false;
delayed_thread = xpthread_create
(NULL, delayed_thread_func, &delayed_thread_check_access);
TEST_COMPARE (pkey_free (keys[0]), 0);
/* Second pkey_free will fail because the key has already been
freed. */
TEST_COMPARE (pkey_free (keys[0]),-1);
TEST_COMPARE (errno, EINVAL);
for (int i = 1; i < key_count; ++i)
TEST_COMPARE (pkey_free (keys[i]), 0);
/* Check what happens to running threads which have access to
previously allocated protection keys. The implemented behavior
is somewhat dubious: Ideally, pkey_free should revoke access to
that key and pkey_alloc of the same (numeric) key should not
implicitly confer access to already-running threads, but this is
not what happens in practice. */
{
/* The limit is in place to avoid running indefinitely in case
there many keys available. */
int *keys_array = xcalloc (100000, sizeof (*keys_array));
int keys_allocated = 0;
while (keys_allocated < 100000)
{
int new_key = pkey_alloc (0, PKEY_DISABLE_WRITE);
if (new_key < 0)
{
/* No key reuse observed before running out of keys. */
TEST_COMPARE (errno, ENOSPC);
break;
}
for (int i = 0; i < key_count; ++i)
if (new_key == keys[i])
{
/* We allocated the key with disabled write access.
This should affect the protection state of the
existing page. */
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
xpthread_barrier_wait (&barrier);
struct thread_result *result = xpthread_join (delayed_thread);
/* The thread which was launched before should still have
access to the key. */
TEST_COMPARE (result->access_rights[i], 0);
struct thread_result *result2
= xpthread_join (result->next_thread);
/* Same for a thread which is launched afterwards from
the old thread. */
TEST_COMPARE (result2->access_rights[i], 0);
free (result);
free (result2);
keys_array[keys_allocated++] = new_key;
goto after_key_search;
}
/* Save key for later deallocation. */
keys_array[keys_allocated++] = new_key;
}
after_key_search:
/* Deallocate the keys allocated for testing purposes. */
for (int j = 0; j < keys_allocated; ++j)
TEST_COMPARE (pkey_free (keys_array[j]), 0);
free (keys_array);
}
for (int i = 0; i < key_count; ++i)
xmunmap ((void *) pages[i], pagesize);
xpthread_barrier_destroy (&barrier);
return 0;
}
#include <support/test-driver.c>