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selftests/vm: anon_cow: add R/O longterm tests via gup_test 

Let's trigger a R/O longterm pin on three cases of R/O mapped anonymous
pages:
* exclusive (never shared)
* shared (child still alive)
* previously shared (child no longer alive)

... and make sure that the pin is reliable: whatever we write via the page
tables has to be observable via the pin.

Link: https://lkml.kernel.org/r/20220927110120.106906-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph von Recklinghausen <crecklin@redhat.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2022-09-27 13:01:20 +02:00 committed by Andrew Morton
parent c77369b437
commit 6f1405efc6
1 changed files with 210 additions and 0 deletions
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210
tools/testing/selftests/vm/anon_cow.c
View File

@ -17,6 +17,7 @@
#include <dirent.h>
#include <assert.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include "local_config.h"
@ -24,6 +25,7 @@
#include <liburing.h>
#endif /* LOCAL_CONFIG_HAVE_LIBURING */
#include "../../../../mm/gup_test.h"
#include "../kselftest.h"
#include "vm_util.h"
@ -32,6 +34,7 @@ static int pagemap_fd;
static size_t thpsize;
static int nr_hugetlbsizes;
static size_t hugetlbsizes[10];
static int gup_fd;
static void detect_thpsize(void)
{
@ -503,6 +506,170 @@ static void test_iouring_fork(char *mem, size_t size)
#endif /* LOCAL_CONFIG_HAVE_LIBURING */
enum ro_pin_test {
RO_PIN_TEST_SHARED,
RO_PIN_TEST_PREVIOUSLY_SHARED,
RO_PIN_TEST_RO_EXCLUSIVE,
};
static void do_test_ro_pin(char *mem, size_t size, enum ro_pin_test test,
bool fast)
{
struct pin_longterm_test args;
struct comm_pipes comm_pipes;
char *tmp, buf;
__u64 tmp_val;
int ret;
if (gup_fd < 0) {
ksft_test_result_skip("gup_test not available\n");
return;
}
tmp = malloc(size);
if (!tmp) {
ksft_test_result_fail("malloc() failed\n");
return;
}
ret = setup_comm_pipes(&comm_pipes);
if (ret) {
ksft_test_result_fail("pipe() failed\n");
goto free_tmp;
}
switch (test) {
case RO_PIN_TEST_SHARED:
case RO_PIN_TEST_PREVIOUSLY_SHARED:
/*
* Share the pages with our child. As the pages are not pinned,
* this should just work.
*/
ret = fork();
if (ret < 0) {
ksft_test_result_fail("fork() failed\n");
goto close_comm_pipes;
} else if (!ret) {
write(comm_pipes.child_ready[1], "0", 1);
while (read(comm_pipes.parent_ready[0], &buf, 1) != 1)
;
exit(0);
}
/* Wait until our child is ready. */
while (read(comm_pipes.child_ready[0], &buf, 1) != 1)
;
if (test == RO_PIN_TEST_PREVIOUSLY_SHARED) {
/*
* Tell the child to quit now and wait until it quit.
* The pages should now be mapped R/O into our page
* tables, but they are no longer shared.
*/
write(comm_pipes.parent_ready[1], "0", 1);
wait(&ret);
if (!WIFEXITED(ret))
ksft_print_msg("[INFO] wait() failed\n");
}
break;
case RO_PIN_TEST_RO_EXCLUSIVE:
/*
* Map the page R/O into the page table. Enable softdirty
* tracking to stop the page from getting mapped R/W immediately
* again by mprotect() optimizations. Note that we don't have an
* easy way to test if that worked (the pagemap does not export
* if the page is mapped R/O vs. R/W).
*/
ret = mprotect(mem, size, PROT_READ);
clear_softdirty();
ret |= mprotect(mem, size, PROT_READ | PROT_WRITE);
if (ret) {
ksft_test_result_fail("mprotect() failed\n");
goto close_comm_pipes;
}
break;
default:
assert(false);
}
/* Take a R/O pin. This should trigger unsharing. */
args.addr = (__u64)mem;
args.size = size;
args.flags = fast ? PIN_LONGTERM_TEST_FLAG_USE_FAST : 0;
ret = ioctl(gup_fd, PIN_LONGTERM_TEST_START, &args);
if (ret) {
if (errno == EINVAL)
ksft_test_result_skip("PIN_LONGTERM_TEST_START failed\n");
else
ksft_test_result_fail("PIN_LONGTERM_TEST_START failed\n");
goto wait;
}
/* Modify the page. */
memset(mem, 0xff, size);
/*
* Read back the content via the pin to the temporary buffer and
* test if we observed the modification.
*/
tmp_val = (__u64)tmp;
ret = ioctl(gup_fd, PIN_LONGTERM_TEST_READ, &tmp_val);
if (ret)
ksft_test_result_fail("PIN_LONGTERM_TEST_READ failed\n");
else
ksft_test_result(!memcmp(mem, tmp, size),
"Longterm R/O pin is reliable\n");
ret = ioctl(gup_fd, PIN_LONGTERM_TEST_STOP);
if (ret)
ksft_print_msg("[INFO] PIN_LONGTERM_TEST_STOP failed\n");
wait:
switch (test) {
case RO_PIN_TEST_SHARED:
write(comm_pipes.parent_ready[1], "0", 1);
wait(&ret);
if (!WIFEXITED(ret))
ksft_print_msg("[INFO] wait() failed\n");
break;
default:
break;
}
close_comm_pipes:
close_comm_pipes(&comm_pipes);
free_tmp:
free(tmp);
}
static void test_ro_pin_on_shared(char *mem, size_t size)
{
do_test_ro_pin(mem, size, RO_PIN_TEST_SHARED, false);
}
static void test_ro_fast_pin_on_shared(char *mem, size_t size)
{
do_test_ro_pin(mem, size, RO_PIN_TEST_SHARED, true);
}
static void test_ro_pin_on_ro_previously_shared(char *mem, size_t size)
{
do_test_ro_pin(mem, size, RO_PIN_TEST_PREVIOUSLY_SHARED, false);
}
static void test_ro_fast_pin_on_ro_previously_shared(char *mem, size_t size)
{
do_test_ro_pin(mem, size, RO_PIN_TEST_PREVIOUSLY_SHARED, true);
}
static void test_ro_pin_on_ro_exclusive(char *mem, size_t size)
{
do_test_ro_pin(mem, size, RO_PIN_TEST_RO_EXCLUSIVE, false);
}
static void test_ro_fast_pin_on_ro_exclusive(char *mem, size_t size)
{
do_test_ro_pin(mem, size, RO_PIN_TEST_RO_EXCLUSIVE, true);
}
typedef void (*test_fn)(char *mem, size_t size);
static void do_run_with_base_page(test_fn fn, bool swapout)
@ -850,6 +1017,48 @@ static const struct test_case test_cases[] = {
},
#endif /* LOCAL_CONFIG_HAVE_LIBURING */
/*
* Take a R/O longterm pin on a R/O-mapped shared anonymous page.
* When modifying the page via the page table, the page content change
* must be visible via the pin.
*/
{
"R/O GUP pin on R/O-mapped shared page",
test_ro_pin_on_shared,
},
/* Same as above, but using GUP-fast. */
{
"R/O GUP-fast pin on R/O-mapped shared page",
test_ro_fast_pin_on_shared,
},
/*
* Take a R/O longterm pin on a R/O-mapped exclusive anonymous page that
* was previously shared. When modifying the page via the page table,
* the page content change must be visible via the pin.
*/
{
"R/O GUP pin on R/O-mapped previously-shared page",
test_ro_pin_on_ro_previously_shared,
},
/* Same as above, but using GUP-fast. */
{
"R/O GUP-fast pin on R/O-mapped previously-shared page",
test_ro_fast_pin_on_ro_previously_shared,
},
/*
* Take a R/O longterm pin on a R/O-mapped exclusive anonymous page.
* When modifying the page via the page table, the page content change
* must be visible via the pin.
*/
{
"R/O GUP pin on R/O-mapped exclusive page",
test_ro_pin_on_ro_exclusive,
},
/* Same as above, but using GUP-fast. */
{
"R/O GUP-fast pin on R/O-mapped exclusive page",
test_ro_fast_pin_on_ro_exclusive,
},
};
static void run_test_case(struct test_case const *test_case)
@ -902,6 +1111,7 @@ int main(int argc, char **argv)
ksft_print_header();
ksft_set_plan(nr_test_cases * tests_per_test_case());
gup_fd = open("/sys/kernel/debug/gup_test", O_RDWR);
pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
if (pagemap_fd < 0)
ksft_exit_fail_msg("opening pagemap failed\n");