On 5/9/22 9:00 PM, Suren Baghdasaryan wrote:
Introduce process_mrelease syscall sanity tests. They include tests of
invalid pidfd and flags inputs, attempting to call process_mrelease
with a live process and a valid usage of process_mrelease. Because
process_mrelease has to be used against a process with a pending SIGKILL,
it's possible that the process exits before process_mrelease gets called.
In such cases we retry the test with a victim that allocates twice more
memory up to 1GB. This would require the victim process to spend more
time during exit and process_mrelease has a better chance of catching
the process before it exits.
+1 on Mike's comments on improving the change log. List what is getting
tested as opposed to describing the test code.
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
tools/testing/selftests/vm/Makefile | 1 +
tools/testing/selftests/vm/mrelease_test.c | 176 +++++++++++++++++++++
tools/testing/selftests/vm/run_vmtests.sh | 16 ++
3 files changed, 193 insertions(+)
create mode 100644 tools/testing/selftests/vm/mrelease_test.c
Please update .gitignore with the new executable.
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 04a49e876a46..733fccbff0ef 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -43,6 +43,7 @@ TEST_GEN_FILES += map_populate
TEST_GEN_FILES += memfd_secret
TEST_GEN_FILES += mlock-random-test
TEST_GEN_FILES += mlock2-tests
+TEST_GEN_FILES += mrelease_test
TEST_GEN_FILES += mremap_dontunmap
TEST_GEN_FILES += mremap_test
TEST_GEN_FILES += on-fault-limit
diff --git a/tools/testing/selftests/vm/mrelease_test.c b/tools/testing/selftests/vm/mrelease_test.c
new file mode 100644
index 000000000000..a61061bf8433
--- /dev/null
+++ b/tools/testing/selftests/vm/mrelease_test.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2022 Google LLC
+ */
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "util.h"
+
+static inline int pidfd_open(pid_t pid, unsigned int flags)
+{
+#ifdef __NR_pidfd_open
+ return syscall(__NR_pidfd_open, pid, flags);
+#else
+ errno = ENOSYS;
This isn't an error - this would be skip because this syscall
isn't supported.
+ return -1;
+#endif
Key off of syscall return instead of these ifdefs - same comment
on all of the ifdefs
+}
+
I am not seeing any reason for breaking this code up have a separate
routine for pidfd_open().
+static inline int process_mrelease(int pidfd, unsigned int flags)
+{
+#ifdef __NR_process_mrelease
+ return syscall(__NR_process_mrelease, pidfd, flags);
+#else
+ errno = ENOSYS;
+ return -1;
+#endif> +}
+
Same comments on ifdefs and skips here as well.
+static void write_fault_pages(char *addr, unsigned long nr_pages)
+{
+ unsigned long i;
+
+ for (i = 0; i < nr_pages; i++)
+ *((unsigned long *)(addr + (i * PAGE_SIZE))) = i;
+}
+
+static int alloc_noexit(unsigned long nr_pages, int pipefd)
+{
+ int ppid = getppid();
+ void *buf;
+
+ buf = mmap(NULL, nr_pages * PAGE_SIZE, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANON, 0, 0);
+ if (buf == MAP_FAILED) {
+ perror("mmap");
A bit more descriptive message what the test would do will be helpful.
Also consider if this should be a skip or fail for the test.
+ return 1;
+ }
+
+ write_fault_pages((char *)buf, nr_pages);
+
+ /* Signal the parent that the child is ready */
+ if (write(pipefd, "", 1) < 0) {
+ perror("write");
+ return 1;
+ }
+
+ /* Wait to be killed (when reparenting happens) */
+ while (getppid() == ppid)
+ sleep(1);
+
What happens if reparenting doesn't happen? Will this loop for ever?
This test could hang?
+ munmap(buf, nr_pages * PAGE_SIZE);
+
+ return 0;
+}
+
+
+#define MB(x) (x << 20)
+#define MAX_SIZE_MB 1024
+
+int main(void)
+{
+ int res;
+ int pipefd[2], pidfd;
+ pid_t pid;
+ char byte;
+ size_t size;
+ int negative_tests_done = 0;
+
+ /* Test a wrong pidfd */
+ if (!process_mrelease(-1, 0) || errno != EBADF) {
+ perror("process_mrelease with wring pidfd");
Incorrect spelling "wring/wrong"
+ exit(1);
+ }
+
+ /*
+ * Start the test with 1MB allocation and double every time
+ * process_mrelease fails
+ */
+ for (size = 1; size <= MAX_SIZE_MB; size *= 2) {
+ /*
+ * Pipe for the child to signal when it's done allocating
+ * memory
+ */
+ if (pipe(pipefd)) {
+ perror("pipe");
+ exit(1);
+ }
+ pid = fork();
+ if (pid < 0) {
+ perror("fork");
Close the pipe?
+ exit(1);
+ }
+
+ if (pid == 0) {
+ close(pipefd[0]);
+ res = alloc_noexit(MB(size) / PAGE_SIZE, pipefd[1]);
+ close(pipefd[1]);
+ exit(res);
+ }
+
+ close(pipefd[1]);
+ /* Block until the child is ready */
+ res = read(pipefd[0], &byte, 1);
+ close(pipefd[0]);
+ if (res < 0) {
+ perror("read");
+ exit(1);
+ }
+
+ pidfd = pidfd_open(pid, 0);
+ if (pidfd < 0) {
+ perror("pidfd_open");
+ exit(1);
+ }
+
The code is very hard to read. Add comments to indicate parent and child
paths clearly so reviewers can follow the logic and be able to do effective
review.
+ /* Run negative tests which require a valid child only once */
+ if (!negative_tests_done) {
+ /* Test invalid flags */
+ if (!process_mrelease(pidfd, (unsigned int)-1) ||
+ errno != EINVAL) {
+ perror("process_mrelease with wrong flags");
+ exit(1);
So is this an expected fail or a test fail?
+ }
+ /* Test reapling while process is still alive */
+ if (!process_mrelease(pidfd, 0) ||
+ errno != EINVAL) {
+ perror("process_mrelease on a live process");
So is this an expected fail or a test fail?
+ exit(1);
+ }
+ negative_tests_done = 1;
+ }
Now the above negative_tests_done block could be in a separate function ---
All the others aren't really needed. It will be good for abstraction and
readability.
+
+ if (kill(pid, SIGKILL)) {
+ perror("kill");
Include test results in the change log - so we can see the test report.
+ exit(1);
+ }
+
+ if (!process_mrelease(pidfd, 0)) {
+ /* Terminate the test once process_mrelease succeeds */
+ return 0;
+ }
+
+ /*
+ * Ignore the failure if the child exited before mrelease got
+ * called, increase allocation size and retry the test
+ */
Add more info. on why allocating more memory helps.
+ if (errno != ESRCH) {
+ perror("process_mrelease");
+ exit(1);
+ }
+
+ if (waitpid(pid, NULL, 0) < 0) {
+ perror("waitpid");
+ exit(1);
+ }
+ close(pidfd);
+ }
+
+ printf("All process_mrelease attempts failed!\n");
+ exit(1);
+}
diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
index 352ba00cf26b..1986162fea39 100755
--- a/tools/testing/selftests/vm/run_vmtests.sh
+++ b/tools/testing/selftests/vm/run_vmtests.sh
@@ -287,6 +287,22 @@ else
echo "[PASS]"
fi
+echo "---------------------"
+echo "running mrelease_test"
+echo "---------------------"
+./mrelease_test
+ret_val=$?
+
+if [ $ret_val -eq 0 ]; then
+ echo "[PASS]"
+elif [ $ret_val -eq $ksft_skip ]; then
+ echo "[SKIP]"
+ exitcode=$ksft_skip
+else
+ echo "[FAIL]"
+ exitcode=1
+fi
+
echo "-------------------"
echo "running mremap_test"
echo "-------------------"
In general, the code flow is hard to read to make sure resources
are released e.g: pipefd in all the error paths. The code is broken
up into smaller chunks where it isn't needed in some cases and left
as a large block when it could benefit from abstraction e.g: negative
test block.
Please make changes and send v2.
thanks,
-- Shuah
