Re: [PATCH 1/3] selftests: vm: add process_mrelease tests

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On 5/10/22 10:29 AM, Suren Baghdasaryan wrote:
On Tue, May 10, 2022 at 8:43 AM Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote:

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.

I'll try to improve the description but IMHO it does describe what
it's testing - the process_mrelease syscall with valid and invalid
inputs. I could omit the implementation details if that helps.


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.

Ack.



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.

Ack.


+     return -1;
+#endif

Key off of syscall return instead of these ifdefs - same comment
on all of the ifdefs

Ack. I was using some other test as an example but I guess that was
not a good model.


+}
+

I am not seeing any reason for breaking this code up have a separate
routine for pidfd_open().

I'm a bit unclear what you mean. Do you mean that userspace headers
should already define pidfd_open() and I don't need to define it?


Do you need pidfd_open() or can this be part of main? Without the ifdefs,
it is really a one line code.

thanks,
-- Shuah




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