4 files changed, 204 insertions, 0 deletions
diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index 3cb4fa771ec2..6c2ac4208c27 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -10,6 +10,7 @@ map_populate
 thuge-gen
 compaction_test
 mlock2-tests
+mrelease_test
 mremap_dontunmap
 mremap_test
 on-fault-limit
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index f1228370e99b..8111a33e4824 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -44,6 +44,7 @@ TEST_GEN_FILES += memfd_secret
 TEST_GEN_FILES += migration
 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..96671c2f7d48
--- /dev/null
+++ b/tools/testing/selftests/vm/mrelease_test.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2022 Google LLC
+ */
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "util.h"
+
+#include "../kselftest.h"
+
+#ifndef __NR_pidfd_open
+#define __NR_pidfd_open -1
+#endif
+
+#ifndef __NR_process_mrelease
+#define __NR_process_mrelease -1
+#endif
+
+#define MB(x) (x << 20)
+#define MAX_SIZE_MB 1024
+
+static int alloc_noexit(unsigned long nr_pages, int pipefd)
+{
+	int ppid = getppid();
+	int timeout = 10; /* 10sec timeout to get killed */
+	unsigned long i;
+	char *buf;
+
+	buf = (char *)mmap(NULL, nr_pages * PAGE_SIZE, PROT_READ | PROT_WRITE,
+			   MAP_PRIVATE | MAP_ANON, 0, 0);
+	if (buf == MAP_FAILED) {
+		perror("mmap failed, halting the test");
+		return KSFT_FAIL;
+	}
+
+	for (i = 0; i < nr_pages; i++)
+		*((unsigned long *)(buf + (i * PAGE_SIZE))) = i;
+
+	/* Signal the parent that the child is ready */
+	if (write(pipefd, "", 1) < 0) {
+		perror("write");
+		return KSFT_FAIL;
+	}
+
+	/* Wait to be killed (when reparenting happens) */
+	while (getppid() == ppid && timeout > 0) {
+		sleep(1);
+		timeout--;
+	}
+
+	munmap(buf, nr_pages * PAGE_SIZE);
+
+	return (timeout > 0) ? KSFT_PASS : KSFT_FAIL;
+}
+
+/* The process_mrelease calls in this test are expected to fail */
+static void run_negative_tests(int pidfd)
+{
+	/* Test invalid flags. Expect to fail with EINVAL error code. */
+	if (!syscall(__NR_process_mrelease, pidfd, (unsigned int)-1) ||
+			errno != EINVAL) {
+		perror("process_mrelease with wrong flags");
+		exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
+	}
+	/*
+	 * Test reaping while process is alive with no pending SIGKILL.
+	 * Expect to fail with EINVAL error code.
+	 */
+	if (!syscall(__NR_process_mrelease, pidfd, 0) || errno != EINVAL) {
+		perror("process_mrelease on a live process");
+		exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
+	}
+}
+
+static int child_main(int pipefd[], size_t size)
+{
+	int res;
+
+	/* Allocate and fault-in memory and wait to be killed */
+	close(pipefd[0]);
+	res = alloc_noexit(MB(size) / PAGE_SIZE, pipefd[1]);
+	close(pipefd[1]);
+	return res;
+}
+
+int main(void)
+{
+	int pipefd[2], pidfd;
+	bool success, retry;
+	size_t size;
+	pid_t pid;
+	char byte;
+	int res;
+
+	/* Test a wrong pidfd */
+	if (!syscall(__NR_process_mrelease, -1, 0) || errno != EBADF) {
+		perror("process_mrelease with wrong pidfd");
+		exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
+	}
+
+	/* Start the test with 1MB child memory allocation */
+	size = 1;
+retry:
+	/*
+	 * Pipe for the child to signal when it's done allocating
+	 * memory
+	 */
+	if (pipe(pipefd)) {
+		perror("pipe");
+		exit(KSFT_FAIL);
+	}
+	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		close(pipefd[0]);
+		close(pipefd[1]);
+		exit(KSFT_FAIL);
+	}
+
+	if (pid == 0) {
+		/* Child main routine */
+		res = child_main(pipefd, size);
+		exit(res);
+	}
+
+	/*
+	 * Parent main routine:
+	 * Wait for the child to finish allocations, then kill and reap
+	 */
+	close(pipefd[1]);
+	/* Block until the child is ready */
+	res = read(pipefd[0], &byte, 1);
+	close(pipefd[0]);
+	if (res < 0) {
+		perror("read");
+		if (!kill(pid, SIGKILL))
+			waitpid(pid, NULL, 0);
+		exit(KSFT_FAIL);
+	}
+
+	pidfd = syscall(__NR_pidfd_open, pid, 0);
+	if (pidfd < 0) {
+		perror("pidfd_open");
+		if (!kill(pid, SIGKILL))
+			waitpid(pid, NULL, 0);
+		exit(KSFT_FAIL);
+	}
+
+	/* Run negative tests which require a live child */
+	run_negative_tests(pidfd);
+
+	if (kill(pid, SIGKILL)) {
+		perror("kill");
+		exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
+	}
+
+	success = (syscall(__NR_process_mrelease, pidfd, 0) == 0);
+	if (!success) {
+		/*
+		 * If we failed to reap because the child exited too soon,
+		 * before we could call process_mrelease. Double child's memory
+		 * which causes it to spend more time on cleanup and increases
+		 * our chances of reaping its memory before it exits.
+		 * Retry until we succeed or reach MAX_SIZE_MB.
+		 */
+		if (errno == ESRCH) {
+			retry = (size <= MAX_SIZE_MB);
+		} else {
+			perror("process_mrelease");
+			waitpid(pid, NULL, 0);
+			exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
+		}
+	}
+
+	/* Cleanup to prevent zombies */
+	if (waitpid(pid, NULL, 0) < 0) {
+		perror("waitpid");
+		exit(KSFT_FAIL);
+	}
+	close(pidfd);
+
+	if (!success) {
+		if (retry) {
+			size *= 2;
+			goto retry;
+		}
+		printf("All process_mrelease attempts failed!\n");
+		exit(KSFT_FAIL);
+	}
+
+	printf("Success reaping a child with %zuMB of memory allocations\n",
+	       size);
+	return KSFT_PASS;
+}
diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
index a2302b5faaf2..41fce8bea929 100755
--- a/tools/testing/selftests/vm/run_vmtests.sh
+++ b/tools/testing/selftests/vm/run_vmtests.sh
@@ -141,6 +141,8 @@ run_test ./mlock-random-test
 
 run_test ./mlock2-tests
 
+run_test ./mrelease_test
+
 run_test ./mremap_test
 
 run_test ./thuge-gen