linux-kernel - [RFC PATCH v1 5/8] selftests/nolibc: Add `fork(2)` selftest

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Date:   Thu, 22 Dec 2022 10:51:31 +0700
From:   Ammar Faizi <ammarfaizi2@...weeb.org>
To:     Willy Tarreau <w@....eu>, Shuah Khan <shuah@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Ammar Faizi <ammarfaizi2@...weeb.org>,
        Gilang Fachrezy <gilang4321@...il.com>,
        VNLX Kernel Department <kernel@...x.org>,
        Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>,
        Kanna Scarlet <knscarlet@...weeb.org>,
        Muhammad Rizki <kiizuha@...weeb.org>,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kselftest Mailing List 
        <linux-kselftest@...r.kernel.org>
Subject: [RFC PATCH v1 5/8] selftests/nolibc: Add `fork(2)` selftest

From: Ammar Faizi <ammarfaizi2@...weeb.org>

Ensure the fork() function can create a child process. Also, when the
child exits, the parent must be able to get the child's exit code
via waitpid().

Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>
---
 tools/testing/selftests/nolibc/nolibc-test.c | 45 ++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 8d69f8a0f35a..309cabbddeec 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -442,6 +442,50 @@ int test_getdents64(const char *dir)
 	return ret;
 }
 
+/*
+ * Test fork().
+ * Make sure the exit code can be read from the parent process.
+ */
+static int test_fork_and_exit(int expected_code)
+{
+	int status;
+	int code;
+	pid_t ret;
+	pid_t p;
+
+	p = fork();
+	if (p < 0)
+		return p;
+
+	if (!p)
+		exit(expected_code);
+
+	do {
+		ret = waitpid(p, &status, 0);
+		if (ret < 0)
+			return ret;
+	} while (!WIFEXITED(status));
+
+	code = WEXITSTATUS(status);
+	if (code != expected_code) {
+		printf("test_fork_and_exit(): waitpid(): Invalid exit code: %d; expected = %d\n", code, expected_code);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int test_fork(void)
+{
+	int i;
+
+	for (i = 0; i < 255; i++) {
+		if (test_fork_and_exit(i))
+			return -1;
+	}
+	return 0;
+}
+
 /* Run syscall tests between IDs <min> and <max>.
  * Return 0 on success, non-zero on failure.
  */
@@ -494,6 +538,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(dup3_0);            tmp = dup3(0, 100, 0);  EXPECT_SYSNE(1, tmp, -1); close(tmp); break;
 		CASE_TEST(dup3_m1);           tmp = dup3(-1, 100, 0); EXPECT_SYSER(1, tmp, -1, EBADF); if (tmp != -1) close(tmp); break;
 		CASE_TEST(execve_root);       EXPECT_SYSER(1, execve("/", (char*[]){ [0] = "/", [1] = NULL }, NULL), -1, EACCES); break;
+		CASE_TEST(fork);              EXPECT_SYSZR(1, test_fork()); break;
 		CASE_TEST(getdents64_root);   EXPECT_SYSNE(1, test_getdents64("/"), -1); break;
 		CASE_TEST(getdents64_null);   EXPECT_SYSER(1, test_getdents64("/dev/null"), -1, ENOTDIR); break;
 		CASE_TEST(gettimeofday_null); EXPECT_SYSZR(1, gettimeofday(NULL, NULL)); break;
-- 
Ammar Faizi