5 files changed, 234 insertions, 44 deletions

diff --git a/tools/testing/selftests/pidfd/.gitignore b/tools/testing/selftests/pidfd/.gitignore
index 822a1e63d045..16d84d117bc0 100644
--- a/tools/testing/selftests/pidfd/.gitignore
+++ b/tools/testing/selftests/pidfd/.gitignore
@@ -1 +1,2 @@
+pidfd_open_test
 pidfd_test
diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile
index 4b31c14f273c..720b2d884b3c 100644
--- a/tools/testing/selftests/pidfd/Makefile
+++ b/tools/testing/selftests/pidfd/Makefile
@@ -1,6 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
 CFLAGS += -g -I../../../../usr/include/ -lpthread
 
-TEST_GEN_PROGS := pidfd_test
+TEST_GEN_PROGS := pidfd_test pidfd_open_test
 
 include ../lib.mk
 
diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
new file mode 100644
index 000000000000..8452e910463f
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __PIDFD_H
+#define __PIDFD_H
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/mount.h>
+
+#include "../kselftest.h"
+
+/*
+ * The kernel reserves 300 pids via RESERVED_PIDS in kernel/pid.c
+ * That means, when it wraps around any pid < 300 will be skipped.
+ * So we need to use a pid > 300 in order to test recycling.
+ */
+#define PID_RECYCLE 1000
+
+/*
+ * Define a few custom error codes for the child process to clearly indicate
+ * what is happening. This way we can tell the difference between a system
+ * error, a test error, etc.
+ */
+#define PIDFD_PASS 0
+#define PIDFD_FAIL 1
+#define PIDFD_ERROR 2
+#define PIDFD_SKIP 3
+#define PIDFD_XFAIL 4
+
+int wait_for_pid(pid_t pid)
+{
+        int status, ret;
+
+again:
+        ret = waitpid(pid, &status, 0);
+        if (ret == -1) {
+                if (errno == EINTR)
+                        goto again;
+
+                return -1;
+        }
+
+        if (!WIFEXITED(status))
+                return -1;
+
+        return WEXITSTATUS(status);
+}
+
+
+#endif /* __PIDFD_H */
diff --git a/tools/testing/selftests/pidfd/pidfd_open_test.c b/tools/testing/selftests/pidfd/pidfd_open_test.c
new file mode 100644
index 000000000000..0377133dd6dc
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd_open_test.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/mount.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "pidfd.h"
+#include "../kselftest.h"
+
+static inline int sys_pidfd_open(pid_t pid, unsigned int flags)
+{
+        return syscall(__NR_pidfd_open, pid, flags);
+}
+
+static int safe_int(const char *numstr, int *converted)
+{
+        char *err = NULL;
+        long sli;
+
+        errno = 0;
+        sli = strtol(numstr, &err, 0);
+        if (errno == ERANGE && (sli == LONG_MAX || sli == LONG_MIN))
+                return -ERANGE;
+
+        if (errno != 0 && sli == 0)
+                return -EINVAL;
+
+        if (err == numstr || *err != '\0')
+                return -EINVAL;
+
+        if (sli > INT_MAX || sli < INT_MIN)
+                return -ERANGE;
+
+        *converted = (int)sli;
+        return 0;
+}
+
+static int char_left_gc(const char *buffer, size_t len)
+{
+        size_t i;
+
+        for (i = 0; i < len; i++) {
+                if (buffer[i] == ' ' ||
+                    buffer[i] == '\t')
+                        continue;
+
+                return i;
+        }
+
+        return 0;
+}
+
+static int char_right_gc(const char *buffer, size_t len)
+{
+        int i;
+
+        for (i = len - 1; i >= 0; i--) {
+                if (buffer[i] == ' '  ||
+                    buffer[i] == '\t' ||
+                    buffer[i] == '\n' ||
+                    buffer[i] == '\0')
+                        continue;
+
+                return i + 1;
+        }
+
+        return 0;
+}
+
+static char *trim_whitespace_in_place(char *buffer)
+{
+        buffer += char_left_gc(buffer, strlen(buffer));
+        buffer[char_right_gc(buffer, strlen(buffer))] = '\0';
+        return buffer;
+}
+
+static pid_t get_pid_from_fdinfo_file(int pidfd, const char *key, size_t keylen)
+{
+        int ret;
+        char path[512];
+        FILE *f;
+        size_t n = 0;
+        pid_t result = -1;
+        char *line = NULL;
+
+        snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", pidfd);
+
+        f = fopen(path, "re");
+        if (!f)
+                return -1;
+
+        while (getline(&line, &n, f) != -1) {
+                char *numstr;
+
+                if (strncmp(line, key, keylen))
+                        continue;
+
+                numstr = trim_whitespace_in_place(line + 4);
+                ret = safe_int(numstr, &result);
+                if (ret < 0)
+                        goto out;
+
+                break;
+        }
+
+out:
+        free(line);
+        fclose(f);
+        return result;
+}
+
+int main(int argc, char **argv)
+{
+        int pidfd = -1, ret = 1;