Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

26 files changed, 2749 insertions, 0 deletions

diff --git a/tools/testing/selftests/proc/.gitignore b/tools/testing/selftests/proc/.gitignore
new file mode 100644
index 000000000..a156ac5dd
--- /dev/null
+++ b/tools/testing/selftests/proc/.gitignore
@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/fd-001-lookup
+/fd-002-posix-eq
+/fd-003-kthread
+/proc-fsconfig-hidepid
+/proc-loadavg-001
+/proc-multiple-procfs
+/proc-empty-vm
+/proc-pid-vm
+/proc-self-map-files-001
+/proc-self-map-files-002
+/proc-self-syscall
+/proc-self-wchan
+/proc-subset-pid
+/proc-tid0
+/proc-uptime-001
+/proc-uptime-002
+/read
+/self
+/setns-dcache
+/setns-sysvipc
+/thread-self
diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile
new file mode 100644
index 000000000..cd9536925
--- /dev/null
+++ b/tools/testing/selftests/proc/Makefile
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS += -Wall -O2 -Wno-unused-function
+CFLAGS += -D_GNU_SOURCE
+LDFLAGS += -pthread
+
+TEST_GEN_PROGS :=
+TEST_GEN_PROGS += fd-001-lookup
+TEST_GEN_PROGS += fd-002-posix-eq
+TEST_GEN_PROGS += fd-003-kthread
+TEST_GEN_PROGS += proc-loadavg-001
+TEST_GEN_PROGS += proc-empty-vm
+TEST_GEN_PROGS += proc-pid-vm
+TEST_GEN_PROGS += proc-self-map-files-001
+TEST_GEN_PROGS += proc-self-map-files-002
+TEST_GEN_PROGS += proc-self-syscall
+TEST_GEN_PROGS += proc-self-wchan
+TEST_GEN_PROGS += proc-subset-pid
+TEST_GEN_PROGS += proc-tid0
+TEST_GEN_PROGS += proc-uptime-001
+TEST_GEN_PROGS += proc-uptime-002
+TEST_GEN_PROGS += read
+TEST_GEN_PROGS += self
+TEST_GEN_PROGS += setns-dcache
+TEST_GEN_PROGS += setns-sysvipc
+TEST_GEN_PROGS += thread-self
+TEST_GEN_PROGS += proc-multiple-procfs
+TEST_GEN_PROGS += proc-fsconfig-hidepid
+
+include ../lib.mk
diff --git a/tools/testing/selftests/proc/config b/tools/testing/selftests/proc/config
new file mode 100644
index 000000000..68fbd2b35
--- /dev/null
+++ b/tools/testing/selftests/proc/config
@@ -0,0 +1 @@
+CONFIG_PROC_FS=y
diff --git a/tools/testing/selftests/proc/fd-001-lookup.c b/tools/testing/selftests/proc/fd-001-lookup.c
new file mode 100644
index 000000000..60d7948e7
--- /dev/null
+++ b/tools/testing/selftests/proc/fd-001-lookup.c
@@ -0,0 +1,168 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test /proc/*/fd lookup.
+
+#undef NDEBUG
+#include <assert.h>
+#include <dirent.h>
+#include <errno.h>
+#include <limits.h>
+#include <sched.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "proc.h"
+
+/* lstat(2) has more "coverage" in case non-symlink pops up somehow. */
+static void test_lookup_pass(const char *pathname)
+{
+	struct stat st;
+	ssize_t rv;
+
+	memset(&st, 0, sizeof(struct stat));
+	rv = lstat(pathname, &st);
+	assert(rv == 0);
+	assert(S_ISLNK(st.st_mode));
+}
+
+static void test_lookup_fail(const char *pathname)
+{
+	struct stat st;
+	ssize_t rv;
+
+	rv = lstat(pathname, &st);
+	assert(rv == -1 && errno == ENOENT);
+}
+
+static void test_lookup(unsigned int fd)
+{
+	char buf[64];
+	unsigned int c;
+	unsigned int u;
+	int i;
+
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%u", fd);
+	test_lookup_pass(buf);
+
+	/* leading junk */
+	for (c = 1; c <= 255; c++) {
+		if (c == '/')
+			continue;
+		snprintf(buf, sizeof(buf), "/proc/self/fd/%c%u", c, fd);
+		test_lookup_fail(buf);
+	}
+
+	/* trailing junk */
+	for (c = 1; c <= 255; c++) {
+		if (c == '/')
+			continue;
+		snprintf(buf, sizeof(buf), "/proc/self/fd/%u%c", fd, c);
+		test_lookup_fail(buf);
+	}
+
+	for (i = INT_MIN; i < INT_MIN + 1024; i++) {
+		snprintf(buf, sizeof(buf), "/proc/self/fd/%d", i);
+		test_lookup_fail(buf);
+	}
+	for (i = -1024; i < 0; i++) {
+		snprintf(buf, sizeof(buf), "/proc/self/fd/%d", i);
+		test_lookup_fail(buf);
+	}
+	for (u = INT_MAX - 1024; u <= (unsigned int)INT_MAX + 1024; u++) {
+		snprintf(buf, sizeof(buf), "/proc/self/fd/%u", u);
+		test_lookup_fail(buf);
+	}
+	for (u = UINT_MAX - 1024; u != 0; u++) {
+		snprintf(buf, sizeof(buf), "/proc/self/fd/%u", u);
+		test_lookup_fail(buf);
+	}
+
+
+}
+
+int main(void)
+{
+	struct dirent *de;
+	unsigned int fd, target_fd;
+
+	if (unshare(CLONE_FILES) == -1)
+		return 1;
+
+	/* Wipe fdtable. */
+	do {
+		DIR *d;
+
+		d = opendir("/proc/self/fd");
+		if (!d)
+			return 1;
+
+		de = xreaddir(d);
+		assert(de->d_type == DT_DIR);
+		assert(streq(de->d_name, "."));
+
+		de = xreaddir(d);
+		assert(de->d_type == DT_DIR);
+		assert(streq(de->d_name, ".."));
+next:
+		de = xreaddir(d);
+		if (de) {
+			unsigned long long fd_ull;
+			unsigned int fd;
+			char *end;
+
+			assert(de->d_type == DT_LNK);
+
+			fd_ull = xstrtoull(de->d_name, &end);
+			assert(*end == '\0');
+			assert(fd_ull == (unsigned int)fd_ull);
+
+			fd = fd_ull;
+			if (fd == dirfd(d))
+				goto next;
+			close(fd);
+		}
+
+		closedir(d);
+	} while (de);
+
+	/* Now fdtable is clean. */
+
+	fd = open("/", O_PATH|O_DIRECTORY);
+	assert(fd == 0);
+	test_lookup(fd);
+	close(fd);
+
+	/* Clean again! */
+
+	fd = open("/", O_PATH|O_DIRECTORY);
+	assert(fd == 0);
+	/* Default RLIMIT_NOFILE-1 */
+	target_fd = 1023;
+	while (target_fd > 0) {
+		if (dup2(fd, target_fd) == target_fd)
+			break;
+		target_fd /= 2;
+	}
+	assert(target_fd > 0);
+	close(fd);
+	test_lookup(target_fd);
+	close(target_fd);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/fd-002-posix-eq.c b/tools/testing/selftests/proc/fd-002-posix-eq.c
new file mode 100644
index 000000000..417322ca9
--- /dev/null
+++ b/tools/testing/selftests/proc/fd-002-posix-eq.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that open(/proc/*/fd/*) opens the same file.
+#undef NDEBUG
+#include <assert.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int main(void)
+{
+	int fd0, fd1, fd2;
+	struct stat st0, st1, st2;
+	char buf[64];
+	int rv;
+
+	fd0 = open("/", O_DIRECTORY|O_RDONLY);
+	assert(fd0 >= 0);
+
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%u", fd0);
+	fd1 = open(buf, O_RDONLY);
+	assert(fd1 >= 0);
+
+	snprintf(buf, sizeof(buf), "/proc/thread-self/fd/%u", fd0);
+	fd2 = open(buf, O_RDONLY);
+	assert(fd2 >= 0);
+
+	rv = fstat(fd0, &st0);
+	assert(rv == 0);
+	rv = fstat(fd1, &st1);
+	assert(rv == 0);
+	rv = fstat(fd2, &st2);
+	assert(rv == 0);
+
+	assert(st0.st_dev == st1.st_dev);
+	assert(st0.st_ino == st1.st_ino);
+
+	assert(st0.st_dev == st2.st_dev);
+	assert(st0.st_ino == st2.st_ino);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/fd-003-kthread.c b/tools/testing/selftests/proc/fd-003-kthread.c
new file mode 100644
index 000000000..dc591f97b
--- /dev/null
+++ b/tools/testing/selftests/proc/fd-003-kthread.c
@@ -0,0 +1,178 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that /proc/$KERNEL_THREAD/fd/ is empty.
+
+#undef NDEBUG
+#include <sys/syscall.h>
+#include <assert.h>
+#include <dirent.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "proc.h"
+
+#define PF_KHTREAD 0x00200000
+
+/*
+ * Test for kernel threadness atomically with openat().
+ *
+ * Return /proc/$PID/fd descriptor if process is kernel thread.
+ * Return -1 if a process is userspace process.
+ */
+static int kernel_thread_fd(unsigned int pid)
+{
+	unsigned int flags = 0;
+	char buf[4096];
+	int dir_fd, fd;
+	ssize_t rv;
+
+	snprintf(buf, sizeof(buf), "/proc/%u", pid);
+	dir_fd = open(buf, O_RDONLY|O_DIRECTORY);
+	if (dir_fd == -1)
+		return -1;
+
+	/*
+	 * Believe it or not, struct task_struct::flags is directly exposed
+	 * to userspace!
+	 */
+	fd = openat(dir_fd, "stat", O_RDONLY);
+	if (fd == -1) {
+		close(dir_fd);
+		return -1;
+	}
+	rv = read(fd, buf, sizeof(buf));
+	close(fd);
+	if (0 < rv && rv <= sizeof(buf)) {
+		unsigned long long flags_ull;
+		char *p, *end;
+		int i;
+
+		assert(buf[rv - 1] == '\n');
+		buf[rv - 1] = '\0';
+
+		/* Search backwards: ->comm can contain whitespace and ')'. */
+		for (i = 0; i < 43; i++) {
+			p = strrchr(buf, ' ');
+			assert(p);
+			*p = '\0';
+		}
+
+		p = strrchr(buf, ' ');
+		assert(p);
+
+		flags_ull = xstrtoull(p + 1, &end);
+		assert(*end == '\0');
+		assert(flags_ull == (unsigned int)flags_ull);
+
+		flags = flags_ull;
+	}
+
+	fd = -1;
+	if (flags & PF_KHTREAD) {
+		fd = openat(dir_fd, "fd", O_RDONLY|O_DIRECTORY);
+	}
+	close(dir_fd);
+	return fd;
+}
+
+static void test_readdir(int fd)
+{
+	DIR *d;
+	struct dirent *de;
+
+	d = fdopendir(fd);
+	assert(d);
+
+	de = xreaddir(d);
+	assert(streq(de->d_name, "."));
+	assert(de->d_type == DT_DIR);
+
+	de = xreaddir(d);
+	assert(streq(de->d_name, ".."));
+	assert(de->d_type == DT_DIR);
+
+	de = xreaddir(d);
+	assert(!de);
+}
+
+static inline int sys_statx(int dirfd, const char *pathname, int flags,
+			    unsigned int mask, void *stx)
+{
+	return syscall(SYS_statx, dirfd, pathname, flags, mask, stx);
+}
+
+static void test_lookup_fail(int fd, const char *pathname)
+{
+	char stx[256] __attribute__((aligned(8)));
+	int rv;
+
+	rv = sys_statx(fd, pathname, AT_SYMLINK_NOFOLLOW, 0, (void *)stx);
+	assert(rv == -1 && errno == ENOENT);
+}
+
+static void test_lookup(int fd)
+{
+	char buf[64];
+	unsigned int u;
+	int i;
+
+	for (i = INT_MIN; i < INT_MIN + 1024; i++) {
+		snprintf(buf, sizeof(buf), "%d", i);
+		test_lookup_fail(fd, buf);
+	}
+	for (i = -1024; i < 1024; i++) {
+		snprintf(buf, sizeof(buf), "%d", i);
+		test_lookup_fail(fd, buf);
+	}
+	for (u = INT_MAX - 1024; u < (unsigned int)INT_MAX + 1024; u++) {
+		snprintf(buf, sizeof(buf), "%u", u);
+		test_lookup_fail(fd, buf);
+	}
+	for (u = UINT_MAX - 1024; u != 0; u++) {
+		snprintf(buf, sizeof(buf), "%u", u);
+		test_lookup_fail(fd, buf);
+	}
+}
+
+int main(void)
+{
+	unsigned int pid;
+	int fd;
+
+	/*
+	 * In theory this will loop indefinitely if kernel threads are exiled
+	 * from /proc.
+	 *
+	 * Start with kthreadd.
+	 */
+	pid = 2;
+	while ((fd = kernel_thread_fd(pid)) == -1 && pid < 1024) {
+		pid++;
+	}
+	/* EACCES if run as non-root. */
+	if (pid >= 1024)
+		return 1;
+
+	test_readdir(fd);
+	test_lookup(fd);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-empty-vm.c b/tools/testing/selftests/proc/proc-empty-vm.c
new file mode 100644
index 000000000..7588428b8
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-empty-vm.c
@@ -0,0 +1,388 @@
+/*
+ * Copyright (c) 2022 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Create a process without mappings by unmapping everything at once and
+ * holding it with ptrace(2). See what happens to
+ *
+ *	/proc/${pid}/maps
+ *	/proc/${pid}/numa_maps
+ *	/proc/${pid}/smaps
+ *	/proc/${pid}/smaps_rollup
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/ptrace.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+/*
+ * 0: vsyscall VMA doesn't exist	vsyscall=none
+ * 1: vsyscall VMA is --xp		vsyscall=xonly
+ * 2: vsyscall VMA is r-xp		vsyscall=emulate
+ */
+static volatile int g_vsyscall;
+static const char *g_proc_pid_maps_vsyscall;
+static const char *g_proc_pid_smaps_vsyscall;
+
+static const char proc_pid_maps_vsyscall_0[] = "";
+static const char proc_pid_maps_vsyscall_1[] =
+"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0                  [vsyscall]\n";
+static const char proc_pid_maps_vsyscall_2[] =
+"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]\n";
+
+static const char proc_pid_smaps_vsyscall_0[] = "";
+
+static const char proc_pid_smaps_vsyscall_1[] =
+"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]\n"
+"Size:                  4 kB\n"
+"KernelPageSize:        4 kB\n"
+"MMUPageSize:           4 kB\n"
+"Rss:                   0 kB\n"
+"Pss:                   0 kB\n"
+"Pss_Dirty:             0 kB\n"
+"Shared_Clean:          0 kB\n"
+"Shared_Dirty:          0 kB\n"
+"Private_Clean:         0 kB\n"
+"Private_Dirty:         0 kB\n"
+"Referenced:            0 kB\n"
+"Anonymous:             0 kB\n"
+"LazyFree:              0 kB\n"
+"AnonHugePages:         0 kB\n"
+"ShmemPmdMapped:        0 kB\n"
+"FilePmdMapped:         0 kB\n"
+"Shared_Hugetlb:        0 kB\n"
+"Private_Hugetlb:       0 kB\n"
+"Swap:                  0 kB\n"
+"SwapPss:               0 kB\n"
+"Locked:                0 kB\n"
+"THPeligible:    0\n"
+/*
+ * "ProtectionKey:" field is conditional. It is possible to check it as well,
+ * but I don't have such machine.
+ */
+;
+
+static const char proc_pid_smaps_vsyscall_2[] =
+"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0                  [vsyscall]\n"
+"Size:                  4 kB\n"
+"KernelPageSize:        4 kB\n"
+"MMUPageSize:           4 kB\n"
+"Rss:                   0 kB\n"
+"Pss:                   0 kB\n"
+"Pss_Dirty:             0 kB\n"
+"Shared_Clean:          0 kB\n"
+"Shared_Dirty:          0 kB\n"
+"Private_Clean:         0 kB\n"
+"Private_Dirty:         0 kB\n"
+"Referenced:            0 kB\n"
+"Anonymous:             0 kB\n"
+"LazyFree:              0 kB\n"
+"AnonHugePages:         0 kB\n"
+"ShmemPmdMapped:        0 kB\n"
+"FilePmdMapped:         0 kB\n"
+"Shared_Hugetlb:        0 kB\n"
+"Private_Hugetlb:       0 kB\n"
+"Swap:                  0 kB\n"
+"SwapPss:               0 kB\n"
+"Locked:                0 kB\n"
+"THPeligible:    0\n"
+/*
+ * "ProtectionKey:" field is conditional. It is possible to check it as well,
+ * but I'm too tired.
+ */
+;
+
+static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
+{
+	_exit(EXIT_FAILURE);
+}
+
+static void sigaction_SIGSEGV_vsyscall(int _, siginfo_t *__, void *___)
+{
+	_exit(g_vsyscall);
+}
+
+/*
+ * vsyscall page can't be unmapped, probe it directly.
+ */
+static void vsyscall(void)
+{
+	pid_t pid;
+	int wstatus;
+
+	pid = fork();
+	if (pid < 0) {
+		fprintf(stderr, "fork, errno %d\n", errno);
+		exit(1);
+	}
+	if (pid == 0) {
+		setrlimit(RLIMIT_CORE, &(struct rlimit){});
+
+		/* Hide "segfault at ffffffffff600000" messages. */
+		struct sigaction act = {};
+		act.sa_flags = SA_SIGINFO;
+		act.sa_sigaction = sigaction_SIGSEGV_vsyscall;
+		sigaction(SIGSEGV, &act, NULL);
+
+		g_vsyscall = 0;
+		/* gettimeofday(NULL, NULL); */
+		uint64_t rax = 0xffffffffff600000;
+		asm volatile (
+			"call *%[rax]"
+			: [rax] "+a" (rax)
+			: "D" (NULL), "S" (NULL)
+			: "rcx", "r11"
+		);
+
+		g_vsyscall = 1;
+		*(volatile int *)0xffffffffff600000UL;
+
+		g_vsyscall = 2;
+		exit(g_vsyscall);
+	}
+	waitpid(pid, &wstatus, 0);
+	if (WIFEXITED(wstatus)) {
+		g_vsyscall = WEXITSTATUS(wstatus);
+	} else {
+		fprintf(stderr, "error: vsyscall wstatus %08x\n", wstatus);
+		exit(1);
+	}
+}
+
+static int test_proc_pid_maps(pid_t pid)
+{
+	char buf[4096];
+	snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
+	int fd = open(buf, O_RDONLY);
+	if (fd == -1) {
+		perror("open /proc/${pid}/maps");
+		return EXIT_FAILURE;
+	} else {
+		ssize_t rv = read(fd, buf, sizeof(buf));
+		close(fd);
+		if (g_vsyscall == 0) {
+			assert(rv == 0);
+		} else {
+			size_t len = strlen(g_proc_pid_maps_vsyscall);
+			assert(rv == len);
+			assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
+		}
+		return EXIT_SUCCESS;
+	}
+}
+
+static int test_proc_pid_numa_maps(pid_t pid)
+{
+	char buf[4096];
+	snprintf(buf, sizeof(buf), "/proc/%u/numa_maps", pid);
+	int fd = open(buf, O_RDONLY);
+	if (fd == -1) {
+		if (errno == ENOENT) {
+			/*
+			 * /proc/${pid}/numa_maps is under CONFIG_NUMA,
+			 * it doesn't necessarily exist.
+			 */
+			return EXIT_SUCCESS;
+		}
+		perror("open /proc/${pid}/numa_maps");
+		return EXIT_FAILURE;
+	} else {
+		ssize_t rv = read(fd, buf, sizeof(buf));
+		close(fd);
+		assert(rv == 0);
+		return EXIT_SUCCESS;
+	}
+}
+
+static int test_proc_pid_smaps(pid_t pid)
+{
+	char buf[4096];
+	snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
+	int fd = open(buf, O_RDONLY);
+	if (fd == -1) {
+		if (errno == ENOENT) {
+			/*
+			 * /proc/${pid}/smaps is under CONFIG_PROC_PAGE_MONITOR,
+			 * it doesn't necessarily exist.
+			 */
+			return EXIT_SUCCESS;
+		}
+		perror("open /proc/${pid}/smaps");
+		return EXIT_FAILURE;
+	} else {
+		ssize_t rv = read(fd, buf, sizeof(buf));
+		close(fd);
+		if (g_vsyscall == 0) {
+			assert(rv == 0);
+		} else {
+			size_t len = strlen(g_proc_pid_maps_vsyscall);
+			/* TODO "ProtectionKey:" */
+			assert(rv > len);
+			assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
+		}
+		return EXIT_SUCCESS;
+	}
+}
+
+static const char g_smaps_rollup[] =
+"00000000-00000000 ---p 00000000 00:00 0                                  [rollup]\n"
+"Rss:                   0 kB\n"
+"Pss:                   0 kB\n"
+"Pss_Dirty:             0 kB\n"
+"Pss_Anon:              0 kB\n"
+"Pss_File:              0 kB\n"
+"Pss_Shmem:             0 kB\n"
+"Shared_Clean:          0 kB\n"
+"Shared_Dirty:          0 kB\n"
+"Private_Clean:         0 kB\n"
+"Private_Dirty:         0 kB\n"
+"Referenced:            0 kB\n"
+"Anonymous:             0 kB\n"
+"LazyFree:              0 kB\n"
+"AnonHugePages:         0 kB\n"
+"ShmemPmdMapped:        0 kB\n"
+"FilePmdMapped:         0 kB\n"
+"Shared_Hugetlb:        0 kB\n"
+"Private_Hugetlb:       0 kB\n"
+"Swap:                  0 kB\n"
+"SwapPss:               0 kB\n"
+"Locked:                0 kB\n"
+;
+
+static int test_proc_pid_smaps_rollup(pid_t pid)
+{
+	char buf[4096];
+	snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
+	int fd = open(buf, O_RDONLY);
+	if (fd == -1) {
+		if (errno == ENOENT) {
+			/*
+			 * /proc/${pid}/smaps_rollup is under CONFIG_PROC_PAGE_MONITOR,
+			 * it doesn't necessarily exist.
+			 */
+			return EXIT_SUCCESS;
+		}
+		perror("open /proc/${pid}/smaps_rollup");
+		return EXIT_FAILURE;
+	} else {
+		ssize_t rv = read(fd, buf, sizeof(buf));
+		close(fd);
+		assert(rv == sizeof(g_smaps_rollup) - 1);
+		assert(memcmp(buf, g_smaps_rollup, sizeof(g_smaps_rollup) - 1) == 0);
+		return EXIT_SUCCESS;
+	}
+}
+
+int main(void)
+{
+	int rv = EXIT_SUCCESS;
+
+	vsyscall();
+
+	switch (g_vsyscall) {
+	case 0:
+		g_proc_pid_maps_vsyscall  = proc_pid_maps_vsyscall_0;
+		g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_0;
+		break;
+	case 1:
+		g_proc_pid_maps_vsyscall  = proc_pid_maps_vsyscall_1;
+		g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_1;
+		break;
+	case 2:
+		g_proc_pid_maps_vsyscall  = proc_pid_maps_vsyscall_2;
+		g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_2;
+		break;
+	default:
+		abort();
+	}
+
+	pid_t pid = fork();
+	if (pid == -1) {
+		perror("fork");
+		return EXIT_FAILURE;
+	} else if (pid == 0) {
+		rv = ptrace(PTRACE_TRACEME, 0, NULL, NULL);
+		if (rv != 0) {
+			if (errno == EPERM) {
+				fprintf(stderr,
+"Did you know? ptrace(PTRACE_TRACEME) doesn't work under strace.\n"
+				);
+				kill(getppid(), SIGTERM);
+				return EXIT_FAILURE;
+			}
+			perror("ptrace PTRACE_TRACEME");
+			return EXIT_FAILURE;
+		}
+
+		/*
+		 * Hide "segfault at ..." messages. Signal handler won't run.
+		 */
+		struct sigaction act = {};
+		act.sa_flags = SA_SIGINFO;
+		act.sa_sigaction = sigaction_SIGSEGV;
+		sigaction(SIGSEGV, &act, NULL);
+
+#ifdef __amd64__
+		munmap(NULL, ((size_t)1 << 47) - 4096);
+#else
+#error "implement 'unmap everything'"
+#endif
+		return EXIT_FAILURE;
+	} else {
+		/*
+		 * TODO find reliable way to signal parent that munmap(2) completed.
+		 * Child can't do it directly because it effectively doesn't exist
+		 * anymore. Looking at child's VM files isn't 100% reliable either:
+		 * due to a bug they may not become empty or empty-like.
+		 */
+		sleep(1);
+
+		if (rv == EXIT_SUCCESS) {
+			rv = test_proc_pid_maps(pid);
+		}
+		if (rv == EXIT_SUCCESS) {
+			rv = test_proc_pid_numa_maps(pid);
+		}
+		if (rv == EXIT_SUCCESS) {
+			rv = test_proc_pid_smaps(pid);
+		}
+		if (rv == EXIT_SUCCESS) {
+			rv = test_proc_pid_smaps_rollup(pid);
+		}
+		/*
+		 * TODO test /proc/${pid}/statm, task_statm()
+		 * ->start_code, ->end_code aren't updated by munmap().
+		 * Output can be "0 0 0 2 0 0 0\n" where "2" can be anything.
+		 */
+
+		/* Cut the rope. */
+		int wstatus;
+		waitpid(pid, &wstatus, 0);
+		assert(WIFSTOPPED(wstatus));
+		assert(WSTOPSIG(wstatus) == SIGSEGV);
+	}
+
+	return rv;
+}
diff --git a/tools/testing/selftests/proc/proc-fsconfig-hidepid.c b/tools/testing/selftests/proc/proc-fsconfig-hidepid.c
new file mode 100644
index 000000000..b9af8f537
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-fsconfig-hidepid.c
@@ -0,0 +1,50 @@
+/*
+ * Copyright © 2020 Alexey Gladkov <gladkov.alexey@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <assert.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <linux/mount.h>
+#include <linux/unistd.h>
+
+static inline int fsopen(const char *fsname, unsigned int flags)
+{
+	return syscall(__NR_fsopen, fsname, flags);
+}
+
+static inline int fsconfig(int fd, unsigned int cmd, const char *key, const void *val, int aux)
+{
+	return syscall(__NR_fsconfig, fd, cmd, key, val, aux);
+}
+
+int main(void)
+{
+	int fsfd, ret;
+	int hidepid = 2;
+
+	assert((fsfd = fsopen("proc", 0)) != -1);
+
+	ret = fsconfig(fsfd, FSCONFIG_SET_BINARY, "hidepid", &hidepid, 0);
+	assert(ret == -1);
+	assert(errno == EINVAL);
+
+	assert(!fsconfig(fsfd, FSCONFIG_SET_STRING, "hidepid", "2", 0));
+	assert(!fsconfig(fsfd, FSCONFIG_SET_STRING, "hidepid", "invisible", 0));
+
+	assert(!close(fsfd));
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-loadavg-001.c b/tools/testing/selftests/proc/proc-loadavg-001.c
new file mode 100644
index 000000000..fb4fe9188
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-loadavg-001.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* Test that /proc/loadavg correctly reports last pid in pid namespace. */
+#include <errno.h>
+#include <sched.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+int main(void)
+{
+	pid_t pid;
+	int wstatus;
+
+	if (unshare(CLONE_NEWPID) == -1) {
+		if (errno == ENOSYS || errno == EPERM)
+			return 4;
+		return 1;
+	}
+
+	pid = fork();
+	if (pid == -1)
+		return 1;
+	if (pid == 0) {
+		char buf[128], *p;
+		int fd;
+		ssize_t rv;
+
+		fd = open("/proc/loadavg" , O_RDONLY);
+		if (fd == -1)
+			return 1;
+		rv = read(fd, buf, sizeof(buf));
+		if (rv < 3)
+			return 1;
+		p = buf + rv;
+
+		/* pid 1 */
+		if (!(p[-3] == ' ' && p[-2] == '1' && p[-1] == '\n'))
+			return 1;
+
+		pid = fork();
+		if (pid == -1)
+			return 1;
+		if (pid == 0)
+			return 0;
+		if (waitpid(pid, NULL, 0) == -1)
+			return 1;
+
+		lseek(fd, 0, SEEK_SET);
+		rv = read(fd, buf, sizeof(buf));
+		if (rv < 3)
+			return 1;
+		p = buf + rv;
+
+		/* pid 2 */
+		if (!(p[-3] == ' ' && p[-2] == '2' && p[-1] == '\n'))
+			return 1;
+
+		return 0;
+	}
+
+	if (waitpid(pid, &wstatus, 0) == -1)
+		return 1;
+	if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0)
+		return 0;
+	return 1;
+}
diff --git a/tools/testing/selftests/proc/proc-multiple-procfs.c b/tools/testing/selftests/proc/proc-multiple-procfs.c
new file mode 100644
index 000000000..ab912ad95
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-multiple-procfs.c
@@ -0,0 +1,48 @@
+/*
+ * Copyright © 2020 Alexey Gladkov <gladkov.alexey@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <assert.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+int main(void)
+{
+	struct stat proc_st1, proc_st2;
+	char procbuff[] = "/tmp/proc.XXXXXX/meminfo";
+	char procdir1[] = "/tmp/proc.XXXXXX";
+	char procdir2[] = "/tmp/proc.XXXXXX";
+
+	assert(mkdtemp(procdir1) != NULL);
+	assert(mkdtemp(procdir2) != NULL);
+
+	assert(!mount("proc", procdir1, "proc", 0, "hidepid=1"));
+	assert(!mount("proc", procdir2, "proc", 0, "hidepid=2"));
+
+	snprintf(procbuff, sizeof(procbuff), "%s/meminfo", procdir1);
+	assert(!stat(procbuff, &proc_st1));
+
+	snprintf(procbuff, sizeof(procbuff), "%s/meminfo", procdir2);
+	assert(!stat(procbuff, &proc_st2));
+
+	umount(procdir1);
+	umount(procdir2);
+
+	assert(proc_st1.st_dev != proc_st2.st_dev);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-pid-vm.c b/tools/testing/selftests/proc/proc-pid-vm.c
new file mode 100644
index 000000000..cacbd2a4a
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-pid-vm.c
@@ -0,0 +1,502 @@
+/*
+ * Copyright (c) 2019 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Fork and exec tiny 1 page executable which precisely controls its VM.
+ * Test /proc/$PID/maps
+ * Test /proc/$PID/smaps
+ * Test /proc/$PID/smaps_rollup
+ * Test /proc/$PID/statm
+ *
+ * FIXME require CONFIG_TMPFS which can be disabled
+ * FIXME test other values from "smaps"
+ * FIXME support other archs
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/uio.h>
+#include <linux/kdev_t.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+
+#include "../kselftest.h"
+
+static inline long sys_execveat(int dirfd, const char *pathname, char **argv, char **envp, int flags)
+{
+	return syscall(SYS_execveat, dirfd, pathname, argv, envp, flags);
+}
+
+static void make_private_tmp(void)
+{
+	if (unshare(CLONE_NEWNS) == -1) {
+		if (errno == ENOSYS || errno == EPERM) {
+			exit(4);
+		}
+		exit(1);
+	}
+	if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
+		exit(1);
+	}
+	if (mount(NULL, "/tmp", "tmpfs", 0, NULL) == -1) {
+		exit(1);
+	}
+}
+
+static pid_t pid = -1;
+static void ate(void)
+{
+	if (pid > 0) {
+		kill(pid, SIGTERM);
+	}
+}
+
+struct elf64_hdr {
+	uint8_t e_ident[16];
+	uint16_t e_type;
+	uint16_t e_machine;
+	uint32_t e_version;
+	uint64_t e_entry;
+	uint64_t e_phoff;
+	uint64_t e_shoff;
+	uint32_t e_flags;
+	uint16_t e_ehsize;
+	uint16_t e_phentsize;
+	uint16_t e_phnum;
+	uint16_t e_shentsize;
+	uint16_t e_shnum;
+	uint16_t e_shstrndx;
+};
+
+struct elf64_phdr {
+	uint32_t p_type;
+	uint32_t p_flags;
+	uint64_t p_offset;
+	uint64_t p_vaddr;
+	uint64_t p_paddr;
+	uint64_t p_filesz;
+	uint64_t p_memsz;
+	uint64_t p_align;
+};
+
+#ifdef __x86_64__
+#define PAGE_SIZE 4096
+#define VADDR (1UL << 32)
+#define MAPS_OFFSET 73
+
+#define syscall	0x0f, 0x05
+#define mov_rdi(x)	\
+	0x48, 0xbf,	\
+	(x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff,	\
+	((x)>>32)&0xff, ((x)>>40)&0xff, ((x)>>48)&0xff, ((x)>>56)&0xff
+
+#define mov_rsi(x)	\
+	0x48, 0xbe,	\
+	(x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff,	\
+	((x)>>32)&0xff, ((x)>>40)&0xff, ((x)>>48)&0xff, ((x)>>56)&0xff
+
+#define mov_eax(x)	\
+	0xb8, (x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff
+
+static const uint8_t payload[] = {
+	/* Casually unmap stack, vDSO and everything else. */
+	/* munmap */
+	mov_rdi(VADDR + 4096),
+	mov_rsi((1ULL << 47) - 4096 - VADDR - 4096),
+	mov_eax(11),
+	syscall,
+
+	/* Ping parent. */
+	/* write(0, &c, 1); */
+	0x31, 0xff,					/* xor edi, edi */
+	0x48, 0x8d, 0x35, 0x00, 0x00, 0x00, 0x00,	/* lea rsi, [rip] */
+	0xba, 0x01, 0x00, 0x00, 0x00,			/* mov edx, 1 */
+	mov_eax(1),
+	syscall,
+
+	/* 1: pause(); */
+	mov_eax(34),
+	syscall,
+
+	0xeb, 0xf7,	/* jmp 1b */
+};
+
+static int make_exe(const uint8_t *payload, size_t len)
+{
+	struct elf64_hdr h;
+	struct elf64_phdr ph;
+
+	struct iovec iov[3] = {
+		{&h, sizeof(struct elf64_hdr)},
+		{&ph, sizeof(struct elf64_phdr)},
+		{(void *)payload, len},
+	};
+	int fd, fd1;
+	char buf[64];
+
+	memset(&h, 0, sizeof(h));
+	h.e_ident[0] = 0x7f;
+	h.e_ident[1] = 'E';
+	h.e_ident[2] = 'L';
+	h.e_ident[3] = 'F';
+	h.e_ident[4] = 2;
+	h.e_ident[5] = 1;
+	h.e_ident[6] = 1;
+	h.e_ident[7] = 0;
+	h.e_type = 2;
+	h.e_machine = 0x3e;
+	h.e_version = 1;
+	h.e_entry = VADDR + sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr);
+	h.e_phoff = sizeof(struct elf64_hdr);
+	h.e_shoff = 0;
+	h.e_flags = 0;
+	h.e_ehsize = sizeof(struct elf64_hdr);
+	h.e_phentsize = sizeof(struct elf64_phdr);
+	h.e_phnum = 1;
+	h.e_shentsize = 0;
+	h.e_shnum = 0;
+	h.e_shstrndx = 0;
+
+	memset(&ph, 0, sizeof(ph));
+	ph.p_type = 1;
+	ph.p_flags = (1<<2)|1;
+	ph.p_offset = 0;
+	ph.p_vaddr = VADDR;
+	ph.p_paddr = 0;
+	ph.p_filesz = sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len;
+	ph.p_memsz = sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len;
+	ph.p_align = 4096;
+
+	fd = openat(AT_FDCWD, "/tmp", O_WRONLY|O_EXCL|O_TMPFILE, 0700);
+	if (fd == -1) {
+		exit(1);
+	}
+
+	if (writev(fd, iov, 3) != sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len) {
+		exit(1);
+	}
+
+	/* Avoid ETXTBSY on exec. */
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%u", fd);
+	fd1 = open(buf, O_RDONLY|O_CLOEXEC);
+	close(fd);
+
+	return fd1;
+}
+#endif
+
+/*
+ * 0: vsyscall VMA doesn't exist	vsyscall=none
+ * 1: vsyscall VMA is --xp		vsyscall=xonly
+ * 2: vsyscall VMA is r-xp		vsyscall=emulate
+ */
+static volatile int g_vsyscall;
+static const char *str_vsyscall;
+
+static const char str_vsyscall_0[] = "";
+static const char str_vsyscall_1[] =
+"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0                  [vsyscall]\n";
+static const char str_vsyscall_2[] =
+"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]\n";
+
+#ifdef __x86_64__
+static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
+{
+	_exit(g_vsyscall);
+}
+
+/*
+ * vsyscall page can't be unmapped, probe it directly.
+ */
+static void vsyscall(void)
+{
+	pid_t pid;
+	int wstatus;
+
+	pid = fork();
+	if (pid < 0) {
+		fprintf(stderr, "fork, errno %d\n", errno);
+		exit(1);
+	}
+	if (pid == 0) {
+		struct rlimit rlim = {0, 0};
+		(void)setrlimit(RLIMIT_CORE, &rlim);
+
+		/* Hide "segfault at ffffffffff600000" messages. */
+		struct sigaction act;
+		memset(&act, 0, sizeof(struct sigaction));
+		act.sa_flags = SA_SIGINFO;
+		act.sa_sigaction = sigaction_SIGSEGV;
+		(void)sigaction(SIGSEGV, &act, NULL);
+
+		g_vsyscall = 0;
+		/* gettimeofday(NULL, NULL); */
+		uint64_t rax = 0xffffffffff600000;
+		asm volatile (
+			"call *%[rax]"
+			: [rax] "+a" (rax)
+			: "D" (NULL), "S" (NULL)
+			: "rcx", "r11"
+		);
+
+		g_vsyscall = 1;
+		*(volatile int *)0xffffffffff600000UL;
+
+		g_vsyscall = 2;
+		exit(g_vsyscall);
+	}
+	waitpid(pid, &wstatus, 0);
+	if (WIFEXITED(wstatus)) {
+		g_vsyscall = WEXITSTATUS(wstatus);
+	} else {
+		fprintf(stderr, "error: wstatus %08x\n", wstatus);
+		exit(1);
+	}
+}
+
+int main(void)
+{
+	int pipefd[2];
+	int exec_fd;
+
+	vsyscall();
+	switch (g_vsyscall) {
+	case 0:
+		str_vsyscall = str_vsyscall_0;
+		break;
+	case 1:
+		str_vsyscall = str_vsyscall_1;
+		break;
+	case 2:
+		str_vsyscall = str_vsyscall_2;
+		break;
+	default:
+		abort();
+	}
+
+	atexit(ate);
+
+	make_private_tmp();
+
+	/* Reserve fd 0 for 1-byte pipe ping from child. */
+	close(0);
+	if (open("/", O_RDONLY|O_DIRECTORY|O_PATH) != 0) {
+		return 1;
+	}
+
+	exec_fd = make_exe(payload, sizeof(payload));
+
+	if (pipe(pipefd) == -1) {
+		return 1;
+	}
+	if (dup2(pipefd[1], 0) != 0) {
+		return 1;
+	}
+
+	pid = fork();
+	if (pid == -1) {
+		return 1;
+	}
+	if (pid == 0) {
+		sys_execveat(exec_fd, "", NULL, NULL, AT_EMPTY_PATH);
+		return 1;
+	}
+
+	char _;
+	if (read(pipefd[0], &_, 1) != 1) {
+		return 1;
+	}
+
+	struct stat st;
+	if (fstat(exec_fd, &st) == -1) {
+		return 1;
+	}
+
+	/* Generate "head -n1 /proc/$PID/maps" */
+	char buf0[256];
+	memset(buf0, ' ', sizeof(buf0));
+	int len = snprintf(buf0, sizeof(buf0),
+			"%08lx-%08lx r-xp 00000000 %02lx:%02lx %llu",
+			VADDR, VADDR + PAGE_SIZE,
+			MAJOR(st.st_dev), MINOR(st.st_dev),
+			(unsigned long long)st.st_ino);
+	buf0[len] = ' ';
+	snprintf(buf0 + MAPS_OFFSET, sizeof(buf0) - MAPS_OFFSET,
+		 "/tmp/#%llu (deleted)\n", (unsigned long long)st.st_ino);
+
+	/* Test /proc/$PID/maps */
+	{
+		const size_t len = strlen(buf0) + strlen(str_vsyscall);
+		char buf[256];
+		ssize_t rv;
+		int fd;
+
+		snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
+		fd = open(buf, O_RDONLY);
+		if (fd == -1) {
+			return 1;
+		}
+		rv = read(fd, buf, sizeof(buf));
+		assert(rv == len);
+		assert(memcmp(buf, buf0, strlen(buf0)) == 0);
+		if (g_vsyscall > 0) {
+			assert(memcmp(buf + strlen(buf0), str_vsyscall, strlen(str_vsyscall)) == 0);
+		}
+	}
+
+	/* Test /proc/$PID/smaps */
+	{
+		char buf[4096];
+		ssize_t rv;
+		int fd;
+
+		snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
+		fd = open(buf, O_RDONLY);
+		if (fd == -1) {
+			return 1;
+		}
+		rv = read(fd, buf, sizeof(buf));
+		assert(0 <= rv && rv <= sizeof(buf));
+
+		assert(rv >= strlen(buf0));
+		assert(memcmp(buf, buf0, strlen(buf0)) == 0);
+
+#define RSS1 "Rss:                   4 kB\n"
+#define RSS2 "Rss:                   0 kB\n"
+#define PSS1 "Pss:                   4 kB\n"
+#define PSS2 "Pss:                   0 kB\n"
+		assert(memmem(buf, rv, RSS1, strlen(RSS1)) ||
+		       memmem(buf, rv, RSS2, strlen(RSS2)));
+		assert(memmem(buf, rv, PSS1, strlen(PSS1)) ||
+		       memmem(buf, rv, PSS2, strlen(PSS2)));
+
+		static const char *S[] = {
+			"Size:                  4 kB\n",
+			"KernelPageSize:        4 kB\n",
+			"MMUPageSize:           4 kB\n",
+			"Anonymous:             0 kB\n",
+			"AnonHugePages:         0 kB\n",
+			"Shared_Hugetlb:        0 kB\n",
+			"Private_Hugetlb:       0 kB\n",
+			"Locked:                0 kB\n",
+		};
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(S); i++) {
+			assert(memmem(buf, rv, S[i], strlen(S[i])));
+		}
+
+		if (g_vsyscall > 0) {
+			assert(memmem(buf, rv, str_vsyscall, strlen(str_vsyscall)));
+		}
+	}
+
+	/* Test /proc/$PID/smaps_rollup */
+	{
+		char bufr[256];
+		memset(bufr, ' ', sizeof(bufr));
+		len = snprintf(bufr, sizeof(bufr),
+				"%08lx-%08lx ---p 00000000 00:00 0",
+				VADDR, VADDR + PAGE_SIZE);
+		bufr[len] = ' ';
+		snprintf(bufr + MAPS_OFFSET, sizeof(bufr) - MAPS_OFFSET,
+			 "[rollup]\n");
+
+		char buf[1024];
+		ssize_t rv;
+		int fd;
+
+		snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
+		fd = open(buf, O_RDONLY);
+		if (fd == -1) {
+			return 1;
+		}
+		rv = read(fd, buf, sizeof(buf));
+		assert(0 <= rv && rv <= sizeof(buf));
+
+		assert(rv >= strlen(bufr));
+		assert(memcmp(buf, bufr, strlen(bufr)) == 0);
+
+		assert(memmem(buf, rv, RSS1, strlen(RSS1)) ||
+		       memmem(buf, rv, RSS2, strlen(RSS2)));
+		assert(memmem(buf, rv, PSS1, strlen(PSS1)) ||
+		       memmem(buf, rv, PSS2, strlen(PSS2)));
+
+		static const char *S[] = {
+			"Anonymous:             0 kB\n",
+			"AnonHugePages:         0 kB\n",
+			"Shared_Hugetlb:        0 kB\n",
+			"Private_Hugetlb:       0 kB\n",
+			"Locked:                0 kB\n",
+		};
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(S); i++) {
+			assert(memmem(buf, rv, S[i], strlen(S[i])));
+		}
+	}
+
+	/* Test /proc/$PID/statm */
+	{
+		char buf[64];
+		ssize_t rv;
+		int fd;
+
+		snprintf(buf, sizeof(buf), "/proc/%u/statm", pid);
+		fd = open(buf, O_RDONLY);
+		if (fd == -1) {
+			return 1;
+		}
+		rv = read(fd, buf, sizeof(buf));
+		assert(rv == 7 * 2);
+
+		assert(buf[0] == '1');	/* ->total_vm */
+		assert(buf[1] == ' ');
+		assert(buf[2] == '0' || buf[2] == '1');	/* rss */
+		assert(buf[3] == ' ');
+		assert(buf[4] == '0' || buf[2] == '1');	/* file rss */
+		assert(buf[5] == ' ');
+		assert(buf[6] == '1');	/* ELF executable segments */
+		assert(buf[7] == ' ');
+		assert(buf[8] == '0');
+		assert(buf[9] == ' ');
+		assert(buf[10] == '0');	/* ->data_vm + ->stack_vm */
+		assert(buf[11] == ' ');
+		assert(buf[12] == '0');
+		assert(buf[13] == '\n');
+	}
+
+	return 0;
+}
+#else
+int main(void)
+{
+	return 4;
+}
+#endif
diff --git a/tools/testing/selftests/proc/proc-self-map-files-001.c b/tools/testing/selftests/proc/proc-self-map-files-001.c
new file mode 100644
index 000000000..4209c6428
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-self-map-files-001.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* Test readlink /proc/self/map_files/... */
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <stdlib.h>
+
+static void pass(const char *fmt, unsigned long a, unsigned long b)
+{
+	char name[64];
+	char buf[64];
+
+	snprintf(name, sizeof(name), fmt, a, b);
+	if (readlink(name, buf, sizeof(buf)) == -1)
+		exit(1);
+}
+
+static void fail(const char *fmt, unsigned long a, unsigned long b)
+{
+	char name[64];
+	char buf[64];
+
+	snprintf(name, sizeof(name), fmt, a, b);
+	if (readlink(name, buf, sizeof(buf)) == -1 && errno == ENOENT)
+		return;
+	exit(1);
+}
+
+int main(void)
+{
+	const unsigned int PAGE_SIZE = sysconf(_SC_PAGESIZE);
+	void *p;
+	int fd;
+	unsigned long a, b;
+
+	fd = open("/dev/zero", O_RDONLY);
+	if (fd == -1)
+		return 1;
+
+	p = mmap(NULL, PAGE_SIZE, PROT_NONE, MAP_PRIVATE|MAP_FILE, fd, 0);
+	if (p == MAP_FAILED)
+		return 1;
+
+	a = (unsigned long)p;
+	b = (unsigned long)p + PAGE_SIZE;
+
+	pass("/proc/self/map_files/%lx-%lx", a, b);
+	fail("/proc/self/map_files/ %lx-%lx", a, b);
+	fail("/proc/self/map_files/%lx -%lx", a, b);
+	fail("/proc/self/map_files/%lx- %lx", a, b);
+	fail("/proc/self/map_files/%lx-%lx ", a, b);
+	fail("/proc/self/map_files/0%lx-%lx", a, b);
+	fail("/proc/self/map_files/%lx-0%lx", a, b);
+	if (sizeof(long) == 4) {
+		fail("/proc/self/map_files/100000000%lx-%lx", a, b);
+		fail("/proc/self/map_files/%lx-100000000%lx", a, b);
+	} else if (sizeof(long) == 8) {
+		fail("/proc/self/map_files/10000000000000000%lx-%lx", a, b);
+		fail("/proc/self/map_files/%lx-10000000000000000%lx", a, b);
+	} else
+		return 1;
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-self-map-files-002.c b/tools/testing/selftests/proc/proc-self-map-files-002.c
new file mode 100644
index 000000000..e6aa00a18
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-self-map-files-002.c
@@ -0,0 +1,94 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* Test readlink /proc/self/map_files/... with minimum address. */
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <stdlib.h>
+
+static void pass(const char *fmt, unsigned long a, unsigned long b)
+{
+	char name[64];
+	char buf[64];
+
+	snprintf(name, sizeof(name), fmt, a, b);
+	if (readlink(name, buf, sizeof(buf)) == -1)
+		exit(1);
+}
+
+static void fail(const char *fmt, unsigned long a, unsigned long b)
+{
+	char name[64];
+	char buf[64];
+
+	snprintf(name, sizeof(name), fmt, a, b);
+	if (readlink(name, buf, sizeof(buf)) == -1 && errno == ENOENT)
+		return;
+	exit(1);
+}
+
+int main(void)
+{
+	const int PAGE_SIZE = sysconf(_SC_PAGESIZE);
+	/*
+	 * va_max must be enough bigger than vm.mmap_min_addr, which is
+	 * 64KB/32KB by default. (depends on CONFIG_LSM_MMAP_MIN_ADDR)
+	 */
+	const unsigned long va_max = 1UL << 20;
+	unsigned long va;
+	void *p;
+	int fd;
+	unsigned long a, b;
+
+	fd = open("/dev/zero", O_RDONLY);
+	if (fd == -1)
+		return 1;
+
+	for (va = 0; va < va_max; va += PAGE_SIZE) {
+		p = mmap((void *)va, PAGE_SIZE, PROT_NONE, MAP_PRIVATE|MAP_FILE|MAP_FIXED, fd, 0);
+		if (p == (void *)va)
+			break;
+	}
+	if (va == va_max) {
+		fprintf(stderr, "error: mmap doesn't like you\n");
+		return 1;
+	}
+
+	a = (unsigned long)p;
+	b = (unsigned long)p + PAGE_SIZE;
+
+	pass("/proc/self/map_files/%lx-%lx", a, b);
+	fail("/proc/self/map_files/ %lx-%lx", a, b);
+	fail("/proc/self/map_files/%lx -%lx", a, b);
+	fail("/proc/self/map_files/%lx- %lx", a, b);
+	fail("/proc/self/map_files/%lx-%lx ", a, b);
+	fail("/proc/self/map_files/0%lx-%lx", a, b);
+	fail("/proc/self/map_files/%lx-0%lx", a, b);
+	if (sizeof(long) == 4) {
+		fail("/proc/self/map_files/100000000%lx-%lx", a, b);
+		fail("/proc/self/map_files/%lx-100000000%lx", a, b);
+	} else if (sizeof(long) == 8) {
+		fail("/proc/self/map_files/10000000000000000%lx-%lx", a, b);
+		fail("/proc/self/map_files/%lx-10000000000000000%lx", a, b);
+	} else
+		return 1;
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-self-syscall.c b/tools/testing/selftests/proc/proc-self-syscall.c
new file mode 100644
index 000000000..8511dcfe6
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-self-syscall.c
@@ -0,0 +1,58 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+
+static inline ssize_t sys_read(int fd, void *buf, size_t len)
+{
+	return syscall(SYS_read, fd, buf, len);
+}
+
+int main(void)
+{
+	char buf1[64];
+	char buf2[64];
+	int fd;
+	ssize_t rv;
+
+	fd = open("/proc/self/syscall", O_RDONLY);
+	if (fd == -1) {
+		if (errno == ENOENT)
+			return 4;
+		return 1;
+	}
+
+	/* Do direct system call as libc can wrap anything. */
+	snprintf(buf1, sizeof(buf1), "%ld 0x%lx 0x%lx 0x%lx",
+		 (long)SYS_read, (long)fd, (long)buf2, (long)sizeof(buf2));
+
+	memset(buf2, 0, sizeof(buf2));
+	rv = sys_read(fd, buf2, sizeof(buf2));
+	if (rv < 0)
+		return 1;
+	if (rv < strlen(buf1))
+		return 1;
+	if (strncmp(buf1, buf2, strlen(buf1)) != 0)
+		return 1;
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-self-wchan.c b/tools/testing/selftests/proc/proc-self-wchan.c
new file mode 100644
index 000000000..b467b98a4
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-self-wchan.c
@@ -0,0 +1,40 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+
+int main(void)
+{
+	char buf[64];
+	int fd;
+
+	fd = open("/proc/self/wchan", O_RDONLY);
+	if (fd == -1) {
+		if (errno == ENOENT)
+			return 4;
+		return 1;
+	}
+
+	buf[0] = '\0';
+	if (read(fd, buf, sizeof(buf)) != 1)
+		return 1;
+	if (buf[0] != '0')
+		return 1;
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-subset-pid.c b/tools/testing/selftests/proc/proc-subset-pid.c
new file mode 100644
index 000000000..d1052bcab
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-subset-pid.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2021 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Test that "mount -t proc -o subset=pid" hides everything but pids,
+ * /proc/self and /proc/thread-self.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <stdio.h>
+
+static inline bool streq(const char *a, const char *b)
+{
+	return strcmp(a, b) == 0;
+}
+
+static void make_private_proc(void)
+{
+	if (unshare(CLONE_NEWNS) == -1) {
+		if (errno == ENOSYS || errno == EPERM) {
+			exit(4);
+		}
+		exit(1);
+	}
+	if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
+		exit(1);
+	}
+	if (mount(NULL, "/proc", "proc", 0, "subset=pid") == -1) {
+		exit(1);
+	}
+}
+
+static bool string_is_pid(const char *s)
+{
+	while (1) {
+		switch (*s++) {
+		case '0':case '1':case '2':case '3':case '4':
+		case '5':case '6':case '7':case '8':case '9':
+			continue;
+
+		case '\0':
+			return true;
+
+		default:
+			return false;
+		}
+	}
+}
+
+int main(void)
+{
+	make_private_proc();
+
+	DIR *d = opendir("/proc");
+	assert(d);
+
+	struct dirent *de;
+
+	bool dot = false;
+	bool dot_dot = false;
+	bool self = false;
+	bool thread_self = false;
+
+	while ((de = readdir(d))) {
+		if (streq(de->d_name, ".")) {
+			assert(!dot);
+			dot = true;
+			assert(de->d_type == DT_DIR);
+		} else if (streq(de->d_name, "..")) {
+			assert(!dot_dot);
+			dot_dot = true;
+			assert(de->d_type == DT_DIR);
+		} else if (streq(de->d_name, "self")) {
+			assert(!self);
+			self = true;
+			assert(de->d_type == DT_LNK);
+		} else if (streq(de->d_name, "thread-self")) {
+			assert(!thread_self);
+			thread_self = true;
+			assert(de->d_type == DT_LNK);
+		} else {
+			if (!string_is_pid(de->d_name)) {
+				fprintf(stderr, "d_name '%s'\n", de->d_name);
+				assert(0);
+			}
+			assert(de->d_type == DT_DIR);
+		}
+	}
+
+	char c;
+	int rv = readlink("/proc/cpuinfo", &c, 1);
+	assert(rv == -1 && errno == ENOENT);
+
+	int fd = open("/proc/cpuinfo", O_RDONLY);
+	assert(fd == -1 && errno == ENOENT);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-tid0.c b/tools/testing/selftests/proc/proc-tid0.c
new file mode 100644
index 000000000..58c1d7c90
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-tid0.c
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2021 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that /proc/*/task never contains "0".
+#include <sys/types.h>
+#include <dirent.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <pthread.h>
+
+static pid_t pid = -1;
+
+static void atexit_hook(void)
+{
+	if (pid > 0) {
+		kill(pid, SIGKILL);
+	}
+}
+
+static void *f(void *_)
+{
+	return NULL;
+}
+
+static void sigalrm(int _)
+{
+	exit(0);
+}
+
+int main(void)
+{
+	pid = fork();
+	if (pid == 0) {
+		/* child */
+		while (1) {
+			pthread_t pth;
+			pthread_create(&pth, NULL, f, NULL);
+			pthread_join(pth, NULL);
+		}
+	} else if (pid > 0) {
+		/* parent */
+		atexit(atexit_hook);
+
+		char buf[64];
+		snprintf(buf, sizeof(buf), "/proc/%u/task", pid);
+
+		signal(SIGALRM, sigalrm);
+		alarm(1);
+
+		while (1) {
+			DIR *d = opendir(buf);
+			struct dirent *de;
+			while ((de = readdir(d))) {
+				if (strcmp(de->d_name, "0") == 0) {
+					exit(1);
+				}
+			}
+			closedir(d);
+		}
+
+		return 0;
+	} else {
+		perror("fork");
+		return 1;
+	}
+}
diff --git a/tools/testing/selftests/proc/proc-uptime-001.c b/tools/testing/selftests/proc/proc-uptime-001.c
new file mode 100644
index 000000000..781f7a50f
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-uptime-001.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that values in /proc/uptime increment monotonically.
+#undef NDEBUG
+#include <assert.h>
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "proc-uptime.h"
+
+int main(void)
+{
+	uint64_t start, u0, u1, i0, i1;
+	int fd;
+
+	fd = open("/proc/uptime", O_RDONLY);
+	assert(fd >= 0);
+
+	proc_uptime(fd, &u0, &i0);
+	start = u0;
+	do {
+		proc_uptime(fd, &u1, &i1);
+		assert(u1 >= u0);
+		assert(i1 >= i0);
+		u0 = u1;
+		i0 = i1;
+	} while (u1 - start < 100);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-uptime-002.c b/tools/testing/selftests/proc/proc-uptime-002.c
new file mode 100644
index 000000000..7d0aa22bd
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-uptime-002.c
@@ -0,0 +1,79 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that values in /proc/uptime increment monotonically
+// while shifting across CPUs.
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "proc-uptime.h"
+
+static inline int sys_sched_getaffinity(pid_t pid, unsigned int len, unsigned long *m)
+{
+	return syscall(SYS_sched_getaffinity, pid, len, m);
+}
+
+static inline int sys_sched_setaffinity(pid_t pid, unsigned int len, unsigned long *m)
+{
+	return syscall(SYS_sched_setaffinity, pid, len, m);
+}
+
+int main(void)
+{
+	unsigned int len;
+	unsigned long *m;
+	unsigned int cpu;
+	uint64_t u0, u1, i0, i1;
+	int fd;
+
+	/* find out "nr_cpu_ids" */
+	m = NULL;
+	len = 0;
+	do {
+		len += sizeof(unsigned long);
+		free(m);
+		m = malloc(len);
+	} while (sys_sched_getaffinity(0, len, m) == -1 && errno == EINVAL);
+
+	fd = open("/proc/uptime", O_RDONLY);
+	assert(fd >= 0);
+
+	proc_uptime(fd, &u0, &i0);
+	for (cpu = 0; cpu < len * 8; cpu++) {
+		memset(m, 0, len);
+		m[cpu / (8 * sizeof(unsigned long))] |= 1UL << (cpu % (8 * sizeof(unsigned long)));
+
+		/* CPU might not exist, ignore error */
+		sys_sched_setaffinity(0, len, m);
+
+		proc_uptime(fd, &u1, &i1);
+		assert(u1 >= u0);
+		assert(i1 >= i0);
+		u0 = u1;
+		i0 = i1;
+	}
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/proc-uptime.h b/tools/testing/selftests/proc/proc-uptime.h
new file mode 100644
index 000000000..dc6a42b1d
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-uptime.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "proc.h"
+
+static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
+{
+	uint64_t val1, val2;
+	char buf[64], *p;
+	ssize_t rv;
+
+	/* save "p < end" checks */
+	memset(buf, 0, sizeof(buf));
+	rv = pread(fd, buf, sizeof(buf), 0);
+	assert(0 <= rv && rv <= sizeof(buf));
+	buf[sizeof(buf) - 1] = '\0';
+
+	p = buf;
+
+	val1 = xstrtoull(p, &p);
+	assert(p[0] == '.');
+	assert('0' <= p[1] && p[1] <= '9');
+	assert('0' <= p[2] && p[2] <= '9');
+	assert(p[3] == ' ');
+
+	val2 = (p[1] - '0') * 10 + p[2] - '0';
+	*uptime = val1 * 100 + val2;
+
+	p += 4;
+
+	val1 = xstrtoull(p, &p);
+	assert(p[0] == '.');
+	assert('0' <= p[1] && p[1] <= '9');
+	assert('0' <= p[2] && p[2] <= '9');
+	assert(p[3] == '\n');
+
+	val2 = (p[1] - '0') * 10 + p[2] - '0';
+	*idle = val1 * 100 + val2;
+
+	assert(p + 4 == buf + rv);
+}
diff --git a/tools/testing/selftests/proc/proc.h b/tools/testing/selftests/proc/proc.h
new file mode 100644
index 000000000..b7d57ea40
--- /dev/null
+++ b/tools/testing/selftests/proc/proc.h
@@ -0,0 +1,51 @@
+#pragma once
+#undef NDEBUG
+#include <assert.h>
+#include <dirent.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+
+static inline pid_t sys_getpid(void)
+{
+	return syscall(SYS_getpid);
+}
+
+static inline pid_t sys_gettid(void)
+{
+	return syscall(SYS_gettid);
+}
+
+static inline bool streq(const char *s1, const char *s2)
+{
+	return strcmp(s1, s2) == 0;
+}
+
+static unsigned long long xstrtoull(const char *p, char **end)
+{
+	if (*p == '0') {
+		*end = (char *)p + 1;
+		return 0;
+	} else if ('1' <= *p && *p <= '9') {
+		unsigned long long val;
+
+		errno = 0;
+		val = strtoull(p, end, 10);
+		assert(errno == 0);
+		return val;
+	} else
+		assert(0);
+}
+
+static struct dirent *xreaddir(DIR *d)
+{
+	struct dirent *de;
+
+	errno = 0;
+	de = readdir(d);
+	assert(de || errno == 0);
+	return de;
+}
diff --git a/tools/testing/selftests/proc/read.c b/tools/testing/selftests/proc/read.c
new file mode 100644
index 000000000..35ee78dff
--- /dev/null
+++ b/tools/testing/selftests/proc/read.c
@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test
+// 1) read and lseek on every file in /proc
+// 2) readlink of every symlink in /proc
+// 3) recursively (1) + (2) for every directory in /proc
+// 4) write to /proc/*/clear_refs and /proc/*/task/*/clear_refs
+// 5) write to /proc/sysrq-trigger
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/vfs.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "proc.h"
+
+static void f_reg(DIR *d, const char *filename)
+{
+	char buf[4096];
+	int fd;
+	ssize_t rv;
+
+	/* read from /proc/kmsg can block */
+	fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
+	if (fd == -1)
+		return;
+	/* struct proc_ops::proc_lseek is mandatory if file is seekable. */
+	(void)lseek(fd, 0, SEEK_SET);
+	rv = read(fd, buf, sizeof(buf));
+	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
+	close(fd);
+}
+
+static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
+{
+	int fd;
+	ssize_t rv;
+
+	fd = openat(dirfd(d), filename, O_WRONLY);
+	if (fd == -1)
+		return;
+	rv = write(fd, buf, len);
+	assert((0 <= rv && rv <= len) || rv == -1);
+	close(fd);
+}
+
+static void f_lnk(DIR *d, const char *filename)
+{
+	char buf[4096];
+	ssize_t rv;
+
+	rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
+	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
+}
+
+static void f(DIR *d, unsigned int level)
+{
+	struct dirent *de;
+
+	de = xreaddir(d);
+	assert(de->d_type == DT_DIR);
+	assert(streq(de->d_name, "."));
+
+	de = xreaddir(d);
+	assert(de->d_type == DT_DIR);
+	assert(streq(de->d_name, ".."));
+
+	while ((de = xreaddir(d))) {
+		assert(!streq(de->d_name, "."));
+		assert(!streq(de->d_name, ".."));
+
+		switch (de->d_type) {
+			DIR *dd;
+			int fd;
+
+		case DT_REG:
+			if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
+				f_reg_write(d, de->d_name, "h", 1);
+			} else if (level == 1 && streq(de->d_name, "clear_refs")) {
+				f_reg_write(d, de->d_name, "1", 1);
+			} else if (level == 3 && streq(de->d_name, "clear_refs")) {
+				f_reg_write(d, de->d_name, "1", 1);
+			} else {
+				f_reg(d, de->d_name);
+			}
+			break;
+		case DT_DIR:
+			fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
+			if (fd == -1)
+				continue;
+			dd = fdopendir(fd);
+			if (!dd)
+				continue;
+			f(dd, level + 1);
+			closedir(dd);
+			break;
+		case DT_LNK:
+			f_lnk(d, de->d_name);
+			break;
+		default:
+			assert(0);
+		}
+	}
+}
+
+int main(void)
+{
+	DIR *d;
+	struct statfs sfs;
+
+	d = opendir("/proc");
+	if (!d)
+		return 4;
+
+	/* Ensure /proc is proc. */
+	if (fstatfs(dirfd(d), &sfs) == -1) {
+		return 1;
+	}
+	if (sfs.f_type != 0x9fa0) {
+		fprintf(stderr, "error: unexpected f_type %lx\n", (long)sfs.f_type);
+		return 2;
+	}
+
+	f(d, 0);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/self.c b/tools/testing/selftests/proc/self.c
new file mode 100644
index 000000000..21c15a1ff
--- /dev/null
+++ b/tools/testing/selftests/proc/self.c
@@ -0,0 +1,39 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that /proc/self gives correct TGID.
+#undef NDEBUG
+#include <assert.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "proc.h"
+
+int main(void)
+{
+	char buf1[64], buf2[64];
+	pid_t pid;
+	ssize_t rv;
+
+	pid = sys_getpid();
+	snprintf(buf1, sizeof(buf1), "%u", pid);
+
+	rv = readlink("/proc/self", buf2, sizeof(buf2));
+	assert(rv == strlen(buf1));
+	buf2[rv] = '\0';
+	assert(streq(buf1, buf2));
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/setns-dcache.c b/tools/testing/selftests/proc/setns-dcache.c
new file mode 100644
index 000000000..60ab197a7
--- /dev/null
+++ b/tools/testing/selftests/proc/setns-dcache.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright © 2019 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Test that setns(CLONE_NEWNET) points to new /proc/net content even
+ * if old one is in dcache.
+ *
+ * FIXME /proc/net/unix is under CONFIG_UNIX which can be disabled.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+
+static pid_t pid = -1;
+
+static void f(void)
+{
+	if (pid > 0) {
+		kill(pid, SIGTERM);
+	}
+}
+
+int main(void)
+{
+	int fd[2];
+	char _ = 0;
+	int nsfd;
+
+	atexit(f);
+
+	/* Check for priviledges and syscall availability straight away. */
+	if (unshare(CLONE_NEWNET) == -1) {
+		if (errno == ENOSYS || errno == EPERM) {
+			return 4;
+		}
+		return 1;
+	}
+	/* Distinguisher between two otherwise empty net namespaces. */
+	if (socket(AF_UNIX, SOCK_STREAM, 0) == -1) {
+		return 1;
+	}
+
+	if (pipe(fd) == -1) {
+		return 1;
+	}
+
+	pid = fork();
+	if (pid == -1) {
+		return 1;
+	}
+
+	if (pid == 0) {
+		if (unshare(CLONE_NEWNET) == -1) {
+			return 1;
+		}
+
+		if (write(fd[1], &_, 1) != 1) {
+			return 1;
+		}
+
+		pause();
+
+		return 0;
+	}
+
+	if (read(fd[0], &_, 1) != 1) {
+		return 1;
+	}
+
+	{
+		char buf[64];
+		snprintf(buf, sizeof(buf), "/proc/%u/ns/net", pid);
+		nsfd = open(buf, O_RDONLY);
+		if (nsfd == -1) {
+			return 1;
+		}
+	}
+
+	/* Reliably pin dentry into dcache. */
+	(void)open("/proc/net/unix", O_RDONLY);
+
+	if (setns(nsfd, CLONE_NEWNET) == -1) {
+		return 1;
+	}
+
+	kill(pid, SIGTERM);
+	pid = 0;
+
+	{
+		char buf[4096];
+		ssize_t rv;
+		int fd;
+
+		fd = open("/proc/net/unix", O_RDONLY);
+		if (fd == -1) {
+			return 1;
+		}
+
+#define S "Num       RefCount Protocol Flags    Type St Inode Path\n"
+		rv = read(fd, buf, sizeof(buf));
+
+		assert(rv == strlen(S));
+		assert(memcmp(buf, S, strlen(S)) == 0);
+	}
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/setns-sysvipc.c b/tools/testing/selftests/proc/setns-sysvipc.c
new file mode 100644
index 000000000..903890c5e
--- /dev/null
+++ b/tools/testing/selftests/proc/setns-sysvipc.c
@@ -0,0 +1,133 @@
+/*
+ * Copyright © 2019 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Test that setns(CLONE_NEWIPC) points to new /proc/sysvipc content even
+ * if old one is in dcache.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+
+static pid_t pid = -1;
+
+static void f(void)
+{
+	if (pid > 0) {
+		kill(pid, SIGTERM);
+	}
+}
+
+int main(void)
+{
+	int fd[2];
+	char _ = 0;
+	int nsfd;
+
+	atexit(f);
+
+	/* Check for priviledges and syscall availability straight away. */
+	if (unshare(CLONE_NEWIPC) == -1) {
+		if (errno == ENOSYS || errno == EPERM) {
+			return 4;
+		}
+		return 1;
+	}
+	/* Distinguisher between two otherwise empty IPC namespaces. */
+	if (shmget(IPC_PRIVATE, 1, IPC_CREAT) == -1) {
+		return 1;
+	}
+
+	if (pipe(fd) == -1) {
+		return 1;
+	}
+
+	pid = fork();
+	if (pid == -1) {
+		return 1;
+	}
+
+	if (pid == 0) {
+		if (unshare(CLONE_NEWIPC) == -1) {
+			return 1;
+		}
+
+		if (write(fd[1], &_, 1) != 1) {
+			return 1;
+		}
+
+		pause();
+
+		return 0;
+	}
+
+	if (read(fd[0], &_, 1) != 1) {
+		return 1;
+	}
+
+	{
+		char buf[64];
+		snprintf(buf, sizeof(buf), "/proc/%u/ns/ipc", pid);
+		nsfd = open(buf, O_RDONLY);
+		if (nsfd == -1) {
+			return 1;
+		}
+	}
+
+	/* Reliably pin dentry into dcache. */
+	(void)open("/proc/sysvipc/shm", O_RDONLY);
+
+	if (setns(nsfd, CLONE_NEWIPC) == -1) {
+		return 1;
+	}
+
+	kill(pid, SIGTERM);
+	pid = 0;
+
+	{
+		char buf[4096];
+		ssize_t rv;
+		int fd;
+
+		fd = open("/proc/sysvipc/shm", O_RDONLY);
+		if (fd == -1) {
+			return 1;
+		}
+
+#define S32 "       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime        rss       swap\n"
+#define S64 "       key      shmid perms                  size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime                   rss                  swap\n"
+		rv = read(fd, buf, sizeof(buf));
+		if (rv == strlen(S32)) {
+			assert(memcmp(buf, S32, strlen(S32)) == 0);
+		} else if (rv == strlen(S64)) {
+			assert(memcmp(buf, S64, strlen(S64)) == 0);
+		} else {
+			assert(0);
+		}
+	}
+
+	return 0;
+}
diff --git a/tools/testing/selftests/proc/thread-self.c b/tools/testing/selftests/proc/thread-self.c
new file mode 100644
index 000000000..4b23b39b7
--- /dev/null
+++ b/tools/testing/selftests/proc/thread-self.c
@@ -0,0 +1,64 @@
+/*
+ * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+// Test that /proc/thread-self gives correct TGID/PID.
+#undef NDEBUG
+#include <assert.h>
+#include <sched.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+
+#include "proc.h"
+
+int f(void *arg)
+{
+	char buf1[64], buf2[64];
+	pid_t pid, tid;
+	ssize_t rv;
+
+	pid = sys_getpid();
+	tid = sys_gettid();
+	snprintf(buf1, sizeof(buf1), "%u/task/%u", pid, tid);
+
+	rv = readlink("/proc/thread-self", buf2, sizeof(buf2));
+	assert(rv == strlen(buf1));
+	buf2[rv] = '\0';
+	assert(streq(buf1, buf2));
+
+	if (arg)
+		exit(0);
+	return 0;
+}
+
+int main(void)
+{
+	const int PAGE_SIZE = sysconf(_SC_PAGESIZE);
+	pid_t pid;
+	void *stack;
+
+	/* main thread */
+	f((void *)0);
+
+	stack = mmap(NULL, 2 * PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+	assert(stack != MAP_FAILED);
+	/* side thread */
+	pid = clone(f, stack + PAGE_SIZE, CLONE_THREAD|CLONE_SIGHAND|CLONE_VM, (void *)1);
+	assert(pid > 0);
+	pause();
+
+	return 0;
+}