pkey: add test for memory protection keys

Memory Protection Keys for Userspace (PKU aka PKEYs) is a Skylake-SP
server feature that provides a mechanism for enforcing page-based
protections, but without requiring modification of the page tables
when an application changes protection domains. It works by dedicating
4 previously ignored bits in each page table entry to a "protection key",
giving 16 possible keys.

Basic method for PKEYs test:
  1. test allocates a pkey(e.g. PKEY_DISABLE_ACCESS) via pkey_alloc()
  2. pkey_mprotect() apply this pkey to a piece of memory buffer
  3. check if the access right of buffer has been changed and take effect
  4. remove the access right(pkey) from this buffer via pkey_mprotect()
  5. check if buffer area can be read or write after removing pkey
  6. pkey_free() releases the pkey after using it

Looping around this basic test on diffenrent types of memory.

Signed-off-by: Li Wang <liwang@redhat.com>
Acked-by: Jan Stancek <jstancek@redhat.com>
Acked-by: Cyril Hrubis <chrubis@suse.cz>

configure.ac

@@ -76,6 +76,7 @@ AC_CHECK_FUNCS([ \
     pidfd_send_signal \
     preadv \
     preadv2 \
+    pkey_mprotect \
     profil \
     pwritev \
     pwritev2 \

runtest/syscalls

@@ -722,6 +722,8 @@ mprotect02 mprotect02
 mprotect03 mprotect03
 mprotect04 mprotect04
 
+pkey01 pkey01
+
 mq_notify01 mq_notify01
 mq_notify02 mq_notify02
 mq_open01 mq_open01

testcases/kernel/syscalls/pkeys/.gitignore

@@ -0,0 +1 @@
+/pkey01

testcases/kernel/syscalls/pkeys/Makefile

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Copyright (c) 2019 Red Hat, Inc.
+
+top_srcdir		?= ../../../..
+
+include $(top_srcdir)/include/mk/testcases.mk
+
+include $(top_srcdir)/include/mk/generic_leaf_target.mk

testcases/kernel/syscalls/pkeys/pkey.h

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2019 Red Hat, Inc.
+ */
+
+#ifndef PKEYS_H
+#define PKEYS_H
+
+#include "tst_test.h"
+#include "lapi/syscalls.h"
+
+#ifndef PKEY_DISABLE_ACCESS
+# define PKEY_DISABLE_ACCESS 0x1
+# define PKEY_DISABLE_WRITE  0x2
+#endif
+
+#ifndef HAVE_PKEY_MPROTECT
+static inline int pkey_mprotect(void *addr, size_t len, int prot, int pkey)
+{
+	return tst_syscall(__NR_pkey_mprotect, addr, len, prot, pkey);
+}
+
+static inline int pkey_alloc(unsigned int flags, unsigned int access_rights)
+{
+	return tst_syscall(__NR_pkey_alloc, flags, access_rights);
+}
+
+static inline int pkey_free(int pkey)
+{
+	return tst_syscall(__NR_pkey_free, pkey);
+}
+#endif /* HAVE_PKEY_MPROTECT */
+
+static inline void check_pkey_support(void)
+{
+	int pkey = pkey_alloc(0, 0);
+
+	if (pkey == -1) {
+		if (errno == ENOSYS)
+			tst_brk(TCONF, "pkey_alloc is not implemented");
+		if (errno == EINVAL)
+			tst_brk(TCONF, "pku is not supported on this CPU");
+		if (errno == ENOSPC)
+			tst_brk(TCONF, "pkeys are not available for test");
+	}
+
+	pkey_free(pkey);
+}
+
+#endif /* PKEYS_H */

testcases/kernel/syscalls/pkeys/pkey01.c

@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2019 Red Hat, Inc.
+ *
+ * Memory Protection Keys for Userspace (PKU aka PKEYs) is a Skylake-SP
+ * server feature that provides a mechanism for enforcing page-based
+ * protections, but without requiring modification of the page tables
+ * when an application changes protection domains. It works by dedicating
+ * 4 previously ignored bits in each page table entry to a "protection key",
+ * giving 16 possible keys.
+ *
+ * Basic method for PKEYs testing:
+ *    1. test allocates a pkey(e.g. PKEY_DISABLE_ACCESS) via pkey_alloc()
+ *    2. pkey_mprotect() apply this pkey to a piece of memory(buffer)
+ *    3. check if access right of the buffer has been changed and take effect
+ *    4. remove the access right(pkey) from this buffer via pkey_mprotect()
+ *    5. check if buffer area can be read or write after removing pkey
+ *    6. pkey_free() releases the pkey after using it
+ *
+ * Looping around this basic test on diffenrent types of memory.
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+
+#include "pkey.h"
+
+#define TEST_FILE "pkey_testfile"
+#define STR "abcdefghijklmnopqrstuvwxyz12345\n"
+#define PATH_VM_NRHPS "/proc/sys/vm/nr_hugepages"
+
+static int size;
+static int no_hugepage;
+
+static const char * const save_restore[] = {
+	"?/proc/sys/vm/nr_hugepages",
+	NULL,
+};
+
+static struct tcase {
+	unsigned long flags;
+	unsigned long access_rights;
+	char *name;
+} tcases[] = {
+	{0, PKEY_DISABLE_ACCESS, "PKEY_DISABLE_ACCESS"},
+	{0, PKEY_DISABLE_WRITE, "PKEY_DISABLE_WRITE"},
+};
+
+static void setup(void)
+{
+	int i, fd;
+
+	if (access("/sys/kernel/mm/hugepages/", F_OK)) {
+		tst_res(TINFO, "Huge page is not supported");
+		size = getpagesize();
+		no_hugepage = 1;
+	} else {
+		int val;
+		SAFE_FILE_PRINTF(PATH_VM_NRHPS, "%d", 1);
+		SAFE_FILE_SCANF(PATH_VM_NRHPS, "%d", &val);
+		if (val != 1)
+			tst_brk(TBROK, "nr_hugepages = %d, but expect %d",
+					val, 1);
+		size = SAFE_READ_MEMINFO("Hugepagesize:") * 1024;
+	}
+
+	check_pkey_support();
+
+	fd = SAFE_OPEN(TEST_FILE, O_RDWR | O_CREAT, 0664);
+	for (i = 0; i < 128; i++)
+		SAFE_WRITE(1, fd, STR, strlen(STR));
+
+	SAFE_CLOSE(fd);
+}
+
+static struct mmap_param {
+	int prot;
+	int flags;
+	int fd;
+} mmap_params[] = {
+	{PROT_READ,  MAP_ANONYMOUS | MAP_PRIVATE, -1},
+	{PROT_READ,  MAP_ANONYMOUS | MAP_SHARED, -1},
+	{PROT_READ,  MAP_ANONYMOUS | MAP_PRIVATE | MAP_HUGETLB, -1},
+	{PROT_READ,  MAP_ANONYMOUS | MAP_SHARED  | MAP_HUGETLB, -1},
+	{PROT_READ,  MAP_PRIVATE, 0},
+	{PROT_READ,  MAP_SHARED, 0},
+
+	{PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1},
+	{PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1},
+	{PROT_WRITE, MAP_PRIVATE, 0},
+	{PROT_WRITE, MAP_SHARED, 0},
+	{PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_HUGETLB, -1},
+	{PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED  | MAP_HUGETLB, -1},
+
+	{PROT_EXEC,  MAP_ANONYMOUS | MAP_PRIVATE, -1},
+	{PROT_EXEC,  MAP_ANONYMOUS | MAP_SHARED, -1},
+	{PROT_EXEC,  MAP_ANONYMOUS | MAP_PRIVATE | MAP_HUGETLB, -1},
+	{PROT_EXEC,  MAP_ANONYMOUS | MAP_SHARED  | MAP_HUGETLB, -1},
+	{PROT_EXEC,  MAP_PRIVATE, 0},
+	{PROT_EXEC,  MAP_SHARED, 0},
+
+	{PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1},
+	{PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1},
+	{PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_HUGETLB, -1},
+	{PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED  | MAP_HUGETLB, -1},
+	{PROT_READ | PROT_WRITE, MAP_PRIVATE, 0},
+	{PROT_READ | PROT_WRITE, MAP_SHARED, 0},
+
+	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, -1},
+	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_SHARED, -1},
+	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE | MAP_HUGETLB, -1},
+	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_SHARED  | MAP_HUGETLB, -1},
+	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, 0},
+	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED, 0},
+};
+
+static char *flag_to_str(int flags)
+{
+	switch (flags) {
+	case MAP_PRIVATE:
+		return "MAP_PRIVATE";
+	case MAP_SHARED:
+		return "MAP_SHARED";
+	case MAP_ANONYMOUS | MAP_PRIVATE:
+		return "MAP_ANONYMOUS|MAP_PRIVATE";
+	case MAP_ANONYMOUS | MAP_SHARED:
+		return "MAP_ANONYMOUS|MAP_SHARED";
+	case MAP_ANONYMOUS | MAP_PRIVATE | MAP_HUGETLB:
+		return "MAP_ANONYMOUS|MAP_PRIVATE|MAP_HUGETLB";
+	case MAP_ANONYMOUS | MAP_SHARED  | MAP_HUGETLB:
+		return "MAP_ANONYMOUS|MAP_SHARED|MAP_HUGETLB";
+	default:
+		return "UNKNOWN FLAGS";
+	}
+}
+
+static void pkey_test(struct tcase *tc, struct mmap_param *mpa)
+{
+	pid_t pid;
+	char *buffer;
+	int pkey, status;
+	int fd = mpa->fd;
+
+	if (no_hugepage && (mpa->flags & MAP_HUGETLB)) {
+		tst_res(TINFO, "Skip test on (%s) buffer", flag_to_str(mpa->flags));
+		return;
+	}
+
+	if (fd == 0)
+		fd = SAFE_OPEN(TEST_FILE, O_RDWR | O_CREAT, 0664);
+
+	buffer = SAFE_MMAP(NULL, size, mpa->prot, mpa->flags, fd, 0);
+
+	pkey = pkey_alloc(tc->flags, tc->access_rights);
+	if (pkey == -1)
+		tst_brk(TBROK | TERRNO, "pkey_alloc failed");
+
+	tst_res(TINFO, "Set %s on (%s) buffer", tc->name, flag_to_str(mpa->flags));
+	if (pkey_mprotect(buffer, size, mpa->prot, pkey) == -1)
+		tst_brk(TBROK | TERRNO, "pkey_mprotect failed");
+
+	pid = SAFE_FORK();
+	if (pid == 0) {
+		tst_no_corefile(0);
+
+		switch (tc->access_rights) {
+		case PKEY_DISABLE_ACCESS:
+			tst_res(TFAIL | TERRNO,
+				"Read buffer success, buffer[0] = %d", *buffer);
+		break;
+		case PKEY_DISABLE_WRITE:
+			*buffer = 'a';
+		break;
+		}
+		exit(0);
+	}
+
+	SAFE_WAITPID(pid, &status, 0);
+
+        if (WIFSIGNALED(status) && WTERMSIG(status) == SIGSEGV)
+		tst_res(TPASS, "Child ended by %s as expected", tst_strsig(SIGSEGV));
+        else
+                tst_res(TFAIL, "Child: %s", tst_strstatus(status));
+
+	tst_res(TINFO, "Remove %s from the buffer", tc->name);
+	if (pkey_mprotect(buffer, size, mpa->prot, 0x0) == -1)
+		tst_brk(TBROK | TERRNO, "pkey_mprotect failed");
+
+	switch (mpa->prot) {
+	case PROT_READ:
+		tst_res(TPASS, "Read buffer success, buffer[0] = %d", *buffer);
+	break;
+	case PROT_WRITE:
+		*buffer = 'a';
+	break;
+	case PROT_READ | PROT_WRITE:
+	case PROT_READ | PROT_WRITE | PROT_EXEC:
+		*buffer = 'a';
+		tst_res(TPASS, "Read & Write buffer success, buffer[0] = %d", *buffer);
+	break;
+	}
+
+	if (fd >= 0)
+		SAFE_CLOSE(fd);
+
+	SAFE_MUNMAP(buffer, size);
+
+	if (pkey_free(pkey) == -1)
+		tst_brk(TBROK | TERRNO, "pkey_free failed");
+}
+
+static void verify_pkey(unsigned int i)
+{
+	long unsigned int j;
+	struct mmap_param *mpa;
+
+	struct tcase *tc = &tcases[i];
+
+	for (j = 0; j < ARRAY_SIZE(mmap_params); j++) {
+		mpa = &mmap_params[j];
+
+		pkey_test(tc, mpa);
+	}
+}
+
+static struct tst_test test = {
+	.tcnt = ARRAY_SIZE(tcases),
+	.needs_root = 1,
+	.needs_tmpdir = 1,
+	.forks_child = 1,
+	.test = verify_pkey,
+	.setup = setup,
+	.save_restore = save_restore,
+};