[PATCH v2 2/2] selftests: livepatch: Test livepatching a heavily called syscall

[Marcos Paulo de Souza <mpdesouza@suse.com>]

Syscalls are called a tricky way. Some architectures add a prefix to the
syscall name (SYSCALL_WRAPPER).

This new test creates one userspace process per online cpu calling getpid
continuously and tries to livepatch the getpid function. Add the correct
function prefix for all archs that select HAS_SYSCALL_WRAPPER.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
 tools/testing/selftests/livepatch/Makefile    |  12 +-
 .../selftests/livepatch/test-syscall.sh       |  52 ++++++
 .../test_binaries/test_klp-call_getpid.c      |  48 ++++++
 .../selftests/livepatch/test_modules/Makefile |   3 +-
 .../livepatch/test_modules/test_klp_syscall.c | 150 ++++++++++++++++++
 5 files changed, 261 insertions(+), 4 deletions(-)
 create mode 100755 tools/testing/selftests/livepatch/test-syscall.sh
 create mode 100644 tools/testing/selftests/livepatch/test_binaries/test_klp-call_getpid.c
 create mode 100644 tools/testing/selftests/livepatch/test_modules/test_klp_syscall.c

diff --git a/tools/testing/selftests/livepatch/Makefile b/tools/testing/selftests/livepatch/Makefile
index 5ef492b87bb1..35014197184e 100644
--- a/tools/testing/selftests/livepatch/Makefile
+++ b/tools/testing/selftests/livepatch/Makefile
@@ -1,10 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0
+include ../../../build/Build.include
+include ../../../scripts/Makefile.arch
+include ../../../scripts/Makefile.include
 
 TEST_FILES := settings \
 		test_modules
 
 # We need the test_modules dir in order to make gen_tar and install to work
-TEST_GEN_PROGS_EXTENDED := test_modules/test_klp_atomic_replace.ko \
+TEST_GEN_PROGS_EXTENDED := test_binaries/test_klp-call_getpid \
+			test_modules/test_klp_atomic_replace.ko \
 			test_modules/test_klp_callbacks_busy.ko \
 			test_modules/test_klp_callbacks_demo.ko \
 			test_modules/test_klp_callbacks_demo2.ko \
@@ -13,7 +17,8 @@ TEST_GEN_PROGS_EXTENDED := test_modules/test_klp_atomic_replace.ko \
 			test_modules/test_klp_state.ko \
 			test_modules/test_klp_state2.ko \
 			test_modules/test_klp_state3.ko \
-			test_modules/test_klp_shadow_vars.ko
+			test_modules/test_klp_shadow_vars.ko \
+			test_modules/test_klp_syscall.ko
 
 TEST_PROGS_EXTENDED := functions.sh
 TEST_PROGS := \
@@ -21,7 +26,8 @@ TEST_PROGS := \
 	test-callbacks.sh \
 	test-shadow-vars.sh \
 	test-state.sh \
-	test-ftrace.sh
+	test-ftrace.sh \
+	test-syscall.sh
 
 # override lib.mk's default rules
 OVERRIDE_TARGETS := 1
diff --git a/tools/testing/selftests/livepatch/test-syscall.sh b/tools/testing/selftests/livepatch/test-syscall.sh
new file mode 100755
index 000000000000..fb3270de7f1f
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test-syscall.sh
@@ -0,0 +1,52 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022 SUSE
+# Author: Marcos Paulo de Souza <mpdesouza@suse.com>
+
+. $(dirname $0)/functions.sh
+
+MOD_SYSCALL=test_klp_syscall
+
+setup_config
+
+# - Start _NRPROC processes calling getpid and load a livepatch to patch the
+#   getpid syscall
+
+start_test "patch getpid syscall while being heavily hammered"
+
+for i in $(seq 0 $(( $(getconf _NPROCESSORS_ONLN) -1)) ); do
+	./test_binaries/test_klp-call_getpid &
+	pids[$i]="$!"
+done
+
+pid_list=$(echo ${pids[@]} | tr ' ' ',')
+load_lp $MOD_SYSCALL klp_pids=$pid_list
+
+pending_pids=$(cat /sys/kernel/test_klp_syscall/npids)
+
+for pid in ${pids[@]}; do
+	kill $pid || true
+done
+
+disable_lp $MOD_SYSCALL
+unload_lp $MOD_SYSCALL
+
+if [[ "$pending_pids" != "0" ]]; then
+	echo -e "FAIL\n\n"
+	die "processes not livepatched: $pending_pids"
+fi
+
+check_result "% insmod test_modules/$MOD_SYSCALL.ko klp_pids=$pid_list
+livepatch: enabling patch '$MOD_SYSCALL'
+livepatch: '$MOD_SYSCALL': initializing patching transition
+livepatch: '$MOD_SYSCALL': starting patching transition
+livepatch: '$MOD_SYSCALL': completing patching transition
+livepatch: '$MOD_SYSCALL': patching complete
+% echo 0 > /sys/kernel/livepatch/$MOD_SYSCALL/enabled
+livepatch: '$MOD_SYSCALL': initializing unpatching transition
+livepatch: '$MOD_SYSCALL': starting unpatching transition
+livepatch: '$MOD_SYSCALL': completing unpatching transition
+livepatch: '$MOD_SYSCALL': unpatching complete
+% rmmod $MOD_SYSCALL"
+
+exit 0
diff --git a/tools/testing/selftests/livepatch/test_binaries/test_klp-call_getpid.c b/tools/testing/selftests/livepatch/test_binaries/test_klp-call_getpid.c
new file mode 100644
index 000000000000..ec470660dee6
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test_binaries/test_klp-call_getpid.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 SUSE
+ * Author: Libor Pechacek <lpechacek@suse.cz>
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <signal.h>
+
+static int stop = 0;
+static int sig_int;
+
+void hup_handler(int signum)
+{
+	stop = 1;
+}
+
+void int_handler(int signum)
+{
+	stop = 1;
+	sig_int = 1;
+}
+
+int main(int argc, char *argv[])
+{
+	pid_t orig_pid, pid;
+	long count = 0;
+
+	signal(SIGHUP, &hup_handler);
+	signal(SIGINT, &int_handler);
+
+	orig_pid = syscall(SYS_getpid);
+
+	while (!stop) {
+		pid = syscall(SYS_getpid);
+		if (pid != orig_pid)
+			return 1;
+		count++;
+	}
+
+	if (sig_int)
+		printf("%ld iterations done\n", count);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/livepatch/test_modules/Makefile b/tools/testing/selftests/livepatch/test_modules/Makefile
index 1eab43b741cd..ebb754accf46 100644
--- a/tools/testing/selftests/livepatch/test_modules/Makefile
+++ b/tools/testing/selftests/livepatch/test_modules/Makefile
@@ -10,7 +10,8 @@ obj-m += test_klp_atomic_replace.o \
 	test_klp_state.o \
 	test_klp_state2.o \
 	test_klp_state3.o \
-	test_klp_shadow_vars.o
+	test_klp_shadow_vars.o \
+	test_klp_syscall.o
 
 %.ko:
 	make -C $(KDIR) M=$(TESTMODS_DIR) $@
diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_syscall.c b/tools/testing/selftests/livepatch/test_modules/test_klp_syscall.c
new file mode 100644
index 000000000000..e90f4ac8e7a4
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test_modules/test_klp_syscall.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017-2022 SUSE
+ * Authors: Libor Pechacek <lpechacek@suse.cz>
+ *          Nicolai Stange <nstange@suse.de>
+ *          Marcos Paulo de Souza <mpdesouza@suse.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/livepatch.h>
+
+#if defined(__x86_64__)
+#define FN_PREFIX __x64_
+#elif defined(__s390x__)
+#define FN_PREFIX __s390x_
+#elif defined(__aarch64__)
+#define FN_PREFIX __arm64_
+#else
+/* powerpc does not select ARCH_HAS_SYSCALL_WRAPPER */
+#define FN_PREFIX
+#endif
+
+struct klp_pid_t {
+	pid_t pid;
+	struct list_head list;
+};
+static LIST_HEAD(klp_pid_list);
+
+/* Protects klp_pid_list */
+static DEFINE_MUTEX(kpid_mutex);
+
+static int klp_pids[NR_CPUS];
+static unsigned int npids;
+module_param_array(klp_pids, int, &npids, 0);
+
+static ssize_t npids_show(struct kobject *kobj, struct kobj_attribute *attr,
+			  char *buf)
+{
+	return sprintf(buf, "%u\n", npids);
+}
+
+static struct kobj_attribute klp_attr = __ATTR_RO(npids);
+static struct kobject *klp_kobj;
+
+static void free_klp_pid_list(void)
+{
+	struct klp_pid_t *kpid, *temp;
+
+	mutex_lock(&kpid_mutex);
+	list_for_each_entry_safe(kpid, temp, &klp_pid_list, list) {
+		list_del(&kpid->list);
+		kfree(kpid);
+	}
+	mutex_unlock(&kpid_mutex);
+}
+
+asmlinkage long lp_sys_getpid(void)
+{
+	struct klp_pid_t *kpid, *temp;
+
+	/*
+	 * For each thread calling getpid, check if the pid exists in
+	 * klp_pid_list. If yes, decrement the npids variable and remove the pid
+	 * from the list. npids will be later used to ensure that all pids
+	 * transitioned to the liveaptched state.
+	 */
+	mutex_lock(&kpid_mutex);
+	list_for_each_entry_safe(kpid, temp, &klp_pid_list, list) {
+		if (current->pid == kpid->pid) {
+			list_del(&kpid->list);
+			kfree(kpid);
+			npids--;
+			break;
+		}
+	}
+	mutex_unlock(&kpid_mutex);
+
+	return task_tgid_vnr(current);
+}
+
+static struct klp_func vmlinux_funcs[] = {
+	{
+		.old_name = __stringify(FN_PREFIX) "sys_getpid",
+		.new_func = lp_sys_getpid,
+	}, {}
+};
+
+static struct klp_object objs[] = {
+	{
+		/* name being NULL means vmlinux */
+		.funcs = vmlinux_funcs,
+	}, {}
+};
+
+static struct klp_patch patch = {
+	.mod = THIS_MODULE,
+	.objs = objs,
+};
+
+static int livepatch_init(void)
+{
+	int ret;
+	struct klp_pid_t *kpid;
+
+	if (npids > 0) {
+		int i;
+
+		for (i = 0; i < npids; i++) {
+			kpid = kmalloc(sizeof(struct klp_pid_t), GFP_KERNEL);
+			if (!kpid)
+				goto err_mem;
+
+			kpid->pid = klp_pids[i];
+			list_add(&kpid->list, &klp_pid_list);
+		}
+	}
+
+	klp_kobj = kobject_create_and_add("test_klp_syscall", kernel_kobj);
+	if (!klp_kobj)
+		goto err_mem;
+
+	ret = sysfs_create_file(klp_kobj, &klp_attr.attr);
+	if (ret) {
+		kobject_put(klp_kobj);
+		goto out_klp_pid_list;
+	}
+
+	return klp_enable_patch(&patch);
+
+err_mem:
+	ret = -ENOMEM;
+out_klp_pid_list:
+	free_klp_pid_list();
+
+	return ret;
+}
+
+static void livepatch_exit(void)
+{
+	free_klp_pid_list();
+	kobject_put(klp_kobj);
+}
+
+module_init(livepatch_init);
+module_exit(livepatch_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");
-- 
2.35.3