[PATCH 3/3] selftests/livepatch: Test of the API for specifying functions to search for on a stack

Miroslav Benes
2021-11-19T09:03:35Z

Add a test for the API which allows the user to specify functions which
are then searched for on any tasks's stack during a transition process.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
---
lib/Kconfig.debug | 1 +
lib/livepatch/Makefile | 4 +-
lib/livepatch/test_klp_funcstack_demo.c | 61 +++++++++++++
lib/livepatch/test_klp_funcstack_mod.c | 72 +++++++++++++++
tools/testing/selftests/livepatch/Makefile | 3 +-
.../selftests/livepatch/test-func-stack.sh | 88 +++++++++++++++++++
6 files changed, 227 insertions(+), 2 deletions(-)
create mode 100644 lib/livepatch/test_klp_funcstack_demo.c
create mode 100644 lib/livepatch/test_klp_funcstack_mod.c
create mode 100755 tools/testing/selftests/livepatch/test-func-stack.sh

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ef7ce18b4f5..aa4c97098f41 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2529,6 +2529,7 @@ config TEST_LIVEPATCH
default n
depends on DYNAMIC_DEBUG
depends on LIVEPATCH
+ depends on DEBUG_FS
depends on m
help
Test kernel livepatching features for correctness. The tests will
diff --git a/lib/livepatch/Makefile b/lib/livepatch/Makefile
index dcc912b3478f..584e3b8b5415 100644
--- a/lib/livepatch/Makefile
+++ b/lib/livepatch/Makefile
@@ -11,4 +11,6 @@ obj-$(CONFIG_TEST_LIVEPATCH) += test_klp_atomic_replace.o \
test_klp_shadow_vars.o \
test_klp_state.o \
test_klp_state2.o \
- test_klp_state3.o
+ test_klp_state3.o \
+ test_klp_funcstack_mod.o \
+ test_klp_funcstack_demo.o
diff --git a/lib/livepatch/test_klp_funcstack_demo.c b/lib/livepatch/test_klp_funcstack_demo.c
new file mode 100644
index 000000000000..902798077f05
--- /dev/null
+++ b/lib/livepatch/test_klp_funcstack_demo.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2021 Miroslav Benes <mbenes@suse.cz>
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/livepatch.h>
+
+static int funcstack;
+module_param(funcstack, int, 0644);
+MODULE_PARM_DESC(funcstack, "func_stack (default=0)");
+
+static noinline void livepatch_child2_function(void)
+{
+ pr_info("%s\n", __func__);
+}
+
+static struct klp_func funcs[] = {
+ {
+ .old_name = "child2_function",
+ .new_func = livepatch_child2_function,
+ }, {}
+};
+
+static struct klp_func funcs_stack[] = {
+ {
+ .old_name = "parent_function",
+ }, {}
+};
+
+static struct klp_object objs[] = {
+ {
+ .name = "test_klp_funcstack_mod",
+ .funcs = funcs,
+ }, {}
+};
+
+static struct klp_patch patch = {
+ .mod = THIS_MODULE,
+ .objs = objs,
+};
+
+static int test_klp_funcstack_demo_init(void)
+{
+ if (funcstack)
+ objs[0].funcs_stack = funcs_stack;
+
+ return klp_enable_patch(&patch);
+}
+
+static void test_klp_funcstack_demo_exit(void)
+{
+}
+
+module_init(test_klp_funcstack_demo_init);
+module_exit(test_klp_funcstack_demo_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");
+MODULE_AUTHOR("Miroslav Benes <mbenes@suse.cz>");
+MODULE_DESCRIPTION("Livepatch test: func_stack demo");
diff --git a/lib/livepatch/test_klp_funcstack_mod.c b/lib/livepatch/test_klp_funcstack_mod.c
new file mode 100644
index 000000000000..127c6093d890
--- /dev/null
+++ b/lib/livepatch/test_klp_funcstack_mod.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2021 Miroslav Benes <mbenes@suse.cz>
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+
+static int sleep_length = 10000;
+module_param(sleep_length, int, 0644);
+MODULE_PARM_DESC(sleep_length, "length of sleep in seconds (default=10)");
+
+static noinline void child_function(void)
+{
+ pr_info("%s enter\n", __func__);
+ msleep(sleep_length);
+ pr_info("%s exit\n", __func__);
+}
+
+static noinline void child2_function(void)
+{
+ pr_info("%s\n", __func__);
+}
+
+static noinline void parent_function(void)
+{
+ pr_info("%s enter\n", __func__);
+ child_function();
+ child2_function();
+ pr_info("%s exit\n", __func__);
+}
+
+static int parent_function_get(void *data, u64 *val)
+{
+ *val = 0;
+ parent_function();
+
+ return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(fops_parent_function, parent_function_get, NULL, "%llu\n");
+
+static struct dentry *debugfs_dir;
+
+static int test_klp_funcstack_mod_init(void)
+{
+ struct dentry *d;
+
+ debugfs_dir = debugfs_create_dir("test_klp_funcstack", NULL);
+ if (IS_ERR(debugfs_dir))
+ return PTR_ERR(debugfs_dir);
+
+ d = debugfs_create_file("parent_function", 0400, debugfs_dir, NULL,
+ &fops_parent_function);
+ if (IS_ERR(d))
+ debugfs_remove_recursive(debugfs_dir);
+
+ return 0;
+}
+
+static void test_klp_funcstack_mod_exit(void)
+{
+ debugfs_remove_recursive(debugfs_dir);
+}
+
+module_init(test_klp_funcstack_mod_init);
+module_exit(test_klp_funcstack_mod_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Miroslav Benes <mbenes@suse.cz>");
+MODULE_DESCRIPTION("Livepatch test: func_stack module");
diff --git a/tools/testing/selftests/livepatch/Makefile b/tools/testing/selftests/livepatch/Makefile
index 1acc9e1fa3fb..40f8a3a2e9aa 100644
--- a/tools/testing/selftests/livepatch/Makefile
+++ b/tools/testing/selftests/livepatch/Makefile
@@ -6,7 +6,8 @@ TEST_PROGS := \
test-callbacks.sh \
test-shadow-vars.sh \
test-state.sh \
- test-ftrace.sh
+ test-ftrace.sh \
+ test-func-stack.sh

TEST_FILES := settings

diff --git a/tools/testing/selftests/livepatch/test-func-stack.sh b/tools/testing/selftests/livepatch/test-func-stack.sh
new file mode 100755
index 000000000000..b7da62c9f5a1
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test-func-stack.sh
@@ -0,0 +1,88 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 Miroslav Benes <mbenes@suse.cz>
+
+. $(dirname $0)/functions.sh
+
+MOD_TARGET=test_klp_funcstack_mod
+MOD_LIVEPATCH=test_klp_funcstack_demo
+
+setup_config
+
+# - load a target module and call its parent_function(). It will sleep in its
+# child_function() callee.
+# - load a live patch with new child2_function() called from parent_function()
+# too. The patching does not wait for child_function() to return, because
+# child2_function() is not on any stack.
+# - clean up afterwards
+
+start_test "non-blocking patching without the function on a stack"
+
+load_mod $MOD_TARGET
+
+(cat /sys/kernel/debug/test_klp_funcstack/parent_function) >/dev/null &
+PID=$!
+
+load_lp $MOD_LIVEPATCH
+
+wait $PID
+
+disable_lp $MOD_LIVEPATCH
+unload_lp $MOD_LIVEPATCH
+unload_mod $MOD_TARGET
+
+check_result "% modprobe $MOD_TARGET
+$MOD_TARGET: parent_function enter
+$MOD_TARGET: child_function enter
+% modprobe $MOD_LIVEPATCH
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: '$MOD_LIVEPATCH': starting patching transition
+livepatch: '$MOD_LIVEPATCH': completing patching transition
+livepatch: '$MOD_LIVEPATCH': patching complete
+$MOD_TARGET: child_function exit
+$MOD_LIVEPATCH: livepatch_child2_function
+$MOD_TARGET: parent_function exit
+% echo 0 > /sys/kernel/livepatch/$MOD_LIVEPATCH/enabled
+livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
+livepatch: '$MOD_LIVEPATCH': starting unpatching transition
+livepatch: '$MOD_LIVEPATCH': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH': unpatching complete
+% rmmod $MOD_LIVEPATCH
+% rmmod $MOD_TARGET"
+
+# Similar to the previous test but now the patching has to wait for
+# child2_function() to return, because parent_function() is also checked for.
+
+start_test "patching delayed due to the function on a stack"
+
+load_mod $MOD_TARGET
+
+(cat /sys/kernel/debug/test_klp_funcstack/parent_function) >/dev/null &
+
+load_lp $MOD_LIVEPATCH funcstack=1
+disable_lp $MOD_LIVEPATCH
+unload_lp $MOD_LIVEPATCH
+unload_mod $MOD_TARGET
+
+check_result "% modprobe $MOD_TARGET
+$MOD_TARGET: parent_function enter
+$MOD_TARGET: child_function enter
+% modprobe $MOD_LIVEPATCH funcstack=1
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: '$MOD_LIVEPATCH': starting patching transition
+$MOD_TARGET: child_function exit
+$MOD_TARGET: child2_function
+$MOD_TARGET: parent_function exit
+livepatch: '$MOD_LIVEPATCH': completing patching transition
+livepatch: '$MOD_LIVEPATCH': patching complete
+% echo 0 > /sys/kernel/livepatch/$MOD_LIVEPATCH/enabled
+livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
+livepatch: '$MOD_LIVEPATCH': starting unpatching transition
+livepatch: '$MOD_LIVEPATCH': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH': unpatching complete
+% rmmod $MOD_LIVEPATCH
+% rmmod $MOD_TARGET"
+
+exit 0
--
2.33.1