add sysfs entry "patched" for each klp_object

I was debugging an issue that a livepatch appears to be attached, but actually not. It turns out that there is a mismatch in module name (abc-xyz vs. abc_xyz), klp_find_object_module failed to find the module. Add a sysfs entry for each klp_object, so that it is easier to debug such issues.

Changes v2 => v3:
1. Improve selftest. (Petr Mladek and Joe Lawrence)

Changes v1 => v2:
1. Add selftest. (Petr Mladek)
2. Update documentation. (Petr Mladek)
3. Use sysfs_emit. (Petr Mladek)

Song Liu (2):
livepatch: add sysfs entry "patched" for each klp_object selftests/livepatch: add sysfs test

 .../ABI/testing/sysfs-kernel-livepatch        |  8 ++
 kernel/livepatch/core.c                       | 18 ++++
 tools/testing/selftests/livepatch/Makefile    |  3 +-
 .../testing/selftests/livepatch/functions.sh  | 34 ++++++++
 .../testing/selftests/livepatch/test-sysfs.sh | 86 +++++++++++++++++++
 5 files changed, 148 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/livepatch/test-sysfs.sh

--
2.30.2

Add per klp_object sysfs entry "patched". It makes it easier to debug typos in the module name.

---
I was debugging an issue that a livepatch appears to be attached, but actually not. It turns out that there is a mismatch in module name (abc-xyz vs. abc_xyz), klp_find_object_module failed to find the module.

---
 .../ABI/testing/sysfs-kernel-livepatch         |  8 ++++++++
 kernel/livepatch/core.c                        | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

index bea7bd5a1d5f..ebe39a3cea39 100644
@@ -55,6 +55,14 @@ Description:
 		The object directory contains subdirectories for each function
 		that is patched within the object.
 
+What:		/sys/kernel/livepatch/<patch>/<object>/patched
+Date:		August 2022
+KernelVersion:	6.0.0
+Contact:	[email protected]
+Description:
+		An attribute which indicates whether the object is currently
+		patched.
+
 What:		/sys/kernel/livepatch/<patch>/<object>/<function,sympos>
 Date:		Nov 2014
 KernelVersion:	3.19.0

index bc475e62279d..67eb9f9168f3 100644
@@ -325,6 +325,7 @@ int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
  * /sys/kernel/livepatch/<patch>/transition
  * /sys/kernel/livepatch/<patch>/force
  * /sys/kernel/livepatch/<patch>/<object>
+ * /sys/kernel/livepatch/<patch>/<object>/patched
  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
  */
 static int __klp_disable_patch(struct klp_patch *patch);

@@ -431,6 +432,22 @@ static struct attribute *klp_patch_attrs[] = {
 };
 ATTRIBUTE_GROUPS(klp_patch);
 
+static ssize_t patched_show(struct kobject *kobj,
+			    struct kobj_attribute *attr, char *buf)
+{
+	struct klp_object *obj;
+
+	obj = container_of(kobj, struct klp_object, kobj);
+	return sysfs_emit(buf, "%d\n", obj->patched);
+}
+
+static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
+static struct attribute *klp_object_attrs[] = {
+	&patched_kobj_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(klp_object);
+
 static void klp_free_object_dynamic(struct klp_object *obj)
 {
 	kfree(obj->name);

@@ -576,6 +593,7 @@ static void klp_kobj_release_object(struct kobject *kobj)
 static struct kobj_type klp_ktype_object = {
 	.release = klp_kobj_release_object,
 	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = klp_object_groups,
 };
 
 static void klp_kobj_release_func(struct kobject *kobj)

2.30.2

Just a note. Signed-off-by of the author is always the first entry. It is followed by Acked-by, Reviewed-by, Tested-by, ... in the order in which they arrived.

I have fixed the ordering when pushing the patch.

Add a test for livepatch sysfs entries.

---
 tools/testing/selftests/livepatch/Makefile    |  3 +-
 .../testing/selftests/livepatch/functions.sh  | 34 ++++++++
 .../testing/selftests/livepatch/test-sysfs.sh | 86 +++++++++++++++++++
 3 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/livepatch/test-sysfs.sh

index 1acc9e1fa3fb..02fadc9d55e0 100644
@@ -6,7 +6,8 @@ TEST_PROGS := \
 	test-callbacks.sh \
 	test-shadow-vars.sh \
 	test-state.sh \
-	test-ftrace.sh
+	test-ftrace.sh \
+	test-sysfs.sh
 
 TEST_FILES := settings
 

index 9230b869371d..433e23dd9dcb 100644
@@ -6,6 +6,7 @@
 
 MAX_RETRIES=600
 RETRY_INTERVAL=".1"	# seconds
+KLP_SYSFS_DIR="/sys/kernel/livepatch"
 
 # Kselftest framework requirement - SKIP code is 4
 ksft_skip=4

@@ -308,3 +309,36 @@ function check_result {
 
 	cleanup_dmesg_file
 }
+
+# check_sysfs_rights(modname, rel_path, expected_rights) - check sysfs
+# path permissions
+#	modname - livepatch module creating the sysfs interface
+#	rel_path - relative path of the sysfs interface
+#	expected_rights - expected access rights
+function check_sysfs_rights() {
+	local mod="$1"; shift
+	local rel_path="$1"; shift
+	local expected_rights="$1"; shift
+
+	local path="$KLP_SYSFS_DIR/$mod/$rel_path"
+	local rights=$(/bin/stat --format '%A' "$path")
+	if test "$rights" != "$expected_rights" ; then
+		die "Unexpected access rights of $path: $expected_rights vs. $rights"
+	fi
+}
+
+# check_sysfs_value(modname, rel_path, expected_value) - check sysfs value
+#	modname - livepatch module creating the sysfs interface
+#	rel_path - relative path of the sysfs interface
+#	expected_value - expected value read from the file
+function check_sysfs_value() {
+	local mod="$1"; shift
+	local rel_path="$1"; shift
+	local expected_value="$1"; shift
+
+	local path="$KLP_SYSFS_DIR/$mod/$rel_path"
+	local value=`cat $path`
+	if test "$value" != "$expected_value" ; then
+		die "Unexpected value in $path: $expected_value vs. $value"
+	fi
+}

2.30.2

For both patches:

And I have pushed the patchset into livepatching.git, for-6.1/sysfs-patched-object.

Best Regards,
Petr