Livepatching changes for 6.14

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Merge tag 'livepatching-for-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching

Pull livepatching updates from Petr Mladek:

 - Add a sysfs attribute showing the livepatch ordering

 - Some code clean up

* tag 'livepatching-for-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
  selftests: livepatch: add test cases of stack_order sysfs interface
  livepatch: Add stack_order sysfs attribute
  selftests/livepatch: Replace hardcoded module name with variable in test-callbacks.sh

Documentation/ABI/testing/sysfs-kernel-livepatch

@@ -55,6 +55,15 @@ Description:
 		An attribute which indicates whether the patch supports
 		atomic-replace.
 
+What:		/sys/kernel/livepatch/<patch>/stack_order
+Date:		Jan 2025
+KernelVersion:	6.14.0
+Description:
+		This attribute specifies the sequence in which live patch modules
+		are applied to the system. If multiple live patches modify the same
+		function, the implementation with the biggest 'stack_order' number
+		is used, unless a transition is currently in progress.
+
 What:		/sys/kernel/livepatch/<patch>/<object>
 Date:		Nov 2014
 KernelVersion:	3.19.0

kernel/livepatch/core.c

@@ -347,6 +347,7 @@ 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>/replace
+ * /sys/kernel/livepatch/<patch>/stack_order
  * /sys/kernel/livepatch/<patch>/<object>
  * /sys/kernel/livepatch/<patch>/<object>/patched
  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
@@ -452,15 +453,38 @@ static ssize_t replace_show(struct kobject *kobj,
 	return sysfs_emit(buf, "%d\n", patch->replace);
 }
 
+static ssize_t stack_order_show(struct kobject *kobj,
+				struct kobj_attribute *attr, char *buf)
+{
+	struct klp_patch *patch, *this_patch;
+	int stack_order = 0;
+
+	this_patch = container_of(kobj, struct klp_patch, kobj);
+
+	mutex_lock(&klp_mutex);
+
+	klp_for_each_patch(patch) {
+		stack_order++;
+		if (patch == this_patch)
+			break;
+	}
+
+	mutex_unlock(&klp_mutex);
+
+	return sysfs_emit(buf, "%d\n", stack_order);
+}
+
 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
 static struct kobj_attribute replace_kobj_attr = __ATTR_RO(replace);
+static struct kobj_attribute stack_order_kobj_attr = __ATTR_RO(stack_order);
 static struct attribute *klp_patch_attrs[] = {
 	&enabled_kobj_attr.attr,
 	&transition_kobj_attr.attr,
 	&force_kobj_attr.attr,
 	&replace_kobj_attr.attr,
+	&stack_order_kobj_attr.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(klp_patch);

tools/testing/selftests/livepatch/test-callbacks.sh

@@ -259,7 +259,7 @@ $MOD_TARGET: ${MOD_TARGET}_init
 % insmod test_modules/$MOD_LIVEPATCH.ko pre_patch_ret=-19
 livepatch: enabling patch '$MOD_LIVEPATCH'
 livepatch: '$MOD_LIVEPATCH': initializing patching transition
-test_klp_callbacks_demo: pre_patch_callback: vmlinux
+$MOD_LIVEPATCH: pre_patch_callback: vmlinux
 livepatch: pre-patch callback failed for object 'vmlinux'
 livepatch: failed to enable patch '$MOD_LIVEPATCH'
 livepatch: '$MOD_LIVEPATCH': canceling patching transition, going to unpatch

tools/testing/selftests/livepatch/test-sysfs.sh

@@ -5,6 +5,8 @@
 . $(dirname $0)/functions.sh
 
 MOD_LIVEPATCH=test_klp_livepatch
+MOD_LIVEPATCH2=test_klp_callbacks_demo
+MOD_LIVEPATCH3=test_klp_syscall
 
 setup_config
 
@@ -19,6 +21,8 @@ check_sysfs_rights "$MOD_LIVEPATCH" "enabled" "-rw-r--r--"
 check_sysfs_value  "$MOD_LIVEPATCH" "enabled" "1"
 check_sysfs_rights "$MOD_LIVEPATCH" "force" "--w-------"
 check_sysfs_rights "$MOD_LIVEPATCH" "replace" "-r--r--r--"
+check_sysfs_rights "$MOD_LIVEPATCH" "stack_order" "-r--r--r--"
+check_sysfs_value  "$MOD_LIVEPATCH" "stack_order" "1"
 check_sysfs_rights "$MOD_LIVEPATCH" "transition" "-r--r--r--"
 check_sysfs_value  "$MOD_LIVEPATCH" "transition" "0"
 check_sysfs_rights "$MOD_LIVEPATCH" "vmlinux/patched" "-r--r--r--"
@@ -131,4 +135,71 @@ livepatch: '$MOD_LIVEPATCH': completing unpatching transition
 livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
+start_test "sysfs test stack_order value"
+
+load_lp $MOD_LIVEPATCH
+
+check_sysfs_value  "$MOD_LIVEPATCH" "stack_order" "1"
+
+load_lp $MOD_LIVEPATCH2
+
+check_sysfs_value  "$MOD_LIVEPATCH2" "stack_order" "2"
+
+load_lp $MOD_LIVEPATCH3
+
+check_sysfs_value  "$MOD_LIVEPATCH3" "stack_order" "3"
+
+disable_lp $MOD_LIVEPATCH2
+unload_lp $MOD_LIVEPATCH2
+
+check_sysfs_value  "$MOD_LIVEPATCH" "stack_order" "1"
+check_sysfs_value  "$MOD_LIVEPATCH3" "stack_order" "2"
+
+disable_lp $MOD_LIVEPATCH3
+unload_lp $MOD_LIVEPATCH3
+
+disable_lp $MOD_LIVEPATCH
+unload_lp $MOD_LIVEPATCH
+
+check_result "% insmod test_modules/$MOD_LIVEPATCH.ko
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: '$MOD_LIVEPATCH': starting patching transition
+livepatch: '$MOD_LIVEPATCH': completing patching transition
+livepatch: '$MOD_LIVEPATCH': patching complete
+% insmod test_modules/$MOD_LIVEPATCH2.ko
+livepatch: enabling patch '$MOD_LIVEPATCH2'
+livepatch: '$MOD_LIVEPATCH2': initializing patching transition
+$MOD_LIVEPATCH2: pre_patch_callback: vmlinux
+livepatch: '$MOD_LIVEPATCH2': starting patching transition
+livepatch: '$MOD_LIVEPATCH2': completing patching transition
+$MOD_LIVEPATCH2: post_patch_callback: vmlinux
+livepatch: '$MOD_LIVEPATCH2': patching complete
+% insmod test_modules/$MOD_LIVEPATCH3.ko
+livepatch: enabling patch '$MOD_LIVEPATCH3'
+livepatch: '$MOD_LIVEPATCH3': initializing patching transition
+livepatch: '$MOD_LIVEPATCH3': starting patching transition
+livepatch: '$MOD_LIVEPATCH3': completing patching transition
+livepatch: '$MOD_LIVEPATCH3': patching complete
+% echo 0 > $SYSFS_KLP_DIR/$MOD_LIVEPATCH2/enabled
+livepatch: '$MOD_LIVEPATCH2': initializing unpatching transition
+$MOD_LIVEPATCH2: pre_unpatch_callback: vmlinux
+livepatch: '$MOD_LIVEPATCH2': starting unpatching transition
+livepatch: '$MOD_LIVEPATCH2': completing unpatching transition
+$MOD_LIVEPATCH2: post_unpatch_callback: vmlinux
+livepatch: '$MOD_LIVEPATCH2': unpatching complete
+% rmmod $MOD_LIVEPATCH2
+% echo 0 > $SYSFS_KLP_DIR/$MOD_LIVEPATCH3/enabled
+livepatch: '$MOD_LIVEPATCH3': initializing unpatching transition
+livepatch: '$MOD_LIVEPATCH3': starting unpatching transition
+livepatch: '$MOD_LIVEPATCH3': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH3': unpatching complete
+% rmmod $MOD_LIVEPATCH3
+% echo 0 > $SYSFS_KLP_DIR/$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"
+
 exit 0