From 7c3f3261649236156190b097e511a83dcd62c81c Mon Sep 17 00:00:00 2001 From: Denis Aleksandrov Date: Fri, 28 Mar 2025 13:05:57 -0400 Subject: [PATCH] livepatch: Add stack_order sysfs attribute JIRA: https://issues.redhat.com/browse/RHEL-85303 Add "stack_order" sysfs attribute which holds the order in which a live patch module was loaded into the system. A user can then determine an active live patched version of a function. cat /sys/kernel/livepatch/livepatch_1/stack_order -> 1 means that livepatch_1 is the first live patch applied cat /sys/kernel/livepatch/livepatch_module/stack_order -> N means that livepatch_module is the Nth live patch applied Suggested-by: Petr Mladek Suggested-by: Miroslav Benes Suggested-by: Josh Poimboeuf Signed-off-by: Wardenjohn Acked-by: Josh Poimboeuf Reviewed-by: Petr Mladek Tested-by: Petr Mladek Reviewed-by: Miroslav Benes Link: https://lore.kernel.org/r/20241008014856.3729-2-zhangwarden@gmail.com [pmladek@suse.com: Updated kernel version and date in the ABI documentation.] Signed-off-by: Petr Mladek (cherry picked from commit 3dae09de406167123449d9ece1f51855d5bac01a) Signed-off-by: Denis Aleksandrov --- .../ABI/testing/sysfs-kernel-livepatch | 9 +++++++ kernel/livepatch/core.c | 24 +++++++++++++++++++ 2 files changed, 33 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch index 3735d868013d..3c3f36b32b57 100644 --- a/Documentation/ABI/testing/sysfs-kernel-livepatch +++ b/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//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// Date: Nov 2014 KernelVersion: 3.19.0 diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 7c851320456c..4ab342c11e17 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -358,6 +358,7 @@ int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, * /sys/kernel/livepatch//transition * /sys/kernel/livepatch//force * /sys/kernel/livepatch//replace + * /sys/kernel/livepatch//stack_order * /sys/kernel/livepatch// * /sys/kernel/livepatch///patched * /sys/kernel/livepatch/// @@ -463,15 +464,38 @@ 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);