3c33f5b99d
Add support for patching a function multiple times. If multiple patches affect a function, the function in the most recently enabled patch "wins". This enables a cumulative patch upgrade path, where each patch is a superset of previous patches. This requires restructuring the data a little bit. With the current design, where each klp_func struct has its own ftrace_ops, we'd have to unregister the old ops and then register the new ops, because FTRACE_OPS_FL_IPMODIFY prevents us from having two ops registered for the same function at the same time. That would leave a regression window where the function isn't patched at all (not good for a patch upgrade path). This patch replaces the per-klp_func ftrace_ops with a global klp_ops list, with one ftrace_ops per original function. A single ftrace_ops is shared between all klp_funcs which have the same old_addr. This allows the switch between function versions to happen instantaneously by updating the klp_ops struct's func_stack list. The winner is the klp_func at the top of the func_stack (front of the list). [ jkosina@suse.cz: turn WARN_ON() into WARN_ON_ONCE() in ftrace handler to avoid storm in pathological cases ] Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
134 lines
3.8 KiB
C
134 lines
3.8 KiB
C
/*
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* livepatch.h - Kernel Live Patching Core
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*
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* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
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* Copyright (C) 2014 SUSE
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _LINUX_LIVEPATCH_H_
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#define _LINUX_LIVEPATCH_H_
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#if IS_ENABLED(CONFIG_LIVE_PATCHING)
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#include <asm/livepatch.h>
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enum klp_state {
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KLP_DISABLED,
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KLP_ENABLED
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};
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/**
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* struct klp_func - function structure for live patching
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* @old_name: name of the function to be patched
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* @new_func: pointer to the patched function code
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* @old_addr: a hint conveying at what address the old function
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* can be found (optional, vmlinux patches only)
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* @kobj: kobject for sysfs resources
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* @state: tracks function-level patch application state
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* @stack_node: list node for klp_ops func_stack list
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*/
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struct klp_func {
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/* external */
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const char *old_name;
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void *new_func;
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/*
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* The old_addr field is optional and can be used to resolve
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* duplicate symbol names in the vmlinux object. If this
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* information is not present, the symbol is located by name
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* with kallsyms. If the name is not unique and old_addr is
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* not provided, the patch application fails as there is no
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* way to resolve the ambiguity.
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*/
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unsigned long old_addr;
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/* internal */
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struct kobject kobj;
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enum klp_state state;
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struct list_head stack_node;
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};
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/**
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* struct klp_reloc - relocation structure for live patching
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* @loc: address where the relocation will be written
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* @val: address of the referenced symbol (optional,
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* vmlinux patches only)
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* @type: ELF relocation type
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* @name: name of the referenced symbol (for lookup/verification)
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* @addend: offset from the referenced symbol
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* @external: symbol is either exported or within the live patch module itself
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*/
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struct klp_reloc {
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unsigned long loc;
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unsigned long val;
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unsigned long type;
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const char *name;
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int addend;
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int external;
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};
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/**
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* struct klp_object - kernel object structure for live patching
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* @name: module name (or NULL for vmlinux)
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* @relocs: relocation entries to be applied at load time
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* @funcs: function entries for functions to be patched in the object
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* @kobj: kobject for sysfs resources
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* @mod: kernel module associated with the patched object
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* (NULL for vmlinux)
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* @state: tracks object-level patch application state
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*/
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struct klp_object {
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/* external */
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const char *name;
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struct klp_reloc *relocs;
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struct klp_func *funcs;
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/* internal */
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struct kobject *kobj;
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struct module *mod;
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enum klp_state state;
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};
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/**
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* struct klp_patch - patch structure for live patching
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* @mod: reference to the live patch module
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* @objs: object entries for kernel objects to be patched
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* @list: list node for global list of registered patches
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* @kobj: kobject for sysfs resources
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* @state: tracks patch-level application state
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*/
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struct klp_patch {
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/* external */
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struct module *mod;
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struct klp_object *objs;
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/* internal */
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struct list_head list;
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struct kobject kobj;
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enum klp_state state;
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};
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extern int klp_register_patch(struct klp_patch *);
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extern int klp_unregister_patch(struct klp_patch *);
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extern int klp_enable_patch(struct klp_patch *);
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extern int klp_disable_patch(struct klp_patch *);
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#endif /* CONFIG_LIVE_PATCHING */
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#endif /* _LINUX_LIVEPATCH_H_ */
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