From 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 12:05:51 +0200 Subject: Adding upstream version 5.10.209. Signed-off-by: Daniel Baumann --- kernel/livepatch/patch.c | 297 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 297 insertions(+) create mode 100644 kernel/livepatch/patch.c (limited to 'kernel/livepatch/patch.c') diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c new file mode 100644 index 000000000..b552cf2d8 --- /dev/null +++ b/kernel/livepatch/patch.c @@ -0,0 +1,297 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * patch.c - livepatch patching functions + * + * Copyright (C) 2014 Seth Jennings + * Copyright (C) 2014 SUSE + * Copyright (C) 2015 Josh Poimboeuf + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include "core.h" +#include "patch.h" +#include "transition.h" + +static LIST_HEAD(klp_ops); + +struct klp_ops *klp_find_ops(void *old_func) +{ + struct klp_ops *ops; + struct klp_func *func; + + list_for_each_entry(ops, &klp_ops, node) { + func = list_first_entry(&ops->func_stack, struct klp_func, + stack_node); + if (func->old_func == old_func) + return ops; + } + + return NULL; +} + +static void notrace klp_ftrace_handler(unsigned long ip, + unsigned long parent_ip, + struct ftrace_ops *fops, + struct pt_regs *regs) +{ + struct klp_ops *ops; + struct klp_func *func; + int patch_state; + + ops = container_of(fops, struct klp_ops, fops); + + /* + * A variant of synchronize_rcu() is used to allow patching functions + * where RCU is not watching, see klp_synchronize_transition(). + */ + preempt_disable_notrace(); + + func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, + stack_node); + + /* + * func should never be NULL because preemption should be disabled here + * and unregister_ftrace_function() does the equivalent of a + * synchronize_rcu() before the func_stack removal. + */ + if (WARN_ON_ONCE(!func)) + goto unlock; + + /* + * In the enable path, enforce the order of the ops->func_stack and + * func->transition reads. The corresponding write barrier is in + * __klp_enable_patch(). + * + * (Note that this barrier technically isn't needed in the disable + * path. In the rare case where klp_update_patch_state() runs before + * this handler, its TIF_PATCH_PENDING read and this func->transition + * read need to be ordered. But klp_update_patch_state() already + * enforces that.) + */ + smp_rmb(); + + if (unlikely(func->transition)) { + + /* + * Enforce the order of the func->transition and + * current->patch_state reads. Otherwise we could read an + * out-of-date task state and pick the wrong function. The + * corresponding write barrier is in klp_init_transition(). + */ + smp_rmb(); + + patch_state = current->patch_state; + + WARN_ON_ONCE(patch_state == KLP_UNDEFINED); + + if (patch_state == KLP_UNPATCHED) { + /* + * Use the previously patched version of the function. + * If no previous patches exist, continue with the + * original function. + */ + func = list_entry_rcu(func->stack_node.next, + struct klp_func, stack_node); + + if (&func->stack_node == &ops->func_stack) + goto unlock; + } + } + + /* + * NOPs are used to replace existing patches with original code. + * Do nothing! Setting pc would cause an infinite loop. + */ + if (func->nop) + goto unlock; + + klp_arch_set_pc(regs, (unsigned long)func->new_func); + +unlock: + preempt_enable_notrace(); +} + +/* + * Convert a function address into the appropriate ftrace location. + * + * Usually this is just the address of the function, but on some architectures + * it's more complicated so allow them to provide a custom behaviour. + */ +#ifndef klp_get_ftrace_location +static unsigned long klp_get_ftrace_location(unsigned long faddr) +{ + return faddr; +} +#endif + +static void klp_unpatch_func(struct klp_func *func) +{ + struct klp_ops *ops; + + if (WARN_ON(!func->patched)) + return; + if (WARN_ON(!func->old_func)) + return; + + ops = klp_find_ops(func->old_func); + if (WARN_ON(!ops)) + return; + + if (list_is_singular(&ops->func_stack)) { + unsigned long ftrace_loc; + + ftrace_loc = + klp_get_ftrace_location((unsigned long)func->old_func); + if (WARN_ON(!ftrace_loc)) + return; + + WARN_ON(unregister_ftrace_function(&ops->fops)); + WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0)); + + list_del_rcu(&func->stack_node); + list_del(&ops->node); + kfree(ops); + } else { + list_del_rcu(&func->stack_node); + } + + func->patched = false; +} + +static int klp_patch_func(struct klp_func *func) +{ + struct klp_ops *ops; + int ret; + + if (WARN_ON(!func->old_func)) + return -EINVAL; + + if (WARN_ON(func->patched)) + return -EINVAL; + + ops = klp_find_ops(func->old_func); + if (!ops) { + unsigned long ftrace_loc; + + ftrace_loc = + klp_get_ftrace_location((unsigned long)func->old_func); + if (!ftrace_loc) { + pr_err("failed to find location for function '%s'\n", + func->old_name); + return -EINVAL; + } + + ops = kzalloc(sizeof(*ops), GFP_KERNEL); + if (!ops) + return -ENOMEM; + + ops->fops.func = klp_ftrace_handler; + ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS | + FTRACE_OPS_FL_DYNAMIC | + FTRACE_OPS_FL_IPMODIFY | + FTRACE_OPS_FL_PERMANENT; + + list_add(&ops->node, &klp_ops); + + INIT_LIST_HEAD(&ops->func_stack); + list_add_rcu(&func->stack_node, &ops->func_stack); + + ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0); + if (ret) { + pr_err("failed to set ftrace filter for function '%s' (%d)\n", + func->old_name, ret); + goto err; + } + + ret = register_ftrace_function(&ops->fops); + if (ret) { + pr_err("failed to register ftrace handler for function '%s' (%d)\n", + func->old_name, ret); + ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0); + goto err; + } + + + } else { + list_add_rcu(&func->stack_node, &ops->func_stack); + } + + func->patched = true; + + return 0; + +err: + list_del_rcu(&func->stack_node); + list_del(&ops->node); + kfree(ops); + return ret; +} + +static void __klp_unpatch_object(struct klp_object *obj, bool nops_only) +{ + struct klp_func *func; + + klp_for_each_func(obj, func) { + if (nops_only && !func->nop) + continue; + + if (func->patched) + klp_unpatch_func(func); + } + + if (obj->dynamic || !nops_only) + obj->patched = false; +} + + +void klp_unpatch_object(struct klp_object *obj) +{ + __klp_unpatch_object(obj, false); +} + +int klp_patch_object(struct klp_object *obj) +{ + struct klp_func *func; + int ret; + + if (WARN_ON(obj->patched)) + return -EINVAL; + + klp_for_each_func(obj, func) { + ret = klp_patch_func(func); + if (ret) { + klp_unpatch_object(obj); + return ret; + } + } + obj->patched = true; + + return 0; +} + +static void __klp_unpatch_objects(struct klp_patch *patch, bool nops_only) +{ + struct klp_object *obj; + + klp_for_each_object(patch, obj) + if (obj->patched) + __klp_unpatch_object(obj, nops_only); +} + +void klp_unpatch_objects(struct klp_patch *patch) +{ + __klp_unpatch_objects(patch, false); +} + +void klp_unpatch_objects_dynamic(struct klp_patch *patch) +{ + __klp_unpatch_objects(patch, true); +} -- cgit v1.2.3