diff options
Diffstat (limited to '')
| -rw-r--r-- | include/linux/rethook.h | 100 | ||||
| -rw-r--r-- | include/linux/sched.h | 3 | ||||
| -rw-r--r-- | kernel/exit.c | 2 | ||||
| -rw-r--r-- | kernel/fork.c | 3 | ||||
| -rw-r--r-- | kernel/trace/Kconfig | 11 | ||||
| -rw-r--r-- | kernel/trace/Makefile | 1 | ||||
| -rw-r--r-- | kernel/trace/rethook.c | 317 |
7 files changed, 437 insertions, 0 deletions
diff --git a/include/linux/rethook.h b/include/linux/rethook.h new file mode 100644 index 000000000000..c8ac1e5afcd1 --- /dev/null +++ b/include/linux/rethook.h @@ -0,0 +1,100 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Return hooking with list-based shadow stack. + */ +#ifndef _LINUX_RETHOOK_H +#define _LINUX_RETHOOK_H + +#include <linux/compiler.h> +#include <linux/freelist.h> +#include <linux/kallsyms.h> +#include <linux/llist.h> +#include <linux/rcupdate.h> +#include <linux/refcount.h> + +struct rethook_node; + +typedef void (*rethook_handler_t) (struct rethook_node *, void *, struct pt_regs *); + +/** + * struct rethook - The rethook management data structure. + * @data: The user-defined data storage. + * @handler: The user-defined return hook handler. + * @pool: The pool of struct rethook_node. + * @ref: The reference counter. + * @rcu: The rcu_head for deferred freeing. + * + * Don't embed to another data structure, because this is a self-destructive + * data structure when all rethook_node are freed. + */ +struct rethook { + void *data; + rethook_handler_t handler; + struct freelist_head pool; + refcount_t ref; + struct rcu_head rcu; +}; + +/** + * struct rethook_node - The rethook shadow-stack entry node. + * @freelist: The freelist, linked to struct rethook::pool. + * @rcu: The rcu_head for deferred freeing. + * @llist: The llist, linked to a struct task_struct::rethooks. + * @rethook: The pointer to the struct rethook. + * @ret_addr: The storage for the real return address. + * @frame: The storage for the frame pointer. + * + * You can embed this to your extended data structure to store any data + * on each entry of the shadow stack. + */ +struct rethook_node { + union { + struct freelist_node freelist; + struct rcu_head rcu; + }; + struct llist_node llist; + struct rethook *rethook; + unsigned long ret_addr; + unsigned long frame; +}; + +struct rethook *rethook_alloc(void *data, rethook_handler_t handler); +void rethook_free(struct rethook *rh); +void rethook_add_node(struct rethook *rh, struct rethook_node *node); +struct rethook_node *rethook_try_get(struct rethook *rh); +void rethook_recycle(struct rethook_node *node); +void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount); +unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame, + struct llist_node **cur); + +/* Arch dependent code must implement arch_* and trampoline code */ +void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount); +void arch_rethook_trampoline(void); + +/** + * is_rethook_trampoline() - Check whether the address is rethook trampoline + * @addr: The address to be checked + * + * Return true if the @addr is the rethook trampoline address. + */ +static inline bool is_rethook_trampoline(unsigned long addr) +{ + return addr == (unsigned long)dereference_symbol_descriptor(arch_rethook_trampoline); +} + +/* If the architecture needs to fixup the return address, implement it. */ +void arch_rethook_fixup_return(struct pt_regs *regs, + unsigned long correct_ret_addr); + +/* Generic trampoline handler, arch code must prepare asm stub */ +unsigned long rethook_trampoline_handler(struct pt_regs *regs, + unsigned long frame); + +#ifdef CONFIG_RETHOOK +void rethook_flush_task(struct task_struct *tk); +#else +#define rethook_flush_task(tsk) do { } while (0) +#endif + +#endif + diff --git a/include/linux/sched.h b/include/linux/sched.h index 75ba8aa60248..7034f53404e3 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1481,6 +1481,9 @@ struct task_struct { #ifdef CONFIG_KRETPROBES struct llist_head kretprobe_instances; #endif +#ifdef CONFIG_RETHOOK + struct llist_head rethooks; +#endif #ifdef CONFIG_ARCH_HAS_PARANOID_L1D_FLUSH /* diff --git a/kernel/exit.c b/kernel/exit.c index b00a25bb4ab9..2d1803fa8fe6 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -64,6 +64,7 @@ #include <linux/compat.h> #include <linux/io_uring.h> #include <linux/kprobes.h> +#include <linux/rethook.h> #include <linux/uaccess.h> #include <asm/unistd.h> @@ -169,6 +170,7 @@ static void delayed_put_task_struct(struct rcu_head *rhp) struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); kprobe_flush_task(tsk); + rethook_flush_task(tsk); perf_event_delayed_put(tsk); trace_sched_process_free(tsk); put_task_struct(tsk); diff --git a/kernel/fork.c b/kernel/fork.c index a024bf6254df..3db1a4110a25 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2255,6 +2255,9 @@ static __latent_entropy struct task_struct *copy_process( #ifdef CONFIG_KRETPROBES p->kretprobe_instances.first = NULL; #endif +#ifdef CONFIG_RETHOOK + p->rethooks.first = NULL; +#endif /* * Ensure that the cgroup subsystem policies allow the new process to be diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 7ce31abc542b..e75504e42ab8 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -10,6 +10,17 @@ config USER_STACKTRACE_SUPPORT config NOP_TRACER bool +config HAVE_RETHOOK + bool + +config RETHOOK + bool + depends on HAVE_RETHOOK + help + Enable generic return hooking feature. This is an internal + API, which will be used by other function-entry hooking + features like fprobe and kprobes. + config HAVE_FUNCTION_TRACER bool help diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 79255f9de9a4..c6f11a139eac 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -98,6 +98,7 @@ obj-$(CONFIG_UPROBE_EVENTS) += trace_uprobe.o obj-$(CONFIG_BOOTTIME_TRACING) += trace_boot.o obj-$(CONFIG_FTRACE_RECORD_RECURSION) += trace_recursion_record.o obj-$(CONFIG_FPROBE) += fprobe.o +obj-$(CONFIG_RETHOOK) += rethook.o obj-$(CONFIG_TRACEPOINT_BENCHMARK) += trace_benchmark.o diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c new file mode 100644 index 000000000000..ab463a4d2b23 --- /dev/null +++ b/kernel/trace/rethook.c @@ -0,0 +1,317 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define pr_fmt(fmt) "rethook: " fmt + +#include <linux/bug.h> +#include <linux/kallsyms.h> +#include <linux/kprobes.h> +#include <linux/preempt.h> +#include <linux/rethook.h> +#include <linux/slab.h> +#include <linux/sort.h> + +/* Return hook list (shadow stack by list) */ + +/* + * This function is called from delayed_put_task_struct() when a task is + * dead and cleaned up to recycle any kretprobe instances associated with + * this task. These left over instances represent probed functions that + * have been called but will never return. + */ +void rethook_flush_task(struct task_struct *tk) +{ + struct rethook_node *rhn; + struct llist_node *node; + + node = __llist_del_all(&tk->rethooks); + while (node) { + rhn = container_of(node, struct rethook_node, llist); + node = node->next; + preempt_disable(); + rethook_recycle(rhn); + preempt_enable(); + } +} + +static void rethook_free_rcu(struct rcu_head *head) +{ + struct rethook *rh = container_of(head, struct rethook, rcu); + struct rethook_node *rhn; + struct freelist_node *node; + int count = 1; + + node = rh->pool.head; + while (node) { + rhn = container_of(node, struct rethook_node, freelist); + node = node->next; + kfree(rhn); + count++; + } + + /* The rh->ref is the number of pooled node + 1 */ + if (refcount_sub_and_test(count, &rh->ref)) + kfree(rh); +} + +/** + * rethook_free() - Free struct rethook. + * @rh: the struct rethook to be freed. + * + * Free the rethook. Before calling this function, user must ensure the + * @rh::data is cleaned if needed (or, the handler can access it after + * calling this function.) This function will set the @rh to be freed + * after all rethook_node are freed (not soon). And the caller must + * not touch @rh after calling this. + */ +void rethook_free(struct rethook *rh) +{ + rcu_assign_pointer(rh->handler, NULL); + + call_rcu(&rh->rcu, rethook_free_rcu); +} + +/** + * rethook_alloc() - Allocate struct rethook. + * @data: a data to pass the @handler when hooking the return. + * @handler: the return hook callback function. + * + * Allocate and initialize a new rethook with @data and @handler. + * Return NULL if memory allocation fails or @handler is NULL. + * Note that @handler == NULL means this rethook is going to be freed. + */ +struct rethook *rethook_alloc(void *data, rethook_handler_t handler) +{ + struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL); + + if (!rh || !handler) + return NULL; + + rh->data = data; + rh->handler = handler; + rh->pool.head = NULL; + refcount_set(&rh->ref, 1); + + return rh; +} + +/** + * rethook_add_node() - Add a new node to the rethook. + * @rh: the struct rethook. + * @node: the struct rethook_node to be added. + * + * Add @node to @rh. User must allocate @node (as a part of user's + * data structure.) The @node fields are initialized in this function. + */ +void rethook_add_node(struct rethook *rh, struct rethook_node *node) +{ + node->rethook = rh; + freelist_add(&node->freelist, &rh->pool); + refcount_inc(&rh->ref); +} + +static void free_rethook_node_rcu(struct rcu_head *head) +{ + struct rethook_node *node = container_of(head, struct rethook_node, rcu); + + if (refcount_dec_and_test(&node->rethook->ref)) + kfree(node->rethook); + kfree(node); +} + +/** + * rethook_recycle() - return the node to rethook. + * @node: The struct rethook_node to be returned. + * + * Return back the @node to @node::rethook. If the @node::rethook is already + * marked as freed, this will free the @node. + */ +void rethook_recycle(struct rethook_node *node) +{ + lockdep_assert_preemption_disabled(); + + if (likely(READ_ONCE(node->rethook->handler))) + freelist_add(&node->freelist, &node->rethook->pool); + else + call_rcu(&node->rcu, free_rethook_node_rcu); +} +NOKPROBE_SYMBOL(rethook_recycle); + +/** + * rethook_try_get() - get an unused rethook node. + * @rh: The struct rethook which pools the nodes. + * + * Get an unused rethook node from @rh. If the node pool is empty, this + * will return NULL. Caller must disable preemption. + */ +struct rethook_node *rethook_try_get(struct rethook *rh) +{ + rethook_handler_t handler = READ_ONCE(rh->handler); + struct freelist_node *fn; + + lockdep_assert_preemption_disabled(); + + /* Check whether @rh is going to be freed. */ + if (unlikely(!handler)) + return NULL; + + fn = freelist_try_get(&rh->pool); + if (!fn) + return NULL; + + return container_of(fn, struct rethook_node, freelist); +} +NOKPROBE_SYMBOL(rethook_try_get); + +/** + * rethook_hook() - Hook the current function return. + * @node: The struct rethook node to hook the function return. + * @regs: The struct pt_regs for the function entry. + * @mcount: True if this is called from mcount(ftrace) context. + * + * Hook the current running function return. This must be called when the + * function entry (or at least @regs must be the registers of the function + * entry.) @mcount is used for identifying the context. If this is called + * from ftrace (mcount) callback, @mcount must be set true. If this is called + * from the real function entry (e.g. kprobes) @mcount must be set false. + * This is because the way to hook the function return depends on the context. + */ +void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount) +{ + arch_rethook_prepare(node, regs, mcount); + __llist_add(&node->llist, ¤t->rethooks); +} +NOKPROBE_SYMBOL(rethook_hook); + +/* This assumes the 'tsk' is the current task or is not running. */ +static unsigned long __rethook_find_ret_addr(struct task_struct *tsk, + struct llist_node **cur) +{ + struct rethook_node *rh = NULL; + struct llist_node *node = *cur; + + if (!node) + node = tsk->rethooks.first; + else + node = node->next; + + while (node) { + rh = container_of(node, struct rethook_node, llist); + if (rh->ret_addr != (unsigned long)arch_rethook_trampoline) { + *cur = node; + return rh->ret_addr; + } + node = node->next; + } + return 0; +} +NOKPROBE_SYMBOL(__rethook_find_ret_addr); + +/** + * rethook_find_ret_addr -- Find correct return address modified by rethook + * @tsk: Target task + * @frame: A frame pointer + * @cur: a storage of the loop cursor llist_node pointer for next call + * + * Find the correct return address modified by a rethook on @tsk in unsigned + * long type. + * The @tsk must be 'current' or a task which is not running. @frame is a hint + * to get the currect return address - which is compared with the + * rethook::frame field. The @cur is a loop cursor for searching the + * kretprobe return addresses on the @tsk. The '*@cur' should be NULL at the + * first call, but '@cur' itself must NOT NULL. + * + * Returns found address value or zero if not found. + */ +unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame, + struct llist_node **cur) +{ + struct rethook_node *rhn = NULL; + unsigned long ret; + + if (WARN_ON_ONCE(!cur)) + return 0; + + if (WARN_ON_ONCE(tsk != current && task_is_running(tsk))) + return 0; + + do { + ret = __rethook_find_ret_addr(tsk, cur); + if (!ret) + break; + rhn = container_of(*cur, struct rethook_node, llist); + } while (rhn->frame != frame); + + return ret; +} +NOKPROBE_SYMBOL(rethook_find_ret_addr); + +void __weak arch_rethook_fixup_return(struct pt_regs *regs, + unsigned long correct_ret_addr) +{ + /* + * Do nothing by default. If the architecture which uses a + * frame pointer to record real return address on the stack, + * it should fill this function to fixup the return address + * so that stacktrace works from the rethook handler. + */ +} + +/* This function will be called from each arch-defined trampoline. */ +unsigned long rethook_trampoline_handler(struct pt_regs *regs, + unsigned long frame) +{ + struct llist_node *first, *node = NULL; + unsigned long correct_ret_addr; + rethook_handler_t handler; + struct rethook_node *rhn; + + correct_ret_addr = __rethook_find_ret_addr(current, &node); + if (!correct_ret_addr) { + pr_err("rethook: Return address not found! Maybe there is a bug in the kernel\n"); + BUG_ON(1); + } + + instruction_pointer_set(regs, correct_ret_addr); + + /* + * These loops must be protected from rethook_free_rcu() because those + * are accessing 'rhn->rethook'. + */ + preempt_disable(); + + /* + * Run the handler on the shadow stack. Do not unlink the list here because + * stackdump inside the handlers needs to decode it. + */ + first = current->rethooks.first; + while (first) { + rhn = container_of(first, struct rethook_node, llist); + if (WARN_ON_ONCE(rhn->frame != frame)) + break; + handler = READ_ONCE(rhn->rethook->handler); + if (handler) + handler(rhn, rhn->rethook->data, regs); + + if (first == node) + break; + first = first->next; + } + + /* Fixup registers for returning to correct address. */ + arch_rethook_fixup_return(regs, correct_ret_addr); + + /* Unlink used shadow stack */ + first = current->rethooks.first; + current->rethooks.first = node->next; + node->next = NULL; + + while (first) { + rhn = container_of(first, struct rethook_node, llist); + first = first->next; + rethook_recycle(rhn); + } + preempt_enable(); + + return correct_ret_addr; +} +NOKPROBE_SYMBOL(rethook_trampoline_handler); |