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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /kernel/trace/rethook.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'kernel/trace/rethook.c')
-rw-r--r--kernel/trace/rethook.c346
1 files changed, 346 insertions, 0 deletions
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
new file mode 100644
index 000000000..3686626b5
--- /dev/null
+++ b/kernel/trace/rethook.c
@@ -0,0 +1,346 @@
+// 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_stop() - Stop using a rethook.
+ * @rh: the struct rethook to stop.
+ *
+ * Stop using a rethook to prepare for freeing it. If you want to wait for
+ * all running rethook handler before calling rethook_free(), you need to
+ * call this first and wait RCU, and call rethook_free().
+ */
+void rethook_stop(struct rethook *rh)
+{
+ rcu_assign_pointer(rh->handler, NULL);
+}
+
+/**
+ * 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)
+{
+ rethook_stop(rh);
+
+ call_rcu(&rh->rcu, rethook_free_rcu);
+}
+
+static inline rethook_handler_t rethook_get_handler(struct rethook *rh)
+{
+ return (rethook_handler_t)rcu_dereference_check(rh->handler,
+ rcu_read_lock_any_held());
+}
+
+/**
+ * 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) {
+ kfree(rh);
+ return NULL;
+ }
+
+ rh->data = data;
+ rcu_assign_pointer(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)
+{
+ rethook_handler_t handler;
+
+ handler = rethook_get_handler(node->rethook);
+ if (likely(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 = rethook_get_handler(rh);
+ struct freelist_node *fn;
+
+ /* Check whether @rh is going to be freed. */
+ if (unlikely(!handler))
+ return NULL;
+
+ /*
+ * This expects the caller will set up a rethook on a function entry.
+ * When the function returns, the rethook will eventually be reclaimed
+ * or released in the rethook_recycle() with call_rcu().
+ * This means the caller must be run in the RCU-availabe context.
+ */
+ if (unlikely(!rcu_is_watching()))
+ 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, &current->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_notrace();
+
+ /*
+ * 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 = rethook_get_handler(rhn->rethook);
+ 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_notrace();
+
+ return correct_ret_addr;
+}
+NOKPROBE_SYMBOL(rethook_trampoline_handler);