kprobes: Use rethook for kretprobe if possible

Use rethook for kretprobe function return hooking if the arch sets
CONFIG_HAVE_RETHOOK=y. In this case, CONFIG_KRETPROBE_ON_RETHOOK is
set to 'y' automatically, and the kretprobe internal data fields
switches to use rethook. If not, it continues to use kretprobe
specific function return hooks.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164826162556.2455864.12255833167233452047.stgit@devnote2

diff --git a/arch/Kconfig b/arch/Kconfig
index 84bc1de..33e0696 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -164,7 +164,13 @@ config ARCH_USE_BUILTIN_BSWAP
 
 config KRETPROBES
        def_bool y
-       depends on KPROBES && HAVE_KRETPROBES
+       depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
+
+config KRETPROBE_ON_RETHOOK
+       def_bool y
+       depends on HAVE_RETHOOK
+       depends on KRETPROBES
+       select RETHOOK
 
 config USER_RETURN_NOTIFIER
        bool

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 312ff99..1571687 100644 (file)
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -28,6 +28,7 @@
 #include <linux/ftrace.h>
 #include <linux/refcount.h>
 #include <linux/freelist.h>
+#include <linux/rethook.h>
 #include <asm/kprobes.h>
 
 #ifdef CONFIG_KPROBES
@@ -149,13 +150,20 @@ struct kretprobe {
        int maxactive;
        int nmissed;
        size_t data_size;
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+       struct rethook *rh;
+#else
        struct freelist_head freelist;
        struct kretprobe_holder *rph;
+#endif
 };
 
 #define KRETPROBE_MAX_DATA_SIZE        4096
 
 struct kretprobe_instance {
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+       struct rethook_node node;
+#else
        union {
                struct freelist_node freelist;
                struct rcu_head rcu;
@@ -164,6 +172,7 @@ struct kretprobe_instance {
        struct kretprobe_holder *rph;
        kprobe_opcode_t *ret_addr;
        void *fp;
+#endif
        char data[];
 };
 
@@ -186,10 +195,24 @@ extern void kprobe_busy_begin(void);
 extern void kprobe_busy_end(void);
 
 #ifdef CONFIG_KRETPROBES
-extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
-                                  struct pt_regs *regs);
+/* Check whether @p is used for implementing a trampoline. */
 extern int arch_trampoline_kprobe(struct kprobe *p);
 
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri)
+{
+       RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
+               "Kretprobe is accessed from instance under preemptive context");
+
+       return (struct kretprobe *)READ_ONCE(ri->node.rethook->data);
+}
+static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
+{
+       return ri->node.ret_addr;
+}
+#else
+extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
+                                  struct pt_regs *regs);
 void arch_kretprobe_fixup_return(struct pt_regs *regs,
                                 kprobe_opcode_t *correct_ret_addr);
 
@@ -232,6 +255,12 @@ static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance
        return READ_ONCE(ri->rph->rp);
 }
 
+static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
+{
+       return (unsigned long)ri->ret_addr;
+}
+#endif /* CONFIG_KRETPROBE_ON_RETHOOK */
+
 #else /* !CONFIG_KRETPROBES */
 static inline void arch_prepare_kretprobe(struct kretprobe *rp,
                                        struct pt_regs *regs)
@@ -395,7 +424,11 @@ void unregister_kretprobe(struct kretprobe *rp);
 int register_kretprobes(struct kretprobe **rps, int num);
 void unregister_kretprobes(struct kretprobe **rps, int num);
 
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+#define kprobe_flush_task(tk)  do {} while (0)
+#else
 void kprobe_flush_task(struct task_struct *tk);
+#endif
 
 void kprobe_free_init_mem(void);
 
@@ -509,6 +542,19 @@ static inline bool is_kprobe_optinsn_slot(unsigned long addr)
 #endif /* !CONFIG_OPTPROBES */
 
 #ifdef CONFIG_KRETPROBES
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
+{
+       return is_rethook_trampoline(addr);
+}
+
+static nokprobe_inline
+unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
+                                     struct llist_node **cur)
+{
+       return rethook_find_ret_addr(tsk, (unsigned long)fp, cur);
+}
+#else
 static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
 {
        return (void *)addr == kretprobe_trampoline_addr();
@@ -516,6 +562,7 @@ static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
 
 unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
                                      struct llist_node **cur);
+#endif
 #else
 static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
 {

diff --git a/kernel/Makefile b/kernel/Makefile
index 56f4ee9..471d719 100644 (file)
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -108,6 +108,7 @@ obj-$(CONFIG_TRACING) += trace/
 obj-$(CONFIG_TRACE_CLOCK) += trace/
 obj-$(CONFIG_RING_BUFFER) += trace/
 obj-$(CONFIG_TRACEPOINTS) += trace/
+obj-$(CONFIG_RETHOOK) += trace/
 obj-$(CONFIG_IRQ_WORK) += irq_work.o
 obj-$(CONFIG_CPU_PM) += cpu_pm.o
 obj-$(CONFIG_BPF) += bpf/

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 185badc..dbe57df 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1237,6 +1237,27 @@ void kprobes_inc_nmissed_count(struct kprobe *p)
 }
 NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);
 
+static struct kprobe kprobe_busy = {
+       .addr = (void *) get_kprobe,
+};
+
+void kprobe_busy_begin(void)
+{
+       struct kprobe_ctlblk *kcb;
+
+       preempt_disable();
+       __this_cpu_write(current_kprobe, &kprobe_busy);
+       kcb = get_kprobe_ctlblk();
+       kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+}
+
+void kprobe_busy_end(void)
+{
+       __this_cpu_write(current_kprobe, NULL);
+       preempt_enable();
+}
+
+#if !defined(CONFIG_KRETPROBE_ON_RETHOOK)
 static void free_rp_inst_rcu(struct rcu_head *head)
 {
        struct kretprobe_instance *ri = container_of(head, struct kretprobe_instance, rcu);
@@ -1258,26 +1279,6 @@ static void recycle_rp_inst(struct kretprobe_instance *ri)
 }
 NOKPROBE_SYMBOL(recycle_rp_inst);
 
-static struct kprobe kprobe_busy = {
-       .addr = (void *) get_kprobe,
-};
-
-void kprobe_busy_begin(void)
-{
-       struct kprobe_ctlblk *kcb;
-
-       preempt_disable();
-       __this_cpu_write(current_kprobe, &kprobe_busy);
-       kcb = get_kprobe_ctlblk();
-       kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-}
-
-void kprobe_busy_end(void)
-{
-       __this_cpu_write(current_kprobe, NULL);
-       preempt_enable();
-}
-
 /*
  * This function is called from delayed_put_task_struct() when a task is
  * dead and cleaned up to recycle any kretprobe instances associated with
@@ -1327,6 +1328,7 @@ static inline void free_rp_inst(struct kretprobe *rp)
                rp->rph = NULL;
        }
 }
+#endif /* !CONFIG_KRETPROBE_ON_RETHOOK */
 
 /* Add the new probe to 'ap->list'. */
 static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
@@ -1925,6 +1927,7 @@ static struct notifier_block kprobe_exceptions_nb = {
 
 #ifdef CONFIG_KRETPROBES
 
+#if !defined(CONFIG_KRETPROBE_ON_RETHOOK)
 /* This assumes the 'tsk' is the current task or the is not running. */
 static kprobe_opcode_t *__kretprobe_find_ret_addr(struct task_struct *tsk,
                                                  struct llist_node **cur)
@@ -2087,6 +2090,57 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
        return 0;
 }
 NOKPROBE_SYMBOL(pre_handler_kretprobe);
+#else /* CONFIG_KRETPROBE_ON_RETHOOK */
+/*
+ * This kprobe pre_handler is registered with every kretprobe. When probe
+ * hits it will set up the return probe.
+ */
+static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
+{
+       struct kretprobe *rp = container_of(p, struct kretprobe, kp);
+       struct kretprobe_instance *ri;
+       struct rethook_node *rhn;
+
+       rhn = rethook_try_get(rp->rh);
+       if (!rhn) {
+               rp->nmissed++;
+               return 0;
+       }
+
+       ri = container_of(rhn, struct kretprobe_instance, node);
+
+       if (rp->entry_handler && rp->entry_handler(ri, regs))
+               rethook_recycle(rhn);
+       else
+               rethook_hook(rhn, regs, kprobe_ftrace(p));
+
+       return 0;
+}
+NOKPROBE_SYMBOL(pre_handler_kretprobe);
+
+static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
+                                     struct pt_regs *regs)
+{
+       struct kretprobe *rp = (struct kretprobe *)data;
+       struct kretprobe_instance *ri;
+       struct kprobe_ctlblk *kcb;
+
+       /* The data must NOT be null. This means rethook data structure is broken. */
+       if (WARN_ON_ONCE(!data))
+               return;
+
+       __this_cpu_write(current_kprobe, &rp->kp);
+       kcb = get_kprobe_ctlblk();
+       kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+       ri = container_of(rh, struct kretprobe_instance, node);
+       rp->handler(ri, regs);
+
+       __this_cpu_write(current_kprobe, NULL);
+}
+NOKPROBE_SYMBOL(kretprobe_rethook_handler);
+
+#endif /* !CONFIG_KRETPROBE_ON_RETHOOK */
 
 /**
  * kprobe_on_func_entry() -- check whether given address is function entry
@@ -2155,6 +2209,29 @@ int register_kretprobe(struct kretprobe *rp)
                rp->maxactive = num_possible_cpus();
 #endif
        }
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+       rp->rh = rethook_alloc((void *)rp, kretprobe_rethook_handler);
+       if (!rp->rh)
+               return -ENOMEM;
+
+       for (i = 0; i < rp->maxactive; i++) {
+               inst = kzalloc(sizeof(struct kretprobe_instance) +
+                              rp->data_size, GFP_KERNEL);
+               if (inst == NULL) {
+                       rethook_free(rp->rh);
+                       rp->rh = NULL;
+                       return -ENOMEM;
+               }
+               rethook_add_node(rp->rh, &inst->node);
+       }
+       rp->nmissed = 0;
+       /* Establish function entry probe point */
+       ret = register_kprobe(&rp->kp);
+       if (ret != 0) {
+               rethook_free(rp->rh);
+               rp->rh = NULL;
+       }
+#else  /* !CONFIG_KRETPROBE_ON_RETHOOK */
        rp->freelist.head = NULL;
        rp->rph = kzalloc(sizeof(struct kretprobe_holder), GFP_KERNEL);
        if (!rp->rph)
@@ -2179,6 +2256,7 @@ int register_kretprobe(struct kretprobe *rp)
        ret = register_kprobe(&rp->kp);
        if (ret != 0)
                free_rp_inst(rp);
+#endif
        return ret;
 }
 EXPORT_SYMBOL_GPL(register_kretprobe);
@@ -2217,7 +2295,11 @@ void unregister_kretprobes(struct kretprobe **rps, int num)
        for (i = 0; i < num; i++) {
                if (__unregister_kprobe_top(&rps[i]->kp) < 0)
                        rps[i]->kp.addr = NULL;
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+               rethook_free(rps[i]->rh);
+#else
                rps[i]->rph->rp = NULL;
+#endif
        }
        mutex_unlock(&kprobe_mutex);
 
@@ -2225,7 +2307,9 @@ void unregister_kretprobes(struct kretprobe **rps, int num)
        for (i = 0; i < num; i++) {
                if (rps[i]->kp.addr) {
                        __unregister_kprobe_bottom(&rps[i]->kp);
+#ifndef CONFIG_KRETPROBE_ON_RETHOOK
                        free_rp_inst(rps[i]);
+#endif
                }
        }
 }

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index b62fd78..47cebef 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1433,7 +1433,7 @@ __kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
        fbuffer.regs = regs;
        entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
        entry->func = (unsigned long)tk->rp.kp.addr;
-       entry->ret_ip = (unsigned long)ri->ret_addr;
+       entry->ret_ip = get_kretprobe_retaddr(ri);
        store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
 
        trace_event_buffer_commit(&fbuffer);
@@ -1628,7 +1628,7 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
                return;
 
        entry->func = (unsigned long)tk->rp.kp.addr;
-       entry->ret_ip = (unsigned long)ri->ret_addr;
+       entry->ret_ip = get_kretprobe_retaddr(ri);
        store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
        perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
                              head, NULL);