3 files changed, 288 insertions, 11 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 3207a4d26849..934feb39f6be 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -73,6 +73,7 @@ struct uprobe {
 	struct uprobe_consumer	*consumers;
 	struct inode		*inode;		/* Also hold a ref to inode */
 	loff_t			offset;
+	loff_t			ref_ctr_offset;
 	unsigned long		flags;
 
 	/*
@@ -88,6 +89,15 @@ struct uprobe {
 	struct arch_uprobe	arch;
 };
 
+struct delayed_uprobe {
+	struct list_head list;
+	struct uprobe *uprobe;
+	struct mm_struct *mm;
+};
+
+static DEFINE_MUTEX(delayed_uprobe_lock);
+static LIST_HEAD(delayed_uprobe_list);
+
 /*
  * Execute out of line area: anonymous executable mapping installed
  * by the probed task to execute the copy of the original instruction
@@ -282,6 +292,166 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
 	return 1;
 }
 
+static struct delayed_uprobe *
+delayed_uprobe_check(struct uprobe *uprobe, struct mm_struct *mm)
+{
+	struct delayed_uprobe *du;
+
+	list_for_each_entry(du, &delayed_uprobe_list, list)
+		if (du->uprobe == uprobe && du->mm == mm)
+			return du;
+	return NULL;
+}
+
+static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm)
+{
+	struct delayed_uprobe *du;
+
+	if (delayed_uprobe_check(uprobe, mm))
+		return 0;
+
+	du  = kzalloc(sizeof(*du), GFP_KERNEL);
+	if (!du)
+		return -ENOMEM;
+
+	du->uprobe = uprobe;
+	du->mm = mm;
+	list_add(&du->list, &delayed_uprobe_list);
+	return 0;
+}
+
+static void delayed_uprobe_delete(struct delayed_uprobe *du)
+{
+	if (WARN_ON(!du))
+		return;
+	list_del(&du->list);
+	kfree(du);
+}
+
+static void delayed_uprobe_remove(struct uprobe *uprobe, struct mm_struct *mm)
+{
+	struct list_head *pos, *q;
+	struct delayed_uprobe *du;
+
+	if (!uprobe && !mm)
+		return;
+
+	list_for_each_safe(pos, q, &delayed_uprobe_list) {
+		du = list_entry(pos, struct delayed_uprobe, list);
+
+		if (uprobe && du->uprobe != uprobe)
+			continue;
+		if (mm && du->mm != mm)
+			continue;
+
+		delayed_uprobe_delete(du);
+	}
+}
+
+static bool valid_ref_ctr_vma(struct uprobe *uprobe,
+			      struct vm_area_struct *vma)
+{
+	unsigned long vaddr = offset_to_vaddr(vma, uprobe->ref_ctr_offset);
+
+	return uprobe->ref_ctr_offset &&
+		vma->vm_file &&
+		file_inode(vma->vm_file) == uprobe->inode &&
+		(vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
+		vma->vm_start <= vaddr &&
+		vma->vm_end > vaddr;
+}
+
+static struct vm_area_struct *
+find_ref_ctr_vma(struct uprobe *uprobe, struct mm_struct *mm)
+{
+	struct vm_area_struct *tmp;
+
+	for (tmp = mm->mmap; tmp; tmp = tmp->vm_next)
+		if (valid_ref_ctr_vma(uprobe, tmp))
+			return tmp;
+
+	return NULL;
+}
+
+static int
+__update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
+{
+	void *kaddr;
+	struct page *page;
+	struct vm_area_struct *vma;
+	int ret;
+	short *ptr;
+
+	if (!vaddr || !d)
+		return -EINVAL;
+
+	ret = get_user_pages_remote(NULL, mm, vaddr, 1,
+			FOLL_WRITE, &page, &vma, NULL);
+	if (unlikely(ret <= 0)) {
+		/*
+		 * We are asking for 1 page. If get_user_pages_remote() fails,
+		 * it may return 0, in that case we have to return error.
+		 */
+		return ret == 0 ? -EBUSY : ret;
+	}
+
+	kaddr = kmap_atomic(page);
+	ptr = kaddr + (vaddr & ~PAGE_MASK);
+
+	if (unlikely(*ptr + d < 0)) {
+		pr_warn("ref_ctr going negative. vaddr: 0x%lx, "
+			"curr val: %d, delta: %d\n", vaddr, *ptr, d);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	*ptr += d;
+	ret = 0;
+out:
+	kunmap_atomic(kaddr);
+	put_page(page);
+	return ret;
+}
+
+static void update_ref_ctr_warn(struct uprobe *uprobe,
+				struct mm_struct *mm, short d)
+{
+	pr_warn("ref_ctr %s failed for inode: 0x%lx offset: "
+		"0x%llx ref_ctr_offset: 0x%llx of mm: 0x%pK\n",
+		d > 0 ? "increment" : "decrement", uprobe->inode->i_ino,
+		(unsigned long long) uprobe->offset,
+		(unsigned long long) uprobe->ref_ctr_offset, mm);
+}
+
+static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm,
+			  short d)
+{
+	struct vm_area_struct *rc_vma;
+	unsigned long rc_vaddr;
+	int ret = 0;
+
+	rc_vma = find_ref_ctr_vma(uprobe, mm);
+
+	if (rc_vma) {
+		rc_vaddr = offset_to_vaddr(rc_vma, uprobe->ref_ctr_offset);
+		ret = __update_ref_ctr(mm, rc_vaddr, d);
+		if (ret)
+			update_ref_ctr_warn(uprobe, mm, d);
+
+		if (d > 0)
+			return ret;
+	}
+
+	mutex_lock(&delayed_uprobe_lock);
+	if (d > 0)
+		ret = delayed_uprobe_add(uprobe, mm);
+	else
+		delayed_uprobe_remove(uprobe, mm);
+	mutex_unlock(&delayed_uprobe_lock);
+
+	return ret;
+}
+
 /*
  * NOTE:
  * Expect the breakpoint instruction to be the smallest size instruction for
@@ -302,9 +472,13 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
 int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
 			unsigned long vaddr, uprobe_opcode_t opcode)
 {
+	struct uprobe *uprobe;
 	struct page *old_page, *new_page;
 	struct vm_area_struct *vma;
-	int ret;
+	int ret, is_register, ref_ctr_updated = 0;
+
+	is_register = is_swbp_insn(&opcode);
+	uprobe = container_of(auprobe, struct uprobe, arch);
 
 retry:
 	/* Read the page with vaddr into memory */
@@ -317,6 +491,15 @@ retry:
 	if (ret <= 0)
 		goto put_old;
 
+	/* We are going to replace instruction, update ref_ctr. */
+	if (!ref_ctr_updated && uprobe->ref_ctr_offset) {
+		ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1);
+		if (ret)
+			goto put_old;
+
+		ref_ctr_updated = 1;
+	}
+
 	ret = anon_vma_prepare(vma);
 	if (ret)
 		goto put_old;
@@ -337,6 +520,11 @@ put_old:
 
 	if (unlikely(ret == -EAGAIN))
 		goto retry;
+
+	/* Revert back reference counter if instruction update failed. */
+	if (ret && is_register && ref_ctr_updated)
+		update_ref_ctr(uprobe, mm, -1);
+
 	return ret;
 }
 
@@ -378,8 +566,15 @@ static struct uprobe *get_uprobe(struct uprobe *uprobe)
 
 static void put_uprobe(struct uprobe *uprobe)
 {
-	if (atomic_dec_and_test(&uprobe->ref))
+	if (atomic_dec_and_test(&uprobe->ref)) {
+		/*
+		 * If application munmap(exec_vma) before uprobe_unregister()
+		 * gets called, we don't get a chance to remove uprobe from
+		 * delayed_uprobe_list from remove_breakpoint(). Do it here.
+		 */
+		delayed_uprobe_remove(uprobe, NULL);
 		kfree(uprobe);
+	}
 }
 
 static int match_uprobe(struct uprobe *l, struct uprobe *r)
@@ -484,7 +679,8 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
 	return u;
 }
 
-static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
+static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
+				   loff_t ref_ctr_offset)
 {
 	struct uprobe *uprobe, *cur_uprobe;
 
@@ -494,6 +690,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
 
 	uprobe->inode = inode;
 	uprobe->offset = offset;
+	uprobe->ref_ctr_offset = ref_ctr_offset;
 	init_rwsem(&uprobe->register_rwsem);
 	init_rwsem(&uprobe->consumer_rwsem);
 
@@ -895,7 +1092,7 @@ EXPORT_SYMBOL_GPL(uprobe_unregister);
  * else return 0 (success)
  */
 static int __uprobe_register(struct inode *inode, loff_t offset,
-			     struct uprobe_consumer *uc)
+			     loff_t ref_ctr_offset, struct uprobe_consumer *uc)
 {
 	struct uprobe *uprobe;
 	int ret;
@@ -912,7 +1109,7 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
 		return -EINVAL;
 
  retry:
-	uprobe = alloc_uprobe(inode, offset);
+	uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
 	if (!uprobe)
 		return -ENOMEM;
 	/*
@@ -938,10 +1135,17 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
 int uprobe_register(struct inode *inode, loff_t offset,
 		    struct uprobe_consumer *uc)
 {
-	return __uprobe_register(inode, offset, uc);
+	return __uprobe_register(inode, offset, 0, uc);
 }
 EXPORT_SYMBOL_GPL(uprobe_register);
 
+int uprobe_register_refctr(struct inode *inode, loff_t offset,
+			   loff_t ref_ctr_offset, struct uprobe_consumer *uc)
+{
+	return __uprobe_register(inode, offset, ref_ctr_offset, uc);
+}
+EXPORT_SYMBOL_GPL(uprobe_register_refctr);
+
 /*
  * uprobe_apply - unregister an already registered probe.
  * @inode: the file in which the probe has to be removed.
@@ -1060,6 +1264,35 @@ static void build_probe_list(struct inode *inode,
 	spin_unlock(&uprobes_treelock);
 }
 
+/* @vma contains reference counter, not the probed instruction. */
+static int delayed_ref_ctr_inc(struct vm_area_struct *vma)
+{
+	struct list_head *pos, *q;
+	struct delayed_uprobe *du;
+	unsigned long vaddr;
+	int ret = 0, err = 0;
+
+	mutex_lock(&delayed_uprobe_lock);
+	list_for_each_safe(pos, q, &delayed_uprobe_list) {
+		du = list_entry(pos, struct delayed_uprobe, list);
+
+		if (du->mm != vma->vm_mm ||
+		    !valid_ref_ctr_vma(du->uprobe, vma))
+			continue;
+
+		vaddr = offset_to_vaddr(vma, du->uprobe->ref_ctr_offset);
+		ret = __update_ref_ctr(vma->vm_mm, vaddr, 1);
+		if (ret) {
+			update_ref_ctr_warn(du->uprobe, vma->vm_mm, 1);
+			if (!err)
+				err = ret;
+		}
+		delayed_uprobe_delete(du);
+	}
+	mutex_unlock(&delayed_uprobe_lock);
+	return err;
+}
+
 /*
  * Called from mmap_region/vma_adjust with mm->mmap_sem acquired.
  *
@@ -1072,7 +1305,15 @@ int uprobe_mmap(struct vm_area_struct *vma)
 	struct uprobe *uprobe, *u;
 	struct inode *inode;
 
-	if (no_uprobe_events() || !valid_vma(vma, true))
+	if (no_uprobe_events())
+		return 0;
+
+	if (vma->vm_file &&
+	    (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
+	    test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags))
+		delayed_ref_ctr_inc(vma);
+
+	if (!valid_vma(vma, true))
 		return 0;
 
 	inode = file_inode(vma->vm_file);
@@ -1246,6 +1487,10 @@ void uprobe_clear_state(struct mm_struct *mm)
 {
 	struct xol_area *area = mm->uprobes_state.xol_area;
 
+	mutex_lock(&delayed_uprobe_lock);
+	delayed_uprobe_remove(NULL, mm);
+	mutex_unlock(&delayed_uprobe_lock);
+
 	if (!area)
 		return;
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bf6f1d70484d..147be8523560 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4621,7 +4621,7 @@ static const char readme_msg[] =
   "place (kretprobe): [<module>:]<symbol>[+<offset>]|<memaddr>\n"
 #endif
 #ifdef CONFIG_UPROBE_EVENTS
-	"\t    place: <path>:<offset>\n"
+  "   place (uprobe): <path>:<offset>[(ref_ctr_offset)]\n"
 #endif
 	"\t     args: <name>=fetcharg[:type]\n"
 	"\t fetcharg: %<register>, @<address>, @<symbol>[+|-<offset>],\n"
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index e696667da29a..7b85172beab6 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -47,6 +47,7 @@ struct trace_uprobe {
 	struct inode			*inode;
 	char				*filename;
 	unsigned long			offset;
+	unsigned long			ref_ctr_offset;
 	unsigned long			nhit;
 	struct trace_probe		tp;
 };
@@ -352,10 +353,10 @@ end:
 static int create_trace_uprobe(int argc, char **argv)
 {
 	struct trace_uprobe *tu;
-	char *arg, *event, *group, *filename;
+	char *arg, *event, *group, *filename, *rctr, *rctr_end;
 	char buf[MAX_EVENT_NAME_LEN];
 	struct path path;
-	unsigned long offset;
+	unsigned long offset, ref_ctr_offset;
 	bool is_delete, is_return;
 	int i, ret;
 
@@ -364,6 +365,7 @@ static int create_trace_uprobe(int argc, char **argv)
 	is_return = false;
 	event = NULL;
 	group = NULL;
+	ref_ctr_offset = 0;
 
 	/* argc must be >= 1 */
 	if (argv[0][0] == '-')
@@ -438,6 +440,26 @@ static int create_trace_uprobe(int argc, char **argv)
 		goto fail_address_parse;
 	}
 
+	/* Parse reference counter offset if specified. */
+	rctr = strchr(arg, '(');
+	if (rctr) {
+		rctr_end = strchr(rctr, ')');
+		if (rctr > rctr_end || *(rctr_end + 1) != 0) {
+			ret = -EINVAL;
+			pr_info("Invalid reference counter offset.\n");
+			goto fail_address_parse;
+		}
+
+		*rctr++ = '\0';
+		*rctr_end = '\0';
+		ret = kstrtoul(rctr, 0, &ref_ctr_offset);
+		if (ret) {
+			pr_info("Invalid reference counter offset.\n");
+			goto fail_address_parse;
+		}
+	}
+
+	/* Parse uprobe offset. */
 	ret = kstrtoul(arg, 0, &offset);
 	if (ret)
 		goto fail_address_parse;
@@ -472,6 +494,7 @@ static int create_trace_uprobe(int argc, char **argv)
 		goto fail_address_parse;
 	}
 	tu->offset = offset;
+	tu->ref_ctr_offset = ref_ctr_offset;
 	tu->path = path;
 	tu->filename = kstrdup(filename, GFP_KERNEL);
 
@@ -590,6 +613,9 @@ static int probes_seq_show(struct seq_file *m, void *v)
 			trace_event_name(&tu->tp.call), tu->filename,
 			(int)(sizeof(void *) * 2), tu->offset);
 
+	if (tu->ref_ctr_offset)
+		seq_printf(m, "(0x%lx)", tu->ref_ctr_offset);
+
 	for (i = 0; i < tu->tp.nr_args; i++)
 		seq_printf(m, " %s=%s", tu->tp.args[i].name, tu->tp.args[i].comm);
 
@@ -905,7 +931,13 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file,
 
 	tu->consumer.filter = filter;
 	tu->inode = d_real_inode(tu->path.dentry);
-	ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
+	if (tu->ref_ctr_offset) {
+		ret = uprobe_register_refctr(tu->inode, tu->offset,
+				tu->ref_ctr_offset, &tu->consumer);
+	} else {
+		ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
+	}
+
 	if (ret)
 		goto err_buffer;