[RFC PATCH v3 1/6] uretprobes: preparation patch

[Anton Arapov <anton@redhat.com>]

  1/6 and 6/6 patches are here to enclose return probes implementation as well
as prohibit uprobe_register() routine with no consumer set.

v3 changes: (the patch is introduced in v3)
  - check whether at least one of the consumer's handlers were set
  - a 'TODO' cap that will be removed once return probes be implemented

Signed-off-by: Anton Arapov <anton@redhat.com>
---
 include/linux/uprobes.h | 1 +
 kernel/events/uprobes.c | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 02b83db..a28bdee 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -46,6 +46,7 @@ enum uprobe_filter_ctx {
 
 struct uprobe_consumer {
 	int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
+	int (*rp_handler)(struct uprobe_consumer *self, struct pt_regs *regs);
 	bool (*filter)(struct uprobe_consumer *self,
 				enum uprobe_filter_ctx ctx,
 				struct mm_struct *mm);
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a567c8c..d904164 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -828,6 +828,14 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
 	struct uprobe *uprobe;
 	int ret;
 
+	/* Uprobe must have at least one set consumer */
+	if (!uc->handler && !uc->rp_handler)
+		return -EINVAL;
+
+	/* TODO: Implement return probes */
+	if (uc->rp_handler)
+		return -ENOSYS;
+
 	/* Racy, just to catch the obvious mistakes */
 	if (offset > i_size_read(inode))
 		return -EINVAL;
-- 
1.8.1.2