uprobes: Export 'struct return_instance', introduce arch_uretprobe_is_alive()

Add the new "weak" helper, arch_uretprobe_is_alive(), used by
the next patches. It should return true if this return_instance
is still valid. The arch agnostic version just always returns
true.

The patch exports "struct return_instance" for the architectures
which want to override this hook. We can also cleanup
prepare_uretprobe() if we pass the new return_instance to
arch_uretprobe_hijack_return_addr().

Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134016.GA4762@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 5 insertions, 9 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 98e4d97..1c71b62 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -86,15 +86,6 @@ struct uprobe {
 	struct arch_uprobe	arch;
 };
 
-struct return_instance {
-	struct uprobe		*uprobe;
-	unsigned long		func;
-	unsigned long		orig_ret_vaddr; /* original return address */
-	bool			chained;	/* true, if instance is nested */
-
-	struct return_instance	*next;		/* keep as stack */
-};
-
 /*
  * Execute out of line area: anonymous executable mapping installed
  * by the probed task to execute the copy of the original instruction
@@ -1818,6 +1809,11 @@ bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
 	return false;
 }
 
+bool __weak arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs)
+{
+	return true;
+}
+
 /*
  * Run handler and ask thread to singlestep.
  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.