[tip:perf/core] uprobes: Change prepare_uretprobe() to use uprobe_warn()

[tip-bot for Oleg Nesterov <tipbot@zytor.com>]

Commit-ID:  6c58d0e4cc26ea8882928e64c0de9afed4fc37cb
Gitweb:     http://git.kernel.org/tip/6c58d0e4cc26ea8882928e64c0de9afed4fc37cb
Author:     Oleg Nesterov <oleg@redhat.com>
AuthorDate: Tue, 21 Jul 2015 15:40:10 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 31 Jul 2015 10:38:04 +0200

uprobes: Change prepare_uretprobe() to use uprobe_warn()

Turn the last pr_warn() in uprobes.c into uprobe_warn().

While at it:

   - s/kzalloc/kmalloc, we initialize every member of 'ri'

   - remove the pointless comment above the obvious code

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/20150721134010.GA4752@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/uprobes.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index eabdc21..4c941fe 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1541,9 +1541,9 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
 		return;
 	}
 
-	ri = kzalloc(sizeof(struct return_instance), GFP_KERNEL);
+	ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
 	if (!ri)
-		goto fail;
+		return;
 
 	trampoline_vaddr = get_trampoline_vaddr();
 	orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
@@ -1561,8 +1561,7 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
 			 * This situation is not possible. Likely we have an
 			 * attack from user-space.
 			 */
-			pr_warn("uprobe: unable to set uretprobe pid/tgid=%d/%d\n",
-						current->pid, current->tgid);
+			uprobe_warn(current, "handle tail call");
 			goto fail;
 		}
 
@@ -1576,13 +1575,10 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
 	ri->chained = chained;
 
 	utask->depth++;
-
-	/* add instance to the stack */
 	ri->next = utask->return_instances;
 	utask->return_instances = ri;
 
 	return;
-
  fail:
 	kfree(ri);
 }