[PATCH 16/17] uprobes: Allocate ->utask before handler_chain() for tracing handlers

[Namhyung Kim]

From: Oleg Nesterov <oleg@xxxxxxxxxx>

uprobe_trace_print() and uprobe_perf_print() need to pass the additional
info to call_fetch() methods, currently there is no simple way to do this.

current->utask looks like a natural place to hold this info, but we need
to allocate it before handler_chain().

This is a bit unfortunate, perhaps we will find a better solution later,
but this is simnple and should work right now.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 kernel/events/uprobes.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 24b7d6ca871b..3cc8e0bb8acf 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1828,6 +1828,10 @@ static void handle_swbp(struct pt_regs *regs)
 	if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
 		goto out;
 
+	/* Tracing handlers use ->utask to communicate with fetch methods */
+	if (!get_utask())
+		goto out;
+
 	handler_chain(uprobe, regs);
 	if (can_skip_sstep(uprobe, regs))
 		goto out;
-- 
1.7.11.7

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