[PATCH 6.1 128/196] fprobe: Add nr_maxactive to specify rethook_node pool size

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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

[ Upstream commit 59a7a298565aa0ce44ce8e4fbcbb89a19730013a ]

Add nr_maxactive to specify rethook_node pool size. This means
the maximum number of actively running target functions concurrently
for probing by exit_handler. Note that if the running function is
preempted or sleep, it is still counted as 'active'.

Link: https://lkml.kernel.org/r/167526697917.433354.17779774988245113106.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Cc: Florent Revest <revest@xxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Stable-dep-of: 700b2b439766 ("fprobe: Fix to ensure the number of active retprobes is not zero")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 include/linux/fprobe.h | 2 ++
 kernel/trace/fprobe.c  | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index e0d4e61362491..678f741a7b330 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -14,6 +14,7 @@
  * @flags: The status flag.
  * @rethook: The rethook data structure. (internal data)
  * @entry_data_size: The private data storage size.
+ * @nr_maxactive: The max number of active functions.
  * @entry_handler: The callback function for function entry.
  * @exit_handler: The callback function for function exit.
  */
@@ -31,6 +32,7 @@ struct fprobe {
 	unsigned int		flags;
 	struct rethook		*rethook;
 	size_t			entry_data_size;
+	int			nr_maxactive;
 
 	void (*entry_handler)(struct fprobe *fp, unsigned long entry_ip,
 			      struct pt_regs *regs, void *entry_data);
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index be28d1bc84e80..441a373079213 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -143,7 +143,10 @@ static int fprobe_init_rethook(struct fprobe *fp, int num)
 	}
 
 	/* Initialize rethook if needed */
-	size = num * num_possible_cpus() * 2;
+	if (fp->nr_maxactive)
+		size = fp->nr_maxactive;
+	else
+		size = num * num_possible_cpus() * 2;
 	if (size < 0)
 		return -E2BIG;
 
-- 
2.40.1






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