From 6423140ffcb1c5b005199bb2fa34621361ad538d Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 5 Sep 2022 17:55:37 -0400
Subject: [PATCH] Introduce lttng_copy_from_user_check_nofault

This code will be re-used by the bytecode interpreter, so move it out of
the ring buffer.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I482adb5f619944285703425e278a70c601ce99b3
---
 lib/ringbuffer/backend.h  | 10 ++--------
 probes/lttng-probe-user.h | 23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/lib/ringbuffer/backend.h b/lib/ringbuffer/backend.h
index bfadd94b..46dcf1cc 100644
--- a/lib/ringbuffer/backend.h
+++ b/lib/ringbuffer/backend.h
@@ -22,6 +22,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <wrapper/uaccess.h>
+#include <probes/lttng-probe-user.h>
 
 /* Internal helpers */
 #include <wrapper/ringbuffer/backend_internal.h>
@@ -440,14 +441,7 @@ unsigned long lib_ring_buffer_copy_from_user_check_nofault(void *dest,
 						const void __user *src,
 						unsigned long len)
 {
-	unsigned long ret;
-
-	if (!lttng_access_ok(VERIFY_READ, src, len))
-		return 1;
-	pagefault_disable();
-	ret = __copy_from_user_inatomic(dest, src, len);
-	pagefault_enable();
-	return ret;
+	return lttng_copy_from_user_check_nofault(dest, src, len);
 }
 
 #endif /* _LIB_RING_BUFFER_BACKEND_H */
diff --git a/probes/lttng-probe-user.h b/probes/lttng-probe-user.h
index 0939a185..3251f7c6 100644
--- a/probes/lttng-probe-user.h
+++ b/probes/lttng-probe-user.h
@@ -8,10 +8,33 @@
 #ifndef _LTTNG_PROBE_USER_H
 #define _LTTNG_PROBE_USER_H
 
+#include <wrapper/uaccess.h>
+
 /*
  * Calculate string length. Include final null terminating character if there is
  * one, or ends at first fault.
  */
 long lttng_strlen_user_inatomic(const char *addr);
 
+/*
+ * We use __copy_from_user_inatomic to copy userspace data after
+ * checking with access_ok() and disabling page faults.
+ *
+ * Return 0 if OK, nonzero on error.
+ */
+static inline
+unsigned long lttng_copy_from_user_check_nofault(void *dest,
+						 const void __user *src,
+						 unsigned long len)
+{
+	unsigned long ret;
+
+	if (!lttng_access_ok(VERIFY_READ, src, len))
+		return 1;
+	pagefault_disable();
+	ret = __copy_from_user_inatomic(dest, src, len);
+	pagefault_enable();
+	return ret;
+}
+
 #endif /* _LTTNG_PROBE_USER_H */
-- 
2.34.1