Cleanup: Move all source files to src/

[lttng-modules.git] / src / probes / lttng-probe-user.c

diff --git a/src/probes/lttng-probe-user.c b/src/probes/lttng-probe-user.c
new file mode 100644 (file)
index 0000000..009cfed
--- /dev/null
+++ b/src/probes/lttng-probe-user.c
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * lttng-probe-user.c
+ *
+ * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <wrapper/uaccess.h>
+#include <lttng/probe-user.h>
+
+/*
+ * Calculate string length. Include final null terminating character if there is
+ * one, or ends at first fault. Disabling page faults ensures that we can safely
+ * call this from pretty much any context, including those where the caller
+ * holds mmap_sem, or any lock which nests in mmap_sem.
+ */
+long lttng_strlen_user_inatomic(const char *addr)
+{
+       long count = 0;
+       mm_segment_t old_fs;
+
+       if (!addr)
+               return 0;
+
+       old_fs = get_fs();
+       set_fs(KERNEL_DS);
+       pagefault_disable();
+       for (;;) {
+               char v;
+               unsigned long ret;
+
+               if (unlikely(!lttng_access_ok(VERIFY_READ,
+                               (__force const char __user *) addr,
+                               sizeof(v))))
+                       break;
+               ret = __copy_from_user_inatomic(&v,
+                       (__force const char __user *)(addr),
+                       sizeof(v));
+               if (unlikely(ret > 0))
+                       break;
+               count++;
+               if (unlikely(!v))
+                       break;
+               addr++;
+       }
+       pagefault_enable();
+       set_fs(old_fs);
+       return count;
+}
+EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic);