um: Add kerneldoc for segv_handler

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/kernel/trap.c

@@ -183,6 +183,16 @@ void fatal_sigsegv(void)
 	os_dump_core();
 }
 
+/**
+ * segv_handler() - the SIGSEGV handler
+ * @sig:	the signal number
+ * @unused_si:	the signal info struct; unused in this handler
+ * @regs:	the ptrace register information
+ *
+ * The handler first extracts the faultinfo from the UML ptrace regs struct.
+ * If the userfault did not happen in an UML userspace process, bad_segv is called.
+ * Otherwise the signal did happen in a cloned userspace process, handle it.
+ */
 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
 	struct faultinfo * fi = UPT_FAULTINFO(regs);