function::sprint_ubacktrace — Return stack back trace for current user-space task as string.
Returns a simple backtrace for the current task. One line per
address. Includes the symbol name (or hex address if symbol
couldn't be resolved) and module name (if found). Includes the
offset from the start of the function if found, otherwise the
offset will be added to the module (if found, between
brackets). Returns the backtrace as string (each line terminated by
a newline character). Note that the returned stack will be
truncated to MAXSTRINGLEN, to print fuller and richer stacks use
print_ubacktrace. Equivalent to sprint_ustack(
but more efficient (no need to translate between hex strings and
final backtrace string).