GCC expects __stack_chk_fail() to be noreturn[^1]. Returning from __stack_chk_fail() can thus lead to subtle failures.
When crashing, use a volatile NULL pointer dereference. Ideally we would like to "abort()" here, but doing so would require two more syscall definitions just for a cold function. After all, the function isn't even used at all if -fno-stack-protector is specified.
Also, don't say "stack smashing" (unlike glibc). The preloader currently initializes the stack canary value to a fixed value (0), which serves little value in protecting against actual buffer overrun attacks.
[^1]: https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gccint/Stack-Smashing-Protection.ht...
-- v2: loader: Don't return from __stack_chk_fail() stub in preloader.