x86/xen: Mark cpu_bringup_and_idle() as dead_end_function

The asm_cpu_bringup_and_idle() function is required to push the return
value on the stack in order to make ORC happy, but the only reason
objtool doesn't complain is because of a happy accident.

The thing is that asm_cpu_bringup_and_idle() doesn't return, so
validate_branch() never terminates and falls through to the next
function, which in the normal case is the hypercall_page. And that, as
it happens, is 4095 NOPs and a RET.

Make asm_cpu_bringup_and_idle() terminate on it's own, by making the
function it calls as a dead-end. This way we no longer rely on what
code happens to come after.

Fixes: c3881eb58d ("x86/xen: Make the secondary CPU idle tasks reliable")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/20210624095147.693801717@infradead.org
This commit is contained in:
Peter Zijlstra 2021-06-24 11:41:00 +02:00
parent 6880fa6c56
commit 9af9dcf11b

View File

@ -173,6 +173,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
"rewind_stack_do_exit", "rewind_stack_do_exit",
"kunit_try_catch_throw", "kunit_try_catch_throw",
"xen_start_kernel", "xen_start_kernel",
"cpu_bringup_and_idle",
}; };
if (!func) if (!func)