From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 9af9dcf11bda3e2c0e24c1acaacb8685ad974e93 ]
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: c3881eb58d56 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- tools/objtool/check.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 06b5c164ae931..8bffc004f4e53 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -173,6 +173,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, "rewind_stack_do_exit", "kunit_try_catch_throw", "xen_start_kernel", + "cpu_bringup_and_idle", };
if (!func)