From b36ab509e1817e60f73ce297494f0de1b7ed2c08 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 24 Jun 2021 11:41:00 +0200 Subject: [PATCH] x86/xen: Mark cpu_bringup_and_idle() as dead_end_function [ 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) Reviewed-by: Juergen Gross Reviewed-by: Miroslav Benes Link: https://lore.kernel.org/r/20210624095147.693801717@infradead.org Signed-off-by: Sasha Levin --- tools/objtool/check.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index ec15cad..4261f93 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -157,6 +157,7 @@ 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) -- 2.7.4