From: Peter Zijlstra Date: Thu, 24 Jun 2021 09:41:00 +0000 (+0200) Subject: x86/xen: Mark cpu_bringup_and_idle() as dead_end_function X-Git-Tag: v5.4.196~3 X-Git-Url: https://git.fsl.cs.sunysb.edu/?a=commitdiff_plain;h=10a221e2d3d8cf53be4e55c92257197688cfe54f;p=wrapfs-5.4.y.git x86/xen: Mark cpu_bringup_and_idle() as dead_end_function commit 9af9dcf11bda3e2c0e24c1acaacb8685ad974e93 upstream. 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: Greg Kroah-Hartman --- diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 06aaf04e629c..bae6b261481d 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -144,6 +144,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, "usercopy_abort", "machine_real_restart", "rewind_stack_do_exit", + "cpu_bringup_and_idle", }; if (!func)