From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
[ 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@xxxxxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Link: https://lore.kernel.org/r/20210624095147.693801717@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
tools/objtool/check.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index ec15cadbb3d3e..4261f93ce06f9 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)
--
2.33.0
