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Commit 10a221e2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Greg Kroah-Hartman
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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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/20210624095147.693801717@infradead.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent a12884ff

tools/objtool/check.c

+1 −0
Original line number Diff line number Diff line
@@ -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)