This is a note to let you know that I've just added the patch titled
x86/xen: Mark cpu_bringup_and_idle() as dead_end_function
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-xen-mark-cpu_bringup_and_idle-as-dead_end_function.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 9af9dcf11bda3e2c0e24c1acaacb8685ad974e93 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu, 24 Jun 2021 11:41:00 +0200
Subject: x86/xen: Mark cpu_bringup_and_idle() as dead_end_function
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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) <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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/objtool/check.c | 1 +
1 file changed, 1 insertion(+)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -144,6 +144,7 @@ static bool __dead_end_function(struct o
"usercopy_abort",
"machine_real_restart",
"rewind_stack_do_exit",
+ "cpu_bringup_and_idle",
};
if (!func)
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-5.4/crypto-x86-chacha20-avoid-spurious-jumps-to-other-fu.patch
queue-5.4/x86-xen-mark-cpu_bringup_and_idle-as-dead_end_function.patch
queue-5.4/perf-fix-sys_perf_event_open-race-against-self.patch
