[PATCH 5.10 37/84] clocksource: hyper-v: unexport __init-annotated hv_init_clocksource()

Greg Kroah-Hartman
2022-06-20T13:12:18Z

From: Masahiro Yamada <masahiroy@kernel.org>

[ Upstream commit 245b993d8f6c4e25f19191edfbd8080b645e12b1 ]

EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.

modpost used to detect it, but it has been broken for a decade.

Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.

There are two ways to fix it:

- Remove __init
- Remove EXPORT_SYMBOL

I chose the latter for this case because the only in-tree call-site,
arch/x86/kernel/cpu/mshyperv.c is never compiled as modular.
(CONFIG_HYPERVISOR_GUEST is boolean)

Fixes: dd2cb348613b ("clocksource/drivers: Continue making Hyper-V clocksource ISA agnostic")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220606050238.4162200-1-masahiroy@kernel.org
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/clocksource/hyperv_timer.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index ba04cb381cd3..7c617d8dff3f 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -472,4 +472,3 @@ void __init hv_init_clocksource(void)
hv_sched_clock_offset = hv_read_reference_counter();
hv_setup_sched_clock(read_hv_sched_clock_msr);
}
-EXPORT_SYMBOL_GPL(hv_init_clocksource);
--
2.35.1