Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.10 03/12] tick/nohz: unexport __init-annotated tick_nohz_full_setup() | Date | Thu, 30 Jun 2022 15:47:08 +0200 |
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From: Masahiro Yamada <masahiroy@kernel.org>
commit 2390095113e98fc52fffe35c5206d30d9efe3f78 upstream.
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 had been broken for a decade.
Commit 28438794aba4 ("modpost: fix section mismatch check for exported init/exit sections") fixed it so modpost started to warn it again, then this showed up:
MODPOST vmlinux.symvers WARNING: modpost: vmlinux.o(___ksymtab_gpl+tick_nohz_full_setup+0x0): Section mismatch in reference from the variable __ksymtab_tick_nohz_full_setup to the function .init.text:tick_nohz_full_setup() The symbol tick_nohz_full_setup is exported and annotated __init Fix this by removing the __init annotation of tick_nohz_full_setup or drop the export.
Drop the export because tick_nohz_full_setup() is only called from the built-in code in kernel/sched/isolation.c.
Fixes: ae9e557b5be2 ("time: Export tick start/stop functions for rcutorture") Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Backlund <tmb@tmb.nu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- kernel/time/tick-sched.c | 1 - 1 file changed, 1 deletion(-)
--- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -425,7 +425,6 @@ void __init tick_nohz_full_setup(cpumask cpumask_copy(tick_nohz_full_mask, cpumask); tick_nohz_full_running = true; } -EXPORT_SYMBOL_GPL(tick_nohz_full_setup); static int tick_nohz_cpu_down(unsigned int cpu) {
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