jump_label: Annotate entries that operate on __init code earlier
authorArd Biesheuvel <ard.biesheuvel@linaro.org>
Wed, 19 Sep 2018 06:51:42 +0000 (23:51 -0700)
committerThomas Gleixner <tglx@linutronix.de>
Thu, 27 Sep 2018 15:56:48 +0000 (17:56 +0200)
commit19483677684b6ca01606f58503cb79cdfbbc7c72
treef2b8dc759e74ffbcc5f599dde452867bb342bf69
parentb34006c4258c9c86597b6b7123d6a9a3513d6cd7
jump_label: Annotate entries that operate on __init code earlier

Jump table entries are mostly read-only, with the exception of the
init and module loader code that defuses entries that point into init
code when the code being referred to is freed.

For robustness, it would be better to move these entries into the
ro_after_init section, but clearing the 'code' member of each jump
table entry referring to init code at module load time races with the
module_enable_ro() call that remaps the ro_after_init section read
only, so we'd like to do it earlier.

So given that whether such an entry refers to init code can be decided
much earlier, we can pull this check forward. Since we may still need
the code entry at this point, let's switch to setting a low bit in the
'key' member just like we do to annotate the default state of a jump
table entry.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Jessica Yu <jeyu@kernel.org>
Link: https://lkml.kernel.org/r/20180919065144.25010-8-ard.biesheuvel@linaro.org
include/linux/jump_label.h
init/main.c
kernel/jump_label.c