On Wed, Jun 27, 2018 at 06:06:02PM +0200, Ard Biesheuvel wrote: > On a randomly chosen distro kernel build for arm64, vmlinux.o shows the > following sections, containing jump label entries, and the associated > RELA relocation records, respectively: > > ... > [38088] __jump_table PROGBITS 0000000000000000 00e19f30 > 000000000002ea10 0000000000000000 WA 0 0 8 > [38089] .rela__jump_table RELA 0000000000000000 01fd8bb0 > 000000000008be30 0000000000000018 I 38178 38088 8 > ... > > In other words, we have 190 KB worth of 'struct jump_entry' instances, > and 573 KB worth of RELA entries to relocate each entry's code, target > and key members. This means the RELA section occupies 10% of the .init > segment, and the two sections combined represent 5% of vmlinux's entire > memory footprint. > > So let's switch from 64-bit absolute references to 32-bit relative > references: this reduces the size of the __jump_table by 50%, and gets > rid of the RELA section entirely. > > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/jump_label.h | 16 ++++------------ > arch/arm64/kernel/jump_label.c | 6 +++--- > 3 files changed, 8 insertions(+), 15 deletions(-)
Looks good, cheers: Acked-by: Will Deacon <will.dea...@arm.com> Will
