On 2022-03-08 22:38, Nick Desaulniers wrote:
Dear stable kernel maintainers,
Please consider cherry-picking
commit 6c23d54f4cb8 ("arm64: Import latest memcpy()/memmove() implementation")
to v5.10.y. It first landed in v5.14-rc1.
It fixes a linkage failure observed when building kernels for ChromeOS
under AutoFDO:
ld.lld: error: arch/arm64/lib/lib.a(memmove.o):(function __memmove:
.text+0x8): relocation R_AARCH64_CONDBR19 out of range: -6331272 is
not in [-1048576, 1048575]; references __memcpy
defined in arch/arm64/lib/lib.a(memcpy.o)
(The prior version of memmove used assembler conditional branches to
memcpy; under AutoFDO the linker will decide where best to place
memmove; it may be > 1MB away from memcpy. After this patch, memcpy
and memmove are the same function).
Just beware that the new implementation turned out to be really good at
finding places where __iomem pointers are erroneously being passed to
memcpy(), by more readily triggering alignment faults, so there is a
non-zero possibility of functional regressions if any of those places
are still present in 5.10.y (particularly any which had "naturally"
disappeared before 5.14). At least one of them still isn't fixed in
mainline, but that one's so obscure I wouldn't consider it a major
concern by itself.
Thanks,
Robin.
