freebsd-dev/sys/riscv
Kristof Provost 52bb6100e9 riscv: Fix copyin/copyout
r343275 introduced a performance optimisation to the copyin/copyout
routines by attempting to copy word-per-word rather than byte-per-byte
where possible.

This optimisation failed to account for cases where the buffer is longer
than XLEN_BYTES, but due to misalignment does not not allow for any
word-sized copies. E.g. a 9 byte buffer (with XLEN_BYTES == 8) which is
misaligned by 2 bytes. The code nevertheless did a single full-word
copy, which meant we copied too much data. This potentially clobbered
other data.

This is most easily demonstrated by a simple `sysctl -a`.

Fix it by not assuming that we'll always have at least one full-word
copy to do, but instead checking the remaining length first.

Reviewed by:	markj@, mhorne@, br@ (previous version)
MFC after:	1 week
Sponsored by:	Axiado
Differential Revision:	https://reviews.freebsd.org/D21100
2019-07-29 14:59:14 +00:00
..
conf sys: Remove DEV_RANDOM device option 2019-06-21 00:16:30 +00:00
include RISC-V: expose extension bits in AT_HWCAP 2019-06-11 00:55:54 +00:00
riscv riscv: Fix copyin/copyout 2019-07-29 14:59:14 +00:00