tree fa118be31e1bd66fb80c8b0c77aff60b5a5d05d5
parent 78ecb2ab5ec952e4dbfe8bc97da0b3e3906ea400
author Ilya Leoshkevich <iii@linux.ibm.com> 1612989902 +0100
committer Oleksandr Tymoshenko <ovt@google.com> 1619573674 +0000

bpf: Fix subreg optimization for BPF_FETCH

All 32-bit variants of BPF_FETCH (add, and, or, xor, xchg, cmpxchg)
define a 32-bit subreg and thus have zext_dst set. Their encoding,
however, uses dst_reg field as a base register, which causes
opt_subreg_zext_lo32_rnd_hi32() to zero-extend said base register
instead of the one the insn really defines (r0 or src_reg).

Fix by properly choosing a register being defined, similar to how
check_atomic() already does that.

Change-Id: I71fe565d5ded9edf8ec7113a1410d9dda0d899d8
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210210204502.83429-1-iii@linux.ibm.com
SOURCE=UPSTREAM(b2e37a7114ef52b862b4421ed4cd40c4ed2a0642)
BUG=b:153508410