[PATCH bpf-next v2 4/8] arm32, bpf: add support for unconditional bswap instruction

Puranjay Mohan
2023-09-06T18:34:25Z

The cpuv4 added a new unconditional bswap instruction with following
behaviour:

BPF_ALU64 | BPF_TO_LE | BPF_END with imm = 16/32/64 means:
dst = bswap16(dst)
dst = bswap32(dst)
dst = bswap64(dst)

As we already support converting to big-endian from little-endian we can
use the same for unconditional bswap. just treat the unconditional scenario
the same as big-endian conversion.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
---
arch/arm/net/bpf_jit_32.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 56ea8022e989..f837db5c71b1 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1633,8 +1633,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
/* dst = htobe(dst) */
case BPF_ALU | BPF_END | BPF_FROM_LE:
case BPF_ALU | BPF_END | BPF_FROM_BE:
+ /* dst = bswap(dst) */
+ case BPF_ALU64 | BPF_END | BPF_TO_LE:
rd = arm_bpf_get_reg64(dst, tmp, ctx);
- if (BPF_SRC(code) == BPF_FROM_LE)
+ if (BPF_SRC(code) == BPF_FROM_LE && BPF_CLASS(code) != BPF_ALU64)
goto emit_bswap_uxt;
switch (imm) {
case 16:
--
2.39.2