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

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Message-Id: <20230905210621.1711859-5-puranjay12@gmail.com>
Date:   Tue,  5 Sep 2023 21:06:17 +0000
From:   Puranjay Mohan <puranjay12@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Shubham Bansal <illusionist.neo@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     puranjay12@...il.com
Subject: [PATCH bpf-next 4/8] arm32, bpf: add support for unconditional bswap instruction

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.
Since ARM32 is always little-endian, just treat the unconditional scenario
the same as big-endian conversion.

Signed-off-by: Puranjay Mohan <puranjay12@...il.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 0a30188de660..09496203f13e 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1632,8 +1632,10 @@ 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