diff mbox series

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

Message ID 20230905210621.1711859-5-puranjay12@gmail.com
State Superseded
Headers show
Series arm32, bpf: add support for cpuv4 insns | expand

Commit Message

Puranjay Mohan Sept. 5, 2023, 9:06 p.m. UTC
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@gmail.com>
---
 arch/arm/net/bpf_jit_32.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Puranjay Mohan Sept. 6, 2023, 9:31 a.m. UTC | #1
On Tue, Sep 05 2023, Russell King (Oracle) wrote:

> On Tue, Sep 05, 2023 at 09:06:17PM +0000, Puranjay Mohan wrote:
>> 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
>
> This is not true. Arm32 BPF is disabled for BE32 but not for BE8. It's
> entirely possible to build a kernel using BE8 for ARMv7 and have the
> BPF JIT enabled:
>
>         select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
>
> So it's not true to say "Since ARM32 is always little-endian".

Sure, I will change the commit message in next version.

Thanks,
Puranjay
diff mbox series

Patch

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: