Re: [PATCH bpf-next 2/4] bpf: arm64: Add support for indirect jumps

[Anton Protopopov <a.s.protopopov@gmail.com>]

On 25/11/17 12:46AM, Puranjay Mohan wrote:
> Add support for a new instruction
> 
> 	BPF_JMP|BPF_X|BPF_JA, SRC=0, DST=Rx, off=0, imm=0
> 
> which does an indirect jump to a location stored in Rx.  The register
> Rx should have type PTR_TO_INSN. This new type assures that the Rx
> register contains a value (or a range of values) loaded from a
> correct jump table – map of type instruction array.
> 
> ARM64 JIT supports indirect jumps to all registers through the A64_BR()
> macro, use it to implement this new instruction.
> 
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> ---
>  arch/arm64/net/bpf_jit_comp.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 4a2afc0cefc4..4cfb549f2b43 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -1452,6 +1452,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
>  		emit(A64_ASR(is64, dst, dst, imm), ctx);
>  		break;
>  
> +	/* JUMP reg */
> +	case BPF_JMP | BPF_JA | BPF_X:
> +		emit(A64_BR(dst), ctx);
> +		break;
>  	/* JUMP off */
>  	case BPF_JMP | BPF_JA:
>  	case BPF_JMP32 | BPF_JA:
> -- 
> 2.47.3
> 

Reviewed-by: Anton Protopopov <a.s.protopopov@gmail.com>