Commit 21a099ab authored May 05, 2020 by Luke Nelson Committed by Daniel Borkmann May 06, 2020

bpf, riscv: Optimize FROM_LE using verifier_zext on RV64



This patch adds two optimizations for BPF_ALU BPF_END BPF_FROM_LE in
the RV64 BPF JIT.

First, it enables the verifier zero-extension optimization to avoid zero
extension when imm == 32. Second, it avoids generating code for imm ==
64, since it is equivalent to a no-op.

Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200506000320.28965-3-luke.r.nels@gmail.com

parent 0224b2ac

arch/riscv/net/bpf_jit_comp64.c

+14 −6

Original line number	Diff line number	Diff line
		@@ -542,13 +542,21 @@ int bpf_jit_emit_insn(const struct bpf_insn insn, struct rv_jit_context ctx,

		/* dst = BSWAP##imm(dst) */
		case BPF_ALU \| BPF_END \| BPF_FROM_LE:
		{
		int shift = 64 - imm;

		emit(rv_slli(rd, rd, shift), ctx);
		emit(rv_srli(rd, rd, shift), ctx);
		switch (imm) {
		case 16:
		emit(rv_slli(rd, rd, 48), ctx);
		emit(rv_srli(rd, rd, 48), ctx);
		break;
		case 32:
		if (!aux->verifier_zext)
		emit_zext_32(rd, ctx);
		break;
		case 64:
		/* Do nothing */
		break;
		}
		break;

		case BPF_ALU \| BPF_END \| BPF_FROM_BE:
		emit(rv_addi(RV_REG_T2, RV_REG_ZERO, 0), ctx);

Admin message