[PATCH bpf-next 2/3] nfp: bpf: support arithmetic right shift by constant (BPF_ARSH | BPF_K)
STALE3059d
REVIEWED: 1 (0M)
From: Jakub Kicinski <hidden>
Date: 2018-05-18 19:12:35
Subsystem:
bpf jit for nfp nics, netronome ethernet drivers, networking drivers, the rest · Maintainers:
Jakub Kicinski, Andrew Lunn, "David S. Miller", Eric Dumazet, Paolo Abeni, Linus Torvalds
1 review trailer.
From: Jiong Wang <redacted> Code logic is similar with logic right shift except we also need to set PREV_ALU result properly, the MSB of which is the bit that will be replicated to fill in all the vacant positions. Signed-off-by: Jiong Wang <redacted> Reviewed-by: Jakub Kicinski <redacted> --- drivers/net/ethernet/netronome/nfp/bpf/jit.c | 34 ++++++++++++++++++++ drivers/net/ethernet/netronome/nfp/nfp_asm.h | 1 + 2 files changed, 35 insertions(+)
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
index 4cff08771951..f73242c4da2f 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/jit.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/jit.c@@ -1916,6 +1916,39 @@ static int shr_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta) return 0; } +/* Code logic is the same as __shr_imm64 except ashr requires signedness bit + * told through PREV_ALU result. + */ +static int ashr_imm64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta) +{ + const struct bpf_insn *insn = &meta->insn; + u8 dst = insn->dst_reg * 2; + + if (insn->imm < 32) { + emit_shf(nfp_prog, reg_both(dst), reg_a(dst + 1), SHF_OP_NONE, + reg_b(dst), SHF_SC_R_DSHF, insn->imm); + /* Set signedness bit. */ + emit_alu(nfp_prog, reg_none(), reg_a(dst + 1), ALU_OP_OR, + reg_imm(0)); + emit_shf(nfp_prog, reg_both(dst + 1), reg_none(), SHF_OP_ASHR, + reg_b(dst + 1), SHF_SC_R_SHF, insn->imm); + } else if (insn->imm == 32) { + /* NOTE: this also helps setting signedness bit. */ + wrp_reg_mov(nfp_prog, dst, dst + 1); + emit_shf(nfp_prog, reg_both(dst + 1), reg_none(), SHF_OP_ASHR, + reg_b(dst + 1), SHF_SC_R_SHF, 31); + } else if (insn->imm > 32) { + emit_alu(nfp_prog, reg_none(), reg_a(dst + 1), ALU_OP_OR, + reg_imm(0)); + emit_shf(nfp_prog, reg_both(dst), reg_none(), SHF_OP_ASHR, + reg_b(dst + 1), SHF_SC_R_SHF, insn->imm - 32); + emit_shf(nfp_prog, reg_both(dst + 1), reg_none(), SHF_OP_ASHR, + reg_b(dst + 1), SHF_SC_R_SHF, 31); + } + + return 0; +} + static int mov_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta) { const struct bpf_insn *insn = &meta->insn;
@@ -2742,6 +2775,7 @@ static const instr_cb_t instr_cb[256] = { [BPF_ALU64 | BPF_LSH | BPF_K] = shl_imm64, [BPF_ALU64 | BPF_RSH | BPF_X] = shr_reg64, [BPF_ALU64 | BPF_RSH | BPF_K] = shr_imm64, + [BPF_ALU64 | BPF_ARSH | BPF_K] = ashr_imm64, [BPF_ALU | BPF_MOV | BPF_X] = mov_reg, [BPF_ALU | BPF_MOV | BPF_K] = mov_imm, [BPF_ALU | BPF_XOR | BPF_X] = xor_reg,
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_asm.h b/drivers/net/ethernet/netronome/nfp/nfp_asm.h
index fa826bd9c668..f6677bc9875a 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_asm.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_asm.h@@ -174,6 +174,7 @@ enum shf_op { SHF_OP_NONE = 0, SHF_OP_AND = 2, SHF_OP_OR = 5, + SHF_OP_ASHR = 6, }; enum shf_sc {
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2.17.0