nfp: bpf: support arithmetic right shift by constant (BPF_ARSH | BPF_K)

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 <jiong.wang@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
index 4cff087..f73242c 100644 (file)
--- 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 fa826bd..f6677bc 100644 (file)
--- 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 {