> From: Konstantin Ananyev [mailto:konstantin.ananyev@intel.com]
> Sent: Wednesday, May 27, 2020 4:17 PM
>
> Make x86 JIT to generate native code for
> (BPF_ABS | <size> | BPF_LD) and (BPF_IND | <size> | BPF_LD)
> instructions.
>
> Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> ---
[...]
> +/*
> + * helper function, used by emit_ld_mbuf().
> + * generates code for 'fast_path':
> + * calculate load offset and check is it inside first packet segment.
> + */
> +static void
> +emit_ldmb_fast_path(struct bpf_jit_state *st, const uint32_t
> rg[EBPF_REG_7],
> + uint32_t sreg, uint32_t mode, uint32_t sz, uint32_t imm,
> + const int32_t ofs[LDMB_OFS_NUM])
> +{
> + /* make R2 contain *off* value */
> +
> + if (sreg != rg[EBPF_REG_2]) {
> + emit_mov_imm(st, EBPF_ALU64 | EBPF_MOV | BPF_K,
> + rg[EBPF_REG_2], imm);
> + if (mode == BPF_IND)
> + emit_alu_reg(st, EBPF_ALU64 | BPF_ADD | BPF_X,
> + sreg, rg[EBPF_REG_2]);
> + } else
> + /* BPF_IND with sreg == R2 */
> + emit_alu_imm(st, EBPF_ALU64 | BPF_ADD | BPF_K,
> + rg[EBPF_REG_2], imm);
> +
> + /* R3 = mbuf->data_len */
> + emit_ld_reg(st, BPF_LDX | BPF_MEM | BPF_H,
> + rg[EBPF_REG_6], rg[EBPF_REG_3],
> + offsetof(struct rte_mbuf, data_len));
> +
> + /* R3 = R3 - R2 */
> + emit_alu_reg(st, EBPF_ALU64 | BPF_SUB | BPF_X,
> + rg[EBPF_REG_2], rg[EBPF_REG_3]);
> +
> + /* JSLT R3, <sz> <slow_path> */
> + emit_cmp_imm(st, EBPF_ALU64, rg[EBPF_REG_3], sz);
> + emit_abs_jcc(st, BPF_JMP | EBPF_JSLT | BPF_K, ofs[LDMB_SLP_OFS]);
> +
[...]
> +
> +/*
> + * emit code for BPF_ABS/BPF_IND load.
> + * generates the following construction:
> + * fast_path:
> + * off = ins->sreg + ins->imm
> + * if (mbuf->data_len - off < ins->opsz)
> + * goto slow_path;
> + * ptr = mbuf->buf_addr + mbuf->data_off + off;
> + * goto fin_part;
> + * slow_path:
> + * typeof(ins->opsz) buf; //allocate space on the stack
> + * ptr = __rte_pktmbuf_read(mbuf, off, ins->opsz, &buf);
> + * if (ptr == NULL)
> + * goto exit_label;
> + * fin_part:
> + * res = *(typeof(ins->opsz))ptr;
> + * res = bswap(res);
> + */
[...]
The comparison for jumping to the slow path looks correct now.
I haven't reviewed it all in depth, but it certainly deserves an:
Acked-by: Morten Brørup <mb@smartsharesystems.com>
@@ -87,6 +87,14 @@ enum {
REG_TMP1 = R10,
};
+/* LD_ABS/LD_IMM offsets */
+enum {
+ LDMB_FSP_OFS, /* fast-path */
+ LDMB_SLP_OFS, /* slow-path */
+ LDMB_FIN_OFS, /* final part */
+ LDMB_OFS_NUM
+};
+
/*
* callee saved registers list.
* keep RBP as the last one.
@@ -100,6 +108,9 @@ struct bpf_jit_state {
uint32_t num;
int32_t off;
} exit;
+ struct {
+ uint32_t stack_ofs;
+ } ldmb;
uint32_t reguse;
int32_t *off;
uint8_t *ins;
@@ -1024,6 +1035,166 @@ emit_div(struct bpf_jit_state *st, uint32_t op, uint32_t sreg, uint32_t dreg,
emit_mov_reg(st, EBPF_ALU64 | EBPF_MOV | BPF_X, REG_TMP1, RDX);
}
+/*
+ * helper function, used by emit_ld_mbuf().
+ * generates code for 'fast_path':
+ * calculate load offset and check is it inside first packet segment.
+ */
+static void
+emit_ldmb_fast_path(struct bpf_jit_state *st, const uint32_t rg[EBPF_REG_7],
+ uint32_t sreg, uint32_t mode, uint32_t sz, uint32_t imm,
+ const int32_t ofs[LDMB_OFS_NUM])
+{
+ /* make R2 contain *off* value */
+
+ if (sreg != rg[EBPF_REG_2]) {
+ emit_mov_imm(st, EBPF_ALU64 | EBPF_MOV | BPF_K,
+ rg[EBPF_REG_2], imm);
+ if (mode == BPF_IND)
+ emit_alu_reg(st, EBPF_ALU64 | BPF_ADD | BPF_X,
+ sreg, rg[EBPF_REG_2]);
+ } else
+ /* BPF_IND with sreg == R2 */
+ emit_alu_imm(st, EBPF_ALU64 | BPF_ADD | BPF_K,
+ rg[EBPF_REG_2], imm);
+
+ /* R3 = mbuf->data_len */
+ emit_ld_reg(st, BPF_LDX | BPF_MEM | BPF_H,
+ rg[EBPF_REG_6], rg[EBPF_REG_3],
+ offsetof(struct rte_mbuf, data_len));
+
+ /* R3 = R3 - R2 */
+ emit_alu_reg(st, EBPF_ALU64 | BPF_SUB | BPF_X,
+ rg[EBPF_REG_2], rg[EBPF_REG_3]);
+
+ /* JSLT R3, <sz> <slow_path> */
+ emit_cmp_imm(st, EBPF_ALU64, rg[EBPF_REG_3], sz);
+ emit_abs_jcc(st, BPF_JMP | EBPF_JSLT | BPF_K, ofs[LDMB_SLP_OFS]);
+
+ /* R3 = mbuf->data_off */
+ emit_ld_reg(st, BPF_LDX | BPF_MEM | BPF_H,
+ rg[EBPF_REG_6], rg[EBPF_REG_3],
+ offsetof(struct rte_mbuf, data_off));
+
+ /* R0 = mbuf->buf_addr */
+ emit_ld_reg(st, BPF_LDX | BPF_MEM | EBPF_DW,
+ rg[EBPF_REG_6], rg[EBPF_REG_0],
+ offsetof(struct rte_mbuf, buf_addr));
+
+ /* R0 = R0 + R3 */
+ emit_alu_reg(st, EBPF_ALU64 | BPF_ADD | BPF_X,
+ rg[EBPF_REG_3], rg[EBPF_REG_0]);
+
+ /* R0 = R0 + R2 */
+ emit_alu_reg(st, EBPF_ALU64 | BPF_ADD | BPF_X,
+ rg[EBPF_REG_2], rg[EBPF_REG_0]);
+
+ /* JMP <fin_part> */
+ emit_abs_jmp(st, ofs[LDMB_FIN_OFS]);
+}
+
+/*
+ * helper function, used by emit_ld_mbuf().
+ * generates code for 'slow_path':
+ * call __rte_pktmbuf_read() and check return value.
+ */
+static void
+emit_ldmb_slow_path(struct bpf_jit_state *st, const uint32_t rg[EBPF_REG_7],
+ uint32_t sz)
+{
+ /* make R3 contain *len* value (1/2/4) */
+
+ emit_mov_imm(st, EBPF_ALU64 | EBPF_MOV | BPF_K, rg[EBPF_REG_3], sz);
+
+ /* make R4 contain (RBP - ldmb.stack_ofs) */
+
+ emit_mov_reg(st, EBPF_ALU64 | EBPF_MOV | BPF_X, RBP, rg[EBPF_REG_4]);
+ emit_alu_imm(st, EBPF_ALU64 | BPF_SUB | BPF_K, rg[EBPF_REG_4],
+ st->ldmb.stack_ofs);
+
+ /* make R1 contain mbuf ptr */
+
+ emit_mov_reg(st, EBPF_ALU64 | EBPF_MOV | BPF_X,
+ rg[EBPF_REG_6], rg[EBPF_REG_1]);
+
+ /* call rte_pktmbuf_read */
+ emit_call(st, (uintptr_t)__rte_pktmbuf_read);
+
+ /* check that return value (R0) is not zero */
+ emit_tst_reg(st, EBPF_ALU64, rg[EBPF_REG_0], rg[EBPF_REG_0]);
+ emit_abs_jcc(st, BPF_JMP | BPF_JEQ | BPF_K, st->exit.off);
+}
+
+/*
+ * helper function, used by emit_ld_mbuf().
+ * generates final part of code for BPF_ABS/BPF_IND load:
+ * perform data load and endianness conversion.
+ * expects dreg to contain valid data pointer.
+ */
+static void
+emit_ldmb_fin(struct bpf_jit_state *st, uint32_t dreg, uint32_t opsz,
+ uint32_t sz)
+{
+ emit_ld_reg(st, BPF_LDX | BPF_MEM | opsz, dreg, dreg, 0);
+ if (sz != sizeof(uint8_t))
+ emit_be2le(st, dreg, sz * CHAR_BIT);
+}
+
+/*
+ * emit code for BPF_ABS/BPF_IND load.
+ * generates the following construction:
+ * fast_path:
+ * off = ins->sreg + ins->imm
+ * if (mbuf->data_len - off < ins->opsz)
+ * goto slow_path;
+ * ptr = mbuf->buf_addr + mbuf->data_off + off;
+ * goto fin_part;
+ * slow_path:
+ * typeof(ins->opsz) buf; //allocate space on the stack
+ * ptr = __rte_pktmbuf_read(mbuf, off, ins->opsz, &buf);
+ * if (ptr == NULL)
+ * goto exit_label;
+ * fin_part:
+ * res = *(typeof(ins->opsz))ptr;
+ * res = bswap(res);
+ */
+static void
+emit_ld_mbuf(struct bpf_jit_state *st, uint32_t op, uint32_t sreg, uint32_t imm)
+{
+ uint32_t i, mode, opsz, sz;
+ uint32_t rg[EBPF_REG_7];
+ int32_t ofs[LDMB_OFS_NUM];
+
+ mode = BPF_MODE(op);
+ opsz = BPF_SIZE(op);
+ sz = bpf_size(opsz);
+
+ for (i = 0; i != RTE_DIM(rg); i++)
+ rg[i] = ebpf2x86[i];
+
+ /* fill with fake offsets */
+ for (i = 0; i != RTE_DIM(ofs); i++)
+ ofs[i] = st->sz + INT8_MAX;
+
+ /* dry run first to calculate jump offsets */
+
+ ofs[LDMB_FSP_OFS] = st->sz;
+ emit_ldmb_fast_path(st, rg, sreg, mode, sz, imm, ofs);
+ ofs[LDMB_SLP_OFS] = st->sz;
+ emit_ldmb_slow_path(st, rg, sz);
+ ofs[LDMB_FIN_OFS] = st->sz;
+ emit_ldmb_fin(st, rg[EBPF_REG_0], opsz, sz);
+
+ RTE_VERIFY(ofs[LDMB_FIN_OFS] - ofs[LDMB_FSP_OFS] <= INT8_MAX);
+
+ /* reset dry-run code and do a proper run */
+
+ st->sz = ofs[LDMB_FSP_OFS];
+ emit_ldmb_fast_path(st, rg, sreg, mode, sz, imm, ofs);
+ emit_ldmb_slow_path(st, rg, sz);
+ emit_ldmb_fin(st, rg[EBPF_REG_0], opsz, sz);
+}
+
static void
emit_prolog(struct bpf_jit_state *st, int32_t stack_size)
{
@@ -1121,6 +1292,7 @@ emit(struct bpf_jit_state *st, const struct rte_bpf *bpf)
/* reset state fields */
st->sz = 0;
st->exit.num = 0;
+ st->ldmb.stack_ofs = bpf->stack_sz;
emit_prolog(st, bpf->stack_sz);
@@ -1240,6 +1412,15 @@ emit(struct bpf_jit_state *st, const struct rte_bpf *bpf)
emit_ld_imm64(st, dr, ins[0].imm, ins[1].imm);
i++;
break;
+ /* load absolute/indirect instructions */
+ case (BPF_LD | BPF_ABS | BPF_B):
+ case (BPF_LD | BPF_ABS | BPF_H):
+ case (BPF_LD | BPF_ABS | BPF_W):
+ case (BPF_LD | BPF_IND | BPF_B):
+ case (BPF_LD | BPF_IND | BPF_H):
+ case (BPF_LD | BPF_IND | BPF_W):
+ emit_ld_mbuf(st, op, sr, ins->imm);
+ break;
/* store instructions */
case (BPF_STX | BPF_MEM | BPF_B):
case (BPF_STX | BPF_MEM | BPF_H):
@@ -70,6 +70,7 @@ struct bpf_verifier {
uint64_t stack_sz;
uint32_t nb_nodes;
uint32_t nb_jcc_nodes;
+ uint32_t nb_ldmb_nodes;
uint32_t node_colour[MAX_NODE_COLOUR];
uint32_t edge_type[MAX_EDGE_TYPE];
struct bpf_eval_state *evst;
@@ -2020,6 +2021,14 @@ validate(struct bpf_verifier *bvf)
rc |= add_edge(bvf, node, i + 2);
i++;
break;
+ case (BPF_LD | BPF_ABS | BPF_B):
+ case (BPF_LD | BPF_ABS | BPF_H):
+ case (BPF_LD | BPF_ABS | BPF_W):
+ case (BPF_LD | BPF_IND | BPF_B):
+ case (BPF_LD | BPF_IND | BPF_H):
+ case (BPF_LD | BPF_IND | BPF_W):
+ bvf->nb_ldmb_nodes++;
+ /* fallthrough */
default:
rc |= add_edge(bvf, node, i + 1);
break;
@@ -2320,8 +2329,14 @@ bpf_validate(struct rte_bpf *bpf)
free(bvf.in);
/* copy collected info */
- if (rc == 0)
+ if (rc == 0) {
bpf->stack_sz = bvf.stack_sz;
+ /* for LD_ABS/LD_IND, we'll need extra space on the stack */
+ if (bvf.nb_ldmb_nodes != 0)
+ bpf->stack_sz = RTE_ALIGN_CEIL(bpf->stack_sz +
+ sizeof(uint64_t), sizeof(uint64_t));
+ }
+
return rc;
}