Implement JIT support for the indirect jump instruction (BPF_JMP | BPF_JA | BPF_X), a.k.a. gotox, which lets a BPF program jump through a BPF_MAP_TYPE_INSN_ARRAY jump table. Emit "jalr zero, rd, 0" and hand the xlated to jitted offsets to bpf_prog_update_insn_ptrs(), which is what fills in the jump table entries; without that call the load fails with -EFAULT in bpf_insn_array_ready(). ctx->offset[] holds the offset of the insn *following* insn i, as bpf_prog_fill_jited_linfo() expects, so it is shifted by one and offset[0] comes from the prologue length. build_body() now records both halves of a multi-insn record, so no slot keeps a fabricated offset. Only the RV64 JIT is covered; RV32 keeps failing to load as before. Signed-off-by: Chen Pei Reviewed-by: Björn Töpel Acked-by: Björn Töpel Reviewed-by: Pu Lehui --- Changes since v2: - Pick up Pu Lehui's Reviewed-by; no code change. Changes since v1: - Reword the code comment to say "shift ctx->offset[] by one". arch/riscv/net/bpf_jit_comp64.c | 5 +++++ arch/riscv/net/bpf_jit_core.c | 16 ++++++++++++++-- 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index ed0a6f871dea..9de3749fb268 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -1691,6 +1691,11 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, emit_zextw(rd, rd, ctx); break; + /* JUMP reg */ + case BPF_JMP | BPF_JA | BPF_X: + emit_jalr(RV_REG_ZERO, rd, 0, ctx); + break; + /* JUMP off */ case BPF_JMP | BPF_JA: case BPF_JMP32 | BPF_JA: diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c index 470a6ace5662..5265dd5bd39e 100644 --- a/arch/riscv/net/bpf_jit_core.c +++ b/arch/riscv/net/bpf_jit_core.c @@ -26,10 +26,13 @@ static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset) int ret; ret = bpf_jit_emit_insn(insn, ctx, extra_pass); - if (ret > 0) - i++; /* skip the next instruction */ if (offset) offset[i] = ctx->ninsns; + if (ret > 0) { + i++; /* skip the next instruction */ + if (offset) + offset[i] = ctx->ninsns; + } if (ret < 0) return ret; } @@ -176,6 +179,15 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr for (i = 0; i < prog->len; i++) ctx->offset[i] = ninsns_rvoff(ctx->offset[i]); bpf_prog_fill_jited_linfo(prog, ctx->offset); + + /* + * bpf_prog_update_insn_ptrs() wants the start of each insn, so + * shift ctx->offset[] by one and get insn 0 from the prologue. + */ + for (i = prog->len - 1; i > 0; i--) + ctx->offset[i] = ctx->offset[i - 1]; + ctx->offset[0] = ninsns_rvoff(ctx->prologue_len); + bpf_prog_update_insn_ptrs(prog, ctx->offset, jit_data->ro_image); out_offset: kvfree(ctx->offset); kfree(jit_data); -- 2.50.1