riscv, bpf: Optimize calls

Instead of using emit_imm() and emit_jalr() which can expand to six
instructions, start using jal or auipc+jalr.

Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216091343.23260-8-bjorn.topel@gmail.com

diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
index 46cff09..8d7e334 100644 (file)
--- a/arch/riscv/net/bpf_jit_comp.c
+++ b/arch/riscv/net/bpf_jit_comp.c
@@ -811,11 +811,12 @@ static void emit_sext_32_rd(u8 *rd, struct rv_jit_context *ctx)
        *rd = RV_REG_T2;
 }
 
-static void emit_jump_and_link(u8 rd, int rvoff, struct rv_jit_context *ctx)
+static void emit_jump_and_link(u8 rd, s64 rvoff, bool force_jalr,
+                              struct rv_jit_context *ctx)
 {
        s64 upper, lower;
 
-       if (is_21b_int(rvoff)) {
+       if (rvoff && is_21b_int(rvoff) && !force_jalr) {
                emit(rv_jal(rd, rvoff >> 1), ctx);
                return;
        }
@@ -832,6 +833,28 @@ static bool is_signed_bpf_cond(u8 cond)
                cond == BPF_JSGE || cond == BPF_JSLE;
 }
 
+static int emit_call(bool fixed, u64 addr, struct rv_jit_context *ctx)
+{
+       s64 off = 0;
+       u64 ip;
+       u8 rd;
+
+       if (addr && ctx->insns) {
+               ip = (u64)(long)(ctx->insns + ctx->ninsns);
+               off = addr - ip;
+               if (!is_32b_int(off)) {
+                       pr_err("bpf-jit: target call addr %pK is out of range\n",
+                              (void *)addr);
+                       return -ERANGE;
+               }
+       }
+
+       emit_jump_and_link(RV_REG_RA, off, !fixed, ctx);
+       rd = bpf_to_rv_reg(BPF_REG_0, ctx);
+       emit(rv_addi(rd, RV_REG_A0, 0), ctx);
+       return 0;
+}
+
 static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
                     bool extra_pass)
 {
@@ -1107,7 +1130,7 @@ out_be:
        /* JUMP off */
        case BPF_JMP | BPF_JA:
                rvoff = rv_offset(i, off, ctx);
-               emit_jump_and_link(RV_REG_ZERO, rvoff, ctx);
+               emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx);
                break;
 
        /* IF (dst COND src) JUMP off */
@@ -1209,7 +1232,7 @@ out_be:
        case BPF_JMP | BPF_CALL:
        {
                bool fixed;
-               int i, ret;
+               int ret;
                u64 addr;
 
                mark_call(ctx);
@@ -1217,20 +1240,9 @@ out_be:
                                            &fixed);
                if (ret < 0)
                        return ret;
-               if (fixed) {
-                       emit_imm(RV_REG_T1, addr, ctx);
-               } else {
-                       i = ctx->ninsns;
-                       emit_imm(RV_REG_T1, addr, ctx);
-                       for (i = ctx->ninsns - i; i < 8; i++) {
-                               /* nop */
-                               emit(rv_addi(RV_REG_ZERO, RV_REG_ZERO, 0),
-                                    ctx);
-                       }
-               }
-               emit(rv_jalr(RV_REG_RA, RV_REG_T1, 0), ctx);
-               rd = bpf_to_rv_reg(BPF_REG_0, ctx);
-               emit(rv_addi(rd, RV_REG_A0, 0), ctx);
+               ret = emit_call(fixed, addr, ctx);
+               if (ret)
+                       return ret;
                break;
        }
        /* tail call */
@@ -1245,7 +1257,7 @@ out_be:
                        break;
 
                rvoff = epilogue_offset(ctx);
-               emit_jump_and_link(RV_REG_ZERO, rvoff, ctx);
+               emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx);
                break;
 
        /* dst = imm64 */
@@ -1508,7 +1520,7 @@ static void build_epilogue(struct rv_jit_context *ctx)
        __build_epilogue(false, ctx);
 }
 
-static int build_body(struct rv_jit_context *ctx, bool extra_pass)
+static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
 {
        const struct bpf_prog *prog = ctx->prog;
        int i;
@@ -1520,12 +1532,12 @@ static int build_body(struct rv_jit_context *ctx, bool extra_pass)
                ret = emit_insn(insn, ctx, extra_pass);
                if (ret > 0) {
                        i++;
-                       if (ctx->insns == NULL)
-                               ctx->offset[i] = ctx->ninsns;
+                       if (offset)
+                               offset[i] = ctx->ninsns;
                        continue;
                }
-               if (ctx->insns == NULL)
-                       ctx->offset[i] = ctx->ninsns;
+               if (offset)
+                       offset[i] = ctx->ninsns;
                if (ret)
                        return ret;
        }
@@ -1553,8 +1565,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
        struct bpf_prog *tmp, *orig_prog = prog;
        int pass = 0, prev_ninsns = 0, i;
        struct rv_jit_data *jit_data;
+       unsigned int image_size = 0;
        struct rv_jit_context *ctx;
-       unsigned int image_size;
 
        if (!prog->jit_requested)
                return orig_prog;
@@ -1599,36 +1611,51 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
        for (i = 0; i < 16; i++) {
                pass++;
                ctx->ninsns = 0;
-               if (build_body(ctx, extra_pass)) {
+               if (build_body(ctx, extra_pass, ctx->offset)) {
                        prog = orig_prog;
                        goto out_offset;
                }
                build_prologue(ctx);
                ctx->epilogue_offset = ctx->ninsns;
                build_epilogue(ctx);
-               if (ctx->ninsns == prev_ninsns)
-                       break;
+
+               if (ctx->ninsns == prev_ninsns) {
+                       if (jit_data->header)
+                               break;
+
+                       image_size = sizeof(u32) * ctx->ninsns;
+                       jit_data->header =
+                               bpf_jit_binary_alloc(image_size,
+                                                    &jit_data->image,
+                                                    sizeof(u32),
+                                                    bpf_fill_ill_insns);
+                       if (!jit_data->header) {
+                               prog = orig_prog;
+                               goto out_offset;
+                       }
+
+                       ctx->insns = (u32 *)jit_data->image;
+                       /* Now, when the image is allocated, the image
+                        * can potentially shrink more (auipc/jalr ->
+                        * jal).
+                        */
+               }
                prev_ninsns = ctx->ninsns;
        }
 
-       /* Allocate image, now that we know the size. */
-       image_size = sizeof(u32) * ctx->ninsns;
-       jit_data->header = bpf_jit_binary_alloc(image_size, &jit_data->image,
-                                               sizeof(u32),
-                                               bpf_fill_ill_insns);
-       if (!jit_data->header) {
+       if (i == 16) {
+               pr_err("bpf-jit: image did not converge in <%d passes!\n", i);
+               bpf_jit_binary_free(jit_data->header);
                prog = orig_prog;
                goto out_offset;
        }
 
-       /* Second, real pass, that acutally emits the image. */
-       ctx->insns = (u32 *)jit_data->image;
 skip_init_ctx:
        pass++;
        ctx->ninsns = 0;
 
        build_prologue(ctx);
-       if (build_body(ctx, extra_pass)) {
+       if (build_body(ctx, extra_pass, NULL)) {
                bpf_jit_binary_free(jit_data->header);
                prog = orig_prog;
                goto out_offset;