1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Common functionality for RV32 and RV64 BPF JIT compilers
4 *
5 * Copyright (c) 2019 Björn Töpel <bjorn.topel@gmail.com>
6 *
7 */
8
9 #include <linux/bpf.h>
10 #include <linux/filter.h>
11 #include "bpf_jit.h"
12
13 /* Number of iterations to try until offsets converge. */
14 #define NR_JIT_ITERATIONS 16
15
build_body(struct rv_jit_context * ctx,bool extra_pass,int * offset)16 static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
17 {
18 const struct bpf_prog *prog = ctx->prog;
19 int i;
20
21 for (i = 0; i < prog->len; i++) {
22 const struct bpf_insn *insn = &prog->insnsi[i];
23 int ret;
24
25 ret = bpf_jit_emit_insn(insn, ctx, extra_pass);
26 /* BPF_LD | BPF_IMM | BPF_DW: skip the next instruction. */
27 if (ret > 0)
28 i++;
29 if (offset)
30 offset[i] = ctx->ninsns;
31 if (ret < 0)
32 return ret;
33 }
34 return 0;
35 }
36
bpf_jit_needs_zext(void)37 bool bpf_jit_needs_zext(void)
38 {
39 return true;
40 }
41
bpf_int_jit_compile(struct bpf_prog * prog)42 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
43 {
44 bool tmp_blinded = false, extra_pass = false;
45 struct bpf_prog *tmp, *orig_prog = prog;
46 int pass = 0, prev_ninsns = 0, i;
47 struct rv_jit_data *jit_data;
48 struct rv_jit_context *ctx;
49 unsigned int image_size = 0;
50
51 if (!prog->jit_requested)
52 return orig_prog;
53
54 tmp = bpf_jit_blind_constants(prog);
55 if (IS_ERR(tmp))
56 return orig_prog;
57 if (tmp != prog) {
58 tmp_blinded = true;
59 prog = tmp;
60 }
61
62 jit_data = prog->aux->jit_data;
63 if (!jit_data) {
64 jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
65 if (!jit_data) {
66 prog = orig_prog;
67 goto out;
68 }
69 prog->aux->jit_data = jit_data;
70 }
71
72 ctx = &jit_data->ctx;
73
74 if (ctx->offset) {
75 extra_pass = true;
76 image_size = sizeof(*ctx->insns) * ctx->ninsns;
77 goto skip_init_ctx;
78 }
79
80 ctx->prog = prog;
81 ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
82 if (!ctx->offset) {
83 prog = orig_prog;
84 goto out_offset;
85 }
86 for (i = 0; i < prog->len; i++) {
87 prev_ninsns += 32;
88 ctx->offset[i] = prev_ninsns;
89 }
90
91 for (i = 0; i < NR_JIT_ITERATIONS; i++) {
92 pass++;
93 ctx->ninsns = 0;
94 if (build_body(ctx, extra_pass, ctx->offset)) {
95 prog = orig_prog;
96 goto out_offset;
97 }
98 bpf_jit_build_prologue(ctx);
99 ctx->epilogue_offset = ctx->ninsns;
100 bpf_jit_build_epilogue(ctx);
101
102 if (ctx->ninsns == prev_ninsns) {
103 if (jit_data->header)
104 break;
105
106 image_size = sizeof(*ctx->insns) * ctx->ninsns;
107 jit_data->header =
108 bpf_jit_binary_alloc(image_size,
109 &jit_data->image,
110 sizeof(u32),
111 bpf_fill_ill_insns);
112 if (!jit_data->header) {
113 prog = orig_prog;
114 goto out_offset;
115 }
116
117 ctx->insns = (u16 *)jit_data->image;
118 /*
119 * Now, when the image is allocated, the image can
120 * potentially shrink more (auipc/jalr -> jal).
121 */
122 }
123 prev_ninsns = ctx->ninsns;
124 }
125
126 if (i == NR_JIT_ITERATIONS) {
127 pr_err("bpf-jit: image did not converge in <%d passes!\n", i);
128 if (jit_data->header)
129 bpf_jit_binary_free(jit_data->header);
130 prog = orig_prog;
131 goto out_offset;
132 }
133
134 skip_init_ctx:
135 pass++;
136 ctx->ninsns = 0;
137
138 bpf_jit_build_prologue(ctx);
139 if (build_body(ctx, extra_pass, NULL)) {
140 bpf_jit_binary_free(jit_data->header);
141 prog = orig_prog;
142 goto out_offset;
143 }
144 bpf_jit_build_epilogue(ctx);
145
146 if (bpf_jit_enable > 1)
147 bpf_jit_dump(prog->len, image_size, pass, ctx->insns);
148
149 prog->bpf_func = (void *)ctx->insns;
150 prog->jited = 1;
151 prog->jited_len = image_size;
152
153 bpf_flush_icache(jit_data->header, ctx->insns + ctx->ninsns);
154
155 if (!prog->is_func || extra_pass) {
156 out_offset:
157 kfree(ctx->offset);
158 kfree(jit_data);
159 prog->aux->jit_data = NULL;
160 }
161 out:
162
163 if (tmp_blinded)
164 bpf_jit_prog_release_other(prog, prog == orig_prog ?
165 tmp : orig_prog);
166 return prog;
167 }
168