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 <linux/memory.h> 12 #include <asm/patch.h> 13 #include <asm/cfi.h> 14 #include "bpf_jit.h" 15 16 /* Number of iterations to try until offsets converge. */ 17 #define NR_JIT_ITERATIONS 32 18 19 static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset) 20 { 21 const struct bpf_prog *prog = ctx->prog; 22 int i; 23 24 for (i = 0; i < prog->len; i++) { 25 const struct bpf_insn *insn = &prog->insnsi[i]; 26 int ret; 27 28 ret = bpf_jit_emit_insn(insn, ctx, extra_pass); 29 /* BPF_LD | BPF_IMM | BPF_DW: skip the next instruction. */ 30 if (ret > 0) 31 i++; 32 if (offset) 33 offset[i] = ctx->ninsns; 34 if (ret < 0) 35 return ret; 36 } 37 return 0; 38 } 39 40 bool bpf_jit_needs_zext(void) 41 { 42 return true; 43 } 44 45 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 46 { 47 unsigned int prog_size = 0, extable_size = 0; 48 bool tmp_blinded = false, extra_pass = false; 49 struct bpf_prog *tmp, *orig_prog = prog; 50 int pass = 0, prev_ninsns = 0, i; 51 struct rv_jit_data *jit_data; 52 struct rv_jit_context *ctx; 53 54 if (!prog->jit_requested) 55 return orig_prog; 56 57 tmp = bpf_jit_blind_constants(prog); 58 if (IS_ERR(tmp)) 59 return orig_prog; 60 if (tmp != prog) { 61 tmp_blinded = true; 62 prog = tmp; 63 } 64 65 jit_data = prog->aux->jit_data; 66 if (!jit_data) { 67 jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL); 68 if (!jit_data) { 69 prog = orig_prog; 70 goto out; 71 } 72 prog->aux->jit_data = jit_data; 73 } 74 75 ctx = &jit_data->ctx; 76 77 if (ctx->offset) { 78 extra_pass = true; 79 prog_size = sizeof(*ctx->insns) * ctx->ninsns; 80 goto skip_init_ctx; 81 } 82 83 ctx->prog = prog; 84 ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL); 85 if (!ctx->offset) { 86 prog = orig_prog; 87 goto out_offset; 88 } 89 90 if (build_body(ctx, extra_pass, NULL)) { 91 prog = orig_prog; 92 goto out_offset; 93 } 94 95 for (i = 0; i < prog->len; i++) { 96 prev_ninsns += 32; 97 ctx->offset[i] = prev_ninsns; 98 } 99 100 for (i = 0; i < NR_JIT_ITERATIONS; i++) { 101 pass++; 102 ctx->ninsns = 0; 103 104 bpf_jit_build_prologue(ctx, bpf_is_subprog(prog)); 105 ctx->prologue_len = ctx->ninsns; 106 107 if (build_body(ctx, extra_pass, ctx->offset)) { 108 prog = orig_prog; 109 goto out_offset; 110 } 111 112 ctx->epilogue_offset = ctx->ninsns; 113 bpf_jit_build_epilogue(ctx); 114 115 if (ctx->ninsns == prev_ninsns) { 116 if (jit_data->header) 117 break; 118 /* obtain the actual image size */ 119 extable_size = prog->aux->num_exentries * 120 sizeof(struct exception_table_entry); 121 prog_size = sizeof(*ctx->insns) * ctx->ninsns; 122 123 jit_data->ro_header = 124 bpf_jit_binary_pack_alloc(prog_size + extable_size, 125 &jit_data->ro_image, sizeof(u32), 126 &jit_data->header, &jit_data->image, 127 bpf_fill_ill_insns); 128 if (!jit_data->ro_header) { 129 prog = orig_prog; 130 goto out_offset; 131 } 132 133 /* 134 * Use the image(RW) for writing the JITed instructions. But also save 135 * the ro_image(RX) for calculating the offsets in the image. The RW 136 * image will be later copied to the RX image from where the program 137 * will run. The bpf_jit_binary_pack_finalize() will do this copy in the 138 * final step. 139 */ 140 ctx->ro_insns = (u16 *)jit_data->ro_image; 141 ctx->insns = (u16 *)jit_data->image; 142 /* 143 * Now, when the image is allocated, the image can 144 * potentially shrink more (auipc/jalr -> jal). 145 */ 146 } 147 prev_ninsns = ctx->ninsns; 148 } 149 150 if (i == NR_JIT_ITERATIONS) { 151 pr_err("bpf-jit: image did not converge in <%d passes!\n", i); 152 prog = orig_prog; 153 goto out_free_hdr; 154 } 155 156 if (extable_size) 157 prog->aux->extable = (void *)ctx->ro_insns + prog_size; 158 159 skip_init_ctx: 160 pass++; 161 ctx->ninsns = 0; 162 ctx->nexentries = 0; 163 164 bpf_jit_build_prologue(ctx, bpf_is_subprog(prog)); 165 if (build_body(ctx, extra_pass, NULL)) { 166 prog = orig_prog; 167 goto out_free_hdr; 168 } 169 bpf_jit_build_epilogue(ctx); 170 171 if (bpf_jit_enable > 1) 172 bpf_jit_dump(prog->len, prog_size, pass, ctx->insns); 173 174 prog->bpf_func = (void *)ctx->ro_insns + cfi_get_offset(); 175 prog->jited = 1; 176 prog->jited_len = prog_size - cfi_get_offset(); 177 178 if (!prog->is_func || extra_pass) { 179 if (WARN_ON(bpf_jit_binary_pack_finalize(prog, jit_data->ro_header, 180 jit_data->header))) { 181 /* ro_header has been freed */ 182 jit_data->ro_header = NULL; 183 prog = orig_prog; 184 goto out_offset; 185 } 186 /* 187 * The instructions have now been copied to the ROX region from 188 * where they will execute. 189 * Write any modified data cache blocks out to memory and 190 * invalidate the corresponding blocks in the instruction cache. 191 */ 192 bpf_flush_icache(jit_data->ro_header, ctx->ro_insns + ctx->ninsns); 193 for (i = 0; i < prog->len; i++) 194 ctx->offset[i] = ninsns_rvoff(ctx->offset[i]); 195 bpf_prog_fill_jited_linfo(prog, ctx->offset); 196 out_offset: 197 kfree(ctx->offset); 198 kfree(jit_data); 199 prog->aux->jit_data = NULL; 200 } 201 out: 202 203 if (tmp_blinded) 204 bpf_jit_prog_release_other(prog, prog == orig_prog ? 205 tmp : orig_prog); 206 return prog; 207 208 out_free_hdr: 209 if (jit_data->header) { 210 bpf_arch_text_copy(&jit_data->ro_header->size, &jit_data->header->size, 211 sizeof(jit_data->header->size)); 212 bpf_jit_binary_pack_free(jit_data->ro_header, jit_data->header); 213 } 214 goto out_offset; 215 } 216 217 u64 bpf_jit_alloc_exec_limit(void) 218 { 219 return BPF_JIT_REGION_SIZE; 220 } 221 222 void *bpf_jit_alloc_exec(unsigned long size) 223 { 224 return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START, 225 BPF_JIT_REGION_END, GFP_KERNEL, 226 PAGE_KERNEL, 0, NUMA_NO_NODE, 227 __builtin_return_address(0)); 228 } 229 230 void bpf_jit_free_exec(void *addr) 231 { 232 return vfree(addr); 233 } 234 235 void *bpf_arch_text_copy(void *dst, void *src, size_t len) 236 { 237 int ret; 238 239 mutex_lock(&text_mutex); 240 ret = patch_text_nosync(dst, src, len); 241 mutex_unlock(&text_mutex); 242 243 if (ret) 244 return ERR_PTR(-EINVAL); 245 246 return dst; 247 } 248 249 int bpf_arch_text_invalidate(void *dst, size_t len) 250 { 251 int ret; 252 253 mutex_lock(&text_mutex); 254 ret = patch_text_set_nosync(dst, 0, len); 255 mutex_unlock(&text_mutex); 256 257 return ret; 258 } 259 260 void bpf_jit_free(struct bpf_prog *prog) 261 { 262 if (prog->jited) { 263 struct rv_jit_data *jit_data = prog->aux->jit_data; 264 struct bpf_binary_header *hdr; 265 266 /* 267 * If we fail the final pass of JIT (from jit_subprogs), 268 * the program may not be finalized yet. Call finalize here 269 * before freeing it. 270 */ 271 if (jit_data) { 272 bpf_jit_binary_pack_finalize(prog, jit_data->ro_header, jit_data->header); 273 kfree(jit_data); 274 } 275 hdr = bpf_jit_binary_pack_hdr(prog); 276 bpf_jit_binary_pack_free(hdr, NULL); 277 WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); 278 } 279 280 bpf_prog_unlock_free(prog); 281 } 282