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/text-patching.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 if (ret > 0) 30 i++; /* skip the next instruction */ 31 if (offset) 32 offset[i] = ctx->ninsns; 33 if (ret < 0) 34 return ret; 35 } 36 return 0; 37 } 38 39 bool bpf_jit_needs_zext(void) 40 { 41 return true; 42 } 43 44 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 45 { 46 unsigned int prog_size = 0, extable_size = 0; 47 bool tmp_blinded = false, extra_pass = false; 48 struct bpf_prog *tmp, *orig_prog = prog; 49 int pass = 0, prev_ninsns = 0, i; 50 struct rv_jit_data *jit_data; 51 struct rv_jit_context *ctx; 52 53 if (!prog->jit_requested) 54 return orig_prog; 55 56 tmp = bpf_jit_blind_constants(prog); 57 if (IS_ERR(tmp)) 58 return orig_prog; 59 if (tmp != prog) { 60 tmp_blinded = true; 61 prog = tmp; 62 } 63 64 jit_data = prog->aux->jit_data; 65 if (!jit_data) { 66 jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL); 67 if (!jit_data) { 68 prog = orig_prog; 69 goto out; 70 } 71 prog->aux->jit_data = jit_data; 72 } 73 74 ctx = &jit_data->ctx; 75 76 if (ctx->offset) { 77 extra_pass = true; 78 prog_size = sizeof(*ctx->insns) * ctx->ninsns; 79 goto skip_init_ctx; 80 } 81 82 ctx->arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena); 83 ctx->user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena); 84 ctx->prog = prog; 85 ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL); 86 if (!ctx->offset) { 87 prog = orig_prog; 88 goto out_offset; 89 } 90 91 if (build_body(ctx, extra_pass, NULL)) { 92 prog = orig_prog; 93 goto out_offset; 94 } 95 96 for (i = 0; i < prog->len; i++) { 97 prev_ninsns += 32; 98 ctx->offset[i] = prev_ninsns; 99 } 100 101 for (i = 0; i < NR_JIT_ITERATIONS; i++) { 102 pass++; 103 ctx->ninsns = 0; 104 105 bpf_jit_build_prologue(ctx, bpf_is_subprog(prog)); 106 ctx->prologue_len = ctx->ninsns; 107 108 if (build_body(ctx, extra_pass, ctx->offset)) { 109 prog = orig_prog; 110 goto out_offset; 111 } 112 113 ctx->epilogue_offset = ctx->ninsns; 114 bpf_jit_build_epilogue(ctx); 115 116 if (ctx->ninsns == prev_ninsns) { 117 if (jit_data->header) 118 break; 119 /* obtain the actual image size */ 120 extable_size = prog->aux->num_exentries * 121 sizeof(struct exception_table_entry); 122 prog_size = sizeof(*ctx->insns) * ctx->ninsns; 123 124 jit_data->ro_header = 125 bpf_jit_binary_pack_alloc(prog_size + extable_size, 126 &jit_data->ro_image, sizeof(u32), 127 &jit_data->header, &jit_data->image, 128 bpf_fill_ill_insns); 129 if (!jit_data->ro_header) { 130 prog = orig_prog; 131 goto out_offset; 132 } 133 134 /* 135 * Use the image(RW) for writing the JITed instructions. But also save 136 * the ro_image(RX) for calculating the offsets in the image. The RW 137 * image will be later copied to the RX image from where the program 138 * will run. The bpf_jit_binary_pack_finalize() will do this copy in the 139 * final step. 140 */ 141 ctx->ro_insns = (u16 *)jit_data->ro_image; 142 ctx->insns = (u16 *)jit_data->image; 143 /* 144 * Now, when the image is allocated, the image can 145 * potentially shrink more (auipc/jalr -> jal). 146 */ 147 } 148 prev_ninsns = ctx->ninsns; 149 } 150 151 if (i == NR_JIT_ITERATIONS) { 152 pr_err("bpf-jit: image did not converge in <%d passes!\n", i); 153 prog = orig_prog; 154 goto out_free_hdr; 155 } 156 157 if (extable_size) 158 prog->aux->extable = (void *)ctx->ro_insns + prog_size; 159 160 skip_init_ctx: 161 pass++; 162 ctx->ninsns = 0; 163 ctx->nexentries = 0; 164 165 bpf_jit_build_prologue(ctx, bpf_is_subprog(prog)); 166 if (build_body(ctx, extra_pass, NULL)) { 167 prog = orig_prog; 168 goto out_free_hdr; 169 } 170 bpf_jit_build_epilogue(ctx); 171 172 if (bpf_jit_enable > 1) 173 bpf_jit_dump(prog->len, prog_size, pass, ctx->insns); 174 175 prog->bpf_func = (void *)ctx->ro_insns + cfi_get_offset(); 176 prog->jited = 1; 177 prog->jited_len = prog_size - cfi_get_offset(); 178 179 if (!prog->is_func || extra_pass) { 180 if (WARN_ON(bpf_jit_binary_pack_finalize(jit_data->ro_header, 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_arch_text_copy(void *dst, void *src, size_t len) 223 { 224 int ret; 225 226 mutex_lock(&text_mutex); 227 ret = patch_text_nosync(dst, src, len); 228 mutex_unlock(&text_mutex); 229 230 if (ret) 231 return ERR_PTR(-EINVAL); 232 233 return dst; 234 } 235 236 int bpf_arch_text_invalidate(void *dst, size_t len) 237 { 238 int ret; 239 240 mutex_lock(&text_mutex); 241 ret = patch_text_set_nosync(dst, 0, len); 242 mutex_unlock(&text_mutex); 243 244 return ret; 245 } 246 247 void bpf_jit_free(struct bpf_prog *prog) 248 { 249 if (prog->jited) { 250 struct rv_jit_data *jit_data = prog->aux->jit_data; 251 struct bpf_binary_header *hdr; 252 253 /* 254 * If we fail the final pass of JIT (from jit_subprogs), 255 * the program may not be finalized yet. Call finalize here 256 * before freeing it. 257 */ 258 if (jit_data) { 259 bpf_jit_binary_pack_finalize(jit_data->ro_header, jit_data->header); 260 kfree(jit_data); 261 } 262 hdr = bpf_jit_binary_pack_hdr(prog); 263 bpf_jit_binary_pack_free(hdr, NULL); 264 WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); 265 } 266 267 bpf_prog_unlock_free(prog); 268 } 269