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_verifier_env *env, struct bpf_prog *prog) 45 { 46 unsigned int prog_size = 0, extable_size = 0; 47 bool extra_pass = false; 48 int pass = 0, prev_ninsns = 0, i; 49 struct rv_jit_data *jit_data; 50 struct rv_jit_context *ctx; 51 52 if (!prog->jit_requested) 53 return prog; 54 55 jit_data = prog->aux->jit_data; 56 if (!jit_data) { 57 jit_data = kzalloc_obj(*jit_data); 58 if (!jit_data) { 59 return prog; 60 } 61 prog->aux->jit_data = jit_data; 62 } 63 64 ctx = &jit_data->ctx; 65 66 if (ctx->offset) { 67 extra_pass = true; 68 prog_size = sizeof(*ctx->insns) * ctx->ninsns; 69 goto skip_init_ctx; 70 } 71 72 ctx->arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena); 73 ctx->user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena); 74 ctx->prog = prog; 75 ctx->offset = kzalloc_objs(int, prog->len); 76 if (!ctx->offset) 77 goto out_offset; 78 79 if (build_body(ctx, extra_pass, NULL)) 80 goto out_offset; 81 82 for (i = 0; i < prog->len; i++) { 83 prev_ninsns += 32; 84 ctx->offset[i] = prev_ninsns; 85 } 86 87 for (i = 0; i < NR_JIT_ITERATIONS; i++) { 88 pass++; 89 ctx->ninsns = 0; 90 91 bpf_jit_build_prologue(ctx, bpf_is_subprog(prog)); 92 ctx->prologue_len = ctx->ninsns; 93 94 if (build_body(ctx, extra_pass, ctx->offset)) 95 goto out_offset; 96 97 ctx->epilogue_offset = ctx->ninsns; 98 bpf_jit_build_epilogue(ctx); 99 100 if (ctx->ninsns == prev_ninsns) { 101 if (jit_data->header) 102 break; 103 /* obtain the actual image size */ 104 extable_size = prog->aux->num_exentries * 105 sizeof(struct exception_table_entry); 106 prog_size = sizeof(*ctx->insns) * ctx->ninsns; 107 108 jit_data->ro_header = 109 bpf_jit_binary_pack_alloc(prog_size + extable_size, 110 &jit_data->ro_image, sizeof(u32), 111 &jit_data->header, &jit_data->image, 112 bpf_fill_ill_insns); 113 if (!jit_data->ro_header) 114 goto out_offset; 115 116 /* 117 * Use the image(RW) for writing the JITed instructions. But also save 118 * the ro_image(RX) for calculating the offsets in the image. The RW 119 * image will be later copied to the RX image from where the program 120 * will run. The bpf_jit_binary_pack_finalize() will do this copy in the 121 * final step. 122 */ 123 ctx->ro_insns = (u16 *)jit_data->ro_image; 124 ctx->insns = (u16 *)jit_data->image; 125 /* 126 * Now, when the image is allocated, the image can 127 * potentially shrink more (auipc/jalr -> jal). 128 */ 129 } 130 prev_ninsns = ctx->ninsns; 131 } 132 133 if (i == NR_JIT_ITERATIONS) { 134 pr_err("bpf-jit: image did not converge in <%d passes!\n", i); 135 goto out_free_hdr; 136 } 137 138 if (extable_size) 139 prog->aux->extable = (void *)ctx->ro_insns + prog_size; 140 141 skip_init_ctx: 142 pass++; 143 ctx->ninsns = 0; 144 ctx->nexentries = 0; 145 146 bpf_jit_build_prologue(ctx, bpf_is_subprog(prog)); 147 if (build_body(ctx, extra_pass, NULL)) 148 goto out_free_hdr; 149 bpf_jit_build_epilogue(ctx); 150 151 if (bpf_jit_enable > 1) 152 bpf_jit_dump(prog->len, prog_size, pass, ctx->insns); 153 154 if (!prog->is_func || extra_pass) { 155 if (WARN_ON(bpf_jit_binary_pack_finalize(jit_data->ro_header, jit_data->header))) { 156 /* ro_header has been freed */ 157 jit_data->ro_header = NULL; 158 jit_data->header = NULL; 159 goto out_free_hdr; 160 } 161 } 162 163 prog->bpf_func = (void *)ctx->ro_insns + cfi_get_offset(); 164 prog->jited = 1; 165 prog->jited_len = prog_size - cfi_get_offset(); 166 167 if (!prog->is_func || extra_pass) { 168 for (i = 0; i < prog->len; i++) 169 ctx->offset[i] = ninsns_rvoff(ctx->offset[i]); 170 bpf_prog_fill_jited_linfo(prog, ctx->offset); 171 out_offset: 172 kfree(ctx->offset); 173 kfree(jit_data); 174 prog->aux->jit_data = NULL; 175 } 176 177 return prog; 178 179 out_free_hdr: 180 if (extra_pass) { 181 prog->bpf_func = NULL; 182 prog->jited = 0; 183 prog->jited_len = 0; 184 } 185 if (jit_data->header) { 186 bpf_arch_text_copy(&jit_data->ro_header->size, &jit_data->header->size, 187 sizeof(jit_data->header->size)); 188 bpf_jit_binary_pack_free(jit_data->ro_header, jit_data->header); 189 } 190 goto out_offset; 191 } 192 193 u64 bpf_jit_alloc_exec_limit(void) 194 { 195 return BPF_JIT_REGION_SIZE; 196 } 197 198 void *bpf_arch_text_copy(void *dst, void *src, size_t len) 199 { 200 int ret; 201 202 mutex_lock(&text_mutex); 203 ret = patch_text_nosync(dst, src, len); 204 mutex_unlock(&text_mutex); 205 206 if (ret) 207 return ERR_PTR(-EINVAL); 208 209 return dst; 210 } 211 212 int bpf_arch_text_invalidate(void *dst, size_t len) 213 { 214 int ret; 215 216 mutex_lock(&text_mutex); 217 ret = patch_text_set_nosync(dst, 0, len); 218 mutex_unlock(&text_mutex); 219 220 return ret; 221 } 222 223 void bpf_jit_free(struct bpf_prog *prog) 224 { 225 if (prog->jited) { 226 struct rv_jit_data *jit_data = prog->aux->jit_data; 227 struct bpf_binary_header *hdr; 228 229 /* 230 * If we fail the final pass of JIT (from jit_subprogs), 231 * the program may not be finalized yet. Call finalize here 232 * before freeing it. 233 */ 234 if (jit_data) { 235 bpf_jit_binary_pack_finalize(jit_data->ro_header, jit_data->header); 236 kfree(jit_data); 237 } 238 hdr = bpf_jit_binary_pack_hdr(prog); 239 bpf_jit_binary_pack_free(hdr, NULL); 240 WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); 241 } 242 243 bpf_prog_unlock_free(prog); 244 } 245