1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com 3 * Copyright (c) 2016 Facebook 4 * Copyright (c) 2018 Covalent IO, Inc. http://covalent.io 5 */ 6 #include <uapi/linux/btf.h> 7 #include <linux/kernel.h> 8 #include <linux/types.h> 9 #include <linux/bpf.h> 10 #include <linux/bpf_verifier.h> 11 #include <linux/math64.h> 12 13 static bool bpf_verifier_log_attr_valid(const struct bpf_verifier_log *log) 14 { 15 /* ubuf and len_total should both be specified (or not) together */ 16 if (!!log->ubuf != !!log->len_total) 17 return false; 18 /* log buf without log_level is meaningless */ 19 if (log->ubuf && log->level == 0) 20 return false; 21 if (log->level & ~BPF_LOG_MASK) 22 return false; 23 if (log->len_total > UINT_MAX >> 2) 24 return false; 25 return true; 26 } 27 28 int bpf_vlog_init(struct bpf_verifier_log *log, u32 log_level, 29 char __user *log_buf, u32 log_size) 30 { 31 log->level = log_level; 32 log->ubuf = log_buf; 33 log->len_total = log_size; 34 35 /* log attributes have to be sane */ 36 if (!bpf_verifier_log_attr_valid(log)) 37 return -EINVAL; 38 39 return 0; 40 } 41 42 static void bpf_vlog_update_len_max(struct bpf_verifier_log *log, u32 add_len) 43 { 44 /* add_len includes terminal \0, so no need for +1. */ 45 u64 len = log->end_pos + add_len; 46 47 /* log->len_max could be larger than our current len due to 48 * bpf_vlog_reset() calls, so we maintain the max of any length at any 49 * previous point 50 */ 51 if (len > UINT_MAX) 52 log->len_max = UINT_MAX; 53 else if (len > log->len_max) 54 log->len_max = len; 55 } 56 57 void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt, 58 va_list args) 59 { 60 u64 cur_pos; 61 u32 new_n, n; 62 63 n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args); 64 65 if (log->level == BPF_LOG_KERNEL) { 66 bool newline = n > 0 && log->kbuf[n - 1] == '\n'; 67 68 pr_err("BPF: %s%s", log->kbuf, newline ? "" : "\n"); 69 return; 70 } 71 72 n += 1; /* include terminating zero */ 73 bpf_vlog_update_len_max(log, n); 74 75 if (log->level & BPF_LOG_FIXED) { 76 /* check if we have at least something to put into user buf */ 77 new_n = 0; 78 if (log->end_pos < log->len_total) { 79 new_n = min_t(u32, log->len_total - log->end_pos, n); 80 log->kbuf[new_n - 1] = '\0'; 81 } 82 83 cur_pos = log->end_pos; 84 log->end_pos += n - 1; /* don't count terminating '\0' */ 85 86 if (log->ubuf && new_n && 87 copy_to_user(log->ubuf + cur_pos, log->kbuf, new_n)) 88 goto fail; 89 } else { 90 u64 new_end, new_start; 91 u32 buf_start, buf_end, new_n; 92 93 new_end = log->end_pos + n; 94 if (new_end - log->start_pos >= log->len_total) 95 new_start = new_end - log->len_total; 96 else 97 new_start = log->start_pos; 98 99 log->start_pos = new_start; 100 log->end_pos = new_end - 1; /* don't count terminating '\0' */ 101 102 if (!log->ubuf) 103 return; 104 105 new_n = min(n, log->len_total); 106 cur_pos = new_end - new_n; 107 div_u64_rem(cur_pos, log->len_total, &buf_start); 108 div_u64_rem(new_end, log->len_total, &buf_end); 109 /* new_end and buf_end are exclusive indices, so if buf_end is 110 * exactly zero, then it actually points right to the end of 111 * ubuf and there is no wrap around 112 */ 113 if (buf_end == 0) 114 buf_end = log->len_total; 115 116 /* if buf_start > buf_end, we wrapped around; 117 * if buf_start == buf_end, then we fill ubuf completely; we 118 * can't have buf_start == buf_end to mean that there is 119 * nothing to write, because we always write at least 120 * something, even if terminal '\0' 121 */ 122 if (buf_start < buf_end) { 123 /* message fits within contiguous chunk of ubuf */ 124 if (copy_to_user(log->ubuf + buf_start, 125 log->kbuf + n - new_n, 126 buf_end - buf_start)) 127 goto fail; 128 } else { 129 /* message wraps around the end of ubuf, copy in two chunks */ 130 if (copy_to_user(log->ubuf + buf_start, 131 log->kbuf + n - new_n, 132 log->len_total - buf_start)) 133 goto fail; 134 if (copy_to_user(log->ubuf, 135 log->kbuf + n - buf_end, 136 buf_end)) 137 goto fail; 138 } 139 } 140 141 return; 142 fail: 143 log->ubuf = NULL; 144 } 145 146 void bpf_vlog_reset(struct bpf_verifier_log *log, u64 new_pos) 147 { 148 char zero = 0; 149 u32 pos; 150 151 if (WARN_ON_ONCE(new_pos > log->end_pos)) 152 return; 153 154 if (!bpf_verifier_log_needed(log) || log->level == BPF_LOG_KERNEL) 155 return; 156 157 /* if position to which we reset is beyond current log window, 158 * then we didn't preserve any useful content and should adjust 159 * start_pos to end up with an empty log (start_pos == end_pos) 160 */ 161 log->end_pos = new_pos; 162 if (log->end_pos < log->start_pos) 163 log->start_pos = log->end_pos; 164 165 if (!log->ubuf) 166 return; 167 168 if (log->level & BPF_LOG_FIXED) 169 pos = log->end_pos + 1; 170 else 171 div_u64_rem(new_pos, log->len_total, &pos); 172 173 if (pos < log->len_total && put_user(zero, log->ubuf + pos)) 174 log->ubuf = NULL; 175 } 176 177 static void bpf_vlog_reverse_kbuf(char *buf, int len) 178 { 179 int i, j; 180 181 for (i = 0, j = len - 1; i < j; i++, j--) 182 swap(buf[i], buf[j]); 183 } 184 185 static int bpf_vlog_reverse_ubuf(struct bpf_verifier_log *log, int start, int end) 186 { 187 /* we split log->kbuf into two equal parts for both ends of array */ 188 int n = sizeof(log->kbuf) / 2, nn; 189 char *lbuf = log->kbuf, *rbuf = log->kbuf + n; 190 191 /* Read ubuf's section [start, end) two chunks at a time, from left 192 * and right side; within each chunk, swap all the bytes; after that 193 * reverse the order of lbuf and rbuf and write result back to ubuf. 194 * This way we'll end up with swapped contents of specified 195 * [start, end) ubuf segment. 196 */ 197 while (end - start > 1) { 198 nn = min(n, (end - start ) / 2); 199 200 if (copy_from_user(lbuf, log->ubuf + start, nn)) 201 return -EFAULT; 202 if (copy_from_user(rbuf, log->ubuf + end - nn, nn)) 203 return -EFAULT; 204 205 bpf_vlog_reverse_kbuf(lbuf, nn); 206 bpf_vlog_reverse_kbuf(rbuf, nn); 207 208 /* we write lbuf to the right end of ubuf, while rbuf to the 209 * left one to end up with properly reversed overall ubuf 210 */ 211 if (copy_to_user(log->ubuf + start, rbuf, nn)) 212 return -EFAULT; 213 if (copy_to_user(log->ubuf + end - nn, lbuf, nn)) 214 return -EFAULT; 215 216 start += nn; 217 end -= nn; 218 } 219 220 return 0; 221 } 222 223 int bpf_vlog_finalize(struct bpf_verifier_log *log, u32 *log_size_actual) 224 { 225 u32 sublen; 226 int err; 227 228 *log_size_actual = 0; 229 if (!log || log->level == 0 || log->level == BPF_LOG_KERNEL) 230 return 0; 231 232 if (!log->ubuf) 233 goto skip_log_rotate; 234 /* If we never truncated log, there is nothing to move around. */ 235 if (log->start_pos == 0) 236 goto skip_log_rotate; 237 238 /* Otherwise we need to rotate log contents to make it start from the 239 * buffer beginning and be a continuous zero-terminated string. Note 240 * that if log->start_pos != 0 then we definitely filled up entire log 241 * buffer with no gaps, and we just need to shift buffer contents to 242 * the left by (log->start_pos % log->len_total) bytes. 243 * 244 * Unfortunately, user buffer could be huge and we don't want to 245 * allocate temporary kernel memory of the same size just to shift 246 * contents in a straightforward fashion. Instead, we'll be clever and 247 * do in-place array rotation. This is a leetcode-style problem, which 248 * could be solved by three rotations. 249 * 250 * Let's say we have log buffer that has to be shifted left by 7 bytes 251 * (spaces and vertical bar is just for demonstrative purposes): 252 * E F G H I J K | A B C D 253 * 254 * First, we reverse entire array: 255 * D C B A | K J I H G F E 256 * 257 * Then we rotate first 4 bytes (DCBA) and separately last 7 bytes 258 * (KJIHGFE), resulting in a properly rotated array: 259 * A B C D | E F G H I J K 260 * 261 * We'll utilize log->kbuf to read user memory chunk by chunk, swap 262 * bytes, and write them back. Doing it byte-by-byte would be 263 * unnecessarily inefficient. Altogether we are going to read and 264 * write each byte twice, for total 4 memory copies between kernel and 265 * user space. 266 */ 267 268 /* length of the chopped off part that will be the beginning; 269 * len(ABCD) in the example above 270 */ 271 div_u64_rem(log->start_pos, log->len_total, &sublen); 272 sublen = log->len_total - sublen; 273 274 err = bpf_vlog_reverse_ubuf(log, 0, log->len_total); 275 err = err ?: bpf_vlog_reverse_ubuf(log, 0, sublen); 276 err = err ?: bpf_vlog_reverse_ubuf(log, sublen, log->len_total); 277 if (err) 278 log->ubuf = NULL; 279 280 skip_log_rotate: 281 *log_size_actual = log->len_max; 282 283 /* properly initialized log has either both ubuf!=NULL and len_total>0 284 * or ubuf==NULL and len_total==0, so if this condition doesn't hold, 285 * we got a fault somewhere along the way, so report it back 286 */ 287 if (!!log->ubuf != !!log->len_total) 288 return -EFAULT; 289 290 /* did truncation actually happen? */ 291 if (log->ubuf && log->len_max > log->len_total) 292 return -ENOSPC; 293 294 return 0; 295 } 296 297 /* log_level controls verbosity level of eBPF verifier. 298 * bpf_verifier_log_write() is used to dump the verification trace to the log, 299 * so the user can figure out what's wrong with the program 300 */ 301 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env, 302 const char *fmt, ...) 303 { 304 va_list args; 305 306 if (!bpf_verifier_log_needed(&env->log)) 307 return; 308 309 va_start(args, fmt); 310 bpf_verifier_vlog(&env->log, fmt, args); 311 va_end(args); 312 } 313 EXPORT_SYMBOL_GPL(bpf_verifier_log_write); 314 315 __printf(2, 3) void bpf_log(struct bpf_verifier_log *log, 316 const char *fmt, ...) 317 { 318 va_list args; 319 320 if (!bpf_verifier_log_needed(log)) 321 return; 322 323 va_start(args, fmt); 324 bpf_verifier_vlog(log, fmt, args); 325 va_end(args); 326 } 327 EXPORT_SYMBOL_GPL(bpf_log); 328