1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2007 Robert N. M. Watson 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 /* 30 * DDB capture support: capture kernel debugger output into a fixed-size 31 * buffer for later dumping to disk or extraction from user space. 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_ddb.h" 38 39 #include <sys/param.h> 40 #include <sys/conf.h> 41 #include <sys/kernel.h> 42 #include <sys/kerneldump.h> 43 #include <sys/malloc.h> 44 #include <sys/msgbuf.h> 45 #include <sys/priv.h> 46 #include <sys/sx.h> 47 #include <sys/sysctl.h> 48 #include <sys/systm.h> 49 50 #include <ddb/ddb.h> 51 #include <ddb/db_lex.h> 52 53 /* 54 * While it would be desirable to use a small block-sized buffer and dump 55 * incrementally to disk in fixed-size blocks, it's not possible to enter 56 * kernel dumper routines without restarting the kernel, which is undesirable 57 * in the midst of debugging. Instead, we maintain a large static global 58 * buffer that we fill from DDB's output routines. 59 * 60 * We enforce an invariant at runtime that buffer sizes are even multiples of 61 * the textdump block size, which is a design choice that we might want to 62 * reconsider. 63 */ 64 static MALLOC_DEFINE(M_DDB_CAPTURE, "ddb_capture", "DDB capture buffer"); 65 66 #ifndef DDB_CAPTURE_DEFAULTBUFSIZE 67 #define DDB_CAPTURE_DEFAULTBUFSIZE 48*1024 68 #endif 69 #ifndef DDB_CAPTURE_MAXBUFSIZE 70 #define DDB_CAPTURE_MAXBUFSIZE 5*1024*1024 71 #endif 72 #define DDB_CAPTURE_FILENAME "ddb.txt" /* Captured DDB output. */ 73 74 static char *db_capture_buf; 75 static u_int db_capture_bufsize = DDB_CAPTURE_DEFAULTBUFSIZE; 76 static u_int db_capture_maxbufsize = DDB_CAPTURE_MAXBUFSIZE; /* Read-only. */ 77 static u_int db_capture_bufoff; /* Next location to write in buffer. */ 78 static u_int db_capture_bufpadding; /* Amount of zero padding. */ 79 static int db_capture_inpager; /* Suspend capture in pager. */ 80 static int db_capture_inprogress; /* DDB capture currently in progress. */ 81 82 struct sx db_capture_sx; /* Lock against user thread races. */ 83 SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx"); 84 85 static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture, 86 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 87 "DDB capture options"); 88 89 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD, 90 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer"); 91 92 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD, 93 &db_capture_maxbufsize, 0, 94 "Maximum value for debug.ddb.capture.bufsize"); 95 96 SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD, 97 &db_capture_inprogress, 0, "DDB output capture in progress"); 98 99 /* 100 * Boot-time allocation of the DDB capture buffer, if any. Force all buffer 101 * sizes, including the maximum size, to be rounded to block sizes. 102 */ 103 static void 104 db_capture_sysinit(__unused void *dummy) 105 { 106 107 TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize); 108 db_capture_maxbufsize = roundup(db_capture_maxbufsize, 109 TEXTDUMP_BLOCKSIZE); 110 db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE); 111 if (db_capture_bufsize > db_capture_maxbufsize) 112 db_capture_bufsize = db_capture_maxbufsize; 113 if (db_capture_bufsize != 0) 114 db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE, 115 M_WAITOK); 116 } 117 SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit, 118 NULL); 119 120 /* 121 * Run-time adjustment of the capture buffer. 122 */ 123 static int 124 sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS) 125 { 126 u_int len, size; 127 char *buf; 128 int error; 129 130 size = db_capture_bufsize; 131 error = sysctl_handle_int(oidp, &size, 0, req); 132 if (error || req->newptr == NULL) 133 return (error); 134 size = roundup(size, TEXTDUMP_BLOCKSIZE); 135 if (size > db_capture_maxbufsize) 136 return (EINVAL); 137 sx_xlock(&db_capture_sx); 138 if (size != 0) { 139 /* 140 * Potentially the buffer is quite large, so if we can't 141 * allocate it, fail rather than waiting. 142 */ 143 buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT); 144 if (buf == NULL) { 145 sx_xunlock(&db_capture_sx); 146 return (ENOMEM); 147 } 148 len = min(db_capture_bufoff, size); 149 } else { 150 buf = NULL; 151 len = 0; 152 } 153 if (db_capture_buf != NULL && buf != NULL) 154 bcopy(db_capture_buf, buf, len); 155 if (db_capture_buf != NULL) 156 free(db_capture_buf, M_DDB_CAPTURE); 157 db_capture_bufoff = len; 158 db_capture_buf = buf; 159 db_capture_bufsize = size; 160 sx_xunlock(&db_capture_sx); 161 162 KASSERT(db_capture_bufoff <= db_capture_bufsize, 163 ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize")); 164 KASSERT(db_capture_bufsize <= db_capture_maxbufsize, 165 ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize")); 166 167 return (0); 168 } 169 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, 170 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 171 sysctl_debug_ddb_capture_bufsize, "IU", 172 "Size of DDB capture buffer"); 173 174 /* 175 * Sysctl to read out the capture buffer from userspace. We require 176 * privilege as sensitive process/memory information may be accessed. 177 */ 178 static int 179 sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS) 180 { 181 int error; 182 char ch; 183 184 error = priv_check(req->td, PRIV_DDB_CAPTURE); 185 if (error) 186 return (error); 187 188 sx_slock(&db_capture_sx); 189 error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff); 190 sx_sunlock(&db_capture_sx); 191 if (error) 192 return (error); 193 ch = '\0'; 194 return (SYSCTL_OUT(req, &ch, sizeof(ch))); 195 } 196 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, 197 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, 198 sysctl_debug_ddb_capture_data, "A", 199 "DDB capture data"); 200 201 /* 202 * Routines for capturing DDB output into a fixed-size buffer. These are 203 * invoked from DDB's input and output routines. If we hit the limit on the 204 * buffer, we simply drop further data. 205 */ 206 void 207 db_capture_write(char *buffer, u_int buflen) 208 { 209 u_int len; 210 211 if (db_capture_inprogress == 0 || db_capture_inpager) 212 return; 213 len = min(buflen, db_capture_bufsize - db_capture_bufoff); 214 bcopy(buffer, db_capture_buf + db_capture_bufoff, len); 215 db_capture_bufoff += len; 216 217 KASSERT(db_capture_bufoff <= db_capture_bufsize, 218 ("db_capture_write: bufoff > bufsize")); 219 } 220 221 void 222 db_capture_writech(char ch) 223 { 224 225 return (db_capture_write(&ch, sizeof(ch))); 226 } 227 228 void 229 db_capture_enterpager(void) 230 { 231 232 db_capture_inpager = 1; 233 } 234 235 void 236 db_capture_exitpager(void) 237 { 238 239 db_capture_inpager = 0; 240 } 241 242 /* 243 * Zero out any bytes left in the last block of the DDB capture buffer. This 244 * is run shortly before writing the blocks to disk, rather than when output 245 * capture is stopped, in order to avoid injecting nul's into the middle of 246 * output. 247 */ 248 static void 249 db_capture_zeropad(void) 250 { 251 u_int len; 252 253 len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize - 254 db_capture_bufoff) % TEXTDUMP_BLOCKSIZE); 255 bzero(db_capture_buf + db_capture_bufoff, len); 256 db_capture_bufpadding = len; 257 } 258 259 /* 260 * Reset capture state, which flushes buffers. 261 */ 262 static void 263 db_capture_reset(void) 264 { 265 266 db_capture_inprogress = 0; 267 db_capture_bufoff = 0; 268 db_capture_bufpadding = 0; 269 } 270 271 /* 272 * Start capture. Only one session is allowed at any time, but we may 273 * continue a previous session, so the buffer isn't reset. 274 */ 275 static void 276 db_capture_start(void) 277 { 278 279 if (db_capture_inprogress) { 280 db_printf("Capture already started\n"); 281 return; 282 } 283 db_capture_inprogress = 1; 284 } 285 286 /* 287 * Terminate DDB output capture--real work is deferred to db_capture_dump, 288 * which executes outside of the DDB context. We don't zero pad here because 289 * capture may be started again before the dump takes place. 290 */ 291 static void 292 db_capture_stop(void) 293 { 294 295 if (db_capture_inprogress == 0) { 296 db_printf("Capture not started\n"); 297 return; 298 } 299 db_capture_inprogress = 0; 300 } 301 302 /* 303 * Dump DDB(4) captured output (and resets capture buffers). 304 */ 305 void 306 db_capture_dump(struct dumperinfo *di) 307 { 308 u_int offset; 309 310 if (db_capture_bufoff == 0) 311 return; 312 313 db_capture_zeropad(); 314 textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME, 315 db_capture_bufoff); 316 (void)textdump_writenextblock(di, textdump_block_buffer); 317 for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding; 318 offset += TEXTDUMP_BLOCKSIZE) 319 (void)textdump_writenextblock(di, db_capture_buf + offset); 320 db_capture_bufoff = 0; 321 db_capture_bufpadding = 0; 322 } 323 324 /*- 325 * DDB(4) command to manage capture: 326 * 327 * capture on - start DDB output capture 328 * capture off - stop DDB output capture 329 * capture reset - reset DDB capture buffer (also stops capture) 330 * capture status - print DDB output capture status 331 */ 332 static void 333 db_capture_usage(void) 334 { 335 336 db_error("capture [on|off|reset|status]\n"); 337 } 338 339 void 340 db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif) 341 { 342 int t; 343 344 t = db_read_token(); 345 if (t != tIDENT) { 346 db_capture_usage(); 347 return; 348 } 349 if (db_read_token() != tEOL) 350 db_error("?\n"); 351 if (strcmp(db_tok_string, "on") == 0) 352 db_capture_start(); 353 else if (strcmp(db_tok_string, "off") == 0) 354 db_capture_stop(); 355 else if (strcmp(db_tok_string, "reset") == 0) 356 db_capture_reset(); 357 else if (strcmp(db_tok_string, "status") == 0) { 358 db_printf("%u/%u bytes used\n", db_capture_bufoff, 359 db_capture_bufsize); 360 if (db_capture_inprogress) 361 db_printf("capture is on\n"); 362 else 363 db_printf("capture is off\n"); 364 } else 365 db_capture_usage(); 366 } 367