1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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, CTLFLAG_RW, 0, 86 "DDB capture options"); 87 88 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD, 89 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer"); 90 91 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD, 92 &db_capture_maxbufsize, 0, 93 "Maximum value for debug.ddb.capture.bufsize"); 94 95 SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD, 96 &db_capture_inprogress, 0, "DDB output capture in progress"); 97 98 /* 99 * Boot-time allocation of the DDB capture buffer, if any. Force all buffer 100 * sizes, including the maximum size, to be rounded to block sizes. 101 */ 102 static void 103 db_capture_sysinit(__unused void *dummy) 104 { 105 106 TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize); 107 db_capture_maxbufsize = roundup(db_capture_maxbufsize, 108 TEXTDUMP_BLOCKSIZE); 109 db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE); 110 if (db_capture_bufsize > db_capture_maxbufsize) 111 db_capture_bufsize = db_capture_maxbufsize; 112 if (db_capture_bufsize != 0) 113 db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE, 114 M_WAITOK); 115 } 116 SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit, 117 NULL); 118 119 /* 120 * Run-time adjustment of the capture buffer. 121 */ 122 static int 123 sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS) 124 { 125 u_int len, size; 126 char *buf; 127 int error; 128 129 size = db_capture_bufsize; 130 error = sysctl_handle_int(oidp, &size, 0, req); 131 if (error || req->newptr == NULL) 132 return (error); 133 size = roundup(size, TEXTDUMP_BLOCKSIZE); 134 if (size > db_capture_maxbufsize) 135 return (EINVAL); 136 sx_xlock(&db_capture_sx); 137 if (size != 0) { 138 /* 139 * Potentially the buffer is quite large, so if we can't 140 * allocate it, fail rather than waiting. 141 */ 142 buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT); 143 if (buf == NULL) { 144 sx_xunlock(&db_capture_sx); 145 return (ENOMEM); 146 } 147 len = min(db_capture_bufoff, size); 148 } else { 149 buf = NULL; 150 len = 0; 151 } 152 if (db_capture_buf != NULL && buf != NULL) 153 bcopy(db_capture_buf, buf, len); 154 if (db_capture_buf != NULL) 155 free(db_capture_buf, M_DDB_CAPTURE); 156 db_capture_bufoff = len; 157 db_capture_buf = buf; 158 db_capture_bufsize = size; 159 sx_xunlock(&db_capture_sx); 160 161 KASSERT(db_capture_bufoff <= db_capture_bufsize, 162 ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize")); 163 KASSERT(db_capture_bufsize <= db_capture_maxbufsize, 164 ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize")); 165 166 return (0); 167 } 168 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, CTLTYPE_UINT|CTLFLAG_RW, 169 0, 0, sysctl_debug_ddb_capture_bufsize, "IU", 170 "Size of DDB capture buffer"); 171 172 /* 173 * Sysctl to read out the capture buffer from userspace. We require 174 * privilege as sensitive process/memory information may be accessed. 175 */ 176 static int 177 sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS) 178 { 179 int error; 180 char ch; 181 182 error = priv_check(req->td, PRIV_DDB_CAPTURE); 183 if (error) 184 return (error); 185 186 sx_slock(&db_capture_sx); 187 error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff); 188 sx_sunlock(&db_capture_sx); 189 if (error) 190 return (error); 191 ch = '\0'; 192 return (SYSCTL_OUT(req, &ch, sizeof(ch))); 193 } 194 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD, 195 NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data"); 196 197 /* 198 * Routines for capturing DDB output into a fixed-size buffer. These are 199 * invoked from DDB's input and output routines. If we hit the limit on the 200 * buffer, we simply drop further data. 201 */ 202 void 203 db_capture_write(char *buffer, u_int buflen) 204 { 205 u_int len; 206 207 if (db_capture_inprogress == 0 || db_capture_inpager) 208 return; 209 len = min(buflen, db_capture_bufsize - db_capture_bufoff); 210 bcopy(buffer, db_capture_buf + db_capture_bufoff, len); 211 db_capture_bufoff += len; 212 213 KASSERT(db_capture_bufoff <= db_capture_bufsize, 214 ("db_capture_write: bufoff > bufsize")); 215 } 216 217 void 218 db_capture_writech(char ch) 219 { 220 221 return (db_capture_write(&ch, sizeof(ch))); 222 } 223 224 void 225 db_capture_enterpager(void) 226 { 227 228 db_capture_inpager = 1; 229 } 230 231 void 232 db_capture_exitpager(void) 233 { 234 235 db_capture_inpager = 0; 236 } 237 238 /* 239 * Zero out any bytes left in the last block of the DDB capture buffer. This 240 * is run shortly before writing the blocks to disk, rather than when output 241 * capture is stopped, in order to avoid injecting nul's into the middle of 242 * output. 243 */ 244 static void 245 db_capture_zeropad(void) 246 { 247 u_int len; 248 249 len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize - 250 db_capture_bufoff) % TEXTDUMP_BLOCKSIZE); 251 bzero(db_capture_buf + db_capture_bufoff, len); 252 db_capture_bufpadding = len; 253 } 254 255 /* 256 * Reset capture state, which flushes buffers. 257 */ 258 static void 259 db_capture_reset(void) 260 { 261 262 db_capture_inprogress = 0; 263 db_capture_bufoff = 0; 264 db_capture_bufpadding = 0; 265 } 266 267 /* 268 * Start capture. Only one session is allowed at any time, but we may 269 * continue a previous session, so the buffer isn't reset. 270 */ 271 static void 272 db_capture_start(void) 273 { 274 275 if (db_capture_inprogress) { 276 db_printf("Capture already started\n"); 277 return; 278 } 279 db_capture_inprogress = 1; 280 } 281 282 /* 283 * Terminate DDB output capture--real work is deferred to db_capture_dump, 284 * which executes outside of the DDB context. We don't zero pad here because 285 * capture may be started again before the dump takes place. 286 */ 287 static void 288 db_capture_stop(void) 289 { 290 291 if (db_capture_inprogress == 0) { 292 db_printf("Capture not started\n"); 293 return; 294 } 295 db_capture_inprogress = 0; 296 } 297 298 /* 299 * Dump DDB(4) captured output (and resets capture buffers). 300 */ 301 void 302 db_capture_dump(struct dumperinfo *di) 303 { 304 u_int offset; 305 306 if (db_capture_bufoff == 0) 307 return; 308 309 db_capture_zeropad(); 310 textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME, 311 db_capture_bufoff); 312 (void)textdump_writenextblock(di, textdump_block_buffer); 313 for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding; 314 offset += TEXTDUMP_BLOCKSIZE) 315 (void)textdump_writenextblock(di, db_capture_buf + offset); 316 db_capture_bufoff = 0; 317 db_capture_bufpadding = 0; 318 } 319 320 /*- 321 * DDB(4) command to manage capture: 322 * 323 * capture on - start DDB output capture 324 * capture off - stop DDB output capture 325 * capture reset - reset DDB capture buffer (also stops capture) 326 * capture status - print DDB output capture status 327 */ 328 static void 329 db_capture_usage(void) 330 { 331 332 db_error("capture [on|off|reset|status]\n"); 333 } 334 335 void 336 db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif) 337 { 338 int t; 339 340 t = db_read_token(); 341 if (t != tIDENT) { 342 db_capture_usage(); 343 return; 344 } 345 if (db_read_token() != tEOL) 346 db_error("?\n"); 347 if (strcmp(db_tok_string, "on") == 0) 348 db_capture_start(); 349 else if (strcmp(db_tok_string, "off") == 0) 350 db_capture_stop(); 351 else if (strcmp(db_tok_string, "reset") == 0) 352 db_capture_reset(); 353 else if (strcmp(db_tok_string, "status") == 0) { 354 db_printf("%u/%u bytes used\n", db_capture_bufoff, 355 db_capture_bufsize); 356 if (db_capture_inprogress) 357 db_printf("capture is on\n"); 358 else 359 db_printf("capture is off\n"); 360 } else 361 db_capture_usage(); 362 } 363