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