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