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 #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, 84 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 85 "DDB capture options"); 86 87 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD, 88 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer"); 89 90 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD, 91 &db_capture_maxbufsize, 0, 92 "Maximum value for debug.ddb.capture.bufsize"); 93 94 SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD, 95 &db_capture_inprogress, 0, "DDB output capture in progress"); 96 97 /* 98 * Boot-time allocation of the DDB capture buffer, if any. Force all buffer 99 * sizes, including the maximum size, to be rounded to block sizes. 100 */ 101 static void 102 db_capture_sysinit(__unused void *dummy) 103 { 104 105 TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize); 106 db_capture_maxbufsize = roundup(db_capture_maxbufsize, 107 TEXTDUMP_BLOCKSIZE); 108 db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE); 109 if (db_capture_bufsize > db_capture_maxbufsize) 110 db_capture_bufsize = db_capture_maxbufsize; 111 if (db_capture_bufsize != 0) 112 db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE, 113 M_WAITOK); 114 } 115 SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit, 116 NULL); 117 118 /* 119 * Run-time adjustment of the capture buffer. 120 */ 121 static int 122 sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS) 123 { 124 u_int len, size; 125 char *buf; 126 int error; 127 128 size = db_capture_bufsize; 129 error = sysctl_handle_int(oidp, &size, 0, req); 130 if (error || req->newptr == NULL) 131 return (error); 132 size = roundup(size, TEXTDUMP_BLOCKSIZE); 133 if (size > db_capture_maxbufsize) 134 return (EINVAL); 135 sx_xlock(&db_capture_sx); 136 if (size != 0) { 137 /* 138 * Potentially the buffer is quite large, so if we can't 139 * allocate it, fail rather than waiting. 140 */ 141 buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT); 142 if (buf == NULL) { 143 sx_xunlock(&db_capture_sx); 144 return (ENOMEM); 145 } 146 len = min(db_capture_bufoff, size); 147 } else { 148 buf = NULL; 149 len = 0; 150 } 151 if (db_capture_buf != NULL && buf != NULL) 152 bcopy(db_capture_buf, buf, len); 153 if (db_capture_buf != NULL) 154 free(db_capture_buf, M_DDB_CAPTURE); 155 db_capture_bufoff = len; 156 db_capture_buf = buf; 157 db_capture_bufsize = size; 158 sx_xunlock(&db_capture_sx); 159 160 KASSERT(db_capture_bufoff <= db_capture_bufsize, 161 ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize")); 162 KASSERT(db_capture_bufsize <= db_capture_maxbufsize, 163 ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize")); 164 165 return (0); 166 } 167 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, 168 CTLTYPE_UINT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, 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, 195 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, 196 sysctl_debug_ddb_capture_data, "A", 197 "DDB capture data"); 198 199 /* 200 * Routines for capturing DDB output into a fixed-size buffer. These are 201 * invoked from DDB's input and output routines. If we hit the limit on the 202 * buffer, we simply drop further data. 203 */ 204 void 205 db_capture_write(char *buffer, u_int buflen) 206 { 207 u_int len; 208 209 if (db_capture_inprogress == 0 || db_capture_inpager) 210 return; 211 len = min(buflen, db_capture_bufsize - db_capture_bufoff); 212 bcopy(buffer, db_capture_buf + db_capture_bufoff, len); 213 db_capture_bufoff += len; 214 215 KASSERT(db_capture_bufoff <= db_capture_bufsize, 216 ("db_capture_write: bufoff > bufsize")); 217 } 218 219 void 220 db_capture_writech(char ch) 221 { 222 223 return (db_capture_write(&ch, sizeof(ch))); 224 } 225 226 void 227 db_capture_enterpager(void) 228 { 229 230 db_capture_inpager = 1; 231 } 232 233 void 234 db_capture_exitpager(void) 235 { 236 237 db_capture_inpager = 0; 238 } 239 240 /* 241 * Zero out any bytes left in the last block of the DDB capture buffer. This 242 * is run shortly before writing the blocks to disk, rather than when output 243 * capture is stopped, in order to avoid injecting nul's into the middle of 244 * output. 245 */ 246 static void 247 db_capture_zeropad(void) 248 { 249 u_int len; 250 251 len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize - 252 db_capture_bufoff) % TEXTDUMP_BLOCKSIZE); 253 bzero(db_capture_buf + db_capture_bufoff, len); 254 db_capture_bufpadding = len; 255 } 256 257 /* 258 * Reset capture state, which flushes buffers. 259 */ 260 static void 261 db_capture_reset(void) 262 { 263 264 db_capture_inprogress = 0; 265 db_capture_bufoff = 0; 266 db_capture_bufpadding = 0; 267 } 268 269 /* 270 * Start capture. Only one session is allowed at any time, but we may 271 * continue a previous session, so the buffer isn't reset. 272 */ 273 static void 274 db_capture_start(void) 275 { 276 277 if (db_capture_inprogress) { 278 db_printf("Capture already started\n"); 279 return; 280 } 281 db_capture_inprogress = 1; 282 } 283 284 /* 285 * Terminate DDB output capture--real work is deferred to db_capture_dump, 286 * which executes outside of the DDB context. We don't zero pad here because 287 * capture may be started again before the dump takes place. 288 */ 289 static void 290 db_capture_stop(void) 291 { 292 293 if (db_capture_inprogress == 0) { 294 db_printf("Capture not started\n"); 295 return; 296 } 297 db_capture_inprogress = 0; 298 } 299 300 /* 301 * Dump DDB(4) captured output (and resets capture buffers). 302 */ 303 void 304 db_capture_dump(struct dumperinfo *di) 305 { 306 u_int offset; 307 308 if (db_capture_bufoff == 0) 309 return; 310 311 db_capture_zeropad(); 312 textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME, 313 db_capture_bufoff); 314 (void)textdump_writenextblock(di, textdump_block_buffer); 315 for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding; 316 offset += TEXTDUMP_BLOCKSIZE) 317 (void)textdump_writenextblock(di, db_capture_buf + offset); 318 db_capture_bufoff = 0; 319 db_capture_bufpadding = 0; 320 } 321 322 /*- 323 * DDB(4) command to manage capture: 324 * 325 * capture on - start DDB output capture 326 * capture off - stop DDB output capture 327 * capture reset - reset DDB capture buffer (also stops capture) 328 * capture status - print DDB output capture status 329 */ 330 static void 331 db_capture_usage(void) 332 { 333 334 db_error("capture [on|off|reset|status]\n"); 335 } 336 337 void 338 db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif) 339 { 340 int t; 341 342 t = db_read_token(); 343 if (t != tIDENT) { 344 db_capture_usage(); 345 return; 346 } 347 if (db_read_token() != tEOL) 348 db_error("?\n"); 349 if (strcmp(db_tok_string, "on") == 0) 350 db_capture_start(); 351 else if (strcmp(db_tok_string, "off") == 0) 352 db_capture_stop(); 353 else if (strcmp(db_tok_string, "reset") == 0) 354 db_capture_reset(); 355 else if (strcmp(db_tok_string, "status") == 0) { 356 db_printf("%u/%u bytes used\n", db_capture_bufoff, 357 db_capture_bufsize); 358 if (db_capture_inprogress) 359 db_printf("capture is on\n"); 360 else 361 db_printf("capture is off\n"); 362 } else 363 db_capture_usage(); 364 } 365