db_capture.c revision 174910
1174910Srwatson/*- 2174910Srwatson * Copyright (c) 2007 Robert N. M. Watson 3174910Srwatson * All rights reserved. 4174910Srwatson * 5174910Srwatson * Redistribution and use in source and binary forms, with or without 6174910Srwatson * modification, are permitted provided that the following conditions 7174910Srwatson * are met: 8174910Srwatson * 1. Redistributions of source code must retain the above copyright 9174910Srwatson * notice, this list of conditions and the following disclaimer. 10174910Srwatson * 2. Redistributions in binary form must reproduce the above copyright 11174910Srwatson * notice, this list of conditions and the following disclaimer in the 12174910Srwatson * documentation and/or other materials provided with the distribution. 13174910Srwatson * 14174910Srwatson * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15174910Srwatson * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16174910Srwatson * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17174910Srwatson * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18174910Srwatson * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19174910Srwatson * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20174910Srwatson * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21174910Srwatson * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22174910Srwatson * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23174910Srwatson * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24174910Srwatson * SUCH DAMAGE. 25174910Srwatson */ 26174910Srwatson 27174910Srwatson/* 28174910Srwatson * DDB capture support: capture kernel debugger output into a fixed-size 29174910Srwatson * buffer for later dumping to disk or extraction from user space. 30174910Srwatson */ 31174910Srwatson 32174910Srwatson#include <sys/cdefs.h> 33174910Srwatson__FBSDID("$FreeBSD: head/sys/ddb/db_capture.c 174910 2007-12-25 23:06:51Z rwatson $"); 34174910Srwatson 35174910Srwatson#include <sys/param.h> 36174910Srwatson#include <sys/conf.h> 37174910Srwatson#include <sys/kernel.h> 38174910Srwatson#include <sys/kerneldump.h> 39174910Srwatson#include <sys/malloc.h> 40174910Srwatson#include <sys/msgbuf.h> 41174910Srwatson#include <sys/priv.h> 42174910Srwatson#include <sys/sx.h> 43174910Srwatson#include <sys/sysctl.h> 44174910Srwatson#include <sys/systm.h> 45174910Srwatson 46174910Srwatson#include <ddb/ddb.h> 47174910Srwatson#include <ddb/db_lex.h> 48174910Srwatson 49174910Srwatson/* 50174910Srwatson * While it would be desirable to use a small block-sized buffer and dump 51174910Srwatson * incrementally to disk in fixed-size blocks, it's not possible to enter 52174910Srwatson * kernel dumper routines without restarting the kernel, which is undesirable 53174910Srwatson * in the midst of debugging. Instead, we maintain a large static global 54174910Srwatson * buffer that we fill from DDB's output routines. 55174910Srwatson */ 56174910Srwatsonstatic MALLOC_DEFINE(M_DB_CAPTURE, "db_capture", "DDB capture buffer"); 57174910Srwatson 58174910Srwatson#define DB_CAPTURE_DEFAULTBUFSIZE 48*1024 59174910Srwatson#define DB_CAPTURE_MAXBUFSIZE 512*1024 60174910Srwatson 61174910Srwatsonstatic char *db_capture_buf; 62174910Srwatsonstatic u_int db_capture_bufsize = DB_CAPTURE_DEFAULTBUFSIZE; 63174910Srwatsonstatic u_int db_capture_maxbufsize = DB_CAPTURE_MAXBUFSIZE; /* Read-only. */ 64174910Srwatsonstatic u_int db_capture_bufoff; /* Next location to write in buffer. */ 65174910Srwatsonstatic int db_capture_inpager; /* Suspend capture in pager. */ 66174910Srwatsonstatic int db_capture_inprogress; /* DDB capture currently in progress. */ 67174910Srwatson 68174910Srwatsonstruct sx db_capture_sx; /* Lock against user thread races. */ 69174910SrwatsonSX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx"); 70174910Srwatson 71174910Srwatsonstatic SYSCTL_NODE(_debug_ddb, OID_AUTO, capture, CTLFLAG_RW, 0, 72174910Srwatson "DDB capture options"); 73174910Srwatson 74174910SrwatsonSYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bytes, CTLFLAG_RD, 75174910Srwatson &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer"); 76174910Srwatson 77174910SrwatsonSYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD, 78174910Srwatson &db_capture_maxbufsize, 0, 79174910Srwatson "Maximum value for debug.ddb.capture.bufsize"); 80174910Srwatson 81174910Srwatson/* 82174910Srwatson * Boot-time allocation of the DDB capture buffer, if any. 83174910Srwatson */ 84174910Srwatsonstatic void 85174910Srwatsondb_capture_sysinit(__unused void *dummy) 86174910Srwatson{ 87174910Srwatson 88174910Srwatson TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize); 89174910Srwatson if (db_capture_bufsize > DB_CAPTURE_MAXBUFSIZE) 90174910Srwatson db_capture_bufsize = DB_CAPTURE_MAXBUFSIZE; 91174910Srwatson 92174910Srwatson if (db_capture_bufsize != 0) 93174910Srwatson db_capture_buf = malloc(db_capture_bufsize, M_DB_CAPTURE, 94174910Srwatson M_WAITOK); 95174910Srwatson} 96174910SrwatsonSYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit, 97174910Srwatson NULL); 98174910Srwatson 99174910Srwatson/* 100174910Srwatson * Run-time adjustment of the capture buffer. 101174910Srwatson */ 102174910Srwatsonstatic int 103174910Srwatsonsysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS) 104174910Srwatson{ 105174910Srwatson u_int len, size; 106174910Srwatson char *buf; 107174910Srwatson int error; 108174910Srwatson 109174910Srwatson size = db_capture_bufsize; 110174910Srwatson error = sysctl_handle_int(oidp, &size, 0, req); 111174910Srwatson if (error || req->newptr == NULL) 112174910Srwatson return (error); 113174910Srwatson if (size > DB_CAPTURE_MAXBUFSIZE) 114174910Srwatson return (EINVAL); 115174910Srwatson 116174910Srwatson sx_xlock(&db_capture_sx); 117174910Srwatson if (size != 0) { 118174910Srwatson /* 119174910Srwatson * Potentially the buffer is quite large, so if we can't 120174910Srwatson * allocate it, fail rather than waiting. 121174910Srwatson */ 122174910Srwatson buf = malloc(size, M_DB_CAPTURE, M_NOWAIT); 123174910Srwatson if (buf == NULL) { 124174910Srwatson sx_xunlock(&db_capture_sx); 125174910Srwatson return (ENOMEM); 126174910Srwatson } 127174910Srwatson len = min(db_capture_bufoff, size); 128174910Srwatson } else { 129174910Srwatson buf = NULL; 130174910Srwatson len = 0; 131174910Srwatson } 132174910Srwatson if (db_capture_buf != NULL && buf != NULL) 133174910Srwatson bcopy(db_capture_buf, buf, len); 134174910Srwatson if (db_capture_buf != NULL) 135174910Srwatson free(db_capture_buf, M_DB_CAPTURE); 136174910Srwatson db_capture_bufoff = len; 137174910Srwatson db_capture_buf = buf; 138174910Srwatson db_capture_bufsize = size; 139174910Srwatson sx_xunlock(&db_capture_sx); 140174910Srwatson 141174910Srwatson KASSERT(db_capture_bufoff <= db_capture_bufsize, 142174910Srwatson ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize")); 143174910Srwatson KASSERT(db_capture_bufsize <= DB_CAPTURE_MAXBUFSIZE, 144174910Srwatson ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize")); 145174910Srwatson 146174910Srwatson return (0); 147174910Srwatson} 148174910SrwatsonSYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, CTLTYPE_UINT|CTLFLAG_RW, 149174910Srwatson 0, 0, sysctl_debug_ddb_capture_bufsize, "IU", 150174910Srwatson "Size of DDB capture buffer"); 151174910Srwatson 152174910Srwatson/* 153174910Srwatson * Sysctl to read out the capture buffer from userspace. We require 154174910Srwatson * privilege as sensitive process/memory information may be accessed. 155174910Srwatson */ 156174910Srwatsonstatic int 157174910Srwatsonsysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS) 158174910Srwatson{ 159174910Srwatson int error; 160174910Srwatson char ch; 161174910Srwatson 162174910Srwatson error = priv_check(req->td, PRIV_DDB_CAPTURE); 163174910Srwatson if (error) 164174910Srwatson return (error); 165174910Srwatson 166174910Srwatson sx_slock(&db_capture_sx); 167174910Srwatson error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff); 168174910Srwatson sx_sunlock(&db_capture_sx); 169174910Srwatson if (error) 170174910Srwatson return (error); 171174910Srwatson ch = '\0'; 172174910Srwatson return (SYSCTL_OUT(req, &ch, sizeof(ch))); 173174910Srwatson} 174174910SrwatsonSYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD, 175174910Srwatson NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data"); 176174910Srwatson 177174910Srwatson/* 178174910Srwatson * Routines for capturing DDB output into a fixed-size buffer. These are 179174910Srwatson * invoked from DDB's input and output routines. If we hit the limit on the 180174910Srwatson * buffer, we simply drop further data. 181174910Srwatson */ 182174910Srwatsonvoid 183174910Srwatsondb_capture_write(char *buffer, u_int buflen) 184174910Srwatson{ 185174910Srwatson u_int len; 186174910Srwatson 187174910Srwatson if (db_capture_inprogress == 0 || db_capture_inpager) 188174910Srwatson return; 189174910Srwatson len = min(buflen, db_capture_bufsize - db_capture_bufoff); 190174910Srwatson bcopy(buffer, db_capture_buf + db_capture_bufoff, len); 191174910Srwatson db_capture_bufoff += len; 192174910Srwatson 193174910Srwatson KASSERT(db_capture_bufoff <= db_capture_bufsize, 194174910Srwatson ("db_capture_write: bufoff > bufsize")); 195174910Srwatson} 196174910Srwatson 197174910Srwatsonvoid 198174910Srwatsondb_capture_writech(char ch) 199174910Srwatson{ 200174910Srwatson 201174910Srwatson return (db_capture_write(&ch, sizeof(ch))); 202174910Srwatson} 203174910Srwatson 204174910Srwatsonvoid 205174910Srwatsondb_capture_enterpager(void) 206174910Srwatson{ 207174910Srwatson 208174910Srwatson db_capture_inpager = 1; 209174910Srwatson} 210174910Srwatson 211174910Srwatsonvoid 212174910Srwatsondb_capture_exitpager(void) 213174910Srwatson{ 214174910Srwatson 215174910Srwatson db_capture_inpager = 0; 216174910Srwatson} 217174910Srwatson 218174910Srwatson/* 219174910Srwatson * Reset capture state, which flushes buffers. 220174910Srwatson */ 221174910Srwatsonstatic void 222174910Srwatsondb_capture_reset(void) 223174910Srwatson{ 224174910Srwatson 225174910Srwatson db_capture_inprogress = 0; 226174910Srwatson db_capture_bufoff = 0; 227174910Srwatson} 228174910Srwatson 229174910Srwatson/* 230174910Srwatson * Start capture. Only one session is allowed at any time, but we may 231174910Srwatson * continue a previous session, so the buffer isn't reset. 232174910Srwatson */ 233174910Srwatsonstatic void 234174910Srwatsondb_capture_start(void) 235174910Srwatson{ 236174910Srwatson 237174910Srwatson if (db_capture_inprogress) { 238174910Srwatson db_printf("Capture already started\n"); 239174910Srwatson return; 240174910Srwatson } 241174910Srwatson db_capture_inprogress = 1; 242174910Srwatson} 243174910Srwatson 244174910Srwatson/* 245174910Srwatson * Terminate DDB output capture. 246174910Srwatson */ 247174910Srwatsonstatic void 248174910Srwatsondb_capture_stop(void) 249174910Srwatson{ 250174910Srwatson 251174910Srwatson if (db_capture_inprogress == 0) { 252174910Srwatson db_printf("Capture not started\n"); 253174910Srwatson return; 254174910Srwatson } 255174910Srwatson db_capture_inprogress = 0; 256174910Srwatson} 257174910Srwatson 258174910Srwatson/*- 259174910Srwatson * DDB(4) command to manage capture: 260174910Srwatson * 261174910Srwatson * capture on - start DDB output capture 262174910Srwatson * capture off - stop DDB output capture 263174910Srwatson * capture reset - reset DDB capture buffer (also stops capture) 264174910Srwatson * capture status - print DDB output capture status 265174910Srwatson */ 266174910Srwatsonstatic void 267174910Srwatsondb_capture_usage(void) 268174910Srwatson{ 269174910Srwatson 270174910Srwatson db_error("capture [on|off|reset|status]\n"); 271174910Srwatson} 272174910Srwatson 273174910Srwatsonvoid 274174910Srwatsondb_capture_cmd(db_expr_t addr, boolean_t have_addr, db_expr_t count, 275174910Srwatson char *modif) 276174910Srwatson{ 277174910Srwatson int t; 278174910Srwatson 279174910Srwatson t = db_read_token(); 280174910Srwatson if (t != tIDENT) { 281174910Srwatson db_capture_usage(); 282174910Srwatson return; 283174910Srwatson } 284174910Srwatson if (db_read_token() != tEOL) 285174910Srwatson db_error("?\n"); 286174910Srwatson if (strcmp(db_tok_string, "on") == 0) 287174910Srwatson db_capture_start(); 288174910Srwatson else if (strcmp(db_tok_string, "off") == 0) 289174910Srwatson db_capture_stop(); 290174910Srwatson else if (strcmp(db_tok_string, "reset") == 0) 291174910Srwatson db_capture_reset(); 292174910Srwatson else if (strcmp(db_tok_string, "status") == 0) { 293174910Srwatson db_printf("%u/%u bytes used\n", db_capture_bufoff, 294174910Srwatson db_capture_bufsize); 295174910Srwatson if (db_capture_inprogress) 296174910Srwatson db_printf("capture is on\n"); 297174910Srwatson else 298174910Srwatson db_printf("capture is off\n"); 299174910Srwatson } else 300174910Srwatson db_capture_usage(); 301174910Srwatson} 302