/*-
* Copyright (c) 2007 Robert N. M. Watson
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* DDB capture support: capture kernel debugger output into a fixed-size
* buffer for later dumping to disk or extraction from user space.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include <sys/param.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/kerneldump.h>
#include <sys/malloc.h>
#include <sys/msgbuf.h>
#include <sys/priv.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <ddb/ddb.h>
#include <ddb/db_lex.h>
/*
* While it would be desirable to use a small block-sized buffer and dump
* incrementally to disk in fixed-size blocks, it's not possible to enter
* kernel dumper routines without restarting the kernel, which is undesirable
* in the midst of debugging. Instead, we maintain a large static global
* buffer that we fill from DDB's output routines.
*
* We enforce an invariant at runtime that buffer sizes are even multiples of
* the textdump block size, which is a design choice that we might want to
* reconsider.
*/
static MALLOC_DEFINE(M_DDB_CAPTURE, "ddb_capture", "DDB capture buffer");
#ifndef DDB_CAPTURE_DEFAULTBUFSIZE
#define DDB_CAPTURE_DEFAULTBUFSIZE 48*1024
#endif
#ifndef DDB_CAPTURE_MAXBUFSIZE
#define DDB_CAPTURE_MAXBUFSIZE 5*1024*1024
#endif
#define DDB_CAPTURE_FILENAME "ddb.txt" /* Captured DDB output. */
static char *db_capture_buf;
static u_int db_capture_bufsize = DDB_CAPTURE_DEFAULTBUFSIZE;
static u_int db_capture_maxbufsize = DDB_CAPTURE_MAXBUFSIZE; /* Read-only. */
static u_int db_capture_bufoff; /* Next location to write in buffer. */
static u_int db_capture_bufpadding; /* Amount of zero padding. */
static int db_capture_inpager; /* Suspend capture in pager. */
static int db_capture_inprogress; /* DDB capture currently in progress. */
struct sx db_capture_sx; /* Lock against user thread races. */
SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx");
static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture, CTLFLAG_RW, 0,
"DDB capture options");
SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
&db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
&db_capture_maxbufsize, 0,
"Maximum value for debug.ddb.capture.bufsize");
SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD,
&db_capture_inprogress, 0, "DDB output capture in progress");
/*
* Boot-time allocation of the DDB capture buffer, if any. Force all buffer
* sizes, including the maximum size, to be rounded to block sizes.
*/
static void
db_capture_sysinit(__unused void *dummy)
{
TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize);
db_capture_maxbufsize = roundup(db_capture_maxbufsize,
TEXTDUMP_BLOCKSIZE);
db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE);
if (db_capture_bufsize > db_capture_maxbufsize)
db_capture_bufsize = db_capture_maxbufsize;
if (db_capture_bufsize != 0)
db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE,
M_WAITOK);
}
SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit,
NULL);
/*
* Run-time adjustment of the capture buffer.
*/
static int
sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)
{
u_int len, size;
char *buf;
int error;
size = db_capture_bufsize;
error = sysctl_handle_int(oidp, &size, 0, req);
if (error || req->newptr == NULL)
return (error);
size = roundup(size, TEXTDUMP_BLOCKSIZE);
if (size > db_capture_maxbufsize)
return (EINVAL);
sx_xlock(&db_capture_sx);
if (size != 0) {
/*
* Potentially the buffer is quite large, so if we can't
* allocate it, fail rather than waiting.
*/
buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT);
if (buf == NULL) {
sx_xunlock(&db_capture_sx);
return (ENOMEM);
}
len = min(db_capture_bufoff, size);
} else {
buf = NULL;
len = 0;
}
if (db_capture_buf != NULL && buf != NULL)
bcopy(db_capture_buf, buf, len);
if (db_capture_buf != NULL)
free(db_capture_buf, M_DDB_CAPTURE);
db_capture_bufoff = len;
db_capture_buf = buf;
db_capture_bufsize = size;
sx_xunlock(&db_capture_sx);
KASSERT(db_capture_bufoff <= db_capture_bufsize,
("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize"));
KASSERT(db_capture_bufsize <= db_capture_maxbufsize,
("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize"));
return (0);
}
SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, CTLTYPE_UINT|CTLFLAG_RW,
0, 0, sysctl_debug_ddb_capture_bufsize, "IU",
"Size of DDB capture buffer");
/*
* Sysctl to read out the capture buffer from userspace. We require
* privilege as sensitive process/memory information may be accessed.
*/
static int
sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)
{
int error;
char ch;
error = priv_check(req->td, PRIV_DDB_CAPTURE);
if (error)
return (error);
sx_slock(&db_capture_sx);
error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff);
sx_sunlock(&db_capture_sx);
if (error)
return (error);
ch = '\0';
return (SYSCTL_OUT(req, &ch, sizeof(ch)));
}
SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data");
/*
* Routines for capturing DDB output into a fixed-size buffer. These are
* invoked from DDB's input and output routines. If we hit the limit on the
* buffer, we simply drop further data.
*/
void
db_capture_write(char *buffer, u_int buflen)
{
u_int len;
if (db_capture_inprogress == 0 || db_capture_inpager)
return;
len = min(buflen, db_capture_bufsize - db_capture_bufoff);
bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
db_capture_bufoff += len;
KASSERT(db_capture_bufoff <= db_capture_bufsize,
("db_capture_write: bufoff > bufsize"));
}
void
db_capture_writech(char ch)
{
return (db_capture_write(&ch, sizeof(ch)));
}
void
db_capture_enterpager(void)
{
db_capture_inpager = 1;
}
void
db_capture_exitpager(void)
{
db_capture_inpager = 0;
}
/*
* Zero out any bytes left in the last block of the DDB capture buffer. This
* is run shortly before writing the blocks to disk, rather than when output
* capture is stopped, in order to avoid injecting nul's into the middle of
* output.
*/
static void
db_capture_zeropad(void)
{
u_int len;
len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
bzero(db_capture_buf + db_capture_bufoff, len);
db_capture_bufpadding = len;
}
/*
* Reset capture state, which flushes buffers.
*/
static void
db_capture_reset(void)
{
db_capture_inprogress = 0;
db_capture_bufoff = 0;
db_capture_bufpadding = 0;
}
/*
* Start capture. Only one session is allowed at any time, but we may
* continue a previous session, so the buffer isn't reset.
*/
static void
db_capture_start(void)
{
if (db_capture_inprogress) {
db_printf("Capture already started\n");
return;
}
db_capture_inprogress = 1;
}
/*
* Terminate DDB output capture--real work is deferred to db_capture_dump,
* which executes outside of the DDB context. We don't zero pad here because
* capture may be started again before the dump takes place.
*/
static void
db_capture_stop(void)
{
if (db_capture_inprogress == 0) {
db_printf("Capture not started\n");
return;
}
db_capture_inprogress = 0;
}
/*
* Dump DDB(4) captured output (and resets capture buffers).
*/
void
db_capture_dump(struct dumperinfo *di)
{
u_int offset;
if (db_capture_bufoff == 0)
return;
db_capture_zeropad();
textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
db_capture_bufoff);
(void)textdump_writenextblock(di, textdump_block_buffer);
for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
offset += TEXTDUMP_BLOCKSIZE)
(void)textdump_writenextblock(di, db_capture_buf + offset);
db_capture_bufoff = 0;
db_capture_bufpadding = 0;
}
/*-
* DDB(4) command to manage capture:
*
* capture on - start DDB output capture
* capture off - stop DDB output capture
* capture reset - reset DDB capture buffer (also stops capture)
* capture status - print DDB output capture status
*/
static void
db_capture_usage(void)
{
db_error("capture [on|off|reset|status]\n");
}
void
db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
{
int t;
t = db_read_token();
if (t != tIDENT) {
db_capture_usage();
return;
}
if (db_read_token() != tEOL)
db_error("?\n");
if (strcmp(db_tok_string, "on") == 0)
db_capture_start();
else if (strcmp(db_tok_string, "off") == 0)
db_capture_stop();
else if (strcmp(db_tok_string, "reset") == 0)
db_capture_reset();
else if (strcmp(db_tok_string, "status") == 0) {
db_printf("%u/%u bytes used\n", db_capture_bufoff,
db_capture_bufsize);
if (db_capture_inprogress)
db_printf("capture is on\n");
else
db_printf("capture is off\n");
} else
db_capture_usage();
}
