FreeBSD/Linux Kernel Cross Reference
sys/gdb/gdb_cons.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2006 Sam Leffler
      * 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 AUTHORS ``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 AUTHORS 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.
     */
    
    /* 
     * Support for redirecting console msgs to gdb.  We register
     * a pseudo console to hook cnputc and send stuff to the gdb
     * port.  The only trickiness here is buffering output so this
     * isn't dog slow.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/cons.h>
    #include <sys/kdb.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/reboot.h>
    #include <sys/sysctl.h>
    
    #include <machine/gdb_machdep.h>
    #include <machine/kdb.h>
    
    #include <gdb/gdb.h>
    #include <gdb/gdb_int.h>
    
    struct gdbcons {
            int     npending;
            /* /2 for hex conversion, -6 for protocol glue */
            char    buf[GDB_BUFSZ/2 - 6];
            struct callout flush;
    };
    static struct gdbcons state = { -1 };
    
    static  int gdbcons_enable = 0;
    SYSCTL_INT(_debug_gdb, OID_AUTO, cons, CTLFLAG_RWTUN, &gdbcons_enable, 0,
            "copy console messages to GDB");
    /* Legacy sysctl alias */
    SYSCTL_INT(_debug, OID_AUTO, gdbcons, CTLFLAG_RWTUN, &gdbcons_enable,
            0, "copy console messages to GDB");
    
    static void
    gdb_cnprobe(struct consdev *cp)
    {
            sprintf(cp->cn_name, "gdb");
            cp->cn_pri = CN_LOW;            /* XXX no way to say "write only" */
    }
    
    static void
    gdb_cninit(struct consdev *cp)
    {
            struct gdbcons *c = &state;
    
            /* setup tx buffer and callout */
            if (c->npending == -1) {
                    c->npending = 0;
                    callout_init(&c->flush, 1);
                    cp->cn_arg = c;
            }
    }
    
    static void
    gdb_cnterm(struct consdev *cp)
    {
    }
    
    static void
    gdb_cngrab(struct consdev *cp)
    {
    }
    
    static void
   gdb_cnungrab(struct consdev *cp)
   {
   }
   
   static int
   gdb_cngetc(struct consdev *cp)
   {
           return -1;
   }
   
   static void
   gdb_tx_puthex(int c)
   {
           const char *hex = "0123456789abcdef";
   
           gdb_tx_char(hex[(c>>4)&0xf]);
           gdb_tx_char(hex[(c>>0)&0xf]);
   }
   
   static void
   gdb_cnflush(void *arg)
   {
           struct gdbcons *gc = arg;
           int i;
   
           gdb_tx_begin('O');
           for (i = 0; i < gc->npending; i++)
                   gdb_tx_puthex(gc->buf[i]);
           gdb_tx_end();
           gc->npending = 0;
   }
   
   /*
    * This glop is to figure out when it's safe to use callouts
    * to defer buffer flushing.  There's probably a better way
    * and/or an earlier point in the boot process when it's ok.
    */
   static int calloutok = 0;
   static void
   oktousecallout(void *data __unused)
   {
           calloutok = 1;
   }
   SYSINIT(gdbhack, SI_SUB_LAST, SI_ORDER_MIDDLE, oktousecallout, NULL);
   
   static void
   gdb_cnputc(struct consdev *cp, int c)
   {
           struct gdbcons *gc;
   
           if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
                   gc = cp->cn_arg;
                   if (gc->npending != 0) {
                           /*
                            * Cancel any pending callout and flush the
                            * buffer if there's no space for this byte.
                            */
                           if (calloutok)
                                   callout_stop(&gc->flush);
                           if (gc->npending == sizeof(gc->buf))
                                   gdb_cnflush(gc);
                   }
                   gc->buf[gc->npending++] = c;
                   /*
                    * Flush on end of line; this is especially helpful
                    * during boot when we don't have callouts to flush
                    * the buffer.  Otherwise we defer flushing; a 1/4 
                    * second is a guess.
                    */
                   if (c == '\n')
                           gdb_cnflush(gc);
                   else if (calloutok)
                           callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
           }
   }
   
   CONSOLE_DRIVER(gdb);
   
   /*
    * Our console device only gets attached if the system is booted
    * with RB_MULTIPLE set so gdb_init also calls us to attach the
    * console so we're setup regardless.
    */
   void
   gdb_consinit(void)
   {
           gdb_cnprobe(&gdb_consdev);
           gdb_cninit(&gdb_consdev);
           cnadd(&gdb_consdev);
   }

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