src/arch/i386/core/gdbmach.c

   1 /*
   2  * Copyright (C) 2008 Stefan Hajnoczi <stefanha@gmail.com>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <stddef.h>
  20 #include <stdio.h>
  21 #include <assert.h>
  22 #include <gpxe/uaccess.h>
  23 #include <gpxe/gdbstub.h>
  24 #include <gdbmach.h>
  25
  26 /** @file
  27  *
  28  * GDB architecture-specific bits for i386
  29  *
  30  */
  31
  32 enum {
  33         DR7_CLEAR = 0x00000400,    /* disable hardware breakpoints */
  34         DR6_CLEAR = 0xffff0ff0,    /* clear breakpoint status */
  35 };
  36
  37 /** Hardware breakpoint, fields stored in x86 bit pattern form */
  38 struct hwbp {
  39         int type;           /* type (1=write watchpoint, 3=access watchpoint) */
  40         unsigned long addr; /* linear address */
  41         size_t len;         /* length (0=1-byte, 1=2-byte, 3=4-byte) */
  42         int enabled;
  43 };
  44
  45 static struct hwbp hwbps [ 4 ];
  46 static gdbreg_t dr7 = DR7_CLEAR;
  47
  48 static struct hwbp *gdbmach_find_hwbp ( int type, unsigned long addr, size_t len ) {
  49         struct hwbp *available = NULL;
  50         unsigned int i;
  51         for ( i = 0; i < sizeof hwbps / sizeof hwbps [ 0 ]; i++ ) {
  52                 if ( hwbps [ i ].type == type && hwbps [ i ].addr == addr && hwbps [ i ].len == len ) {
  53                         return &hwbps [ i ];
  54                 }
  55                 if ( !hwbps [ i ].enabled ) {
  56                         available = &hwbps [ i ];
  57                 }
  58         }
  59         return available;
  60 }
  61
  62 static void gdbmach_commit_hwbp ( struct hwbp *bp ) {
  63         unsigned int regnum = bp - hwbps;
  64
  65         /* Set breakpoint address */
  66         assert ( regnum < ( sizeof hwbps / sizeof hwbps [ 0 ] ) );
  67         switch ( regnum ) {
  68                 case 0:
  69                         __asm__ __volatile__ ( "movl %0, %%dr0\n" : : "r" ( bp->addr ) );
  70                         break;
  71                 case 1:
  72                         __asm__ __volatile__ ( "movl %0, %%dr1\n" : : "r" ( bp->addr ) );
  73                         break;
  74                 case 2:
  75                         __asm__ __volatile__ ( "movl %0, %%dr2\n" : : "r" ( bp->addr ) );
  76                         break;
  77                 case 3:
  78                         __asm__ __volatile__ ( "movl %0, %%dr3\n" : : "r" ( bp->addr ) );
  79                         break;
  80         }
  81
  82         /* Set type */
  83         dr7 &= ~( 0x3 << ( 16 + 4 * regnum ) );
  84         dr7 |= bp->type << ( 16 + 4 * regnum );
  85
  86         /* Set length */
  87         dr7 &= ~( 0x3 << ( 18 + 4 * regnum ) );
  88         dr7 |= bp->len << ( 18 + 4 * regnum );
  89
  90         /* Set/clear local enable bit */
  91         dr7 &= ~( 0x3 << 2 * regnum );
  92         dr7 |= bp->enabled << 2 * regnum;
  93 }
  94
  95 int gdbmach_set_breakpoint ( int type, unsigned long addr, size_t len, int enable ) {
  96         struct hwbp *bp;
  97
  98         /* Check and convert breakpoint type to x86 type */
  99         switch ( type ) {
 100                 case GDBMACH_WATCH:
 101                         type = 0x1;
 102                         break;
 103                 case GDBMACH_AWATCH:
 104                         type = 0x3;
 105                         break;
 106                 default:
 107                         return 0; /* unsupported breakpoint type */
 108         }
 109
 110         /* Only lengths 1, 2, and 4 are supported */
 111         if ( len != 2 && len != 4 ) {
 112                 len = 1;
 113         }
 114         len--; /* convert to x86 breakpoint length bit pattern */
 115
 116         /* Calculate linear address by adding segment base */
 117         addr += virt_offset;
 118
 119         /* Set up the breakpoint */
 120         bp = gdbmach_find_hwbp ( type, addr, len );
 121         if ( !bp ) {
 122                 return 0; /* ran out of hardware breakpoints */
 123         }
 124         bp->type = type;
 125         bp->addr = addr;
 126         bp->len = len;
 127         bp->enabled = enable;
 128         gdbmach_commit_hwbp ( bp );
 129         return 1;
 130 }
 131
 132 static void gdbmach_disable_hwbps ( void ) {
 133         /* Store and clear hardware breakpoints */
 134         __asm__ __volatile__ ( "movl %0, %%dr7\n" : : "r" ( DR7_CLEAR ) );
 135 }
 136
 137 static void gdbmach_enable_hwbps ( void ) {
 138         /* Clear breakpoint status register */
 139         __asm__ __volatile__ ( "movl %0, %%dr6\n" : : "r" ( DR6_CLEAR ) );
 140
 141         /* Restore hardware breakpoints */
 142         __asm__ __volatile__ ( "movl %0, %%dr7\n" : : "r" ( dr7 ) );
 143 }
 144
 145 __asmcall void gdbmach_handler ( int signo, gdbreg_t *regs ) {
 146         gdbmach_disable_hwbps();
 147         gdbstub_handler ( signo, regs );
 148         gdbmach_enable_hwbps();
 149 }