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/*
* Copyright (C) 2008 Stefan Hajnoczi <stefanha@gmail.com>.
* Copyright (C) 2016 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* You can also choose to distribute this program under the terms of
* the Unmodified Binary Distribution Licence (as given in the file
* COPYING.UBDL), provided that you have satisfied its requirements.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <stddef.h>
#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/uaccess.h>
#include <ipxe/gdbstub.h>
#include <librm.h>
#include <gdbmach.h>
/** @file
*
* GDB architecture-specific bits for x86
*
*/
/** Number of hardware breakpoints */
#define NUM_HWBP 4
/** Debug register 7: Global breakpoint enable */
#define DR7_G( bp ) ( 2 << ( 2 * (bp) ) )
/** Debug register 7: Global exact breakpoint enable */
#define DR7_GE ( 1 << 9 )
/** Debug register 7: Break on data writes */
#define DR7_RWLEN_WRITE 0x11110000
/** Debug register 7: Break on data access */
#define DR7_RWLEN_ACCESS 0x33330000
/** Debug register 7: One-byte length */
#define DR7_RWLEN_1 0x00000000
/** Debug register 7: Two-byte length */
#define DR7_RWLEN_2 0x44440000
/** Debug register 7: Four-byte length */
#define DR7_RWLEN_4 0xcccc0000
/** Debug register 7: Eight-byte length */
#define DR7_RWLEN_8 0x88880000
/** Debug register 7: Breakpoint R/W and length mask */
#define DR7_RWLEN_MASK( bp ) ( 0xf0000 << ( 4 * (bp) ) )
/** Hardware breakpoint addresses (debug registers 0-3) */
static unsigned long dr[NUM_HWBP];
/** Active value of debug register 7 */
static unsigned long dr7 = DR7_GE;
/**
* Update debug registers
*
*/
static void gdbmach_update ( void ) {
/* Set debug registers */
__asm__ __volatile__ ( "mov %0, %%dr0" : : "r" ( dr[0] ) );
__asm__ __volatile__ ( "mov %0, %%dr1" : : "r" ( dr[1] ) );
__asm__ __volatile__ ( "mov %0, %%dr2" : : "r" ( dr[2] ) );
__asm__ __volatile__ ( "mov %0, %%dr3" : : "r" ( dr[3] ) );
__asm__ __volatile__ ( "mov %0, %%dr7" : : "r" ( dr7 ) );
}
/**
* Find reusable or available hardware breakpoint
*
* @v addr Linear address
* @v rwlen Control bits
* @ret bp Hardware breakpoint, or negative error
*/
static int gdbmach_find ( unsigned long addr, unsigned int rwlen ) {
unsigned int i;
int bp = -ENOENT;
/* Look for a reusable or available breakpoint */
for ( i = 0 ; i < NUM_HWBP ; i++ ) {
/* If breakpoint is not enabled, then it is available */
if ( ! ( dr7 & DR7_G ( i ) ) ) {
bp = i;
continue;
}
/* If breakpoint is enabled and has the same address
* and control bits, then reuse it.
*/
if ( ( dr[i] == addr ) &&
( ( ( dr7 ^ rwlen ) & DR7_RWLEN_MASK ( i ) ) == 0 ) ) {
bp = i;
break;
}
}
return bp;
}
/**
* Set hardware breakpoint
*
* @v type GDB breakpoint type
* @v addr Virtual address
* @v len Length
* @v enable Enable (not disable) breakpoint
* @ret rc Return status code
*/
int gdbmach_set_breakpoint ( int type, unsigned long addr, size_t len,
int enable ) {
unsigned int rwlen;
unsigned long mask;
int bp;
/* Parse breakpoint type */
switch ( type ) {
case GDBMACH_WATCH:
rwlen = DR7_RWLEN_WRITE;
break;
case GDBMACH_AWATCH:
rwlen = DR7_RWLEN_ACCESS;
break;
default:
return -ENOTSUP;
}
/* Parse breakpoint length */
switch ( len ) {
case 1:
rwlen |= DR7_RWLEN_1;
break;
case 2:
rwlen |= DR7_RWLEN_2;
break;
case 4:
rwlen |= DR7_RWLEN_4;
break;
case 8:
rwlen |= DR7_RWLEN_8;
break;
default:
return -ENOTSUP;
}
/* Convert to linear address */
if ( sizeof ( physaddr_t ) <= sizeof ( uint32_t ) )
addr = virt_to_phys ( ( void * ) addr );
/* Find reusable or available hardware breakpoint */
bp = gdbmach_find ( addr, rwlen );
if ( bp < 0 )
return ( enable ? -ENOBUFS : 0 );
/* Configure this breakpoint */
DBGC ( &dr[0], "GDB bp %d at %p+%zx type %d (%sabled)\n",
bp, ( ( void * ) addr ), len, type, ( enable ? "en" : "dis" ) );
dr[bp] = addr;
mask = DR7_RWLEN_MASK ( bp );
dr7 = ( ( dr7 & ~mask ) | ( rwlen & mask ) );
mask = DR7_G ( bp );
dr7 &= ~mask;
if ( enable )
dr7 |= mask;
/* Update debug registers */
gdbmach_update();
return 0;
}
/**
* Handle exception
*
* @v signo GDB signal number
* @v regs Register dump
*/
__asmcall void gdbmach_handler ( int signo, gdbreg_t *regs ) {
unsigned long dr7_disabled = DR7_GE;
unsigned long dr6_clear = 0;
/* Temporarily disable breakpoints */
__asm__ __volatile__ ( "mov %0, %%dr7\n" : : "r" ( dr7_disabled ) );
/* Handle exception */
DBGC ( &dr[0], "GDB signal %d\n", signo );
DBGC2_HDA ( &dr[0], 0, regs, ( GDBMACH_NREGS * sizeof ( *regs ) ) );
gdbstub_handler ( signo, regs );
DBGC ( &dr[0], "GDB signal %d returning\n", signo );
DBGC2_HDA ( &dr[0], 0, regs, ( GDBMACH_NREGS * sizeof ( *regs ) ) );
/* Clear breakpoint status register */
__asm__ __volatile__ ( "mov %0, %%dr6\n" : : "r" ( dr6_clear ) );
/* Re-enable breakpoints */
__asm__ __volatile__ ( "mov %0, %%dr7\n" : : "r" ( dr7 ) );
}
/**
* CPU exception vectors
*
* Note that we cannot intercept anything from INT8 (double fault)
* upwards, since these overlap by default with IRQ0-7.
*/
static void * gdbmach_vectors[] = {
gdbmach_sigfpe, /* Divide by zero */
gdbmach_sigtrap, /* Debug trap */
NULL, /* Non-maskable interrupt */
gdbmach_sigtrap, /* Breakpoint */
gdbmach_sigstkflt, /* Overflow */
gdbmach_sigstkflt, /* Bound range exceeded */
gdbmach_sigill, /* Invalid opcode */
};
/**
* Initialise GDB
*/
void gdbmach_init ( void ) {
unsigned int i;
/* Hook CPU exception vectors */
for ( i = 0 ; i < ( sizeof ( gdbmach_vectors ) /
sizeof ( gdbmach_vectors[0] ) ) ; i++ ) {
if ( gdbmach_vectors[i] )
set_interrupt_vector ( i, gdbmach_vectors[i] );
}
}
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