[gdb] Add support for x86_64

Signed-off-by: Michael Brown <mcb30@ipxe.org>

2 files changed, 252 insertions, 0 deletions

diff --git a/src/arch/x86/core/gdbmach.c b/src/arch/x86/core/gdbmach.c
new file mode 100644
index 000000000..af6abfedd
--- /dev/null
+++ b/src/arch/x86/core/gdbmach.c
@@ -0,0 +1,251 @@
+/*
+ * 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] );
+	}
+}
diff --git a/src/arch/x86/include/bits/errfile.h b/src/arch/x86/include/bits/errfile.h
index 0d1617d20..9eb4b5488 100644
--- a/src/arch/x86/include/bits/errfile.h
+++ b/src/arch/x86/include/bits/errfile.h
@@ -22,6 +22,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_apm		( ERRFILE_ARCH | ERRFILE_CORE | 0x000b0000 )
 #define ERRFILE_vesafb		( ERRFILE_ARCH | ERRFILE_CORE | 0x000c0000 )
 #define ERRFILE_int13con	( ERRFILE_ARCH | ERRFILE_CORE | 0x000d0000 )
+#define ERRFILE_gdbmach		( ERRFILE_ARCH | ERRFILE_CORE | 0x000e0000 )
 
 #define ERRFILE_bootsector     ( ERRFILE_ARCH | ERRFILE_IMAGE | 0x00000000 )
 #define ERRFILE_bzimage	       ( ERRFILE_ARCH | ERRFILE_IMAGE | 0x00010000 )