--- /dev/null
+/*
+ * Copyright (C) 2007 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.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/**
+ * @file
+ *
+ * x86 bootsector image format
+ *
+ */
+
+#include <errno.h>
+#include <realmode.h>
+#include <biosint.h>
+#include <bootsector.h>
+#include <ipxe/console.h>
+
+/** Vector for storing original INT 18 handler
+ *
+ * We do not chain to this vector, so there is no need to place it in
+ * .text16.
+ */
+static struct segoff int18_vector;
+
+/** Vector for storing original INT 19 handler
+ *
+ * We do not chain to this vector, so there is no need to place it in
+ * .text16.
+ */
+static struct segoff int19_vector;
+
+/** Restart point for INT 18 or 19 */
+extern void bootsector_exec_fail ( void );
+
+/**
+ * Jump to preloaded bootsector
+ *
+ * @v segment Real-mode segment
+ * @v offset Real-mode offset
+ * @v drive Drive number to pass to boot sector
+ * @ret rc Return status code
+ */
+int call_bootsector ( unsigned int segment, unsigned int offset,
+ unsigned int drive ) {
+ int discard_b, discard_D, discard_d;
+
+ /* Reset console, since boot sector will probably use it */
+ console_reset();
+
+ DBG ( "Booting from boot sector at %04x:%04x\n", segment, offset );
+
+ /* Hook INTs 18 and 19 to capture failure paths */
+ hook_bios_interrupt ( 0x18, ( unsigned int ) bootsector_exec_fail,
+ &int18_vector );
+ hook_bios_interrupt ( 0x19, ( unsigned int ) bootsector_exec_fail,
+ &int19_vector );
+
+ /* Boot the loaded sector
+ *
+ * We assume that the boot sector may completely destroy our
+ * real-mode stack, so we preserve everything we need in
+ * static storage.
+ */
+ __asm__ __volatile__ ( REAL_CODE ( /* Save return address off-stack */
+ "popw %%cs:saved_retaddr\n\t"
+ /* Save stack pointer */
+ "movw %%ss, %%ax\n\t"
+ "movw %%ax, %%cs:saved_ss\n\t"
+ "movw %%sp, %%cs:saved_sp\n\t"
+ /* Save frame pointer (gcc bug) */
+ "movl %%ebp, %%cs:saved_ebp\n\t"
+ /* Prepare jump to boot sector */
+ "pushw %%bx\n\t"
+ "pushw %%di\n\t"
+ /* Clear all registers */
+ "xorl %%eax, %%eax\n\t"
+ "xorl %%ebx, %%ebx\n\t"
+ "xorl %%ecx, %%ecx\n\t"
+ /* %edx contains drive number */
+ "xorl %%esi, %%esi\n\t"
+ "xorl %%edi, %%edi\n\t"
+ "xorl %%ebp, %%ebp\n\t"
+ "movw %%ax, %%ds\n\t"
+ "movw %%ax, %%es\n\t"
+ "movw %%ax, %%fs\n\t"
+ "movw %%ax, %%gs\n\t"
+ /* Jump to boot sector */
+ "sti\n\t"
+ "lret\n\t"
+ /* Preserved variables */
+ "\nsaved_ebp: .long 0\n\t"
+ "\nsaved_ss: .word 0\n\t"
+ "\nsaved_sp: .word 0\n\t"
+ "\nsaved_retaddr: .word 0\n\t"
+ /* Boot failure return point */
+ "\nbootsector_exec_fail:\n\t"
+ /* Restore frame pointer (gcc bug) */
+ "movl %%cs:saved_ebp, %%ebp\n\t"
+ /* Restore stack pointer */
+ "movw %%cs:saved_ss, %%ax\n\t"
+ "movw %%ax, %%ss\n\t"
+ "movw %%cs:saved_sp, %%sp\n\t"
+ /* Return via saved address */
+ "jmp *%%cs:saved_retaddr\n\t" )
+ : "=b" ( discard_b ), "=D" ( discard_D ),
+ "=d" ( discard_d )
+ : "b" ( segment ), "D" ( offset ),
+ "d" ( drive )
+ : "eax", "ecx", "esi" );
+
+ DBG ( "Booted disk returned via INT 18 or 19\n" );
+
+ /* Unhook INTs 18 and 19 */
+ unhook_bios_interrupt ( 0x18, ( unsigned int ) bootsector_exec_fail,
+ &int18_vector );
+ unhook_bios_interrupt ( 0x19, ( unsigned int ) bootsector_exec_fail,
+ &int19_vector );
+
+ return -ECANCELED;
+}
Code Review / kvmfornfv.git / blobdiff