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Add int13_boot(), to allow booting from INT 13 emulated drives.

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This commit is contained in:
Michael Brown 2006-05-14 13:44:47 +00:00
parent b4f941b257
commit 4435667a00
2 changed files with 89 additions and 0 deletions
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1
src/arch/i386/include/int13.h
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@ -153,5 +153,6 @@ struct int13_disk_parameters {
extern void register_int13_drive ( struct int13_drive *drive );
extern void unregister_int13_drive ( struct int13_drive *drive );
extern int int13_boot ( unsigned int drive );
#endif /* INT13_H */

88
src/arch/i386/interface/pcbios/int13.c
View File

@ -16,7 +16,10 @@
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdint.h>
#include <limits.h>
#include <byteswap.h>
#include <errno.h>
#include <assert.h>
#include <gpxe/list.h>
#include <gpxe/blockdev.h>
@ -41,6 +44,16 @@ static struct segoff __text16 ( int13_vector );
/** Assembly wrapper */
extern void int13_wrapper ( void );
/** 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;
/** Restart point for INT 18 */
extern void int13_exec_fail ( void );
/** List of registered emulated drives */
static LIST_HEAD ( drives );
@ -473,3 +486,78 @@ void unregister_int13_drive ( struct int13_drive *drive ) {
if ( list_empty ( &drives ) )
unhook_int13();
}
/**
* Attempt to boot from an INT 13 drive
*
* @v drive Drive number
* @ret rc Return status code
*
* This boots from the specified INT 13 drive by loading the Master
* Boot Record to 0000:7c00 and jumping to it. INT 18 is hooked to
* capture an attempt by the MBR to boot the next device. (This is
* the closest thing to a return path from an MBR).
*
* Note that this function can never return success, by definition.
*/
int int13_boot ( unsigned int drive ) {
int status, signature;
int d0, d1;
DBG ( "Booting from INT 13 drive %02x\n", drive );
/* Use INT 13 to read the boot sector */
REAL_EXEC ( rm_int13_boot,
"pushw $0\n\t"
"popw %%es\n\t"
"int $0x13\n\t"
"jc 1f\n\t"
"xorl %%eax, %%eax\n\t"
"\n1:\n\t"
"movzwl %%es:0x7dfe, %%ebx\n\t",
4,
OUT_CONSTRAINTS ( "=a" ( status ), "=b" ( signature ),
"=c" ( d0 ), "=d" ( drive ) ),
IN_CONSTRAINTS ( "0" ( 0x0201 ), "1" ( 0x7c00 ),
"2" ( 0x0001 ), "3" ( drive ) ),
CLOBBER ( "ebp" ) );
if ( status )
return -EIO;
/* Check signature is correct */
if ( signature != be16_to_cpu ( 0x55aa ) ) {
DBG ( "Invalid disk signature %#04x (should be 0x55aa)\n",
cpu_to_be16 ( signature ) );
return -ENOEXEC;
}
/* Hook INT 18 to capture failure path */
hook_bios_interrupt ( 0x18, ( unsigned int ) int13_exec_fail,
&int18_vector );
/* Boot the loaded sector */
REAL_EXEC ( rm_int13_exec,
"movw %%ss, %%ax\n\t" /* Preserve stack pointer */
"movw %%ax, %%cs:int13_exec_saved_ss\n\t"
"movw %%sp, %%cs:int13_exec_saved_sp\n\t"
"ljmp $0, $0x7c00\n\t"
"\nint13_exec_saved_ss: .word 0\n\t"
"\nint13_exec_saved_sp: .word 0\n\t"
"\nint13_exec_fail:\n\t"
"movw %%cs:int13_exec_saved_ss, %%ax\n\t"
"movw %%ax, %%ss\n\t"
"movw %%cs:int13_exec_saved_sp, %%sp\n\t"
"\n99:\n\t",
1,
OUT_CONSTRAINTS ( "=d" ( d1 ) ),
IN_CONSTRAINTS ( "d" ( drive ) ),
CLOBBER ( "eax", "ebx", "ecx", "esi", "edi", "ebp" ) );
DBG ( "Booted disk returned via INT 18\n" );
/* Unhook INT 18 */
unhook_bios_interrupt ( 0x18, ( unsigned int ) int13_exec_fail,
&int18_vector );
return -ECANCELED;
}