xNBA/src/include/gpxe/uaccess.h

#ifndef _GPXE_UACCESS_H
#define _GPXE_UACCESS_H

/**
 * @file
 *
 * Access to external ("user") memory
 *
 * gPXE often needs to transfer data between internal and external
 * buffers.  On i386, the external buffers may require access via a
 * different segment, and the buffer address cannot be encoded into a
 * simple void * pointer.  The @c userptr_t type encapsulates the
 * information needed to identify an external buffer, and the
 * copy_to_user() and copy_from_user() functions provide methods for
 * transferring data between internal and external buffers.
 *
 * Note that userptr_t is an opaque type; in particular, performing
 * arithmetic upon a userptr_t is not allowed.
 *
 */

#include <bits/uaccess.h>

#endif /* _GPXE_UACCESS_H */
Add the concept of a "user pointer" (similar to the void __user * in the kernel), which encapsulates the information needed to refer to an external buffer. Under normal operation, this can just be a void * equivalent, but under -DKEEP_IT_REAL it would be a segoff_t equivalent. Use this concept to avoid the need for bounce buffers in int13.c, which reduces memory usage and opens up the possibility of using multi-sector reads. Extend the block-device API and the SCSI block device implementation to support multi-sector reads. Update iscsi.c to use user buffers. Move the obsolete portions of realmode.h to old_realmode.h. MS-DOS now boots an order of magnitude faster over iSCSI (~10 seconds from power-up to C:> prompt in bochs). 2006-05-19 15:06:51 +00:00			`#ifndef _GPXE_UACCESS_H`
			`#define _GPXE_UACCESS_H`

			`/**`
			`* @file`
			`*`
			`* Access to external ("user") memory`
			`*`
			`* gPXE often needs to transfer data between internal and external`
			`* buffers. On i386, the external buffers may require access via a`
			`* different segment, and the buffer address cannot be encoded into a`
			`* simple void * pointer. The @c userptr_t type encapsulates the`
			`* information needed to identify an external buffer, and the`
			`* copy_to_user() and copy_from_user() functions provide methods for`
			`* transferring data between internal and external buffers.`
			`*`
			`* Note that userptr_t is an opaque type; in particular, performing`
			`* arithmetic upon a userptr_t is not allowed.`
			`*`
			`*/`

			`#include <bits/uaccess.h>`

			`#endif /* _GPXE_UACCESS_H */`