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[xferbuf] Add xfer_buffer() to provide direct access to underlying buffer 

Allow data transfer buffer users to provide direct access to their
underlying data transfer buffer.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2015-07-20 12:15:21 +01:00
parent cbbd6b761e
commit 07b0d4fa30
2 changed files with 44 additions and 0 deletions
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39
src/core/xferbuf.c
View File

@ -283,3 +283,42 @@ struct xfer_buffer_operations xferbuf_umalloc_operations = {
.write = xferbuf_umalloc_write,
.read = xferbuf_umalloc_read,
};
/**
* Get underlying data transfer buffer
*
* @v interface Data transfer interface
* @ret xferbuf Data transfer buffer, or NULL on error
*
* This call will check that the xfer_buffer() handler belongs to the
* destination interface which also provides xfer_deliver() for this
* interface.
*
* This is done to prevent accidental accesses to a data transfer
* buffer which may be located behind a non-transparent datapath via a
* series of pass-through interfaces.
*/
struct xfer_buffer * xfer_buffer ( struct interface *intf ) {
struct interface *dest;
xfer_buffer_TYPE ( void * ) *op =
intf_get_dest_op ( intf, xfer_buffer, &dest );
void *object = intf_object ( dest );
struct interface *xfer_deliver_dest;
struct xfer_buffer *xferbuf;
/* Check that this operation is provided by the same interface
* which handles xfer_deliver().
*/
intf_get_dest_op ( intf, xfer_deliver, &xfer_deliver_dest );
if ( op && ( dest == xfer_deliver_dest ) ) {
xferbuf = op ( object );
} else {
/* Default is to not have a data transfer buffer */
xferbuf = NULL;
}
intf_put ( xfer_deliver_dest );
intf_put ( dest );
return xferbuf;
}

5
src/include/ipxe/xferbuf.h
View File

@ -12,6 +12,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <stdint.h>
#include <ipxe/iobuf.h>
#include <ipxe/uaccess.h>
#include <ipxe/interface.h>
#include <ipxe/xfer.h>
/** A data transfer buffer */
@ -97,4 +98,8 @@ extern int xferbuf_deliver ( struct xfer_buffer *xferbuf,
struct io_buffer *iobuf,
struct xfer_metadata *meta );
extern struct xfer_buffer * xfer_buffer ( struct interface *intf );
#define xfer_buffer_TYPE( object_type ) \
typeof ( struct xfer_buffer * ( object_type ) )
#endif /* _IPXE_XFERBUF_H */