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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>
tags/v1.20.1
Michael Brown 9 years ago
parent
commit
07b0d4fa30
2 changed files with 44 additions and 0 deletions
  1. 39
    0
      src/core/xferbuf.c
  2. 5
    0
      src/include/ipxe/xferbuf.h

+ 39
- 0
src/core/xferbuf.c View File

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

+ 5
- 0
src/include/ipxe/xferbuf.h View File

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

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