From b65f67d443d213bbaf9d7859649f25920e6d6785 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Sun, 20 Apr 2025 17:26:48 +0100 Subject: [PATCH] [uaccess] Change userptr_t to be a pointer type The original motivation for the userptr_t type was to be able to support a pure 16-bit real-mode memory model in which a segment:offset value could be encoded as an unsigned long, with corresponding copy_from_user() and copy_to_user() functions used to perform real-mode segmented memory accesses. Since this memory model was first created almost twenty years ago, no serious effort has been made to support a pure 16-bit mode of operation for iPXE. The constraints imposed by the memory model are becoming increasingly cumbersome to work within: for example, the parsing of devicetree structures is hugely simplified by being able to use and return direct pointers to the names and property values. The devicetree code therefore relies upon virt_to_user(), which is nominally illegal under the userptr_t memory model. Drop support for the concept of a memory location that cannot be reached through a straightforward pointer dereference, by redefining userptr_t to be a simple pointer type. Signed-off-by: Michael Brown --- src/include/ipxe/uaccess.h | 13 +------------ 1 file changed, 1 insertion(+), 12 deletions(-) diff --git a/src/include/ipxe/uaccess.h b/src/include/ipxe/uaccess.h index d8c57adeb..1790e4066 100644 --- a/src/include/ipxe/uaccess.h +++ b/src/include/ipxe/uaccess.h @@ -6,17 +6,6 @@ * * Access to external ("user") memory * - * iPXE 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. - * */ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); @@ -36,7 +25,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); * A pointer to a user buffer * */ -typedef unsigned long userptr_t; +typedef void * userptr_t; /** Equivalent of NULL for user pointers */ #define UNULL ( ( userptr_t ) 0 )