--- /dev/null
+#ifndef _IPXE_UACCESS_H
+#define _IPXE_UACCESS_H
+
+/**
+ * @file
+ *
+ * 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 );
+
+#include <stdint.h>
+#include <string.h>
+#include <ipxe/api.h>
+#include <config/ioapi.h>
+
+/**
+ * A pointer to a user buffer
+ *
+ */
+typedef unsigned long userptr_t;
+
+/** Equivalent of NULL for user pointers */
+#define UNULL ( ( userptr_t ) 0 )
+
+/**
+ * @defgroup uaccess_trivial Trivial user access API implementations
+ *
+ * User access API implementations that can be used by environments in
+ * which virtual addresses allow access to all of memory.
+ *
+ * @{
+ *
+ */
+
+/**
+ * Convert virtual address to user pointer
+ *
+ * @v addr Virtual address
+ * @ret userptr User pointer
+ */
+static inline __always_inline userptr_t
+trivial_virt_to_user ( volatile const void *addr ) {
+ return ( ( userptr_t ) addr );
+}
+
+/**
+ * Convert user pointer to virtual address
+ *
+ * @v userptr User pointer
+ * @v offset Offset from user pointer
+ * @ret addr Virtual address
+ *
+ * This operation is not available under all memory models.
+ */
+static inline __always_inline void *
+trivial_user_to_virt ( userptr_t userptr, off_t offset ) {
+ return ( ( void * ) userptr + offset );
+}
+
+/**
+ * Add offset to user pointer
+ *
+ * @v userptr User pointer
+ * @v offset Offset
+ * @ret userptr New pointer value
+ */
+static inline __always_inline userptr_t
+trivial_userptr_add ( userptr_t userptr, off_t offset ) {
+ return ( userptr + offset );
+}
+
+/**
+ * Subtract user pointers
+ *
+ * @v userptr User pointer
+ * @v subtrahend User pointer to be subtracted
+ * @ret offset Offset
+ */
+static inline __always_inline off_t
+trivial_userptr_sub ( userptr_t userptr, userptr_t subtrahend ) {
+ return ( userptr - subtrahend );
+}
+
+/**
+ * Copy data between user buffers
+ *
+ * @v dest Destination
+ * @v dest_off Destination offset
+ * @v src Source
+ * @v src_off Source offset
+ * @v len Length
+ */
+static inline __always_inline void
+trivial_memcpy_user ( userptr_t dest, off_t dest_off,
+ userptr_t src, off_t src_off, size_t len ) {
+ memcpy ( ( ( void * ) dest + dest_off ),
+ ( ( void * ) src + src_off ), len );
+}
+
+/**
+ * Copy data between user buffers, allowing for overlap
+ *
+ * @v dest Destination
+ * @v dest_off Destination offset
+ * @v src Source
+ * @v src_off Source offset
+ * @v len Length
+ */
+static inline __always_inline void
+trivial_memmove_user ( userptr_t dest, off_t dest_off,
+ userptr_t src, off_t src_off, size_t len ) {
+ memmove ( ( ( void * ) dest + dest_off ),
+ ( ( void * ) src + src_off ), len );
+}
+
+/**
+ * Compare data between user buffers
+ *
+ * @v first First buffer
+ * @v first_off First buffer offset
+ * @v second Second buffer
+ * @v second_off Second buffer offset
+ * @v len Length
+ * @ret diff Difference
+ */
+static inline __always_inline int
+trivial_memcmp_user ( userptr_t first, off_t first_off,
+ userptr_t second, off_t second_off, size_t len ) {
+ return memcmp ( ( ( void * ) first + first_off ),
+ ( ( void * ) second + second_off ), len );
+}
+
+/**
+ * Fill user buffer with a constant byte
+ *
+ * @v buffer User buffer
+ * @v offset Offset within buffer
+ * @v c Constant byte with which to fill
+ * @v len Length
+ */
+static inline __always_inline void
+trivial_memset_user ( userptr_t buffer, off_t offset, int c, size_t len ) {
+ memset ( ( ( void * ) buffer + offset ), c, len );
+}
+
+/**
+ * Find length of NUL-terminated string in user buffer
+ *
+ * @v buffer User buffer
+ * @v offset Offset within buffer
+ * @ret len Length of string (excluding NUL)
+ */
+static inline __always_inline size_t
+trivial_strlen_user ( userptr_t buffer, off_t offset ) {
+ return strlen ( ( void * ) buffer + offset );
+}
+
+/**
+ * Find character in user buffer
+ *
+ * @v buffer User buffer
+ * @v offset Starting offset within buffer
+ * @v c Character to search for
+ * @v len Length of user buffer
+ * @ret offset Offset of character, or <0 if not found
+ */
+static inline __always_inline off_t
+trivial_memchr_user ( userptr_t buffer, off_t offset, int c, size_t len ) {
+ void *found;
+
+ found = memchr ( ( ( void * ) buffer + offset ), c, len );
+ return ( found ? ( found - ( void * ) buffer ) : -1 );
+}
+
+/** @} */
+
+/**
+ * Calculate static inline user access API function name
+ *
+ * @v _prefix Subsystem prefix
+ * @v _api_func API function
+ * @ret _subsys_func Subsystem API function
+ */
+#define UACCESS_INLINE( _subsys, _api_func ) \
+ SINGLE_API_INLINE ( UACCESS_PREFIX_ ## _subsys, _api_func )
+
+/**
+ * Provide an user access API implementation
+ *
+ * @v _prefix Subsystem prefix
+ * @v _api_func API function
+ * @v _func Implementing function
+ */
+#define PROVIDE_UACCESS( _subsys, _api_func, _func ) \
+ PROVIDE_SINGLE_API ( UACCESS_PREFIX_ ## _subsys, _api_func, _func )
+
+/**
+ * Provide a static inline user access API implementation
+ *
+ * @v _prefix Subsystem prefix
+ * @v _api_func API function
+ */
+#define PROVIDE_UACCESS_INLINE( _subsys, _api_func ) \
+ PROVIDE_SINGLE_API_INLINE ( UACCESS_PREFIX_ ## _subsys, _api_func )
+
+/* Include all architecture-independent user access API headers */
+#include <ipxe/efi/efi_uaccess.h>
+#include <ipxe/linux/linux_uaccess.h>
+
+/* Include all architecture-dependent user access API headers */
+#include <bits/uaccess.h>
+
+/**
+ * Convert physical address to user pointer
+ *
+ * @v phys_addr Physical address
+ * @ret userptr User pointer
+ */
+userptr_t phys_to_user ( unsigned long phys_addr );
+
+/**
+ * Convert user pointer to physical address
+ *
+ * @v userptr User pointer
+ * @v offset Offset from user pointer
+ * @ret phys_addr Physical address
+ */
+unsigned long user_to_phys ( userptr_t userptr, off_t offset );
+
+/**
+ * Convert virtual address to user pointer
+ *
+ * @v addr Virtual address
+ * @ret userptr User pointer
+ */
+userptr_t virt_to_user ( volatile const void *addr );
+
+/**
+ * Convert user pointer to virtual address
+ *
+ * @v userptr User pointer
+ * @v offset Offset from user pointer
+ * @ret addr Virtual address
+ *
+ * This operation is not available under all memory models.
+ */
+void * user_to_virt ( userptr_t userptr, off_t offset );
+
+/**
+ * Add offset to user pointer
+ *
+ * @v userptr User pointer
+ * @v offset Offset
+ * @ret userptr New pointer value
+ */
+userptr_t userptr_add ( userptr_t userptr, off_t offset );
+
+/**
+ * Subtract user pointers
+ *
+ * @v userptr User pointer
+ * @v subtrahend User pointer to be subtracted
+ * @ret offset Offset
+ */
+off_t userptr_sub ( userptr_t userptr, userptr_t subtrahend );
+
+/**
+ * Convert virtual address to a physical address
+ *
+ * @v addr Virtual address
+ * @ret phys_addr Physical address
+ */
+static inline __always_inline unsigned long
+virt_to_phys ( volatile const void *addr ) {
+ return user_to_phys ( virt_to_user ( addr ), 0 );
+}
+
+/**
+ * Convert physical address to a virtual address
+ *
+ * @v addr Virtual address
+ * @ret phys_addr Physical address
+ *
+ * This operation is not available under all memory models.
+ */
+static inline __always_inline void * phys_to_virt ( unsigned long phys_addr ) {
+ return user_to_virt ( phys_to_user ( phys_addr ), 0 );
+}
+
+/**
+ * Copy data between user buffers
+ *
+ * @v dest Destination
+ * @v dest_off Destination offset
+ * @v src Source
+ * @v src_off Source offset
+ * @v len Length
+ */
+void memcpy_user ( userptr_t dest, off_t dest_off,
+ userptr_t src, off_t src_off, size_t len );
+
+/**
+ * Copy data to user buffer
+ *
+ * @v dest Destination
+ * @v dest_off Destination offset
+ * @v src Source
+ * @v len Length
+ */
+static inline __always_inline void
+copy_to_user ( userptr_t dest, off_t dest_off, const void *src, size_t len ) {
+ memcpy_user ( dest, dest_off, virt_to_user ( src ), 0, len );
+}
+
+/**
+ * Copy data from user buffer
+ *
+ * @v dest Destination
+ * @v src Source
+ * @v src_off Source offset
+ * @v len Length
+ */
+static inline __always_inline void
+copy_from_user ( void *dest, userptr_t src, off_t src_off, size_t len ) {
+ memcpy_user ( virt_to_user ( dest ), 0, src, src_off, len );
+}
+
+/**
+ * Copy data between user buffers, allowing for overlap
+ *
+ * @v dest Destination
+ * @v dest_off Destination offset
+ * @v src Source
+ * @v src_off Source offset
+ * @v len Length
+ */
+void memmove_user ( userptr_t dest, off_t dest_off,
+ userptr_t src, off_t src_off, size_t len );
+
+/**
+ * Compare data between user buffers
+ *
+ * @v first First buffer
+ * @v first_off First buffer offset
+ * @v second Second buffer
+ * @v second_off Second buffer offset
+ * @v len Length
+ * @ret diff Difference
+ */
+int memcmp_user ( userptr_t first, off_t first_off,
+ userptr_t second, off_t second_off, size_t len );
+
+/**
+ * Fill user buffer with a constant byte
+ *
+ * @v userptr User buffer
+ * @v offset Offset within buffer
+ * @v c Constant byte with which to fill
+ * @v len Length
+ */
+void memset_user ( userptr_t userptr, off_t offset, int c, size_t len );
+
+/**
+ * Find length of NUL-terminated string in user buffer
+ *
+ * @v userptr User buffer
+ * @v offset Offset within buffer
+ * @ret len Length of string (excluding NUL)
+ */
+size_t strlen_user ( userptr_t userptr, off_t offset );
+
+/**
+ * Find character in user buffer
+ *
+ * @v userptr User buffer
+ * @v offset Starting offset within buffer
+ * @v c Character to search for
+ * @v len Length of user buffer
+ * @ret offset Offset of character, or <0 if not found
+ */
+off_t memchr_user ( userptr_t userptr, off_t offset, int c, size_t len );
+
+#endif /* _IPXE_UACCESS_H */
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