include/crypto/scatterwalk.h

   1 /*
   2  * Cryptographic scatter and gather helpers.
   3  *
   4  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   5  * Copyright (c) 2002 Adam J. Richter <adam@yggdrasil.com>
   6  * Copyright (c) 2004 Jean-Luc Cooke <jlcooke@certainkey.com>
   7  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU General Public License as published by the Free
  11  * Software Foundation; either version 2 of the License, or (at your option)
  12  * any later version.
  13  *
  14  */
  15
  16 #ifndef _CRYPTO_SCATTERWALK_H
  17 #define _CRYPTO_SCATTERWALK_H
  18
  19 #include <crypto/algapi.h>
  20 #include <linux/highmem.h>
  21 #include <linux/kernel.h>
  22 #include <linux/scatterlist.h>
  23
  24 static inline void scatterwalk_crypto_chain(struct scatterlist *head,
  25                                             struct scatterlist *sg,
  26                                             int chain, int num)
  27 {
  28         if (chain) {
  29                 head->length += sg->length;
  30                 sg = sg_next(sg);
  31         }
  32
  33         if (sg)
  34                 sg_chain(head, num, sg);
  35         else
  36                 sg_mark_end(head);
  37 }
  38
  39 static inline unsigned long scatterwalk_samebuf(struct scatter_walk *walk_in,
  40                                                 struct scatter_walk *walk_out)
  41 {
  42         return !(((sg_page(walk_in->sg) - sg_page(walk_out->sg)) << PAGE_SHIFT) +
  43                  (int)(walk_in->offset - walk_out->offset));
  44 }
  45
  46 static inline unsigned int scatterwalk_pagelen(struct scatter_walk *walk)
  47 {
  48         unsigned int len = walk->sg->offset + walk->sg->length - walk->offset;
  49         unsigned int len_this_page = offset_in_page(~walk->offset) + 1;
  50         return len_this_page > len ? len : len_this_page;
  51 }
  52
  53 static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk,
  54                                              unsigned int nbytes)
  55 {
  56         unsigned int len_this_page = scatterwalk_pagelen(walk);
  57         return nbytes > len_this_page ? len_this_page : nbytes;
  58 }
  59
  60 static inline void scatterwalk_advance(struct scatter_walk *walk,
  61                                        unsigned int nbytes)
  62 {
  63         walk->offset += nbytes;
  64 }
  65
  66 static inline unsigned int scatterwalk_aligned(struct scatter_walk *walk,
  67                                                unsigned int alignmask)
  68 {
  69         return !(walk->offset & alignmask);
  70 }
  71
  72 static inline struct page *scatterwalk_page(struct scatter_walk *walk)
  73 {
  74         return sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);
  75 }
  76
  77 static inline void scatterwalk_unmap(void *vaddr)
  78 {
  79         kunmap_atomic(vaddr);
  80 }
  81
  82 static inline void scatterwalk_start(struct scatter_walk *walk,
  83                                      struct scatterlist *sg)
  84 {
  85         walk->sg = sg;
  86         walk->offset = sg->offset;
  87 }
  88
  89 static inline void *scatterwalk_map(struct scatter_walk *walk)
  90 {
  91         return kmap_atomic(scatterwalk_page(walk)) +
  92                offset_in_page(walk->offset);
  93 }
  94
  95 static inline void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  96                                         unsigned int more)
  97 {
  98         if (out) {
  99                 struct page *page;
 100
 101                 page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
 102                 /* Test ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE first as
 103                  * PageSlab cannot be optimised away per se due to
 104                  * use of volatile pointer.
 105                  */
 106                 if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE && !PageSlab(page))
 107                         flush_dcache_page(page);
 108         }
 109
 110         if (more && walk->offset >= walk->sg->offset + walk->sg->length)
 111                 scatterwalk_start(walk, sg_next(walk->sg));
 112 }
 113
 114 static inline void scatterwalk_done(struct scatter_walk *walk, int out,
 115                                     int more)
 116 {
 117         if (!more || walk->offset >= walk->sg->offset + walk->sg->length ||
 118             !(walk->offset & (PAGE_SIZE - 1)))
 119                 scatterwalk_pagedone(walk, out, more);
 120 }
 121
 122 void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
 123                             size_t nbytes, int out);
 124 void *scatterwalk_map(struct scatter_walk *walk);
 125
 126 void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 127                               unsigned int start, unsigned int nbytes, int out);
 128
 129 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
 130                                      struct scatterlist *src,
 131                                      unsigned int len);
 132
 133 #endif  /* _CRYPTO_SCATTERWALK_H */