kernel/generic/src/mm/backend_elf.c

   1 /*
   2  * Copyright (c) 2006 Jakub Jermar
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  *   notice, this list of conditions and the following disclaimer.
  11  * - Redistributions in binary form must reproduce the above copyright
  12  *   notice, this list of conditions and the following disclaimer in the
  13  *   documentation and/or other materials provided with the distribution.
  14  * - The name of the author may not be used to endorse or promote products
  15  *   derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /** @addtogroup genericmm
  30  * @{
  31  */
  32
  33 /**
  34  * @file
  35  * @brief       Backend for address space areas backed by an ELF image.
  36  */
  37
  38 #include <lib/elf.h>
  39 #include <debug.h>
  40 #include <arch/types.h>
  41 #include <typedefs.h>
  42 #include <mm/as.h>
  43 #include <mm/frame.h>
  44 #include <mm/slab.h>
  45 #include <mm/page.h>
  46 #include <genarch/mm/page_pt.h>
  47 #include <genarch/mm/page_ht.h>
  48 #include <align.h>
  49 #include <memstr.h>
  50 #include <macros.h>
  51 #include <arch.h>
  52
  53 static int elf_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access);
  54 static void elf_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame);
  55 static void elf_share(as_area_t *area);
  56
  57 mem_backend_t elf_backend = {
  58         .page_fault = elf_page_fault,
  59         .frame_free = elf_frame_free,
  60         .share = elf_share
  61 };
  62
  63 /** Service a page fault in the ELF backend address space area.
  64  *
  65  * The address space area and page tables must be already locked.
  66  *
  67  * @param area Pointer to the address space area.
  68  * @param addr Faulting virtual address.
  69  * @param access Access mode that caused the fault (i.e. read/write/exec).
  70  *
  71  * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).
  72  */
  73 int elf_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access)
  74 {
  75         elf_header_t *elf = area->backend_data.elf;
  76         elf_segment_header_t *entry = area->backend_data.segment;
  77         btree_node_t *leaf;
  78         uintptr_t base, frame;
  79         index_t i;
  80
  81         if (!as_area_check_access(area, access))
  82                 return AS_PF_FAULT;
  83
  84         ASSERT((addr >= entry->p_vaddr) && (addr < entry->p_vaddr + entry->p_memsz));
  85         i = (addr - entry->p_vaddr) >> PAGE_WIDTH;
  86         base = (uintptr_t) (((void *) elf) + entry->p_offset);
  87         ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  88
  89         if (area->sh_info) {
  90                 bool found = false;
  91
  92                 /*
  93                  * The address space area is shared.
  94                  */
  95
  96                 mutex_lock(&area->sh_info->lock);
  97                 frame = (uintptr_t) btree_search(&area->sh_info->pagemap,
  98                         ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);
  99                 if (!frame) {
 100                         int i;
 101
 102                         /*
 103                          * Workaround for valid NULL address.
 104                          */
 105
 106                         for (i = 0; i < leaf->keys; i++) {
 107                                 if (leaf->key[i] == ALIGN_DOWN(addr, PAGE_SIZE)) {
 108                                         found = true;
 109                                         break;
 110                                 }
 111                         }
 112                 }
 113                 if (frame || found) {
 114                         frame_reference_add(ADDR2PFN(frame));
 115                         page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
 116                         if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
 117                                 panic("Could not insert used space.\n");
 118                         mutex_unlock(&area->sh_info->lock);
 119                         return AS_PF_OK;
 120                 }
 121         }
 122
 123         /*
 124          * The area is either not shared or the pagemap does not contain the mapping.
 125          */
 126
 127         if (ALIGN_DOWN(addr, PAGE_SIZE) + PAGE_SIZE < entry->p_vaddr + entry->p_filesz) {
 128                 /*
 129                  * Initialized portion of the segment. The memory is backed
 130                  * directly by the content of the ELF image. Pages are
 131                  * only copied if the segment is writable so that there
 132                  * can be more instantions of the same memory ELF image
 133                  * used at a time. Note that this could be later done
 134                  * as COW.
 135                  */
 136                 if (entry->p_flags & PF_W) {
 137                         frame = (uintptr_t)frame_alloc(ONE_FRAME, 0);
 138                         memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), FRAME_SIZE);
 139
 140                         if (area->sh_info) {
 141                                 frame_reference_add(ADDR2PFN(frame));
 142                                 btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
 143                                         (void *) frame, leaf);
 144                         }
 145
 146                 } else {
 147                         frame = KA2PA(base + i*FRAME_SIZE);
 148                 }
 149         } else if (ALIGN_DOWN(addr, PAGE_SIZE) >= ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
 150                 /*
 151                  * This is the uninitialized portion of the segment.
 152                  * It is not physically present in the ELF image.
 153                  * To resolve the situation, a frame must be allocated
 154                  * and cleared.
 155                  */
 156                 frame = (uintptr_t)frame_alloc(ONE_FRAME, 0);
 157                 memsetb(PA2KA(frame), FRAME_SIZE, 0);
 158
 159                 if (area->sh_info) {
 160                         frame_reference_add(ADDR2PFN(frame));
 161                         btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
 162                                 (void *) frame, leaf);
 163                 }
 164
 165         } else {
 166                 size_t size;
 167                 /*
 168                  * The mixed case.
 169                  * The lower part is backed by the ELF image and
 170                  * the upper part is anonymous memory.
 171                  */
 172                 size = entry->p_filesz - (i<<PAGE_WIDTH);
 173                 frame = (uintptr_t)frame_alloc(ONE_FRAME, 0);
 174                 memsetb(PA2KA(frame) + size, FRAME_SIZE - size, 0);
 175                 memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), size);
 176
 177                 if (area->sh_info) {
 178                         frame_reference_add(ADDR2PFN(frame));
 179                         btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
 180                                 (void *) frame, leaf);
 181                 }
 182
 183         }
 184
 185         if (area->sh_info)
 186                 mutex_unlock(&area->sh_info->lock);
 187
 188         page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
 189         if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
 190                 panic("Could not insert used space.\n");
 191
 192         return AS_PF_OK;
 193 }
 194
 195 /** Free a frame that is backed by the ELF backend.
 196  *
 197  * The address space area and page tables must be already locked.
 198  *
 199  * @param area Pointer to the address space area.
 200  * @param page Page that is mapped to frame. Must be aligned to PAGE_SIZE.
 201  * @param frame Frame to be released.
 202  *
 203  */
 204 void elf_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame)
 205 {
 206         elf_header_t *elf = area->backend_data.elf;
 207         elf_segment_header_t *entry = area->backend_data.segment;
 208         uintptr_t base;
 209         index_t i;
 210
 211         ASSERT((page >= entry->p_vaddr) && (page < entry->p_vaddr + entry->p_memsz));
 212         i = (page - entry->p_vaddr) >> PAGE_WIDTH;
 213         base = (uintptr_t) (((void *) elf) + entry->p_offset);
 214         ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
 215
 216         if (page + PAGE_SIZE < ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
 217                 if (entry->p_flags & PF_W) {
 218                         /*
 219                          * Free the frame with the copy of writable segment data.
 220                          */
 221                         frame_free(frame);
 222                 }
 223         } else {
 224                 /*
 225                  * The frame is either anonymous memory or the mixed case (i.e. lower
 226                  * part is backed by the ELF image and the upper is anonymous).
 227                  * In any case, a frame needs to be freed.
 228                  */
 229                 frame_free(frame);
 230         }
 231 }
 232
 233 /** Share ELF image backed address space area.
 234  *
 235  * If the area is writable, then all mapped pages are duplicated in the pagemap.
 236  * Otherwise only portions of the area that are not backed by the ELF image
 237  * are put into the pagemap.
 238  *
 239  * The address space and address space area must be locked prior to the call.
 240  *
 241  * @param area Address space area.
 242  */
 243 void elf_share(as_area_t *area)
 244 {
 245         elf_segment_header_t *entry = area->backend_data.segment;
 246         link_t *cur;
 247         btree_node_t *leaf, *node;
 248         uintptr_t start_anon = entry->p_vaddr + entry->p_filesz;
 249
 250         /*
 251          * Find the node in which to start linear search.
 252          */
 253         if (area->flags & AS_AREA_WRITE) {
 254                 node = list_get_instance(area->used_space.leaf_head.next, btree_node_t, leaf_link);
 255         } else {
 256                 (void) btree_search(&area->sh_info->pagemap, start_anon, &leaf);
 257                 node = btree_leaf_node_left_neighbour(&area->sh_info->pagemap, leaf);
 258                 if (!node)
 259                         node = leaf;
 260         }
 261
 262         /*
 263          * Copy used anonymous portions of the area to sh_info's page map.
 264          */
 265         mutex_lock(&area->sh_info->lock);
 266         for (cur = &node->leaf_link; cur != &area->used_space.leaf_head; cur = cur->next) {
 267                 int i;
 268
 269                 node = list_get_instance(cur, btree_node_t, leaf_link);
 270
 271                 for (i = 0; i < node->keys; i++) {
 272                         uintptr_t base = node->key[i];
 273                         count_t count = (count_t) node->value[i];
 274                         int j;
 275
 276                         /*
 277                          * Skip read-only areas of used space that are backed
 278                          * by the ELF image.
 279                          */
 280                         if (!(area->flags & AS_AREA_WRITE))
 281                                 if (base + count*PAGE_SIZE <= start_anon)
 282                                         continue;
 283
 284                         for (j = 0; j < count; j++) {
 285                                 pte_t *pte;
 286
 287                                 /*
 288                                  * Skip read-only pages that are backed by the ELF image.
 289                                  */
 290                                 if (!(area->flags & AS_AREA_WRITE))
 291                                         if (base + (j + 1)*PAGE_SIZE <= start_anon)
 292                                                 continue;
 293
 294                                 page_table_lock(area->as, false);
 295                                 pte = page_mapping_find(area->as, base + j*PAGE_SIZE);
 296                                 ASSERT(pte && PTE_VALID(pte) && PTE_PRESENT(pte));
 297                                 btree_insert(&area->sh_info->pagemap, (base + j*PAGE_SIZE) - area->base,
 298                                         (void *) PTE_GET_FRAME(pte), NULL);
 299                                 page_table_unlock(area->as, false);
 300                                 frame_reference_add(ADDR2PFN(PTE_GET_FRAME(pte)));
 301                         }
 302
 303                 }
 304         }
 305         mutex_unlock(&area->sh_info->lock);
 306 }
 307
 308 /** @}
 309  */