Subversion Repositories HelenOS

/*

 * Copyright (C) 2006 Jakub Jermar

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/**

 * @file	backend_elf.c

 * @brief	Backend for address space areas backed by an ELF image.

 */

#include <elf.h>

#include <debug.h>

#include <arch/types.h>

#include <typedefs.h>

#include <mm/as.h>

#include <mm/frame.h>

#include <mm/slab.h>

#include <mm/page.h>

#include <genarch/mm/page_pt.h>

#include <genarch/mm/page_ht.h>

#include <align.h>

#include <memstr.h>

#include <macros.h>

#include <arch.h>

static int elf_page_fault(as_area_t *area, __address addr, pf_access_t access);

static void elf_frame_free(as_area_t *area, __address page, __address frame);

static void elf_share(as_area_t *area);

mem_backend_t elf_backend = {

	.page_fault = elf_page_fault,

	.frame_free = elf_frame_free,

	.share = elf_share

};

/** Service a page fault in the ELF backend address space area.

 *

 * The address space area and page tables must be already locked.

 *

 * @param area Pointer to the address space area.

 * @param addr Faulting virtual address.

 * @param access Access mode that caused the fault (i.e. read/write/exec).

 *

 * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).

 */

int elf_page_fault(as_area_t *area, __address addr, pf_access_t access)

{

	elf_header_t *elf = area->backend_data.elf;

	elf_segment_header_t *entry = area->backend_data.segment;

	btree_node_t *leaf;

	__address base, frame;

	index_t i;

	if (!as_area_check_access(area, access))

		return AS_PF_FAULT;

	ASSERT((addr >= entry->p_vaddr) && (addr < entry->p_vaddr + entry->p_memsz));

	i = (addr - entry->p_vaddr) >> PAGE_WIDTH;

	base = (__address) (((void *) elf) + entry->p_offset);

	ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);

	if (area->sh_info) {

		bool found = false;

		/*

		 * The address space area is shared.

		 */

		mutex_lock(&area->sh_info->lock);

		frame = (__address) btree_search(&area->sh_info->pagemap,

			ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);

		if (!frame) {

			int i;

			/*

			 * Workaround for valid NULL address.

			 */

			for (i = 0; i < leaf->keys; i++) {

				if (leaf->key[i] == ALIGN_DOWN(addr, PAGE_SIZE)) {

					found = true;

					break;

				}

			}

		}

		if (frame || found) {

			frame_reference_add(ADDR2PFN(frame));

			page_mapping_insert(AS, addr, frame, as_area_get_flags(area));

			frame_reference_add(ADDR2PFN(PTE_GET_FRAME(pte)));

			if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))

				panic("Could not insert used space.\n");

			mutex_unlock(&area->sh_info->lock);

			return AS_PF_OK;

		}

	}

	/*

	 * The area is either not shared or the pagemap does not contain the mapping.

	 */

	if (ALIGN_DOWN(addr, PAGE_SIZE) + PAGE_SIZE < entry->p_vaddr + entry->p_filesz) {

		/*

		 * Initialized portion of the segment. The memory is backed

		 * directly by the content of the ELF image. Pages are

		 * only copied if the segment is writable so that there

		 * can be more instantions of the same memory ELF image

		 * used at a time. Note that this could be later done

		 * as COW.

		 */

		if (entry->p_flags & PF_W) {

			frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));

			memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), FRAME_SIZE);

			if (area->sh_info) {

				frame_reference_add(ADDR2PFN(frame));

				btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,

					(void *) frame, leaf);

			}

		} else {

			frame = KA2PA(base + i*FRAME_SIZE);

		}	

	} else if (ALIGN_DOWN(addr, PAGE_SIZE) >= ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {

		/*

		 * This is the uninitialized portion of the segment.

		 * It is not physically present in the ELF image.

		 * To resolve the situation, a frame must be allocated

		 * and cleared.

		 */

		frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));

		memsetb(PA2KA(frame), FRAME_SIZE, 0);

		if (area->sh_info) {

			frame_reference_add(ADDR2PFN(frame));

			btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,

				(void *) frame, leaf);

		}

	} else {

		size_t size;

		/*

		 * The mixed case.

		 * The lower part is backed by the ELF image and

		 * the upper part is anonymous memory.

		 */

		size = entry->p_filesz - (i<<PAGE_WIDTH);

		frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));

		memsetb(PA2KA(frame) + size, FRAME_SIZE - size, 0);

		memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), size);

		if (area->sh_info) {

			frame_reference_add(ADDR2PFN(frame));

			btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,

				(void *) frame, leaf);

		}

	}

	if (area->sh_info)

		mutex_unlock(&area->sh_info->lock);

	page_mapping_insert(AS, addr, frame, as_area_get_flags(area));

	if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))

		panic("Could not insert used space.\n");

	return AS_PF_OK;

}

/** Free a frame that is backed by the ELF backend.

 *

 * The address space area and page tables must be already locked.

 *

 * @param area Pointer to the address space area.

 * @param page Page that is mapped to frame. Must be aligned to PAGE_SIZE.

 * @param frame Frame to be released.

 *

 */

void elf_frame_free(as_area_t *area, __address page, __address frame)

{

	elf_header_t *elf = area->backend_data.elf;

	elf_segment_header_t *entry = area->backend_data.segment;

	__address base;

	index_t i;

	ASSERT((page >= entry->p_vaddr) && (page < entry->p_vaddr + entry->p_memsz));

	i = (page - entry->p_vaddr) >> PAGE_WIDTH;

	base = (__address) (((void *) elf) + entry->p_offset);

	ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);

	if (page + PAGE_SIZE < ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {

		if (entry->p_flags & PF_W) {

			/*

			 * Free the frame with the copy of writable segment data.

			 */

			frame_free(ADDR2PFN(frame));

		}

	} else {

		/*

		 * The frame is either anonymous memory or the mixed case (i.e. lower

		 * part is backed by the ELF image and the upper is anonymous).

		 * In any case, a frame needs to be freed.

		 */

		frame_free(ADDR2PFN(frame)); 

	}

}

/** Share ELF image backed address space area.

 *

 * If the area is writable, then all mapped pages are duplicated in the pagemap.

 * Otherwise only portions of the area that are not backed by the ELF image

 * are put into the pagemap.

 *

 * The address space and address space area must be locked prior to the call.

 *

 * @param area Address space area.

 */

void elf_share(as_area_t *area)

{

	elf_segment_header_t *entry = area->backend_data.segment;

	link_t *cur;

	btree_node_t *leaf, *node;

	__address start_anon = entry->p_vaddr + entry->p_filesz;

	/*

	 * Find the node in which to start linear search.

	 */

	if (area->flags & AS_AREA_WRITE) {

		node = list_get_instance(area->used_space.leaf_head.next, btree_node_t, leaf_link);

	} else {

		(void) btree_search(&area->sh_info->pagemap, start_anon, &leaf);

		node = btree_leaf_node_left_neighbour(&area->sh_info->pagemap, leaf);

		if (!node)

			node = leaf;

	}

	/*

	 * Copy used anonymous portions of the area to sh_info's page map.

	 */

	mutex_lock(&area->sh_info->lock);

	for (cur = &node->leaf_link; cur != &area->used_space.leaf_head; cur = cur->next) {

		int i;

		node = list_get_instance(cur, btree_node_t, leaf_link);

		for (i = 0; i < node->keys; i++) {

			__address base = node->key[i];

			count_t count = (count_t) node->value[i];

			int j;

			/*

			 * Skip read-only areas of used space that are backed

			 * by the ELF image.

			 */

			if (!(area->flags & AS_AREA_WRITE))

				if (base + count*PAGE_SIZE <= start_anon)

					continue;

			for (j = 0; j < count; j++) {

				pte_t *pte;

				/*

				 * Skip read-only pages that are backed by the ELF image.

				 */

				if (!(area->flags & AS_AREA_WRITE))

					if (base + (j + 1)*PAGE_SIZE <= start_anon)

						continue;

				page_table_lock(area->as, false);

				pte = page_mapping_find(area->as, base + j*PAGE_SIZE);

				ASSERT(pte && PTE_VALID(pte) && PTE_PRESENT(pte));

				btree_insert(&area->sh_info->pagemap, (base + j*PAGE_SIZE) - area->base,

					(void *) PTE_GET_FRAME(pte), NULL);

				page_table_unlock(area->as, false);

				frame_reference_add(ADDR2PFN(PTE_GET_FRAME(pte)));

			}

		}

	}

	mutex_unlock(&area->sh_info->lock);

}