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/*

 * Copyright (C) 2006 Sergey Bondari

 * 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    elf.c

 * @brief   Kernel ELF loader.

 */

#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 <align.h>

#include <memstr.h>

#include <macros.h>

#include <arch.h>

static char *error_codes[] = {

    "no error",

    "invalid image",

    "address space error",

    "incompatible image",

    "unsupported image type",

    "irrecoverable error"

};

static int segment_header(elf_segment_header_t *entry, elf_header_t *elf, as_t *as);

static int section_header(elf_section_header_t *entry, elf_header_t *elf, as_t *as);

static int load_segment(elf_segment_header_t *entry, elf_header_t *elf, as_t *as);

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

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

mem_backend_t elf_backend = {

    .backend_page_fault = elf_page_fault,

    .backend_frame_free = elf_frame_free

};

/** ELF loader

 *

 * @param header Pointer to ELF header in memory

 * @param as Created and properly mapped address space

 * @return EE_OK on success

 */

int elf_load(elf_header_t *header, as_t * as)

{

    int i, rc;

    /* Identify ELF */

    if (header->e_ident[EI_MAG0] != ELFMAG0 || header->e_ident[EI_MAG1] != ELFMAG1 ||

        header->e_ident[EI_MAG2] != ELFMAG2 || header->e_ident[EI_MAG3] != ELFMAG3) {

        return EE_INVALID;

    }

    /* Identify ELF compatibility */

    if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING || header->e_machine != ELF_MACHINE ||

        header->e_ident[EI_VERSION] != EV_CURRENT || header->e_version != EV_CURRENT ||

        header->e_ident[EI_CLASS] != ELF_CLASS) {

        return EE_INCOMPATIBLE;

    }

    if (header->e_phentsize != sizeof(elf_segment_header_t))

        return EE_INCOMPATIBLE;

    if (header->e_shentsize != sizeof(elf_section_header_t))

        return EE_INCOMPATIBLE;

    /* Check if the object type is supported. */

    if (header->e_type != ET_EXEC)

        return EE_UNSUPPORTED;

    /* Walk through all segment headers and process them. */

    for (i = 0; i < header->e_phnum; i++) {

        rc = segment_header(&((elf_segment_header_t *)(((__u8 *) header) + header->e_phoff))[i], header, as);

        if (rc != EE_OK)

            return rc;

    }

    /* Inspect all section headers and proccess them. */

    for (i = 0; i < header->e_shnum; i++) {

        rc = section_header(&((elf_section_header_t *)(((__u8 *) header) + header->e_shoff))[i], header, as);

        if (rc != EE_OK)

            return rc;

    }

    return EE_OK;

}

/** Print error message according to error code.

 *

 * @param rc Return code returned by elf_load().

 *

 * @return NULL terminated description of error.

 */

char *elf_error(int rc)

{

    ASSERT(rc < sizeof(error_codes)/sizeof(char *));

    return error_codes[rc];

}

/** Process segment header.

 *

 * @param entry Segment header.

 * @param elf ELF header.

 * @param as Address space into wich the ELF is being loaded.

 *

 * @return EE_OK on success, error code otherwise.

 */

static int segment_header(elf_segment_header_t *entry, elf_header_t *elf, as_t *as)

{

    switch (entry->p_type) {

        case PT_NULL:

        case PT_PHDR:

        break;

        case PT_LOAD:

        return load_segment(entry, elf, as);

        break;

        case PT_DYNAMIC:

        case PT_INTERP:

        case PT_SHLIB:

        case PT_NOTE:

        case PT_LOPROC:

        case PT_HIPROC:

        default:

        return EE_UNSUPPORTED;

        break;

    }

    return EE_OK;

}

/** Load segment described by program header entry.

 *

 * @param entry Program header entry describing segment to be loaded.

 * @param elf ELF header.

 * @param as Address space into wich the ELF is being loaded.

 *

 * @return EE_OK on success, error code otherwise.

 */

int load_segment(elf_segment_header_t *entry, elf_header_t *elf, as_t *as)

{

    as_area_t *a;

    int flags = 0;

    void *backend_data[2] = { elf, entry };

    if (entry->p_align > 1) {

        if ((entry->p_offset % entry->p_align) != (entry->p_vaddr % entry->p_align)) {

            return EE_INVALID;

        }

    }

    if (entry->p_flags & PF_X)

        flags |= AS_AREA_EXEC;

    if (entry->p_flags & PF_W)

        flags |= AS_AREA_WRITE;

    if (entry->p_flags & PF_R)

        flags |= AS_AREA_READ;

    /*

     * Check if the virtual address starts on page boundary.

     */

    if (ALIGN_UP(entry->p_vaddr, PAGE_SIZE) != entry->p_vaddr)

        return EE_UNSUPPORTED;

    a = as_area_create(as, flags, entry->p_memsz, entry->p_vaddr, AS_AREA_ATTR_NONE, &elf_backend, backend_data);

    if (!a)

        return EE_MEMORY;

    /*

     * The segment will be mapped on demand by elf_page_fault().

     */

    return EE_OK;

}

/** Process section header.

 *

 * @param entry Segment header.

 * @param elf ELF header.

 * @param as Address space into wich the ELF is being loaded.

 *

 * @return EE_OK on success, error code otherwise.

 */

static int section_header(elf_section_header_t *entry, elf_header_t *elf, as_t *as)

{

    switch (entry->sh_type) {

        default:

        break;

    }

    return EE_OK;

}

/** 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.

 *

 * @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)

{

    elf_header_t *elf = (elf_header_t *) area->backend_data[0];

    elf_segment_header_t *entry = (elf_segment_header_t *) area->backend_data[1];

    __address base, frame;

    index_t i;

    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 (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);

        } 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);

    } 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);

    }

    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 = (elf_header_t *) area->backend_data[0];

    elf_segment_header_t *entry = (elf_segment_header_t *) area->backend_data[1];

    __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));

    }

}