source: mainline/generic/src/lib/elf.c@ 4bb4836d

/*
 * 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.
 */

#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 <print.h>
#include <align.h>
#include <memstr.h>
#include <macros.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);

/** 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.
 * @parma 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 i, type = 0;
        size_t segment_size;
        __u8 *segment;

        if (entry->p_align > 1) {
                if ((entry->p_offset % entry->p_align) != (entry->p_vaddr % entry->p_align)) {
                        return EE_INVALID;
                }
        }

        /*
         * Check if the segment doesn't interfere with kernel address space.
         */
        if (entry->p_vaddr + ALIGN_UP(entry->p_memsz, PAGE_SIZE) >= USER_ADDRESS_SPACE_END)
                return EE_MEMORY;
        
        if (entry->p_flags & PF_X) {
                type = AS_AREA_TEXT;
        } else if (entry->p_flags & PF_W) {
                type = AS_AREA_DATA;
        } else {
                return EE_UNSUPPORTED;
        }

        /*
         * Check if the virtual address starts on page boundary.
         */
        if (ALIGN_UP(entry->p_vaddr, PAGE_SIZE) != entry->p_vaddr)
                return EE_UNSUPPORTED;

        /*
         * Copying the segment out is certainly necessary for segments with p_filesz < p_memsz
         * because of the effect of .bss-like sections. For security reasons, it looks like a
         * good idea to copy the segment anyway.
         */
        segment_size = ALIGN_UP(max(entry->p_filesz, entry->p_memsz), PAGE_SIZE);
        segment = malloc(segment_size, 0);
        if (entry->p_filesz < entry->p_memsz)
                memsetb((__address) (segment + entry->p_filesz), segment_size - entry->p_filesz, 0);
        memcpy(segment, (void *) (((__address) elf) + entry->p_offset), entry->p_filesz);

        a = as_area_create(as, type, SIZE2FRAMES(entry->p_memsz), entry->p_vaddr);
        if (!a)
                return EE_IRRECOVERABLE;
        
        for (i = 0; i < SIZE2FRAMES(entry->p_filesz); i++) {
                as_set_mapping(as, entry->p_vaddr + i*PAGE_SIZE, KA2PA(((__address) segment) + i*PAGE_SIZE));
        }
        
        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;
}