source: mainline/kernel/generic/src/lib/elf.c@ 5d0500c

/*
 * Copyright (c) 2006 Sergey Bondari
 * 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.
 */

/** @addtogroup generic
 * @{
 */

/**
 * @file
 * @brief Kernel ELF loader.
 */

#include <lib/elf.h>
#include <debug.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>

#include <lib/elf_load.h>

static const 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 *, elf_header_t *, as_t *,
    unsigned int);
static int section_header(elf_section_header_t *, elf_header_t *, as_t *);
static int load_segment(elf_segment_header_t *, elf_header_t *, as_t *);

/** ELF loader
 *
 * @param header Pointer to ELF header in memory
 * @param as     Created and properly mapped address space
 * @param flags  A combination of ELD_F_*
 *
 * @return EE_OK on success
 *
 */
unsigned int elf_load(elf_header_t *header, as_t *as, unsigned int flags)
{
        /* 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;
        
        /* Check if the ELF image starts on a page boundary */
        if (ALIGN_UP((uintptr_t) header, PAGE_SIZE) != (uintptr_t) header)
                return EE_UNSUPPORTED;
        
        /* Walk through all segment headers and process them. */
        elf_half i;
        for (i = 0; i < header->e_phnum; i++) {
                elf_segment_header_t *seghdr =
                    &((elf_segment_header_t *)(((uint8_t *) header) +
                    header->e_phoff))[i];
                
                int rc = segment_header(seghdr, header, as, flags);
                if (rc != EE_OK)
                        return rc;
        }
        
        /* Inspect all section headers and process them. */
        for (i = 0; i < header->e_shnum; i++) {
                elf_section_header_t *sechdr =
                    &((elf_section_header_t *)(((uint8_t *) header) +
                    header->e_shoff))[i];
                
                int rc = section_header(sechdr, 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.
 *
 */
const char *elf_error(unsigned 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, unsigned int flags)
{
        switch (entry->p_type) {
        case PT_NULL:
        case PT_PHDR:
        case PT_NOTE:
                break;
        case PT_LOAD:
                return load_segment(entry, elf, as);
        case PT_DYNAMIC:
        case PT_INTERP:
                // FIXME
                /*
                char *interp = (char *) elf + entry->p_offset;
                if (memcmp((uintptr_t) interp, (uintptr_t) ELF_INTERP_ZSTR,
                    ELF_INTERP_ZLEN) != 0) {
                        return EE_UNSUPPORTED;
                } */
                if ((flags & ELD_F_LOADER) == 0)
                        return EE_LOADER;
                break;
        case PT_SHLIB:
        case PT_LOPROC:
        case PT_HIPROC:
        default:
                return EE_UNSUPPORTED;
        }
        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)
{
        mem_backend_data_t backend_data;
        backend_data.elf = elf;
        backend_data.segment = entry;
        
        if (entry->p_align > 1) {
                if ((entry->p_offset % entry->p_align) !=
                    (entry->p_vaddr % entry->p_align))
                        return EE_INVALID;
        }
        
        unsigned int flags = 0;
        
        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;
        
        flags |= AS_AREA_CACHEABLE;
        
        /*
         * Align vaddr down, inserting a little "gap" at the beginning.
         * Adjust area size, so that its end remains in place.
         *
         */
        uintptr_t base = ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE);
        size_t mem_sz = entry->p_memsz + (entry->p_vaddr - base);
        
        as_area_t *area = as_area_create(as, flags, mem_sz, base,
            AS_AREA_ATTR_NONE, &elf_backend, &backend_data);
        if (!area)
                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) {
        case SHT_PROGBITS:
                if (entry->sh_flags & SHF_TLS) {
                        /* .tdata */
                }
                break;
        case SHT_NOBITS:
                if (entry->sh_flags & SHF_TLS) {
                        /* .tbss */
                }
                break;
        default:
                break;
        }
        
        return EE_OK;
}

/** @}
 */