Subversion Repositories HelenOS

/*

 * Copyright (c) 2006 Sergey Bondari

 * Copyright (c) 2006 Jakub Jermar

 * Copyright (c) 2008 Jiri Svoboda

 * 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   Userspace ELF loader.

 *

 * This module allows loading ELF binaries (both executables and

 * shared objects) from VFS. The current implementation allocates

 * anonymous memory, fills it with segment data and then adjusts

 * the memory areas' flags to the final value. In the future,

 * the segments will be mapped directly from the file.

 */

#include <stdio.h>

#include <sys/types.h>

#include <align.h>

#include <assert.h>

#include <as.h>

#include <unistd.h>

#include <fcntl.h>

#include <loader/pcb.h>

#include "elf.h"

#include "elf_load.h"

#include "arch.h"

static char *error_codes[] = {

    "no error",

    "invalid image",

    "address space error",

    "incompatible image",

    "unsupported image type",

    "irrecoverable error"

};

static unsigned int elf_load(elf_ld_t *elf, size_t so_bias);

static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry);

static int section_header(elf_ld_t *elf, elf_section_header_t *entry);

static int load_segment(elf_ld_t *elf, elf_segment_header_t *entry);

/** Load ELF binary from a file.

 *

 * Load an ELF binary from the specified file. If the file is

 * an executable program, it is loaded unbiased. If it is a shared

 * object, it is loaded with the bias @a so_bias. Some information

 * extracted from the binary is stored in a elf_info_t structure

 * pointed to by @a info.

 *

 * @param file_name Path to the ELF file.

 * @param so_bias   Bias to use if the file is a shared object.

 * @param info      Pointer to a structure for storing information

 *          extracted from the binary.

 *

 * @return EOK on success or negative error code.

 */

int elf_load_file(char *file_name, size_t so_bias, elf_info_t *info)

{

    elf_ld_t elf;

    int fd;

    int rc;

//  printf("open and read '%s'...\n", file_name);

    fd = open(file_name, O_RDONLY);

    if (fd < 0) {

        printf("failed opening file\n");

        return -1;

    }

    elf.fd = fd;

    elf.info = info;

    rc = elf_load(&elf, so_bias);

    close(fd);

    return rc;

}

/** Run an ELF executable.

 *

 * Transfers control to the entry point of an ELF executable loaded

 * earlier with elf_load_file(). This function does not return.

 *

 * @param info  Info structure filled earlier by elf_load_file()

 */

void elf_run(elf_info_t *info, pcb_t *pcb)

{

    program_run(info->entry, pcb);

    /* not reached */

}

/** Create the program control block (PCB).

 *

 * Fills the program control block @a pcb with information from

 * @a info.

 *

 * @param info  Program info structure

 * @return EOK on success or negative error code

 */

void elf_create_pcb(elf_info_t *info, pcb_t *pcb)

{

    pcb->entry = info->entry;

    pcb->dynamic = info->dynamic;

}

/** Load an ELF binary.

 *

 * The @a elf structure contains the loader state, including

 * an open file, from which the binary will be loaded,

 * a pointer to the @c info structure etc.

 *

 * @param elf       Pointer to loader state buffer.

 * @param so_bias   Bias to use if the file is a shared object.

 * @return EE_OK on success or EE_xx error code.

 */

static unsigned int elf_load(elf_ld_t *elf, size_t so_bias)

{

    elf_header_t header_buf;

    elf_header_t *header = &header_buf;

    int i, rc;

    rc = read(elf->fd, header, sizeof(elf_header_t));

    if (rc < 0) {

        printf("read error\n");

        return EE_INVALID;

    }

    elf->header = header;

//  printf("ELF-load:");

    /* 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) {

        printf("invalid header\n");

        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) {

        printf("incompatible data/version/class\n");

        return EE_INCOMPATIBLE;

    }

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

        printf("e_phentsize:%d != %d\n", header->e_phentsize,

            sizeof(elf_segment_header_t));

        return EE_INCOMPATIBLE;

    }

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

        printf("e_shentsize:%d != %d\n", header->e_shentsize,

            sizeof(elf_section_header_t));

        return EE_INCOMPATIBLE;

    }

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

    if (header->e_type != ET_EXEC && header->e_type != ET_DYN) {

        printf("Object type %d is not supported\n", header->e_type);

        return EE_UNSUPPORTED;

    }

    /* Shared objects can be loaded with a bias */

//  printf("Object type: %d\n", header->e_type);

    if (header->e_type == ET_DYN)

        elf->bias = so_bias;

    else

        elf->bias = 0;

//  printf("Bias set to 0x%x\n", elf->bias);

    elf->info->interp = NULL;

    elf->info->dynamic = NULL;

//  printf("parse segments\n");

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

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

        elf_segment_header_t segment_hdr;

        /* Seek to start of segment header */

        lseek(elf->fd, header->e_phoff

                + i * sizeof(elf_segment_header_t), SEEK_SET);

        rc = read(elf->fd, &segment_hdr, sizeof(elf_segment_header_t));

        if (rc < 0) { printf("read error\n"); return EE_INVALID; }

        rc = segment_header(elf, &segment_hdr);

        if (rc != EE_OK)

            return rc;

    }

//  printf("parse sections\n");

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

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

        elf_section_header_t section_hdr;

        /* Seek to start of section header */

        lseek(elf->fd, header->e_shoff

            + i * sizeof(elf_section_header_t), SEEK_SET);

        rc = read(elf->fd, &section_hdr, sizeof(elf_section_header_t));

        if (rc < 0) { printf("read error\n"); return EE_INVALID; }

        rc = section_header(elf, &section_hdr);

        if (rc != EE_OK)

            return rc;

    }

    elf->info->entry =

        (entry_point_t)((uint8_t *)header->e_entry + elf->bias);

//  printf("done\n");

    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(unsigned int rc)

{

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

    return error_codes[rc];

}

/** Process segment header.

 *

 * @param entry Segment header.

 *

 * @return EE_OK on success, error code otherwise.

 */

static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry)

{

    switch (entry->p_type) {

    case PT_NULL:

    case PT_PHDR:

        break;

    case PT_LOAD:

        return load_segment(elf, entry);

        break;

    case PT_INTERP:

        /* Assume silently interp == "/rtld.so" */

        elf->info->interp = "/rtld.so";

        break;

    case PT_DYNAMIC:

    case PT_SHLIB:

    case PT_NOTE:

    case PT_LOPROC:

    case PT_HIPROC:

    default:

        printf("segment p_type %d unknown\n", entry->p_type);

        return EE_UNSUPPORTED;

        break;

    }

    return EE_OK;

}

/** Load segment described by program header entry.

 *

 * @param elf   Loader state.

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

 *

 * @return EE_OK on success, error code otherwise.

 */

int load_segment(elf_ld_t *elf, elf_segment_header_t *entry)

{

    void *a;

    int flags = 0;

    uintptr_t bias;

    uintptr_t base;

    size_t mem_sz;

    int rc;

//  printf("load segment at addr 0x%x, size 0x%x\n", entry->p_vaddr,

//      entry->p_memsz);

    bias = elf->bias;

    if (entry->p_align > 1) {

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

            (entry->p_vaddr % entry->p_align)) {

            printf("align check 1 failed offset%%align=%d, vaddr%%align=%d\n",

            entry->p_offset % entry->p_align,

            entry->p_vaddr % entry->p_align

            );

            return EE_INVALID;

        }

    }

    /* Final flags that will be set for the memory area */

    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;

    base = ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE);

    mem_sz = entry->p_memsz + (entry->p_vaddr - base);

//  printf("map to p_vaddr=0x%x-0x%x...\n", entry->p_vaddr + bias,

//  entry->p_vaddr + bias + ALIGN_UP(entry->p_memsz, PAGE_SIZE));

    /*

     * For the course of loading, the area needs to be readable

     * and writeable.

     */

    a = as_area_create((uint8_t *)base + bias,

        mem_sz, AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE);

    if (a == (void *)(-1)) {

        printf("memory mapping failed\n");

        return EE_MEMORY;

    }

//  printf("as_area_create(0x%lx, 0x%x, %d) -> 0x%lx\n",

//      entry->p_vaddr+bias, entry->p_memsz, flags, (uintptr_t)a);

    /*

     * Load segment data

     */

//  printf("seek to %d\n", entry->p_offset);

    rc = lseek(elf->fd, entry->p_offset, SEEK_SET);

    if (rc < 0) { printf("seek error\n"); return EE_INVALID; }

//  printf("read 0x%x bytes to address 0x%x\n", entry->p_filesz, entry->p_vaddr+bias);

/*  rc = read(fd, (void *)(entry->p_vaddr + bias), entry->p_filesz);

    if (rc < 0) { printf("read error\n"); return EE_INVALID; }*/

    /* Long reads are not possible yet. Load segment picewise */

    unsigned left, now;

    uint8_t *dp;

    left = entry->p_filesz;

    dp = (uint8_t *)(entry->p_vaddr + bias);

    while (left > 0) {

        now = 16384;

        if (now > left) now = left;

//      printf("read %d...", now);

        rc = read(elf->fd, dp, now);

//      printf("->%d\n", rc);

        if (rc < 0) { printf("read error\n"); return EE_INVALID; }

        left -= now;

        dp += now;

    }

//  printf("set area flags to %d\n", flags);

    rc = as_area_change_flags((uint8_t *)entry->p_vaddr + bias, flags);

    if (rc != 0) {

        printf("failed to set memory area flags\n");

        return EE_MEMORY;

    }

    return EE_OK;

}

/** Process section header.

 *

 * @param elf   Loader state.

 * @param entry Segment header.

 *

 * @return EE_OK on success, error code otherwise.

 */

static int section_header(elf_ld_t *elf, elf_section_header_t *entry)

{

    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;

    case SHT_DYNAMIC:

        /* Record pointer to dynamic section into info structure */

        elf->info->dynamic =

            (void *)((uint8_t *)entry->sh_addr + elf->bias);

        printf("dynamic section found at 0x%x\n",

            (uintptr_t)elf->info->dynamic);

        break;

    default:

        break;

    }

    return EE_OK;

}

/** @}

 */