symtab.c

/*
 * Copyright (c) 2010 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.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <elf.h>
#include "include/symtab.h"

static int elf_hdr_check(elf_header_t *hdr);
static int section_hdr_load(int fd, const elf_header_t *ehdr, int idx,
    elf_section_header_t *shdr);
static int chunk_load(int fd, off64_t start, size_t size, void **ptr);
static int read_all(int fd, void *buf, size_t len);

int symtab_load(const char *file_name, symtab_t **symtab)
{
        symtab_t *stab;
        elf_header_t elf_hdr;
        elf_section_header_t sec_hdr;
        off64_t shstrt_start;
        size_t shstrt_size;
        char *shstrt, *sec_name;
        void *data;

        int fd;
        int rc;
        int i;

        bool load_sec, sec_is_symtab;

        *symtab = NULL;

        stab = calloc(1, sizeof(symtab_t));
        if (stab == NULL)
                return ENOMEM;

        fd = open(file_name, O_RDONLY);
        if (fd < 0) {
                printf("failed opening file\n");
                free(stab);
                return ENOENT;
        }

        rc = read_all(fd, &elf_hdr, sizeof(elf_header_t));
        if (rc != EOK) {
                printf("failed reading elf header\n");
                free(stab);
                return EIO;
        }

        rc = elf_hdr_check(&elf_hdr);
        if (rc != EOK) {
                printf("failed header check\n");
                free(stab);
                return ENOTSUP;
        }

        /*
         * Load section header string table.
         */

        rc = section_hdr_load(fd, &elf_hdr, elf_hdr.e_shstrndx, &sec_hdr);
        if (rc != EOK) {
                printf("failed reading shstrt header\n");
                free(stab);
                return ENOTSUP;
        }

        shstrt_start = sec_hdr.sh_offset;
        shstrt_size = sec_hdr.sh_size;

        rc = chunk_load(fd, shstrt_start, shstrt_size, (void **) &shstrt);
        if (rc != EOK) {
                printf("failed loading shstrt\n");
                free(stab);
                return ENOTSUP;
        }

        /* Read all section headers. */
        for (i = 0; i < elf_hdr.e_shnum; ++i) {
                rc = section_hdr_load(fd, &elf_hdr, i, &sec_hdr);
                if (rc != EOK) {
                        free(shstrt);
                        free(stab);
                        return ENOTSUP;
                }

                sec_name = shstrt + sec_hdr.sh_name;
                if (str_cmp(sec_name, ".symtab") == 0 &&
                    sec_hdr.sh_type == SHT_SYMTAB) {
                        load_sec = true;
                        sec_is_symtab = true;
                } else if (str_cmp(sec_name, ".strtab") == 0 &&
                    sec_hdr.sh_type == SHT_STRTAB) {
                        load_sec = true;
                        sec_is_symtab = false;
                } else {
                        load_sec = false;
                }

                if (load_sec) {
                        rc = chunk_load(fd, sec_hdr.sh_offset, sec_hdr.sh_size,
                            &data);
                        if (rc != EOK) {
                                free(shstrt);
                                free(stab);
                                return ENOTSUP;
                        }

                        if (sec_is_symtab) {
                                stab->sym = data;
                                stab->sym_size = sec_hdr.sh_size;
                        } else {
                                stab->strtab = data;
                                stab->strtab_size = sec_hdr.sh_size;
                        }
                }
        }

        free(shstrt);
        close(fd);

        if (stab->sym == NULL || stab->strtab == NULL) {
                /* Tables not found. */
                printf("Symbol table or string table section not found\n");
                free(stab);
                return ENOTSUP;
        }

        *symtab = stab;

        return EOK;
}

void symtab_delete(symtab_t *st)
{
        free(st->sym);
        st->sym = NULL;

        free(st->strtab);
        st->strtab = NULL;

        free(st);
}

int symtab_name_to_addr(symtab_t *st, char *name, uintptr_t *addr)
{
        size_t i;
        char *sname;
        unsigned stype;

        for (i = 0; i < st->sym_size / sizeof(elf_symbol_t); ++i) {
                if (st->sym[i].st_name == 0)
                        continue;

                stype = ELF_ST_TYPE(st->sym[i].st_info);
                if (stype != STT_OBJECT && stype != STT_FUNC)
                        continue;

                sname = st->strtab + st->sym[i].st_name;

                if (str_cmp(sname, name) == 0) {
                        *addr = st->sym[i].st_value;
                        return EOK;
                }
        }

        return ENOENT;
}

int symtab_addr_to_name(symtab_t *st, uintptr_t addr, char **name,
    size_t *offs)
{
        size_t i;
        uintptr_t saddr, best_addr;
        char *sname, *best_name;
        unsigned stype;

        best_name = NULL;
        best_addr = 0;

        for (i = 0; i < st->sym_size / sizeof(elf_symbol_t); ++i) {
                if (st->sym[i].st_name == 0)
                        continue;

                stype = ELF_ST_TYPE(st->sym[i].st_info);
                if (stype != STT_OBJECT && stype != STT_FUNC &&
                    stype != STT_NOTYPE) {
                        continue;
                }

                saddr = st->sym[i].st_value;
                sname = st->strtab + st->sym[i].st_name;

                /* An ugly hack to filter out some special ARM symbols. */
                if (sname[0] == '$')
                        continue;

                if (best_name == NULL || (saddr <= addr && saddr > best_addr)) {
                        best_name = sname;
                        best_addr = saddr;
                }
        }

        if (best_name == NULL)
                return ENOENT;

        *name = best_name;
        *offs = addr - best_addr;
        return EOK;
}

static int elf_hdr_check(elf_header_t *ehdr)
{
        /* TODO */
        return EOK;
}

static int section_hdr_load(int fd, const elf_header_t *elf_hdr, int idx,
    elf_section_header_t *sec_hdr)
{
        int rc;

        rc = lseek(fd, elf_hdr->e_shoff + idx * sizeof(elf_section_header_t),
            SEEK_SET);
        if (rc == (off64_t) -1)
                return EIO;

        rc = read_all(fd, sec_hdr, sizeof(elf_section_header_t));
        if (rc != EOK)
                return EIO;

        return EOK;
}

static int chunk_load(int fd, off64_t start, size_t size, void **ptr)
{
        int rc;

        rc = lseek(fd, start, SEEK_SET);
        if (rc == (off64_t) -1) {
                printf("failed seeking chunk\n");
                *ptr = NULL;
                return EIO;
        }

        *ptr = malloc(size);
        if (*ptr == NULL) {
                printf("failed allocating memory\n");
                return ENOMEM;
        }

        rc = read_all(fd, *ptr, size);
        if (rc != EOK) {
                printf("failed reading chunk\n");
                free(*ptr);
                *ptr = NULL;
                return EIO;
        }

        return EOK;
}

static int read_all(int fd, void *buf, size_t len)
{
        int cnt = 0;

        do {
                buf += cnt;
                len -= cnt;
                cnt = read(fd, buf, len);
        } while (cnt > 0 && (len - cnt) > 0);

        if (cnt < 0)
                return cnt;

        if (len - cnt > 0)
                return EIO;

        return EOK;
}

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