/*      $OpenBSD: i386_nlist.c,v 1.9 2022/12/28 21:30:16 jmc Exp $      */
/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 */

#define ELFSIZE 32

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <nlist.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MINIMUM(a, b)   (((a) < (b)) ? (a) : (b))

static int      __elf_fdnlist(int, struct nlist *);
static int      __elf_is_okay__(Elf_Ehdr *ehdr);

int     nlist_elf32(const char *, struct nlist *);

#define ISLAST(p)       (p->n_name == 0 || p->n_name[0] == 0)

/*
 * __elf_is_okay__ - Determine if ehdr really
 * is ELF and valid for the target platform.
 *
 * WARNING:  This is NOT a ELF ABI function and
 * as such its use should be restricted.
 */
static int
__elf_is_okay__(Elf_Ehdr *ehdr)
{
        int retval = 0;
        /*
         * We need to check magic, class size, endianness,
         * and version before we look at the rest of the
         * Elf_Ehdr structure.  These few elements are
         * represented in a machine independent fashion.
         */

        /*
         * We are constructing a 32-bit executable. So we can't
         * use the libc nlist.c, which would be upset. Manually
         * check for the i386 values for EI_CLASS and e_machine.
         */

        if (IS_ELF(*ehdr) &&
            ehdr->e_ident[EI_CLASS] == ELFCLASS32 &&
            ehdr->e_ident[EI_DATA] == ELF_TARG_DATA &&
            ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) {

                /* Now check the machine dependent header */
                if (ehdr->e_machine == EM_386 &&
                    ehdr->e_version == ELF_TARG_VER)
                        retval = 1;
        }

        return retval;
}

static int
__elf_fdnlist(int fd, struct nlist *list)
{
        struct nlist *p;
        caddr_t strtab;
        Elf_Off symoff = 0, symstroff = 0;
        Elf_Word symsize = 0, symstrsize = 0;
        Elf_Sword nent, cc, i;
        Elf_Sym sbuf[1024];
        Elf_Sym *s;
        Elf_Ehdr ehdr;
        Elf_Shdr *shdr = NULL;
        Elf_Word shdr_size;
        struct stat st;
        int usemalloc = 0;
        size_t left, len;

        /* Make sure obj is OK */
        if (pread(fd, &ehdr, sizeof(Elf_Ehdr), (off_t)0) != sizeof(Elf_Ehdr) ||
            !__elf_is_okay__(&ehdr) || fstat(fd, &st) == -1)
                return (-1);

        /* calculate section header table size */
        shdr_size = ehdr.e_shentsize * ehdr.e_shnum;

        /* Make sure it's not too big to mmap */
        if (SIZE_MAX - ehdr.e_shoff < shdr_size ||
            (S_ISREG(st.st_mode) && ehdr.e_shoff + shdr_size > st.st_size)) {
                errno = EFBIG;
                return (-1);
        }

        /* mmap section header table */
        shdr = (Elf_Shdr *)mmap(NULL, (size_t)shdr_size, PROT_READ,
            MAP_SHARED|MAP_FILE, fd, (off_t) ehdr.e_shoff);
        if (shdr == MAP_FAILED) {
                usemalloc = 1;
                if ((shdr = malloc(shdr_size)) == NULL)
                        return (-1);

                if (pread(fd, shdr, shdr_size, (off_t)ehdr.e_shoff) !=
                    shdr_size) {
                        free(shdr);
                        return (-1);
                }
        }

        /*
         * Find the symbol table entry and its corresponding
         * string table entry.  Version 1.1 of the ABI states
         * that there is only one symbol table but that this
         * could change in the future.
         */
        for (i = 0; i < ehdr.e_shnum; i++) {
                if (shdr[i].sh_type == SHT_SYMTAB) {
                        if (shdr[i].sh_link >= ehdr.e_shnum)
                                continue;
                        symoff = shdr[i].sh_offset;
                        symsize = shdr[i].sh_size;
                        symstroff = shdr[shdr[i].sh_link].sh_offset;
                        symstrsize = shdr[shdr[i].sh_link].sh_size;
                        break;
                }
        }

        /* Flush the section header table */
        if (usemalloc)
                free(shdr);
        else
                munmap((caddr_t)shdr, shdr_size);

        /*
         * clean out any left-over information for all valid entries.
         * Type and value defined to be 0 if not found; historical
         * versions cleared other and desc as well.  Also figure out
         * the largest string length so don't read any more of the
         * string table than we have to.
         *
         * XXX clearing anything other than n_type and n_value violates
         * the semantics given in the man page.
         */
        nent = 0;
        for (p = list; !ISLAST(p); ++p) {
                p->n_type = 0;
                p->n_other = 0;
                p->n_desc = 0;
                p->n_value = 0;
                ++nent;
        }

        /* Don't process any further if object is stripped. */
        /* ELFism - dunno if stripped by looking at header */
        if (symoff == 0)
                return nent;

        /* Check for files too large to mmap. */
        if (SIZE_MAX - symstrsize < symstroff ||
            (S_ISREG(st.st_mode) && symstrsize + symstroff > st.st_size)) {
                errno = EFBIG;
                return (-1);
        }

        /*
         * Map string table into our address space.  This gives us
         * an easy way to randomly access all the strings, without
         * making the memory allocation permanent as with malloc/free
         * (i.e., munmap will return it to the system).
         */
        if (usemalloc) {
                if ((strtab = malloc(symstrsize)) == NULL)
                        return (-1);
                if (pread(fd, strtab, symstrsize, (off_t)symstroff) !=
                    symstrsize) {
                        free(strtab);
                        return (-1);
                }
        } else {
                strtab = mmap(NULL, (size_t)symstrsize, PROT_READ,
                    MAP_SHARED|MAP_FILE, fd, (off_t) symstroff);
                if (strtab == MAP_FAILED)
                        return (-1);
        }

        while (symsize >= sizeof(Elf_Sym)) {
                cc = MINIMUM(symsize, sizeof(sbuf));
                if (pread(fd, sbuf, cc, (off_t)symoff) != cc)
                        break;
                symsize -= cc;
                symoff += cc;
                for (s = sbuf; cc > 0; ++s, cc -= sizeof(*s)) {
                        Elf_Word soff = s->st_name;

                        if (soff == 0 || soff >= symstrsize)
                                continue;
                        left = symstrsize - soff;

                        for (p = list; !ISLAST(p); p++) {
                                char *sym;

                                /*
                                 * First we check for the symbol as it was
                                 * provided by the user. If that fails
                                 * and the first char is an '_', skip over
                                 * the '_' and try again.
                                 * XXX - What do we do when the user really
                                 *       wants '_foo' and there are symbols
                                 *       for both 'foo' and '_foo' in the
                                 *       table and 'foo' is first?
                                 */
                                sym = p->n_name;
                                len = strlen(sym);

                                if ((len >= left ||
                                    strcmp(&strtab[soff], sym) != 0) &&
                                    (sym[0] != '_' || len - 1 >= left ||
                                     strcmp(&strtab[soff], sym + 1) != 0))
                                        continue;

                                p->n_value = s->st_value;

                                /* XXX - type conversion */
                                /*       is pretty rude. */
                                switch(ELF_ST_TYPE(s->st_info)) {
                                case STT_NOTYPE:
                                        switch (s->st_shndx) {
                                        case SHN_UNDEF:
                                                p->n_type = N_UNDF;
                                                break;
                                        case SHN_ABS:
                                                p->n_type = N_ABS;
                                                break;
                                        case SHN_COMMON:
                                                p->n_type = N_COMM;
                                                break;
                                        default:
                                                p->n_type = N_COMM | N_EXT;
                                                break;
                                        }
                                        break;
                                case STT_OBJECT:
                                        p->n_type = N_DATA;
                                        break;
                                case STT_FUNC:
                                        p->n_type = N_TEXT;
                                        break;
                                case STT_FILE:
                                        p->n_type = N_FN;
                                        break;
                                }
                                if (ELF_ST_BIND(s->st_info) == STB_LOCAL)
                                        p->n_type = N_EXT;
                                p->n_desc = 0;
                                p->n_other = 0;
                                if (--nent <= 0)
                                        break;
                        }
                }
        }
        if (usemalloc)
                free(strtab);
        else
                munmap(strtab, symstrsize);
        return (nent);
}

int
nlist_elf32(const char *name, struct nlist *list)
{
        int fd, n;

        fd = open(name, O_RDONLY);
        if (fd == -1)
                return (-1);
        n = __elf_fdnlist(fd, list);
        close(fd);

        return (n);
}