/* $NetBSD: exec_elf32.c,v 1.15 2022/07/08 17:47:47 andvar Exp $ */

/*
 * Copyright (c) 1997, 1998 Christopher G. Demetriou
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *          This product includes software developed for the
 *          NetBSD Project.  See http://www.NetBSD.org/ for
 *          information about NetBSD.
 * 4. 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.
 * 
 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: exec_elf32.c,v 1.15 2022/07/08 17:47:47 andvar Exp $");
#endif
 
#ifndef ELFSIZE
#define ELFSIZE         32
#endif

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

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "extern.h"

#if (defined(NLIST_ELF32) && (ELFSIZE == 32)) || \
    (defined(NLIST_ELF64) && (ELFSIZE == 64))

#include <sys/exec_elf.h>

struct listelem {
        struct listelem *next;
        void *mem;
        off_t file;
        size_t size;
};

static ssize_t
xreadatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
{
        ssize_t rv;

        if (lseek(fd, off, SEEK_SET) != off) {
                perror(fn);
                return -1;
        }
        if ((size_t)(rv = read(fd, buf, size)) != size) {
                fprintf(stderr, "%s: read error: %s\n", fn,
                    rv == -1 ? strerror(errno) : "short read");
                return -1;
        }
        return size;
}

static ssize_t
xwriteatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
{
        ssize_t rv;

        if (lseek(fd, off, SEEK_SET) != off) {
                perror(fn);
                return -1;
        }
        if ((size_t)(rv = write(fd, buf, size)) != size) {
                fprintf(stderr, "%s: write error: %s\n", fn,
                    rv == -1 ? strerror(errno) : "short write");
                return -1;
        }
        return size;
}

static void *
xmalloc(size_t size, const char *fn, const char *use)
{
        void *rv;

        rv = malloc(size);
        if (rv == NULL)
                fprintf(stderr, "%s: out of memory (allocating for %s)\n",
                    fn, use);
        return (rv);
}

static void *
xrealloc(void *ptr, size_t size, const char *fn, const char *use)
{
        void *rv;

        rv = realloc(ptr, size);
        if (rv == NULL) {
                free(ptr);
                fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
                    fn, use);
        }
        return (rv);
}

int
ELFNAMEEND(check)(int fd, const char *fn)
{
        Elf_Ehdr eh;
        struct stat sb;

        /*
         * Check the header to make sure it's an ELF file (of the
         * appropriate size).
         */
        if (fstat(fd, &sb) == -1)
                return 0;
        if (sb.st_size < (off_t)(sizeof eh))
                return 0;
        if (read(fd, &eh, sizeof eh) != sizeof eh)
                return 0;

        if (memcmp(eh.e_ident, ELFMAG, SELFMAG) != 0 ||
            eh.e_ident[EI_CLASS] != ELFCLASS)
                return 0;

        switch (eh.e_machine) {
        ELFDEFNNAME(MACHDEP_ID_CASES)

        default:
                return 0;
        }

        return 1;
}

/*
 * This function 'hides' (some of) ELF executable file's symbols.
 * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
 * Symbols in the global keep list, or which are marked as being undefined,
 * are left alone.
 *
 * An old version of this code shuffled various tables around, turning
 * global symbols to be hidden into local symbols.  That lost on the
 * mips, because CALL16 relocs must reference global symbols, and, if
 * those symbols were being hidden, they were no longer global.
 *
 * The new renaming behaviour doesn't take global symbols out of the
 * namespace.  However, it's ... unlikely that there will ever be
 * any collisions in practice because of the new method.
 */
int
ELFNAMEEND(hide)(int fd, const char *fn)
{
        Elf_Ehdr ehdr;
        Elf_Shdr *shdrp = NULL;
        int symtabsnum, strtabsnum;
        Elf_Sym *symtabp = NULL;
        char *strtabp = NULL, *nstrtabp = NULL;
        Elf_Word j, nsyms;
        Elf_Off stroff, maxoff;
        const char *weirdreason;
        ssize_t shdrsize;
        size_t nstrtab_size, nstrtab_nextoff, fn_size;
        int rv, i, weird;

        rv = 0;
        if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
                goto bad;

        shdrsize = ehdr.e_shnum * ehdr.e_shentsize;
        if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
                goto bad;
        if (xreadatoff(fd, shdrp, ehdr.e_shoff, shdrsize, fn) != shdrsize)
                goto bad;

        symtabsnum = strtabsnum = -1;
        maxoff = stroff = 0;
        weird = 0;
        weirdreason = "???";
        for (i = 0; i < ehdr.e_shnum; i++) {
                if (shdrp[i].sh_offset > maxoff) {
                        maxoff = shdrp[i].sh_offset;
                }
                switch (shdrp[i].sh_type) {
                case SHT_SYMTAB:
                        if (!weird && symtabsnum != -1) {
                                weird = 1;
                                weirdreason = "multiple symbol tables";
                        }
                        symtabsnum = i;
                        strtabsnum = shdrp[i].sh_link;
                        stroff = shdrp[strtabsnum].sh_offset;
                        if (!weird && strtabsnum != (ehdr.e_shnum - 1)) {
                                weird = 1;
                                weirdreason = "string table not last section";
                        }
                        break;
                }
        }
        if (symtabsnum == -1)
                goto out;
        if (!weird && strtabsnum == -1) {
                weird = 1;
                weirdreason = "no string table found";
        }
        if (!weird && stroff != maxoff) {
                weird = 1;
                weirdreason = "string table section not last in file";
        }
        if (weird) {
                fprintf(stderr, "%s: weird executable (%s); unsupported\n", fn,
                    weirdreason);
                goto bad;
        }

        /*
         * load up everything we need
         */

        /* symbol table */
        if ((symtabp = xmalloc(shdrp[symtabsnum].sh_size, fn, "symbol table"))
            == NULL)
                goto bad;
        if ((size_t)xreadatoff(fd, symtabp, shdrp[symtabsnum].sh_offset,
            shdrp[symtabsnum].sh_size, fn) != shdrp[symtabsnum].sh_size)
                goto bad;

        /* string table */
        if ((strtabp = xmalloc(shdrp[strtabsnum].sh_size, fn, "string table"))
            == NULL)
                goto bad;
        if ((size_t)xreadatoff(fd, strtabp, shdrp[strtabsnum].sh_offset,
            shdrp[strtabsnum].sh_size, fn) != shdrp[strtabsnum].sh_size)
                goto bad;

        nsyms = shdrp[symtabsnum].sh_size / shdrp[symtabsnum].sh_entsize;

        nstrtab_size = 256;
        nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
        if (nstrtabp == NULL)
                goto bad;
        nstrtab_nextoff = 0;

        fn_size = strlen(fn);

        for (j = 0; j < nsyms; j++) {
                Elf_Sym *sp = &symtabp[j];
                const char *symname = strtabp + sp->st_name;
                size_t newent_len;

                /*
                 * make sure there's size for the next entry, even if it's
                 * as large as it can be.
                 *
                 * "_$$hide$$ <filename> <symname><NUL>" ->
                 *    9 + 3 + sizes of fn and sym name
                 */
                while ((nstrtab_size - nstrtab_nextoff) <
                    strlen(symname) + fn_size + 12) {
                        nstrtab_size *= 2;
                        nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
                            "new string table");
                        if (nstrtabp == NULL)
                                goto bad;
                }

                sp->st_name = nstrtab_nextoff;

                /* if it's a keeper or is undefined, don't rename it. */
                if (in_keep_list(symname) ||
                    sp->st_shndx == SHN_UNDEF) {
                        newent_len = sprintf(nstrtabp + nstrtab_nextoff,
                            "%s", symname) + 1;
                } else {
                        newent_len = sprintf(nstrtabp + nstrtab_nextoff,
                            "_$$hide$$ %s %s", fn, symname) + 1;
                }
                nstrtab_nextoff += newent_len;
        }       
        shdrp[strtabsnum].sh_size = nstrtab_nextoff;

        /*
         * write new tables to the file
         */
        if (xwriteatoff(fd, shdrp, ehdr.e_shoff, shdrsize, fn) != shdrsize)
                goto bad;
        if ((size_t)xwriteatoff(fd, symtabp, shdrp[symtabsnum].sh_offset,
            shdrp[symtabsnum].sh_size, fn) != shdrp[symtabsnum].sh_size)
                goto bad;
        if ((size_t)xwriteatoff(fd, nstrtabp, shdrp[strtabsnum].sh_offset,
            shdrp[strtabsnum].sh_size, fn) != shdrp[strtabsnum].sh_size)
                goto bad;

out:
        if (shdrp != NULL)
                free(shdrp);
        if (symtabp != NULL)
                free(symtabp);
        if (strtabp != NULL)
                free(strtabp);
        if (nstrtabp != NULL)
                free(nstrtabp);
        return (rv);

bad:
        rv = 1;
        goto out;
}

#endif /* include this size of ELF */