/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1997 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 by Christopher G. Demetriou
 *      for the NetBSD Project.
 * 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.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
__RCSID("$NetBSD: exec_elf32.c,v 1.6 1999/09/20 04:12:16 christos Exp $");
#endif
#endif
#ifndef ELFSIZE
#define ELFSIZE         32
#endif

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

#include <errno.h>
#include <limits.h>
#include <stddef.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))

#define __ELF_WORD_SIZE ELFSIZE
#if (ELFSIZE == 32)
#include <sys/elf32.h>
#define xewtoh(x)       ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
#define htoxew(x)       ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
#define wewtoh(x)       ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
#define htowew(x)       ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
#elif (ELFSIZE == 64)
#include <sys/elf64.h>
#define xewtoh(x)       ((data == ELFDATA2MSB) ? be64toh(x) : le64toh(x))
#define htoxew(x)       ((data == ELFDATA2MSB) ? htobe64(x) : htole64(x))
/* elf64 Elf64_Word are 32 bits */
#define wewtoh(x)       ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
#define htowew(x)       ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
#endif
#include <sys/elf_generic.h>

#define CONCAT(x,y)     __CONCAT(x,y)
#define ELFNAME(x)      CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x)))
#define ELFNAME2(x,y)   CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y))))
#define ELFNAMEEND(x)   CONCAT(x,CONCAT(_elf,ELFSIZE))
#define ELFDEFNNAME(x)  CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x)))
#ifndef ELFCLASS
#define ELFCLASS        CONCAT(ELFCLASS,ELFSIZE)
#endif

#define xe16toh(x)      ((data == ELFDATA2MSB) ? be16toh(x) : le16toh(x))
#define xe32toh(x)      ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
#define htoxe32(x)      ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))

struct shlayout {
        Elf_Shdr *shdr;
        void *bufp;
};

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 __unused)
{
        Elf_Ehdr eh;
        struct stat sb;
        unsigned char data;

        /*
         * 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 (IS_ELF(eh) == 0 || eh.e_ident[EI_CLASS] != ELFCLASS)
                return 0;

        data = eh.e_ident[EI_DATA];

        switch (xe16toh(eh.e_machine)) {
        case EM_386: break;
        case EM_ALPHA: break;
#ifndef EM_AARCH64
#define EM_AARCH64      183
#endif
        case EM_AARCH64: break;
        case EM_ARM: break;
        case EM_MIPS: break;
        case /* EM_MIPS_RS3_LE */ EM_MIPS_RS4_BE: break;
        case EM_PPC: break;
        case EM_PPC64: break;
#ifndef EM_RISCV
#define EM_RISCV        243
#endif
        case EM_RISCV: break;
        case EM_S390: break;
        case EM_SPARCV9: break;
        case EM_X86_64: break;
/*        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;
        struct shlayout *layoutp = NULL;
        Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr, *shstrtabshdr;
        Elf_Shdr shdrshdr;
        Elf_Sym *symtabp = NULL;
        char *shstrtabp = NULL, *strtabp = NULL;
        Elf_Size nsyms, ewi;
        Elf_Off off;
        ssize_t shdrsize;
        int rv, i, weird, l, m, r, strtabidx;
        size_t nstrtab_size, nstrtab_nextoff, fn_size, size;
        char *nstrtabp = NULL;
        unsigned char data;
        const char *weirdreason = NULL;
        void *buf;
        Elf_Half shnum;

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

        data = ehdr.e_ident[EI_DATA];
        shnum = xe16toh(ehdr.e_shnum);

        shdrsize = shnum * xe16toh(ehdr.e_shentsize);
        if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
                goto bad;
        if (xreadatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) !=
            shdrsize)
                goto bad;

        symtabshdr = strtabshdr = shstrtabshdr = NULL;
        weird = 0;
        for (i = 0; i < shnum; i++) {
                switch (xe32toh(shdrp[i].sh_type)) {
                case SHT_SYMTAB:
                        if (symtabshdr != NULL) {
                                weird = 1;
                                weirdreason = "multiple symbol tables";
                        }
                        symtabshdr = &shdrp[i];
                        strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
                        break;
                case SHT_STRTAB:
                        if (i == xe16toh(ehdr.e_shstrndx))
                                shstrtabshdr = &shdrp[i];
                        break;
                }
        }
        if (symtabshdr == NULL)
                goto out;
        if (strtabshdr == NULL) {
                weird = 1;
                weirdreason = "string table does not exist";
        }
        if (shstrtabshdr == NULL) {
                weird = 1;
                weirdreason = "section header string table does not exist";
        }
        if (strtabshdr == shstrtabshdr) {
                weird = 1;
                weirdreason = "combined strtab and shstrtab not supported";
        }
        if (weirdreason == NULL)
                weirdreason = "unsupported";
        if (weird) {
                fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason);
                goto bad;
        }

        /*
         * sort section layout table by offset
         */
        layoutp = xmalloc((shnum + 1) * sizeof(struct shlayout),
            fn, "layout table");
        if (layoutp == NULL)
                goto bad;

        /* add a pseudo entry to represent the section header table */
        shdrshdr.sh_offset = ehdr.e_shoff;
        shdrshdr.sh_size = htoxew(shdrsize);
        shdrshdr.sh_addralign = htoxew(ELFSIZE / 8);
        layoutp[shnum].shdr = &shdrshdr;

        /* insert and sort normal section headers */
        for (i = shnum; i-- != 0;) {
                l = i + 1;
                r = shnum;
                while (l <= r) {
                        m = ( l + r) / 2;
                        if (xewtoh(shdrp[i].sh_offset) >
                            xewtoh(layoutp[m].shdr->sh_offset))
                                l = m + 1;
                        else
                                r = m - 1;
                }

                if (r != i) {
                        memmove(&layoutp[i], &layoutp[i + 1],
                            sizeof(struct shlayout) * (r - i));
                }

                layoutp[r].shdr = &shdrp[i];
                layoutp[r].bufp = NULL;
        }
        ++shnum;

        /*
         * load up everything we need
         */

        /* load section string table for debug use */
        if ((size = xewtoh(shstrtabshdr->sh_size)) == 0)
                goto bad;
        if ((shstrtabp = xmalloc(size, fn, "section string table")) == NULL)
                goto bad;
        if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset),
            size, fn) != size)
                goto bad;
        if (shstrtabp[size - 1] != '\0')
                goto bad;

        /* we need symtab, strtab, and everything behind strtab */
        strtabidx = INT_MAX;
        for (i = 0; i < shnum; i++) {
                if (layoutp[i].shdr == &shdrshdr) {
                        /* not load section header again */
                        layoutp[i].bufp = shdrp;
                        continue;
                }
                if (layoutp[i].shdr == shstrtabshdr) {
                        /* not load section string table again */
                        layoutp[i].bufp = shstrtabp;
                        continue;
                }

                if (layoutp[i].shdr == strtabshdr)
                        strtabidx = i;
                if (layoutp[i].shdr == symtabshdr || i >= strtabidx) {
                        off = xewtoh(layoutp[i].shdr->sh_offset);
                        if ((size = xewtoh(layoutp[i].shdr->sh_size)) == 0)
                                goto bad;
                        layoutp[i].bufp = xmalloc(size, fn,
                            shstrtabp + xewtoh(layoutp[i].shdr->sh_name));
                        if (layoutp[i].bufp == NULL)
                                goto bad;
                        if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) !=
                            size)
                                goto bad;

                        /* set symbol table and string table */
                        if (layoutp[i].shdr == symtabshdr) {
                                symtabp = layoutp[i].bufp;
                        } else if (layoutp[i].shdr == strtabshdr) {
                                strtabp = layoutp[i].bufp;
                                if (strtabp[size - 1] != '\0')
                                        goto bad;
                        }
                }
        }

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

        fn_size = strlen(fn);

        /* Prepare data structures for symbol movement. */
        nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize);

        /* move symbols, making them local */
        for (ewi = 0; ewi < nsyms; ewi++) {
                Elf_Sym *sp = &symtabp[ewi];
                const char *symname = strtabp + xe32toh(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 = htowew(nstrtab_nextoff);

                /* if it's a keeper or is undefined, don't rename it. */
                if (in_keep_list(symname) ||
                    (xe16toh(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;
        }
        strtabshdr->sh_size = htoxew(nstrtab_nextoff);

        /*
         * update section header table in ascending order of offset
         */
        for (i = strtabidx + 1; i < shnum; i++) {
                Elf_Off soff, align;
                soff = xewtoh(layoutp[i - 1].shdr->sh_offset) +
                    xewtoh(layoutp[i - 1].shdr->sh_size);
                align = xewtoh(layoutp[i].shdr->sh_addralign);
                soff = (soff + (align - 1)) & ~(align - 1);
                layoutp[i].shdr->sh_offset = htoxew(soff);
        }

        /*
         * write data to the file in descending order of offset
         */
        for (i = shnum; i-- != 0;) {
                if (layoutp[i].shdr == strtabshdr) {
                        /* new string table */
                        buf = nstrtabp;
                } else
                        buf = layoutp[i].bufp;

                if (layoutp[i].shdr == &shdrshdr ||
                    layoutp[i].shdr == symtabshdr || i >= strtabidx) {
                        if (buf == NULL)
                                goto bad;

                        /*
                         * update the offset of section header table in elf
                         * header if needed.
                         */
                        if (layoutp[i].shdr == &shdrshdr &&
                            ehdr.e_shoff != shdrshdr.sh_offset) {
                                ehdr.e_shoff = shdrshdr.sh_offset;
                                off = offsetof(Elf_Ehdr, e_shoff);
                                size = sizeof(Elf_Off);
                                if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size,
                                    fn) != size)
                                        goto bad;
                        }

                        off = xewtoh(layoutp[i].shdr->sh_offset);
                        size = xewtoh(layoutp[i].shdr->sh_size);
                        if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size)
                                goto bad;
                }
        }

out:
        if (layoutp != NULL) {
                for (i = 0; i < shnum; i++) {
                        if (layoutp[i].bufp != NULL)
                                free(layoutp[i].bufp);
                }
                free(layoutp);
        }
        free(nstrtabp);
        return (rv);

bad:
        rv = 1;
        goto out;
}

#endif /* include this size of ELF */