/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 */

#include "namespace.h"
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <arpa/inet.h>

#include <a.out.h>
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "un-namespace.h"

#include <machine/elf.h>
#include <elf-hints.h>

int __fdnlist(int, struct nlist *);
int __elf_fdnlist(int, struct nlist *);
int __elf_is_okay__(Elf_Ehdr *);

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

        fd = _open(name, O_RDONLY | O_CLOEXEC, 0);
        if (fd < 0)
                return (-1);
        n = __fdnlist(fd, list);
        (void)_close(fd);
        return (n);
}

static struct nlist_handlers {
        int     (*fn)(int fd, struct nlist *list);
} nlist_fn[] = {
        { __elf_fdnlist },
};

int
__fdnlist(int fd, struct nlist *list)
{
        int n = -1;
        unsigned int i;

        for (i = 0; i < nitems(nlist_fn); i++) {
                n = (nlist_fn[i].fn)(fd, list);
                if (n != -1)
                        break;
        }
        return (n);
}

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

static int elf_scan_symtab(Elf_Shdr *, int, int, off_t, size_t, char *, size_t,
    struct nlist *, int);
static void elf_sym_to_nlist(struct nlist *, Elf_Sym *, Elf_Shdr *, int);

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

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

int
__elf_fdnlist(int fd, struct nlist *list)
{
        struct nlist *p;
        Elf_Off symoff = 0, stroff = 0;
        Elf_Size symsize = 0, strsize = 0;
        Elf_Ssize i;
        int nent = -1;
        int errsave;
        Elf_Ehdr ehdr;
        Elf_Shdr *shdr;
        Elf_Size shdr_size;
        void *base;
        struct stat st;

        /* Make sure obj is OK */
        if (lseek(fd, 0, SEEK_SET) == -1 ||
            _read(fd, &ehdr, sizeof(Elf_Ehdr)) != sizeof(Elf_Ehdr) ||
            !__elf_is_okay__(&ehdr) ||
            _fstat(fd, &st) < 0)
                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 (shdr_size > SIZE_T_MAX) {
                errno = EFBIG;
                return (-1);
        }

        /* mmap section header table */
        base = mmap(NULL, (size_t)shdr_size, PROT_READ, MAP_PRIVATE, fd,
            (off_t)ehdr.e_shoff);
        if (base == MAP_FAILED)
                return (-1);
        shdr = (Elf_Shdr *)base;

        /*
         * 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;
        }

        /*
         * Find the symbol table entry and it's 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; nent > 0 && i < ehdr.e_shnum; i++) {
                if (shdr[i].sh_type != SHT_SYMTAB &&
                    shdr[i].sh_type != SHT_DYNSYM)
                        continue;
                symoff = shdr[i].sh_offset;
                symsize = shdr[i].sh_size;
                stroff = shdr[shdr[i].sh_link].sh_offset;
                strsize = shdr[shdr[i].sh_link].sh_size;

                /*
                 * Skip this section if it or its string table is empty or
                 * extends beyond the end of the file, or if the string
                 * table is too large to map into memory.
                 */
                if (symoff == 0 || symsize == 0 ||
                    symsize > SIZE_MAX - symoff ||
                    symoff + symsize > st.st_size ||
                    stroff == 0 || strsize == 0 ||
                    strsize > SIZE_MAX - stroff ||
                    stroff + strsize > st.st_size) {
                        errno = ENOENT;
                        continue;
                }

                /*
                 * 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).
                 */
                base = mmap(NULL, (size_t)strsize, PROT_READ,
                    MAP_PRIVATE, fd, (off_t)stroff);
                if (base == MAP_FAILED)
                        continue;

                nent = elf_scan_symtab(shdr, ehdr.e_shnum, fd, symoff, symsize,
                    base, strsize, list, nent);

                errsave = errno;
                munmap(base, strsize);
                errno = errsave;
        }
        errsave = errno;
        munmap(shdr, shdr_size);
        errno = errsave;
        return (nent);
}

static int
elf_scan_symtab(Elf_Shdr *shdr, int shnum, int fd, off_t symoff, size_t symsize,
    char *strtab, size_t strsize, struct nlist *list, int nent)
{
        Elf_Sym sbuf[1024];
        Elf_Sym *s;
        char *name;
        struct nlist *p;
        Elf_Ssize cc;
        size_t slen;

        if (lseek(fd, symoff, SEEK_SET) == -1)
                return (-1);
        while (symsize > 0 && nent > 0) {
                cc = MIN(symsize, sizeof(sbuf));
                if (_read(fd, sbuf, cc) != cc)
                        break;
                symsize -= cc;
                for (s = sbuf; cc > 0 && nent > 0; ++s, cc -= sizeof(*s)) {
                        if (s->st_name >= strsize)
                                continue;
                        name = strtab + s->st_name;
                        if (name[0] == '\0')
                                continue;
                        slen = strnlen(name, strsize - s->st_name);
                        for (p = list; nent > 0 && !ISLAST(p); p++) {
                                if (strncmp(name, p->n_un.n_name, slen) == 0 &&
                                    p->n_un.n_name[slen] == '\0') {
                                        elf_sym_to_nlist(p, s, shdr, shnum);
                                        --nent;
                                }
                        }
                }
        }
        return (nent);
}

/*
 * Convert an Elf_Sym into an nlist structure.  This fills in only the
 * n_value and n_type members.
 */
static void
elf_sym_to_nlist(struct nlist *nl, Elf_Sym *s, Elf_Shdr *shdr, int shnum)
{
        nl->n_value = s->st_value;

        switch (s->st_shndx) {
        case SHN_UNDEF:
        case SHN_COMMON:
                nl->n_type = N_UNDF;
                break;
        case SHN_ABS:
                nl->n_type = ELF_ST_TYPE(s->st_info) == STT_FILE ?
                    N_FN : N_ABS;
                break;
        default:
                if (s->st_shndx >= shnum)
                        nl->n_type = N_UNDF;
                else {
                        Elf_Shdr *sh = shdr + s->st_shndx;

                        nl->n_type = sh->sh_type == SHT_PROGBITS ?
                            (sh->sh_flags & SHF_WRITE ? N_DATA : N_TEXT) :
                            (sh->sh_type == SHT_NOBITS ? N_BSS : N_UNDF);
                }
                break;
        }

        if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
            ELF_ST_BIND(s->st_info) == STB_WEAK)
                nl->n_type |= N_EXT;
}