/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright 1996-1998 John D. Polstra.
 * 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.
 *
 * 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/param.h>
#include <sys/mman.h>
#include <sys/stat.h>

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

#include "debug.h"
#include "rtld.h"

static Elf_Ehdr *get_elf_header(int, const char *, const struct stat *,
    Elf_Phdr **phdr);
static int convert_flags(int); /* Elf flags -> mmap flags */

static bool
phdr_in_zero_page(const Elf_Ehdr *hdr)
{
        return (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) <= page_size);
}

/*
 * Map a shared object into memory.  The "fd" argument is a file descriptor,
 * which must be open on the object and positioned at its beginning.
 * The "path" argument is a pathname that is used only for error messages.
 *
 * The return value is a pointer to a newly-allocated Obj_Entry structure
 * for the shared object.  Returns NULL on failure.
 */
Obj_Entry *
map_object(int fd, const char *path, const struct stat *sb, bool ismain)
{
        Obj_Entry *obj;
        Elf_Ehdr *hdr;
        int i;
        Elf_Phdr *phdr;
        Elf_Phdr *phlimit;
        Elf_Phdr **segs;
        int nsegs;
        Elf_Phdr *phdyn;
        Elf_Phdr *phinterp;
        Elf_Phdr *phtls;
        caddr_t mapbase;
        size_t mapsize;
        Elf_Addr base_vaddr;
        Elf_Addr base_vlimit;
        caddr_t base_addr;
        int base_flags;
        Elf_Off data_offset;
        Elf_Addr data_vaddr;
        Elf_Addr data_vlimit;
        caddr_t data_addr;
        int data_prot;
        int data_flags;
        Elf_Addr clear_vaddr;
        caddr_t clear_addr;
        caddr_t clear_page;
        Elf_Addr phdr_vaddr;
        size_t nclear, phsize;
        Elf_Addr bss_vaddr;
        Elf_Addr bss_vlimit;
        caddr_t bss_addr;
        Elf_Word stack_flags;
        Elf_Addr note_start;
        Elf_Addr note_end;
        char *note_map;
        size_t note_map_len;
        Elf_Addr text_end;

        hdr = get_elf_header(fd, path, sb, &phdr);
        if (hdr == NULL)
                return (NULL);

        /*
         * Scan the program header entries, and save key information.
         * We expect that the loadable segments are ordered by load address.
         */
        phsize = hdr->e_phnum * sizeof(phdr[0]);
        phlimit = phdr + hdr->e_phnum;
        nsegs = -1;
        phdyn = phinterp = phtls = NULL;
        phdr_vaddr = 0;
        note_start = 0;
        note_end = 0;
        note_map = NULL;
        note_map_len = 0;
        segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
        stack_flags = PF_X | PF_R | PF_W;
        text_end = 0;
        while (phdr < phlimit) {
                switch (phdr->p_type) {
                case PT_INTERP:
                        phinterp = phdr;
                        break;

                case PT_LOAD:
                        segs[++nsegs] = phdr;
                        if ((segs[nsegs]->p_align & (page_size - 1)) != 0) {
                                _rtld_error(
                                    "%s: PT_LOAD segment %d not page-aligned",
                                    path, nsegs);
                                goto error;
                        }
                        if ((segs[nsegs]->p_flags & PF_X) == PF_X) {
                                text_end = MAX(text_end,
                                    rtld_round_page(segs[nsegs]->p_vaddr +
                                    segs[nsegs]->p_memsz));
                        }
                        break;

                case PT_PHDR:
                        phdr_vaddr = phdr->p_vaddr;
                        phsize = phdr->p_memsz;
                        break;

                case PT_DYNAMIC:
                        phdyn = phdr;
                        break;

                case PT_TLS:
                        phtls = phdr;
                        break;

                case PT_GNU_STACK:
                        stack_flags = phdr->p_flags;
                        break;

                case PT_NOTE:
                        if (phdr->p_offset > page_size ||
                            phdr->p_offset + phdr->p_filesz > page_size) {
                                note_map_len = rtld_round_page(phdr->p_offset +
                                    phdr->p_filesz) -
                                    rtld_trunc_page(phdr->p_offset);
                                note_map = mmap(NULL, note_map_len, PROT_READ,
                                    MAP_PRIVATE, fd,
                                    rtld_trunc_page(phdr->p_offset));
                                if (note_map == MAP_FAILED) {
                                        _rtld_error(
                                            "%s: error mapping PT_NOTE (%d)",
                                            path, errno);
                                        goto error;
                                }
                                note_start = (Elf_Addr)(note_map +
                                    phdr->p_offset -
                                    rtld_trunc_page(phdr->p_offset));
                        } else {
                                note_start = (Elf_Addr)(char *)hdr +
                                    phdr->p_offset;
                        }
                        note_end = note_start + phdr->p_filesz;
                        break;
                }

                ++phdr;
        }
        if (phdyn == NULL) {
                _rtld_error("%s: object is not dynamically-linked", path);
                goto error;
        }

        if (nsegs < 0) {
                _rtld_error("%s: too few PT_LOAD segments", path);
                goto error;
        }

        /*
         * Map the entire address space of the object, to stake out our
         * contiguous region, and to establish the base address for relocation.
         */
        base_vaddr = rtld_trunc_page(segs[0]->p_vaddr);
        base_vlimit = rtld_round_page(segs[nsegs]->p_vaddr +
            segs[nsegs]->p_memsz);
        mapsize = base_vlimit - base_vaddr;
        base_addr = (caddr_t)base_vaddr;
        base_flags = MAP_GUARD;
        if (npagesizes > 1 &&  rtld_round_page(segs[0]->p_filesz) >=
            pagesizes[1])
                base_flags |= MAP_ALIGNED_SUPER;
        if (base_vaddr != 0)
                base_flags |= MAP_FIXED | MAP_EXCL;

        mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0);
        if (mapbase == MAP_FAILED) {
                _rtld_error("%s: mmap of entire address space failed: %s",
                    path, rtld_strerror(errno));
                goto error;
        }
        if (base_addr != NULL && mapbase != base_addr) {
                _rtld_error(
                    "%s: mmap returned wrong address: wanted %p, got %p",
                    path, base_addr, mapbase);
                goto error1;
        }

        for (i = 0; i <= nsegs; i++) {
                /* Overlay the segment onto the proper region. */
                data_offset = rtld_trunc_page(segs[i]->p_offset);
                data_vaddr = rtld_trunc_page(segs[i]->p_vaddr);
                data_vlimit = rtld_round_page(segs[i]->p_vaddr +
                    segs[i]->p_filesz);
                data_addr = mapbase + (data_vaddr - base_vaddr);
                data_prot = convert_prot(segs[i]->p_flags);
                data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
                if (data_vlimit != data_vaddr && mmap(data_addr,
                    data_vlimit - data_vaddr, data_prot, data_flags |
                    MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) {
                        _rtld_error("%s: mmap of data failed: %s",
                            path, rtld_strerror(errno));
                        goto error1;
                }

                /* Do BSS setup */
                if (segs[i]->p_filesz != segs[i]->p_memsz) {
                        /* Clear any BSS in the last page of the segment. */
                        clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
                        clear_addr = mapbase + (clear_vaddr - base_vaddr);
                        clear_page = mapbase + (rtld_trunc_page(clear_vaddr) -
                            base_vaddr);

                        if ((nclear = data_vlimit - clear_vaddr) > 0) {
                                /*
                                 * Make sure the end of the segment is
                                 * writable.
                                 */
                                if ((data_prot & PROT_WRITE) == 0 &&
                                    mprotect(clear_page, page_size,
                                    data_prot | PROT_WRITE) == -1) {
                                        _rtld_error("%s: mprotect failed: %s",
                                            path, rtld_strerror(errno));
                                        goto error1;
                                }

                                memset(clear_addr, 0, nclear);

                                /* Reset the data protection back */
                                if ((data_prot & PROT_WRITE) == 0)
                                        mprotect(clear_page, page_size,
                                            data_prot);
                        }

                        /* Overlay the BSS segment onto the proper region. */
                        bss_vaddr = data_vlimit;
                        bss_vlimit = rtld_round_page(segs[i]->p_vaddr +
                            segs[i]->p_memsz);
                        bss_addr = mapbase + (bss_vaddr - base_vaddr);
                        if (bss_vlimit > bss_vaddr) {
                                /* There is something to do */
                                if (mmap(bss_addr, bss_vlimit - bss_vaddr,
                                    data_prot, data_flags | MAP_ANON, -1,
                                    0) == MAP_FAILED) {
                                        _rtld_error(
                                            "%s: mmap of bss failed: %s",
                                            path, rtld_strerror(errno));
                                        goto error1;
                                }
                        }
                }

                if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
                    data_vlimit - data_vaddr + data_offset >=
                    hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr)) {
                        phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
                }
        }

        obj = obj_new();
        if (sb != NULL) {
                obj->dev = sb->st_dev;
                obj->ino = sb->st_ino;
        }
        obj->mapbase = mapbase;
        obj->mapsize = mapsize;
        obj->vaddrbase = base_vaddr;
        obj->relocbase = mapbase - base_vaddr;
        obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr);
        if (hdr->e_entry != 0)
                obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry);
        if (phdr_vaddr != 0) {
                obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr);
        } else {
                obj->phdr = malloc(phsize);
                if (obj->phdr == NULL) {
                        obj_free(obj);
                        _rtld_error("%s: cannot allocate program header",
                            path);
                        goto error1;
                }
                memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff,
                    phsize);
                obj->phdr_alloc = true;
        }
        obj->phnum = phsize / sizeof(*phdr);
        if (phinterp != NULL)
                obj->interp = (const char *)(obj->relocbase +
                    phinterp->p_vaddr);
        if (phtls != NULL) {
                if (ismain)
                        obj->tlsindex = 1;
                else {
                        tls_dtv_generation++;
                        obj->tlsindex = ++tls_max_index;
                }
                obj->tlssize = phtls->p_memsz;
                obj->tlsalign = phtls->p_align;
                obj->tlspoffset = phtls->p_offset;
                obj->tlsinitsize = phtls->p_filesz;
                obj->tlsinit = obj->relocbase + phtls->p_vaddr;
        }
        obj->stack_flags = stack_flags;
        if (note_start < note_end)
                digest_notes(obj, note_start, note_end);
        if (note_map != NULL)
                munmap(note_map, note_map_len);
        munmap(hdr, page_size);
        return (obj);

error1:
        munmap(mapbase, mapsize);
error:
        if (note_map != NULL && note_map != MAP_FAILED)
                munmap(note_map, note_map_len);
        if (!phdr_in_zero_page(hdr))
                munmap(phdr, hdr->e_phnum * sizeof(phdr[0]));
        munmap(hdr, page_size);
        return (NULL);
}

bool
check_elf_headers(const Elf_Ehdr *hdr, const char *path)
{
        if (!IS_ELF(*hdr)) {
                _rtld_error("%s: invalid file format", path);
                return (false);
        }
        if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
            hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
                _rtld_error("%s: unsupported file layout", path);
                return (false);
        }
        if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
            hdr->e_version != EV_CURRENT) {
                _rtld_error("%s: unsupported file version", path);
                return (false);
        }
        if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
                _rtld_error("%s: unsupported file type", path);
                return (false);
        }
        if (hdr->e_machine != ELF_TARG_MACH) {
                _rtld_error("%s: unsupported machine", path);
                return (false);
        }
        if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
                _rtld_error(
            "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)",
                    path);
                return (false);
        }
        return (true);
}

static Elf_Ehdr *
get_elf_header(int fd, const char *path, const struct stat *sbp,
    Elf_Phdr **phdr_p)
{
        Elf_Ehdr *hdr;
        Elf_Phdr *phdr;

        /* Make sure file has enough data for the ELF header */
        if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) {
                _rtld_error("%s: invalid file format", path);
                return (NULL);
        }

        hdr = mmap(NULL, page_size, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ,
            fd, 0);
        if (hdr == MAP_FAILED) {
                _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
                return (NULL);
        }

        /* Make sure the file is valid */
        if (!check_elf_headers(hdr, path))
                goto error;

        /*
         * We rely on the program header being in the first page.  This is
         * not strictly required by the ABI specification, but it seems to
         * always true in practice.  And, it simplifies things considerably.
         */
        if (phdr_in_zero_page(hdr)) {
                phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff);
        } else {
                phdr = mmap(NULL, hdr->e_phnum * sizeof(phdr[0]), PROT_READ,
                    MAP_PRIVATE | MAP_PREFAULT_READ, fd, hdr->e_phoff);
                if (phdr == MAP_FAILED) {
                        _rtld_error("%s: error mapping phdr: %s", path,
                            rtld_strerror(errno));
                        goto error;
                }
        }
        *phdr_p = phdr;
        return (hdr);

error:
        munmap(hdr, page_size);
        return (NULL);
}

void
obj_free(Obj_Entry *obj)
{
        Objlist_Entry *elm;

        if (obj->tls_static)
                free_tls_offset(obj);
        while (obj->needed != NULL) {
                Needed_Entry *needed = obj->needed;

                obj->needed = needed->next;
                free(needed);
        }
        while (!STAILQ_EMPTY(&obj->names)) {
                Name_Entry *entry = STAILQ_FIRST(&obj->names);

                STAILQ_REMOVE_HEAD(&obj->names, link);
                free(entry);
        }
        while (!STAILQ_EMPTY(&obj->dldags)) {
                elm = STAILQ_FIRST(&obj->dldags);
                STAILQ_REMOVE_HEAD(&obj->dldags, link);
                free(elm);
        }
        while (!STAILQ_EMPTY(&obj->dagmembers)) {
                elm = STAILQ_FIRST(&obj->dagmembers);
                STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
                free(elm);
        }
        if (obj->vertab)
                free(obj->vertab);
        if (obj->origin_path)
                free(obj->origin_path);
        if (obj->z_origin)
                free(__DECONST(void *, obj->rpath));
        if (obj->priv)
                free(obj->priv);
        if (obj->path)
                free(obj->path);
        if (obj->phdr_alloc)
                free(__DECONST(void *, obj->phdr));
        free(obj);
}

Obj_Entry *
obj_new(void)
{
        Obj_Entry *obj;

        obj = CNEW(Obj_Entry);
        STAILQ_INIT(&obj->dldags);
        STAILQ_INIT(&obj->dagmembers);
        STAILQ_INIT(&obj->names);
        return (obj);
}

/*
 * Given a set of ELF protection flags, return the corresponding protection
 * flags for MMAP.
 */
int
convert_prot(int elfflags)
{
        int prot = 0;

        if ((elfflags & PF_R) != 0)
                prot |= PROT_READ;
        if ((elfflags & PF_W) != 0)
                prot |= PROT_WRITE;
        if ((elfflags & PF_X) != 0)
                prot |= PROT_EXEC;
        return (prot);
}

static int
convert_flags(int elfflags)
{
        int flags = MAP_PRIVATE; /* All mappings are private */

        /*
         * Readonly mappings are marked "MAP_NOCORE", because they can be
         * reconstructed by a debugger.
         */
        if ((elfflags & PF_W) == 0)
                flags |= MAP_NOCORE;
        return (flags);
}