kernel: some boottime sanitychecks

[minix.git] / libexec / ld.elf_so / map_object.c

/*      $NetBSD: map_object.c,v 1.41 2010/10/16 10:27:07 skrll Exp $     */

/*
 * Copyright 1996 John D. Polstra.
 * Copyright 1996 Matt Thomas <matt@3am-software.com>
 * Copyright 2002 Charles M. Hannum <root@ihack.net>
 * 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 John Polstra.
 * 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
__RCSID("$NetBSD: map_object.c,v 1.41 2010/10/16 10:27:07 skrll Exp $");
#endif /* not lint */

#include <errno.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mman.h>

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

#ifdef __minix
#define munmap minix_munmap
#endif

#define MINIXVERBOSE 0

static int protflags(int);      /* Elf flags -> mmap protection */

#define EA_UNDEF                (~(Elf_Addr)0)

static void Pread(void *addr, size_t size, int fd, off_t off)
{
        int s;
        if((s=pread(fd,addr, size, off)) < 0) {
                _rtld_error("pread failed");
                exit(1);
        }

#if MINIXVERBOSE
        fprintf(stderr, "read 0x%lx bytes from offset 0x%lx to addr 0x%lx\n", size, off, addr);
#endif
}

/*
 * Map a shared object into memory.  The argument is a file descriptor,
 * which must be open on the object and positioned at its beginning.
 *
 * The return value is a pointer to a newly-allocated Obj_Entry structure
 * for the shared object.  Returns NULL on failure.
 */
Obj_Entry *
_rtld_map_object(const char *path, int fd, const struct stat *sb)
{
        Obj_Entry       *obj;
        Elf_Ehdr        *ehdr;
        Elf_Phdr        *phdr;
        size_t           phsize;
        Elf_Phdr        *phlimit;
        Elf_Phdr        *segs[2];
        int              nsegs;
        caddr_t          mapbase = MAP_FAILED;
        size_t           mapsize = 0;
        size_t           bsssize = 0;
        int              mapflags;
        Elf_Off          base_offset;
#ifdef MAP_ALIGNED
        Elf_Addr         base_alignment;
#endif
        Elf_Addr         base_vaddr;
        Elf_Addr         base_vlimit;
        Elf_Addr         text_vlimit;
        int              text_flags;
        caddr_t          base_addr;
        Elf_Off          data_offset;
        Elf_Addr         data_vaddr;
        Elf_Addr         data_vlimit;
        int              data_flags;
        caddr_t          data_addr;
        Elf_Addr         phdr_vaddr;
        size_t           phdr_memsz;
        caddr_t          gap_addr;
        size_t           gap_size;
        int i;
#ifdef RTLD_LOADER
        Elf_Addr         clear_vaddr;
        caddr_t          clear_addr;
        size_t           nclear;
#endif

        if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) {
                _rtld_error("%s: unrecognized file format1", path);
                return NULL;
        }

        obj = _rtld_obj_new();
        obj->path = xstrdup(path);
        obj->pathlen = strlen(path);
        if (sb != NULL) {
                obj->dev = sb->st_dev;
                obj->ino = sb->st_ino;
        }

#ifdef __minix
        ehdr = minix_mmap(NULL, _rtld_pagesz, PROT_READ|PROT_WRITE,
                MAP_PREALLOC|MAP_ANON, -1, (off_t)0);
        Pread(ehdr, _rtld_pagesz, fd, 0);
#if MINIXVERBOSE
        fprintf(stderr, "minix mmap for header: 0x%lx\n", ehdr);
#endif
#else
        ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd,
            (off_t)0);
#endif
        obj->ehdr = ehdr;
        if (ehdr == MAP_FAILED) {
                _rtld_error("%s: read error: %s", path, xstrerror(errno));
                goto bad;
        }
        /* Make sure the file is valid */
        if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 ||
            ehdr->e_ident[EI_CLASS] != ELFCLASS) {
                _rtld_error("%s: unrecognized file format2 [%x != %x]", path,
                    ehdr->e_ident[EI_CLASS], ELFCLASS);
                goto bad;
        }
        /* Elf_e_ident includes class */
        if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
            ehdr->e_version != EV_CURRENT ||
            ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) {
                _rtld_error("%s: unsupported file version", path);
                goto bad;
        }
        if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
                _rtld_error("%s: unsupported file type", path);
                goto bad;
        }
        switch (ehdr->e_machine) {
                ELFDEFNNAME(MACHDEP_ID_CASES)
        default:
                _rtld_error("%s: unsupported machine", path);
                goto bad;
        }

        /*
         * 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.
         */
        assert(ehdr->e_phentsize == sizeof(Elf_Phdr));
        assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <=
            _rtld_pagesz);

        /*
         * Scan the program header entries, and save key information.
         *
         * We rely on there being exactly two load segments, text and data,
         * in that order.
         */
        phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff);
        phsize = ehdr->e_phnum * sizeof(phdr[0]);
        obj->phdr = NULL;
        phdr_vaddr = EA_UNDEF;
        phdr_memsz = 0;
        phlimit = phdr + ehdr->e_phnum;
        nsegs = 0;
        while (phdr < phlimit) {
                switch (phdr->p_type) {
                case PT_INTERP:
                        obj->interp = (void *)(uintptr_t)phdr->p_vaddr;
                        dbg(("%s: PT_INTERP %p", obj->path, obj->interp));
                        break;

                case PT_LOAD:
                        if (nsegs < 2)
                                segs[nsegs] = phdr;
                        ++nsegs;
                        dbg(("%s: PT_LOAD %p", obj->path, phdr));
                        break;

                case PT_PHDR:
                        phdr_vaddr = phdr->p_vaddr;
                        phdr_memsz = phdr->p_memsz;
                        dbg(("%s: PT_PHDR %p phsize %zu", obj->path,
                            (void *)(uintptr_t)phdr_vaddr, phdr_memsz));
                        break;
                
                case PT_DYNAMIC:
                        obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr;
                        dbg(("%s: PT_DYNAMIC %p", obj->path, obj->dynamic));
                        break;
                }

                ++phdr;
        }
        phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff);
        obj->entry = (void *)(uintptr_t)ehdr->e_entry;
        if (!obj->dynamic) {
                _rtld_error("%s: not dynamically linked", path);
                goto bad;
        }
        if (nsegs != 2) {
                _rtld_error("%s: wrong number of segments (%d != 2)", path,
                    nsegs);
                goto bad;
        }

        /*
         * Map the entire address space of the object as a file
         * region to stake out our contiguous region and establish a
         * base for relocation.  We use a file mapping so that
         * the kernel will give us whatever alignment is appropriate
         * for the platform we're running on.
         *
         * We map it using the text protection, map the data segment
         * into the right place, then map an anon segment for the bss
         * and unmap the gaps left by padding to alignment.
         */

#ifdef MAP_ALIGNED
        base_alignment = segs[0]->p_align;
#endif
        base_offset = round_down(segs[0]->p_offset);
        base_vaddr = round_down(segs[0]->p_vaddr);
        base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz);
        text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz);
        text_flags = protflags(segs[0]->p_flags);
        data_offset = round_down(segs[1]->p_offset);
        data_vaddr = round_down(segs[1]->p_vaddr);
        data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz);
        data_flags = protflags(segs[1]->p_flags);
#ifdef RTLD_LOADER
        clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz;
#endif

        obj->textsize = text_vlimit - base_vaddr;
        obj->vaddrbase = base_vaddr;
        obj->isdynamic = ehdr->e_type == ET_DYN;

        obj->phdr_loaded = false;
        for (i = 0; i < nsegs; i++) {
                if (phdr_vaddr != EA_UNDEF &&
                    segs[i]->p_vaddr <= phdr_vaddr &&
                    segs[i]->p_memsz >= phdr_memsz) {
                        obj->phdr_loaded = true;
                        break;
                }
                if (segs[i]->p_offset <= ehdr->e_phoff &&
                    segs[i]->p_memsz >= phsize) {
                        phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff;
                        phdr_memsz = phsize;
                        obj->phdr_loaded = true;
                        break;
                }
        }
        if (obj->phdr_loaded) {
                obj->phdr = (void *)(uintptr_t)phdr_vaddr;
                obj->phsize = phdr_memsz;
        } else {
                Elf_Phdr *buf;
                buf = xmalloc(phsize);
                if (buf == NULL) {
                        _rtld_error("%s: cannot allocate program header", path);
                        goto bad;
                }
                memcpy(buf, phdr, phsize);
                obj->phdr = buf;
                obj->phsize = phsize;
        }
        dbg(("%s: phdr %p phsize %zu (%s)", obj->path, obj->phdr, obj->phsize,
             obj->phdr_loaded ? "loaded" : "allocated"));

        /* Unmap header if it overlaps the first load section. */
        if (base_offset < _rtld_pagesz) {
                munmap(ehdr, _rtld_pagesz);
                obj->ehdr = MAP_FAILED;
        }

        /*
         * Calculate log2 of the base section alignment.
         */
        mapflags = 0;
#ifdef MAP_ALIGNED
        if (base_alignment > _rtld_pagesz) {
                unsigned int log2 = 0;
                for (; base_alignment > 1; base_alignment >>= 1)
                        log2++;
                mapflags = MAP_ALIGNED(log2);
        }
#endif

#ifdef RTLD_LOADER
        base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr;
#else
        base_addr = NULL;
#endif
        mapsize = base_vlimit - base_vaddr;

#ifndef __minix
        mapbase = mmap(base_addr, mapsize, text_flags,
            mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset);
#else
        mapbase = minix_mmap(base_addr, mapsize, PROT_READ|PROT_WRITE,
            MAP_ANON | MAP_PREALLOC, -1, 0);
#if MINIXVERBOSE
        fprintf(stderr, "minix mmap for whole block: 0x%lx-0x%lx\n", mapbase, mapbase+mapsize);
#endif
        Pread(mapbase, obj->textsize, fd, 0);
#endif
        if (mapbase == MAP_FAILED) {
                _rtld_error("mmap of entire address space failed: %s",
                    xstrerror(errno));
                goto bad;
        }

        /* Overlay the data segment onto the proper region. */
        data_addr = mapbase + (data_vaddr - base_vaddr);
#ifdef __minix
        Pread(data_addr, data_vlimit - data_vaddr, fd, data_offset);
#else
        if (mmap(data_addr, data_vlimit - data_vaddr, data_flags,
            MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) ==
            MAP_FAILED) {
                _rtld_error("mmap of data failed: %s", xstrerror(errno));
                goto bad;
        }
#endif

#ifndef __minix
        bsssize= base_vlimit - data_vlimit;
   if(bsssize > 0) {
        /* Overlay the bss segment onto the proper region. */
        if (mmap(mapbase + data_vlimit - base_vaddr, bsssize,
            data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) ==
            MAP_FAILED) {
                _rtld_error("mmap of bss (at 0x%lx, 0x%lx bytes) failed: %s",
                        mapbase + data_vlimit - base_vaddr, bsssize, xstrerror(errno));
                goto bad;
        }
    }

        /* Unmap the gap between the text and data. */
        gap_addr = mapbase + round_up(text_vlimit - base_vaddr);
        gap_size = data_addr - gap_addr;

        if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) {
                _rtld_error("mprotect of text -> data gap failed: %s",
                    xstrerror(errno));
                goto bad;
        }
#endif

#ifdef RTLD_LOADER
        /* Clear any BSS in the last page of the data segment. */
        clear_addr = mapbase + (clear_vaddr - base_vaddr);
        if ((nclear = data_vlimit - clear_vaddr) > 0)
                memset(clear_addr, 0, nclear);

        /* Non-file portion of BSS mapped above. */
#endif

        obj->mapbase = mapbase;
        obj->mapsize = mapsize;
        obj->relocbase = mapbase - base_vaddr;

        if (obj->dynamic)
                obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic);
        if (obj->entry)
                obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry);
        if (obj->interp)
                obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp);
        if (obj->phdr_loaded)
                obj->phdr =  (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr);

        return obj;

bad:
        if (obj->ehdr != MAP_FAILED)
                munmap(obj->ehdr, _rtld_pagesz);
        if (mapbase != MAP_FAILED)
                munmap(mapbase, mapsize);
        _rtld_obj_free(obj);
        return NULL;
}

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

        xfree(obj->path);
        while (obj->needed != NULL) {
                Needed_Entry *needed = obj->needed;
                obj->needed = needed->next;
                xfree(needed);
        }
        while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) {
                SIMPLEQ_REMOVE_HEAD(&obj->dldags, link);
                xfree(elm);
        }
        while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) {
                SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link);
                xfree(elm);
        }
        if (!obj->phdr_loaded)
                xfree((void *)(uintptr_t)obj->phdr);
        xfree(obj);
#ifdef COMBRELOC
        _rtld_combreloc_reset(obj);
#endif
}

Obj_Entry *
_rtld_obj_new(void)
{
        Obj_Entry *obj;

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

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

        if (elfflags & PF_R)
                prot |= PROT_READ;
#ifdef RTLD_LOADER
        if (elfflags & PF_W)
                prot |= PROT_WRITE;
#endif
        if (elfflags & PF_X)
                prot |= PROT_EXEC;
        return prot;
}