FreeBSD-5.3/libexec/rtld-elf/map_object.c
/*-
* 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.
*
* $FreeBSD: src/libexec/rtld-elf/map_object.c,v 1.15 2004/08/03 08:50:58 dfr Exp $
*/
#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 *);
static int convert_prot(int); /* Elf flags -> mmap protection */
static int convert_flags(int); /* Elf flags -> mmap flags */
/*
* 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)
{
Obj_Entry *obj;
Elf_Ehdr *hdr;
int i;
Elf_Phdr *phdr;
Elf_Phdr *phlimit;
Elf_Phdr **segs;
int nsegs;
Elf_Phdr *phdyn;
Elf_Phdr *phphdr;
Elf_Phdr *phinterp;
Elf_Phdr *phtls;
caddr_t mapbase;
size_t mapsize;
Elf_Off base_offset;
Elf_Addr base_vaddr;
Elf_Addr base_vlimit;
caddr_t base_addr;
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;
size_t nclear;
Elf_Addr bss_vaddr;
Elf_Addr bss_vlimit;
caddr_t bss_addr;
hdr = get_elf_header(fd, path);
if (hdr == NULL)
return (NULL);
/*
* 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 *) ((char *)hdr + hdr->e_phoff);
phlimit = phdr + hdr->e_phnum;
nsegs = -1;
phdyn = phphdr = phinterp = phtls = NULL;
segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
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) {
_rtld_error("%s: PT_LOAD segment %d not page-aligned",
path, nsegs);
return NULL;
}
break;
case PT_PHDR:
phphdr = phdr;
break;
case PT_DYNAMIC:
phdyn = phdr;
break;
case PT_TLS:
phtls = phdr;
break;
}
++phdr;
}
if (phdyn == NULL) {
_rtld_error("%s: object is not dynamically-linked", path);
return NULL;
}
if (nsegs < 0) {
_rtld_error("%s: too few PT_LOAD segments", path);
return NULL;
}
/*
* Map the entire address space of the object, to stake out our
* contiguous region, and to establish the base address for relocation.
*/
base_offset = trunc_page(segs[0]->p_offset);
base_vaddr = trunc_page(segs[0]->p_vaddr);
base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
mapsize = base_vlimit - base_vaddr;
base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL;
mapbase = mmap(base_addr, mapsize, convert_prot(segs[0]->p_flags),
convert_flags(segs[0]->p_flags), fd, base_offset);
if (mapbase == (caddr_t) -1) {
_rtld_error("%s: mmap of entire address space failed: %s",
path, strerror(errno));
return NULL;
}
if (base_addr != NULL && mapbase != base_addr) {
_rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
path, base_addr, mapbase);
munmap(mapbase, mapsize);
return NULL;
}
for (i = 0; i <= nsegs; i++) {
/* Overlay the segment onto the proper region. */
data_offset = trunc_page(segs[i]->p_offset);
data_vaddr = trunc_page(segs[i]->p_vaddr);
data_vlimit = 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;
/* Do not call mmap on the first segment - this is redundant */
if (i && mmap(data_addr, data_vlimit - data_vaddr, data_prot,
data_flags, fd, data_offset) == (caddr_t) -1) {
_rtld_error("%s: mmap of data failed: %s", path, strerror(errno));
return NULL;
}
/* 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 + (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 &&
-1 == mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
_rtld_error("%s: mprotect failed: %s", path,
strerror(errno));
return NULL;
}
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 = 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,
MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) {
_rtld_error("%s: mmap of bss failed: %s", path,
strerror(errno));
return NULL;
}
}
}
obj = obj_new();
if (sb != NULL) {
obj->dev = sb->st_dev;
obj->ino = sb->st_ino;
}
obj->mapbase = mapbase;
obj->mapsize = mapsize;
obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
base_vaddr;
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 (phphdr != NULL) {
obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr);
obj->phsize = phphdr->p_memsz;
}
if (phinterp != NULL)
obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
if (phtls != NULL) {
tls_dtv_generation++;
obj->tlsindex = ++tls_max_index;
obj->tlssize = phtls->p_memsz;
obj->tlsalign = phtls->p_align;
obj->tlsinitsize = phtls->p_filesz;
obj->tlsinit = mapbase + phtls->p_vaddr;
}
return obj;
}
static Elf_Ehdr *
get_elf_header (int fd, const char *path)
{
static union {
Elf_Ehdr hdr;
char buf[PAGE_SIZE];
} u;
ssize_t nbytes;
if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) {
_rtld_error("%s: read error: %s", path, strerror(errno));
return NULL;
}
/* Make sure the file is valid */
if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) {
_rtld_error("%s: invalid file format", path);
return NULL;
}
if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS
|| u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) {
_rtld_error("%s: unsupported file layout", path);
return NULL;
}
if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT
|| u.hdr.e_version != EV_CURRENT) {
_rtld_error("%s: unsupported file version", path);
return NULL;
}
if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) {
_rtld_error("%s: unsupported file type", path);
return NULL;
}
if (u.hdr.e_machine != ELF_TARG_MACH) {
_rtld_error("%s: unsupported machine", path);
return NULL;
}
/*
* 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 (u.hdr.e_phentsize != sizeof(Elf_Phdr)) {
_rtld_error(
"%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
return NULL;
}
if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) {
_rtld_error("%s: program header too large", path);
return NULL;
}
return (&u.hdr);
}
void
obj_free(Obj_Entry *obj)
{
Objlist_Entry *elm;
free(obj->path);
while (obj->needed != NULL) {
Needed_Entry *needed = obj->needed;
obj->needed = needed->next;
free(needed);
}
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);
}
free(obj->origin_path);
free(obj->priv);
free(obj);
}
Obj_Entry *
obj_new(void)
{
Obj_Entry *obj;
obj = CNEW(Obj_Entry);
STAILQ_INIT(&obj->dldags);
STAILQ_INIT(&obj->dagmembers);
return obj;
}
/*
* Given a set of ELF protection flags, return the corresponding protection
* flags for MMAP.
*/
static int
convert_prot(int elfflags)
{
int prot = 0;
if (elfflags & PF_R)
prot |= PROT_READ;
if (elfflags & PF_W)
prot |= PROT_WRITE;
if (elfflags & PF_X)
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))
flags |= MAP_NOCORE;
return flags;
}