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NetBSD/libexec/ld.elf_so/map_object.c

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/* $NetBSD: map_object.c,v 1.2 1996/12/17 03:42:44 jonathan Exp $ */
/*
* Copyright 1996 John D. Polstra.
* Copyright 1996 Matt Thomas <matt@3am-software.com>
* 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 <errno.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include "rtld.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)))
static int protflags(int); /* Elf flags -> mmap protection */
/*
* 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)
{
Obj_Entry *obj;
union {
Elf_Ehdr hdr;
char buf[PAGESIZE];
} u;
int nbytes;
Elf_Phdr *phdr;
Elf_Phdr *phlimit;
Elf_Phdr *segs[2];
int nsegs;
Elf_Phdr *phdyn;
Elf_Phdr *phphdr;
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;
#ifdef RTLD_LOADER
Elf_Addr clear_vaddr;
caddr_t clear_addr;
size_t nclear;
Elf_Addr bss_vaddr;
Elf_Addr bss_vlimit;
caddr_t bss_addr;
#endif
if ((nbytes = read(fd, u.buf, PAGESIZE)) == -1) {
_rtld_error("%s: read error: %s", path, xstrerror(errno));
return NULL;
}
/* Make sure the file is valid */
if (nbytes < sizeof(Elf_Ehdr)
|| memcmp(Elf_e_ident, u.hdr.e_ident, Elf_e_siz) != 0) {
_rtld_error("%s: unrecognized file format", path);
return NULL;
}
/* Elf_e_ident includes class */
if (u.hdr.e_ident[Elf_ei_version] != Elf_ev_current
|| u.hdr.e_version != Elf_ev_current
|| u.hdr.e_ident[Elf_ei_data] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) {
_rtld_error("%s: Unsupported file version", path);
return NULL;
}
if (u.hdr.e_type != Elf_et_exec && u.hdr.e_type != Elf_et_dyn) {
_rtld_error("%s: Unsupported file type", path);
return NULL;
}
switch (u.hdr.e_machine) {
ELFDEFNNAME(MACHDEP_ID_CASES)
default:
_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.
*/
assert(u.hdr.e_phentsize == sizeof(Elf_Phdr));
assert(u.hdr.e_phoff + u.hdr.e_phnum*sizeof(Elf_Phdr) <= PAGESIZE);
assert(u.hdr.e_phoff + u.hdr.e_phnum*sizeof(Elf_Phdr) <= nbytes);
/*
* 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 *) (u.buf + u.hdr.e_phoff);
phlimit = phdr + u.hdr.e_phnum;
nsegs = 0;
phdyn = NULL;
phphdr = NULL;
while(phdr < phlimit) {
switch(phdr->p_type) {
case Elf_pt_load:
#ifdef __mips__
/* NetBSD/pmax 1.1 elf toolchain peculiarity */
if (nsegs >= 2) {
_rtld_error("%s: too many sections\n", path);
return NULL;
}
#endif
assert(nsegs < 2);
segs[nsegs] = phdr;
++nsegs;
break;
case Elf_pt_phdr:
phphdr = phdr;
break;
case Elf_pt_dynamic:
phdyn = phdr;
break;
}
++phdr;
}
if (phdyn == NULL) {
_rtld_error("%s: not dynamically-linked", path);
return NULL;
}
assert(nsegs == 2);
#ifdef __i386__
assert(segs[0]->p_align <= PAGESIZE);
assert(segs[1]->p_align <= PAGESIZE);
#endif
/*
* Map the entire address space of the object, to stake out our
* contiguous region, and to establish the base address for relocation.
*/
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);
mapsize = base_vlimit - base_vaddr;
#ifdef RTLD_LOADER
base_addr = u.hdr.e_type == Elf_et_exec ? (caddr_t) base_vaddr : NULL;
#else
base_addr = NULL;
#endif
mapbase = mmap(base_addr, mapsize, protflags(segs[0]->p_flags),
MAP_PRIVATE, fd, base_offset);
if (mapbase == (caddr_t) -1) {
_rtld_error("mmap of entire address space failed: %s", xstrerror(errno));
return NULL;
}
if (base_addr != NULL && mapbase != base_addr) {
_rtld_error("mmap returned wrong address: wanted %p, got %p", base_addr,
mapbase);
munmap(mapbase, mapsize);
return NULL;
}
/* Overlay the data segment onto the proper region. */
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_addr = mapbase + (data_vaddr - base_vaddr);
if (mmap(data_addr, data_vlimit - data_vaddr, protflags(segs[1]->p_flags),
MAP_PRIVATE|MAP_FIXED, fd, data_offset) == (caddr_t) -1) {
_rtld_error("mmap of data failed: %s", xstrerror(errno));
return NULL;
}
#ifdef RTLD_LOADER
/* Clear any BSS in the last page of the data segment. */
clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz;
clear_addr = mapbase + (clear_vaddr - base_vaddr);
if ((nclear = data_vlimit - clear_vaddr) > 0)
memset(clear_addr, 0, nclear);
/* Overlay the BSS segment onto the proper region. */
bss_vaddr = data_vlimit;
bss_vlimit = round_up(segs[1]->p_vaddr + segs[1]->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, protflags(segs[1]->p_flags),
MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) {
_rtld_error("mmap of bss failed: %s", xstrerror(errno));
return NULL;
}
}
#endif
obj = CNEW(Obj_Entry);
obj->mapbase = mapbase;
obj->mapsize = mapsize;
obj->textsize = round_up(segs[0]->p_vaddr + segs[0]->p_memsz) - base_vaddr;
obj->vaddrbase = base_vaddr;
obj->relocbase = mapbase - base_vaddr;
obj->dynamic = (Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
if (u.hdr.e_entry != 0)
obj->entry = (caddr_t) (obj->relocbase + u.hdr.e_entry);
if (phphdr != NULL) {
obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr);
obj->phsize = phphdr->p_memsz;
}
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 & Elf_pf_r) prot |= PROT_READ;
#ifdef RTLD_LOADER
if (elfflags & Elf_pf_w) prot |= PROT_WRITE;
#endif
if (elfflags & Elf_pf_x) prot |= PROT_EXEC;
return prot;
}
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