minix/libexec/ld.elf_so/map_object.c
Ben Gras 6a6b7b5769 ld.so: be more mmap()-behaviour-independent
. if the layout of virtual address regions as returned
	  by mmap() without a location hint changes, ld.so could
	  trip itself up (under minix). this change allocates
	  the full size it needs for every object that's loaded
	  so that if that succeeds, it's sure there's virtual address
	  space for the whole thing no matter what other bits happen
	  to be there already.

	. this fix exposed a bug in the test; at atexit() execution
	  time the loaded object is unmapped, so that part of the
	  test is removed.
2012-06-25 14:13:07 +02:00

474 lines
13 KiB
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;
}