minix/libexec/ld.elf_so/map_object.c
Ben Gras 0b79eac642 mmap: accept non-PROT_WRITE MAP_SHARED mappings
Currently we don't accept writable file mmap()s, as there is no
system in place to guarantee dirty buffers would make it back to
disk. But we can actually accept MAP_SHARED for PROT_READ mappings,
meaning the ranges aren't writable at all (and no private copy is
made as with MAP_PRIVATE), as it turns out a fairly large class of
usage.

	. fail writable MAP_SHARED mappings at runtime
	. reduces some minix-specific patches
	. lets binutils gold build on minix without further patching

Change-Id: If2896c0a555328ac5b324afa706063fc6d86519e
2014-07-28 17:05:20 +02:00

513 lines
14 KiB
C

/* $NetBSD: map_object.c,v 1.52 2013/08/03 13:17:05 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 1.52 2013/08/03 13:17:05 skrll Exp $");
#endif /* not lint */
#include <errno.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"
#if defined(__minix)
#define MINIXVERBOSE 0
#if MINIXVERBOSE
#include <stdio.h>
#endif
#endif /* defined(__minix) */
static int protflags(int); /* Elf flags -> mmap protection */
#define EA_UNDEF (~(Elf_Addr)0)
/*
* 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;
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
Elf_Phdr *phtls;
#endif
size_t phsize;
Elf_Phdr *phlimit;
Elf_Phdr *segs[2];
int nsegs;
caddr_t mapbase = MAP_FAILED;
size_t mapsize = 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;
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
Elf_Addr tls_vaddr = 0; /* Noise GCC */
#endif
Elf_Addr phdr_vaddr;
size_t phdr_memsz;
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
caddr_t gap_addr;
size_t gap_size;
#endif
int i;
#ifdef RTLD_LOADER
Elf_Addr clear_vaddr;
caddr_t clear_addr;
size_t nclear;
#endif
#if defined(__minix)
Elf_Addr bsslen;
#endif /* defined(__minix) */
if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) {
_rtld_error("%s: not ELF file (too short)", 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;
}
ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd,
(off_t)0);
obj->ehdr = ehdr;
if (ehdr == MAP_FAILED) {
#if defined(__minix)
return _rtld_map_object_fallback(path, fd, sb);
#else
_rtld_error("%s: read error: %s", path, xstrerror(errno));
goto bad;
#endif
}
/* Make sure the file is valid */
if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0) {
_rtld_error("%s: not ELF file (magic number bad)", path);
goto bad;
}
if (ehdr->e_ident[EI_CLASS] != ELFCLASS) {
_rtld_error("%s: invalid ELF class %x; expected %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);
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
phtls = NULL;
#endif
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: %s %p phsize %" PRImemsz, obj->path, "PT_LOAD",
(void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
break;
case PT_PHDR:
phdr_vaddr = phdr->p_vaddr;
phdr_memsz = phdr->p_memsz;
dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_PHDR",
(void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
break;
case PT_DYNAMIC:
obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr;
dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_DYNAMIC",
(void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
break;
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
case PT_TLS:
phtls = phdr;
dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_TLS",
(void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
break;
#endif
#ifdef __ARM_EABI__
case PT_ARM_EXIDX:
obj->exidx_start = (void *)(uintptr_t)phdr->p_vaddr;
obj->exidx_sz = phdr->p_memsz;
break;
#endif
}
++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;
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
if (phtls != NULL) {
++_rtld_tls_dtv_generation;
obj->tlsindex = ++_rtld_tls_max_index;
obj->tlssize = phtls->p_memsz;
obj->tlsalign = phtls->p_align;
obj->tlsinitsize = phtls->p_filesz;
tls_vaddr = phtls->p_vaddr;
}
#endif
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;
mapbase = mmap(base_addr, mapsize, text_flags,
mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset);
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);
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;
}
/* Overlay the bss segment onto the proper region. */
#if defined(__minix)
bsslen = base_vlimit - data_vlimit;
if (bsslen > 0 &&
mmap(mapbase + data_vlimit - base_vaddr, bsslen,
#else
if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit,
#endif /* defined(__minix) */
data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) ==
MAP_FAILED) {
_rtld_error("mmap of bss failed: %s", xstrerror(errno));
goto bad;
}
/* Unmap the gap between the text and data. */
#if !defined(__minix)
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 /* !defined(__minix) */
#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
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
if (phtls != NULL)
obj->tlsinit = mapbase + tls_vaddr;
#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);
#ifdef __ARM_EABI__
if (obj->exidx_start)
obj->exidx_start = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->exidx_start);
#endif
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;
Name_Entry *entry;
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
if (obj->tls_done)
_rtld_tls_offset_free(obj);
#endif
xfree(obj->path);
while (obj->needed != NULL) {
Needed_Entry *needed = obj->needed;
obj->needed = needed->next;
xfree(needed);
}
while ((entry = SIMPLEQ_FIRST(&obj->names)) != NULL) {
SIMPLEQ_REMOVE_HEAD(&obj->names, link);
xfree(entry);
}
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->names);
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;
#if defined(__minix)
/* Minix has to map it writable so we can do relocations
* as we don't have mprotect() yet.
*/
prot |= PROT_WRITE;
#endif /* defined(__minix) */
return prot;
}