/* $NetBSD: elf_update.c,v 1.5 2024/03/03 17:37:33 christos Exp $ */
/*-
* Copyright (c) 2006-2011 Joseph Koshy
* 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*/
#if HAVE_NBTOOL_CONFIG_H
# include "nbtool_config.h"
#endif
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <assert.h>
#include <errno.h>
#include <gelf.h>
#include <libelf.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "_libelf.h"
#if ELFTC_HAVE_MMAP
#include <sys/mman.h>
#endif
__RCSID("$NetBSD: elf_update.c,v 1.5 2024/03/03 17:37:33 christos Exp $");
ELFTC_VCSID("Id: elf_update.c 3977 2022-05-01 06:45:34Z jkoshy");
/*
* Layout strategy:
*
* - Case 1: ELF_F_LAYOUT is asserted
* In this case the application has full control over where the
* section header table, program header table, and section data
* will reside. The library only perform error checks.
*
* - Case 2: ELF_F_LAYOUT is not asserted
*
* The library will do the object layout using the following
* ordering:
* - The executable header is placed first, are required by the
* ELF specification.
* - The program header table is placed immediately following the
* executable header.
* - Section data, if any, is placed after the program header
* table, aligned appropriately.
* - The section header table, if needed, is placed last.
*
* There are two sub-cases to be taken care of:
*
* - Case 2a: e->e_cmd == ELF_C_READ or ELF_C_RDWR
*
* In this sub-case, the underlying ELF object may already have
* content in it, which the application may have modified. The
* library will retrieve content from the existing object as
* needed.
*
* - Case 2b: e->e_cmd == ELF_C_WRITE
*
* The ELF object is being created afresh in this sub-case;
* there is no pre-existing content in the underlying ELF
* object.
*/
/*
* The types of extents in an ELF object.
*/
enum elf_extent {
ELF_EXTENT_EHDR,
ELF_EXTENT_PHDR,
ELF_EXTENT_SECTION,
ELF_EXTENT_SHDR
};
/*
* A extent descriptor, used when laying out an ELF object.
*/
struct _Elf_Extent {
SLIST_ENTRY(_Elf_Extent) ex_next;
uint64_t ex_start; /* Start of the region. */
uint64_t ex_size; /* The size of the region. */
enum elf_extent ex_type; /* Type of region. */
void *ex_desc; /* Associated descriptor. */
};
SLIST_HEAD(_Elf_Extent_List, _Elf_Extent);
/*
* Compute the extents of a section, by looking at the data
* descriptors associated with it. The function returns 1
* if successful, or zero if an error was detected.
*/
static int
_libelf_compute_section_extents(Elf *e, Elf_Scn *s, off_t rc)
{
Elf_Data *d;
size_t fsz, msz;
int ec, elftype;
uint32_t sh_type;
uint64_t d_align;
Elf32_Shdr *shdr32;
Elf64_Shdr *shdr64;
struct _Libelf_Data *ld;
uint64_t scn_size, scn_alignment;
uint64_t sh_align, sh_entsize, sh_offset, sh_size;
ec = e->e_class;
shdr32 = &s->s_shdr.s_shdr32;
shdr64 = &s->s_shdr.s_shdr64;
if (ec == ELFCLASS32) {
sh_type = shdr32->sh_type;
sh_align = (uint64_t) shdr32->sh_addralign;
sh_entsize = (uint64_t) shdr32->sh_entsize;
sh_offset = (uint64_t) shdr32->sh_offset;
sh_size = (uint64_t) shdr32->sh_size;
} else {
sh_type = shdr64->sh_type;
sh_align = shdr64->sh_addralign;
sh_entsize = shdr64->sh_entsize;
sh_offset = shdr64->sh_offset;
sh_size = shdr64->sh_size;
}
assert(sh_type != SHT_NULL && sh_type != SHT_NOBITS);
elftype = _libelf_xlate_shtype(sh_type);
if (elftype < ELF_T_FIRST || elftype > ELF_T_LAST) {
LIBELF_SET_ERROR(SECTION, 0);
return (0);
}
if (sh_align == 0)
sh_align = _libelf_falign(elftype, ec);
/*
* Compute the section's size and alignment using the data
* descriptors associated with the section.
*/
if (STAILQ_EMPTY(&s->s_data)) {
/*
* The section's content (if any) has not been read in
* yet. If section is not dirty marked dirty, we can
* reuse the values in the 'sh_size' and 'sh_offset'
* fields of the section header.
*/
if ((s->s_flags & ELF_F_DIRTY) == 0) {
/*
* If the library is doing the layout, then we
* compute the new start offset for the
* section based on the current offset and the
* section's alignment needs.
*
* If the application is doing the layout, we
* can use the value in the 'sh_offset' field
* in the section header directly.
*/
if (e->e_flags & ELF_F_LAYOUT)
goto updatedescriptor;
else
goto computeoffset;
}
/*
* Otherwise, we need to bring in the section's data
* from the underlying ELF object.
*/
if (e->e_cmd != ELF_C_WRITE && elf_getdata(s, NULL) == NULL)
return (0);
}
/*
* Loop through the section's data descriptors.
*/
scn_size = 0L;
scn_alignment = 0;
STAILQ_FOREACH(ld, &s->s_data, d_next) {
d = &ld->d_data;
/*
* The data buffer's type is known.
*/
if (d->d_type >= ELF_T_NUM) {
LIBELF_SET_ERROR(DATA, 0);
return (0);
}
/*
* The data buffer's version is supported.
*/
if (d->d_version != e->e_version) {
LIBELF_SET_ERROR(VERSION, 0);
return (0);
}
/*
* The buffer's alignment is non-zero and a power of
* two.
*/
if ((d_align = d->d_align) == 0 ||
(d_align & (d_align - 1))) {
LIBELF_SET_ERROR(DATA, 0);
return (0);
}
/*
* The data buffer's ELF type, ELF class and ELF version
* should be supported.
*/
if ((msz = _libelf_msize(d->d_type, ec, e->e_version)) == 0)
return (0);
/*
* The buffer's size should be a multiple of the
* memory size of the underlying type.
*/
if (d->d_size % msz) {
LIBELF_SET_ERROR(DATA, 0);
return (0);
}
/*
* If the application is controlling layout, then the
* d_offset field should be compatible with the
* buffer's specified alignment.
*/
if ((e->e_flags & ELF_F_LAYOUT) &&
(d->d_off & (d_align - 1))) {
LIBELF_SET_ERROR(LAYOUT, 0);
return (0);
}
/*
* Compute the section's size.
*/
if (e->e_flags & ELF_F_LAYOUT) {
if ((uint64_t) d->d_off + d->d_size > scn_size)
scn_size = d->d_off + d->d_size;
} else {
scn_size = roundup2(scn_size, d->d_align);
d->d_off = scn_size;
fsz = _libelf_fsize(d->d_type, ec, d->d_version,
(size_t) d->d_size / msz);
scn_size += fsz;
}
/*
* The section's alignment is the maximum alignment
* needed for its data buffers.
*/
if (d_align > scn_alignment)
scn_alignment = d_align;
}
/*
* If the application is requesting full control over the
* layout of the section, check the section's specified size,
* offsets and alignment for sanity.
*/
if (e->e_flags & ELF_F_LAYOUT) {
if (scn_alignment > sh_align ||
sh_offset % sh_align ||
sh_size < scn_size ||
sh_offset % _libelf_falign(elftype, ec)) {
LIBELF_SET_ERROR(LAYOUT, 0);
return (0);
}
goto updatedescriptor;
}
/*
* Otherwise, compute the values in the section header.
*
* The section alignment is the maximum alignment for any of
* its contained data descriptors.
*/
if (scn_alignment > sh_align)
sh_align = scn_alignment;
/*
* If the section entry size is zero, try and fill in an
* appropriate entry size. Per the elf(5) manual page
* sections without fixed-size entries should have their
* 'sh_entsize' field set to zero.
*/
if (sh_entsize == 0 &&
(sh_entsize = _libelf_fsize(elftype, ec, e->e_version,
(size_t) 1)) == 1)
sh_entsize = 0;
sh_size = scn_size;
computeoffset:
/*
* Compute the new offset for the section based on
* the section's alignment needs.
*/
sh_offset = roundup((uint64_t) rc, sh_align);
/*
* Update the section header.
*/
if (ec == ELFCLASS32) {
shdr32->sh_addralign = (uint32_t) sh_align;
shdr32->sh_entsize = (uint32_t) sh_entsize;
shdr32->sh_offset = (uint32_t) sh_offset;
shdr32->sh_size = (uint32_t) sh_size;
} else {
shdr64->sh_addralign = sh_align;
shdr64->sh_entsize = sh_entsize;
shdr64->sh_offset = sh_offset;
shdr64->sh_size = sh_size;
}
updatedescriptor:
/*
* Update the section descriptor.
*/
s->s_size = sh_size;
s->s_offset = sh_offset;
return (1);
}
/*
* Free a list of extent descriptors.
*/
static void
_libelf_release_extents(struct _Elf_Extent_List *extents)
{
struct _Elf_Extent *ex;
while ((ex = SLIST_FIRST(extents)) != NULL) {
SLIST_REMOVE_HEAD(extents, ex_next);
free(ex);
}
}
/*
* Check if an extent 's' defined by [start..start+size) is free.
* This routine assumes that the given extent list is sorted in order
* of ascending extent offsets.
*/
static int
_libelf_extent_is_unused(struct _Elf_Extent_List *extents,
const uint64_t start, const uint64_t size, struct _Elf_Extent **prevt)
{
uint64_t tmax, tmin;
struct _Elf_Extent *t, *pt;
const uint64_t smax = start + size;
/* First, look for overlaps with existing extents. */
pt = NULL;
SLIST_FOREACH(t, extents, ex_next) {
tmin = t->ex_start;
tmax = tmin + t->ex_size;
if (tmax <= start) {
/*
* 't' lies entirely before 's': ...| t |...| s |...
*/
pt = t;
continue;
} else if (smax <= tmin) {
/*
* 's' lies entirely before 't', and after 'pt':
* ...| pt |...| s |...| t |...
*/
assert(pt == NULL ||
pt->ex_start + pt->ex_size <= start);
break;
} else
/* 's' and 't' overlap. */
return (0);
}
if (prevt)
*prevt = pt;
return (1);
}
/*
* Insert an extent into the list of extents.
*/
static int
_libelf_insert_extent(struct _Elf_Extent_List *extents, int type,
uint64_t start, uint64_t size, void *desc)
{
struct _Elf_Extent *ex, *prevt;
assert(type >= ELF_EXTENT_EHDR && type <= ELF_EXTENT_SHDR);
prevt = NULL;
/*
* If the requested range overlaps with an existing extent,
* signal an error.
*/
if (!_libelf_extent_is_unused(extents, start, size, &prevt)) {
LIBELF_SET_ERROR(LAYOUT, 0);
return (0);
}
/* Allocate and fill in a new extent descriptor. */
if ((ex = malloc(sizeof(struct _Elf_Extent))) == NULL) {
LIBELF_SET_ERROR(RESOURCE, errno);
return (0);
}
ex->ex_start = start;
ex->ex_size = size;
ex->ex_desc = desc;
ex->ex_type = type;
/* Insert the region descriptor into the list. */
if (prevt)
SLIST_INSERT_AFTER(prevt, ex, ex_next);
else
SLIST_INSERT_HEAD(extents, ex, ex_next);
return (1);
}
/*
* Recompute section layout.
*/
static off_t
_libelf_resync_sections(Elf *e, off_t rc, struct _Elf_Extent_List *extents)
{
int ec;
Elf_Scn *s;
size_t sh_type;
ec = e->e_class;
/*
* Make a pass through sections, computing the extent of each
* section.
*/
STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) {
if (ec == ELFCLASS32)
sh_type = s->s_shdr.s_shdr32.sh_type;
else
sh_type = s->s_shdr.s_shdr64.sh_type;
if (sh_type == SHT_NOBITS || sh_type == SHT_NULL)
continue;
if (_libelf_compute_section_extents(e, s, rc) == 0)
return ((off_t) -1);
if (s->s_size == 0)
continue;
if (!_libelf_insert_extent(extents, ELF_EXTENT_SECTION,
s->s_offset, s->s_size, s))
return ((off_t) -1);
if ((size_t) rc < s->s_offset + s->s_size)
rc = (off_t) (s->s_offset + s->s_size);
}
return (rc);
}
/*
* Recompute the layout of the ELF object and update the internal data
* structures associated with the ELF descriptor.
*
* Returns the size in bytes the ELF object would occupy in its file
* representation.
*
* After a successful call to this function, the following structures
* are updated:
*
* - The ELF header is updated.
* - All extents in the ELF object are sorted in order of ascending
* addresses. Sections have their section header table entries
* updated. An error is signalled if an overlap was detected among
* extents.
* - Data descriptors associated with sections are checked for valid
* types, offsets and alignment.
*
* After a resync_elf() successfully returns, the ELF descriptor is
* ready for being handed over to _libelf_write_elf().
*/
static off_t
_libelf_resync_elf(Elf *e, struct _Elf_Extent_List *extents)
{
int ec, eh_class;
unsigned int eh_byteorder, eh_version;
size_t align, fsz;
size_t phnum, shnum;
off_t rc, phoff, shoff;
void *ehdr, *phdr;
Elf32_Ehdr *eh32;
Elf64_Ehdr *eh64;
rc = 0;
ec = e->e_class;
assert(ec == ELFCLASS32 || ec == ELFCLASS64);
/*
* Prepare the EHDR.
*/
if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
return ((off_t) -1);
eh32 = ehdr;
eh64 = ehdr;
if (ec == ELFCLASS32) {
eh_byteorder = eh32->e_ident[EI_DATA];
eh_class = eh32->e_ident[EI_CLASS];
phoff = (off_t) eh32->e_phoff;
shoff = (off_t) eh32->e_shoff;
eh_version = eh32->e_version;
} else {
eh_byteorder = eh64->e_ident[EI_DATA];
eh_class = eh64->e_ident[EI_CLASS];
phoff = (off_t) eh64->e_phoff;
shoff = (off_t) eh64->e_shoff;
eh_version = eh64->e_version;
}
if (phoff < 0 || shoff < 0) {
LIBELF_SET_ERROR(HEADER, 0);
return ((off_t) -1);
}
if (eh_version == EV_NONE)
eh_version = EV_CURRENT;
if (eh_version != e->e_version) { /* always EV_CURRENT */
LIBELF_SET_ERROR(VERSION, 0);
return ((off_t) -1);
}
if (eh_class != e->e_class) {
LIBELF_SET_ERROR(CLASS, 0);
return ((off_t) -1);
}
if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) {
LIBELF_SET_ERROR(HEADER, 0);
return ((off_t) -1);
}
shnum = e->e_u.e_elf.e_nscn;
phnum = e->e_u.e_elf.e_nphdr;
e->e_byteorder = eh_byteorder;
#define INITIALIZE_EHDR(E,EC,V) do { \
unsigned int _version = (unsigned int) (V); \
(E)->e_ident[EI_MAG0] = ELFMAG0; \
(E)->e_ident[EI_MAG1] = ELFMAG1; \
(E)->e_ident[EI_MAG2] = ELFMAG2; \
(E)->e_ident[EI_MAG3] = ELFMAG3; \
(E)->e_ident[EI_CLASS] = (unsigned char) (EC); \
(E)->e_ident[EI_VERSION] = (_version & 0xFFU); \
(E)->e_ehsize = (uint16_t) _libelf_fsize(ELF_T_EHDR, \
(EC), _version, (size_t) 1); \
(E)->e_phentsize = (uint16_t) ((phnum == 0) ? 0 : \
_libelf_fsize(ELF_T_PHDR, (EC), _version, \
(size_t) 1)); \
(E)->e_shentsize = (uint16_t) _libelf_fsize(ELF_T_SHDR, \
(EC), _version, (size_t) 1); \
} while (/* CONSTCOND */ 0)
if (ec == ELFCLASS32)
INITIALIZE_EHDR(eh32, ec, eh_version);
else
INITIALIZE_EHDR(eh64, ec, eh_version);
(void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY);
rc += (off_t) _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1);
if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, (uint64_t) rc,
ehdr))
return ((off_t) -1);
/*
* Compute the layout the program header table, if one is
* present. The program header table needs to be aligned to a
* `natural' boundary.
*/
if (phnum) {
fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum);
align = _libelf_falign(ELF_T_PHDR, ec);
if (e->e_flags & ELF_F_LAYOUT) {
/*
* Check offsets for sanity.
*/
if (rc > phoff) {
LIBELF_SET_ERROR(LAYOUT, 0);
return ((off_t) -1);
}
if (phoff % (off_t) align) {
LIBELF_SET_ERROR(LAYOUT, 0);
return ((off_t) -1);
}
} else
phoff = roundup(rc, (off_t) align);
rc = phoff + (off_t) fsz;
phdr = _libelf_getphdr(e, ec);
if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR,
(uint64_t) phoff, fsz, phdr))
return ((off_t) -1);
} else
phoff = 0;
/*
* Compute the layout of the sections associated with the
* file.
*/
if (e->e_cmd != ELF_C_WRITE &&
(e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
_libelf_load_section_headers(e, ehdr) == 0)
return ((off_t) -1);
if ((rc = _libelf_resync_sections(e, rc, extents)) < 0)
return ((off_t) -1);
/*
* Compute the space taken up by the section header table, if
* one is needed.
*
* If ELF_F_LAYOUT has been asserted, the application may have
* placed the section header table in between existing
* sections, so the net size of the file need not increase due
* to the presence of the section header table.
*
* If the library is responsible for laying out the object,
* the section header table is placed after section data.
*/
if (shnum) {
fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum);
align = _libelf_falign(ELF_T_SHDR, ec);
if (e->e_flags & ELF_F_LAYOUT) {
if (shoff % (off_t) align) {
LIBELF_SET_ERROR(LAYOUT, 0);
return ((off_t) -1);
}
} else
shoff = roundup(rc, (off_t) align);
if (shoff + (off_t) fsz > rc)
rc = shoff + (off_t) fsz;
if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR,
(uint64_t) shoff, fsz, NULL))
return ((off_t) -1);
} else
shoff = 0;
/*
* Set the fields of the Executable Header that could potentially use
* extended numbering.
*/
_libelf_setphnum(e, ehdr, ec, phnum);
_libelf_setshnum(e, ehdr, ec, shnum);
/*
* Update the `e_phoff' and `e_shoff' fields if the library is
* doing the layout.
*/
if ((e->e_flags & ELF_F_LAYOUT) == 0) {
if (ec == ELFCLASS32) {
eh32->e_phoff = (uint32_t) phoff;
eh32->e_shoff = (uint32_t) shoff;
} else {
eh64->e_phoff = (uint64_t) phoff;
eh64->e_shoff = (uint64_t) shoff;
}
}
return (rc);
}
/*
* Write out the contents of an ELF section.
*/
static off_t
_libelf_write_scn(Elf *e, unsigned char *nf, struct _Elf_Extent *ex)
{
off_t rc;
int ec, em;
Elf_Scn *s;
int elftype;
Elf_Data *d, dst;
uint32_t sh_type;
struct _Libelf_Data *ld;
uint64_t sh_off, sh_size;
size_t fsz, msz, nobjects;
assert(ex->ex_type == ELF_EXTENT_SECTION);
s = ex->ex_desc;
rc = (off_t) ex->ex_start;
if ((ec = e->e_class) == ELFCLASS32) {
sh_type = s->s_shdr.s_shdr32.sh_type;
sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size;
} else {
sh_type = s->s_shdr.s_shdr64.sh_type;
sh_size = s->s_shdr.s_shdr64.sh_size;
}
/*
* Ignore sections that do not allocate space in the file.
*/
if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0)
return (rc);
elftype = _libelf_xlate_shtype(sh_type);
assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST);
sh_off = s->s_offset;
assert(sh_off % _libelf_falign(elftype, ec) == 0);
em = _libelf_elfmachine(e);
/*
* If the section has a `rawdata' descriptor, and the section
* contents have not been modified, use its contents directly.
* The `s_rawoff' member contains the offset into the original
* file, while `s_offset' contains its new location in the
* destination.
*/
if (STAILQ_EMPTY(&s->s_data)) {
if ((d = elf_rawdata(s, NULL)) == NULL)
return ((off_t) -1);
STAILQ_FOREACH(ld, &s->s_rawdata, d_next) {
d = &ld->d_data;
if ((uint64_t) rc < sh_off + d->d_off)
(void) memset(nf + rc,
LIBELF_PRIVATE(fillchar),
(size_t) (sh_off + d->d_off -
(uint64_t) rc));
rc = (off_t) (sh_off + d->d_off);
assert(d->d_buf != NULL);
assert(d->d_type == ELF_T_BYTE);
assert(d->d_version == e->e_version);
(void) memcpy(nf + rc,
e->e_rawfile + s->s_rawoff + d->d_off,
(size_t) d->d_size);
rc += (off_t) d->d_size;
}
return (rc);
}
/*
* Iterate over the set of data descriptors for this section.
* The prior call to _libelf_resync_elf() would have setup the
* descriptors for this step.
*/
dst.d_version = e->e_version;
STAILQ_FOREACH(ld, &s->s_data, d_next) {
d = &ld->d_data;
if ((msz = _libelf_msize(d->d_type, ec, e->e_version)) == 0)
return ((off_t) -1);
if ((uint64_t) rc < sh_off + d->d_off)
(void) memset(nf + rc,
LIBELF_PRIVATE(fillchar),
(size_t) (sh_off + d->d_off - (uint64_t) rc));
rc = (off_t) (sh_off + d->d_off);
assert(d->d_buf != NULL);
assert(d->d_version == e->e_version);
assert(d->d_size % msz == 0);
assert(msz != 0);
nobjects = (size_t) (d->d_size / msz);
fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects);
dst.d_buf = nf + rc;
dst.d_size = fsz;
if (_libelf_xlate(&dst, d, e->e_byteorder, ec, em, ELF_TOFILE)
== NULL)
return ((off_t) -1);
rc += (off_t) fsz;
}
return (rc);
}
/*
* Write out an ELF Executable Header.
*/
static off_t
_libelf_write_ehdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex)
{
int ec, em;
void *ehdr;
size_t fsz, msz;
Elf_Data dst, src;
assert(ex->ex_type == ELF_EXTENT_EHDR);
assert(ex->ex_start == 0); /* Ehdr always comes first. */
ec = e->e_class;
ehdr = _libelf_ehdr(e, ec, 0);
assert(ehdr != NULL);
fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
if ((msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version)) == 0)
return ((off_t) -1);
em = _libelf_elfmachine(e);
(void) memset(&dst, 0, sizeof(dst));
(void) memset(&src, 0, sizeof(src));
src.d_buf = ehdr;
src.d_size = msz;
src.d_type = ELF_T_EHDR;
src.d_version = dst.d_version = e->e_version;
dst.d_buf = nf;
dst.d_size = fsz;
if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, em, ELF_TOFILE) ==
NULL)
return ((off_t) -1);
return ((off_t) fsz);
}
/*
* Write out an ELF program header table.
*/
static off_t
_libelf_write_phdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex)
{
int ec, em;
void *ehdr;
Elf32_Ehdr *eh32;
Elf64_Ehdr *eh64;
Elf_Data dst, src;
size_t fsz, msz, phnum;
uint64_t phoff;
assert(ex->ex_type == ELF_EXTENT_PHDR);
ec = e->e_class;
ehdr = _libelf_ehdr(e, ec, 0);
assert(ehdr != NULL);
phnum = e->e_u.e_elf.e_nphdr;
assert(phnum > 0);
if (ec == ELFCLASS32) {
eh32 = (Elf32_Ehdr *) ehdr;
phoff = (uint64_t) eh32->e_phoff;
} else {
eh64 = (Elf64_Ehdr *) ehdr;
phoff = eh64->e_phoff;
}
em = _libelf_elfmachine(e);
assert(phoff > 0);
assert(ex->ex_start == phoff);
assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0);
(void) memset(&dst, 0, sizeof(dst));
(void) memset(&src, 0, sizeof(src));
if ((msz = _libelf_msize(ELF_T_PHDR, ec, e->e_version)) == 0)
return ((off_t) -1);
fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum);
assert(fsz > 0);
src.d_buf = _libelf_getphdr(e, ec);
src.d_version = dst.d_version = e->e_version;
src.d_type = ELF_T_PHDR;
src.d_size = phnum * msz;
dst.d_size = fsz;
dst.d_buf = nf + ex->ex_start;
if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, em, ELF_TOFILE) ==
NULL)
return ((off_t) -1);
return ((off_t) (phoff + fsz));
}
/*
* Write out an ELF section header table.
*/
static off_t
_libelf_write_shdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex)
{
int ec, em;
void *ehdr;
Elf_Scn *scn;
uint64_t shoff;
Elf32_Ehdr *eh32;
Elf64_Ehdr *eh64;
size_t fsz, msz, nscn;
Elf_Data dst, src;
assert(ex->ex_type == ELF_EXTENT_SHDR);
ec = e->e_class;
ehdr = _libelf_ehdr(e, ec, 0);
assert(ehdr != NULL);
nscn = e->e_u.e_elf.e_nscn;
if (ec == ELFCLASS32) {
eh32 = (Elf32_Ehdr *) ehdr;
shoff = (uint64_t) eh32->e_shoff;
} else {
eh64 = (Elf64_Ehdr *) ehdr;
shoff = eh64->e_shoff;
}
em = _libelf_elfmachine(e);
assert(nscn > 0);
assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0);
assert(ex->ex_start == shoff);
(void) memset(&dst, 0, sizeof(dst));
(void) memset(&src, 0, sizeof(src));
if ((msz = _libelf_msize(ELF_T_SHDR, ec, e->e_version)) == 0)
return ((off_t) -1);
src.d_type = ELF_T_SHDR;
src.d_size = msz;
src.d_version = dst.d_version = e->e_version;
fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
STAILQ_FOREACH(scn, &e->e_u.e_elf.e_scn, s_next) {
if (ec == ELFCLASS32)
src.d_buf = &scn->s_shdr.s_shdr32;
else
src.d_buf = &scn->s_shdr.s_shdr64;
dst.d_size = fsz;
dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz;
if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, em,
ELF_TOFILE) == NULL)
return ((off_t) -1);
}
return ((off_t) (ex->ex_start + nscn * fsz));
}
/*
* Write out the file image.
*
* The original file could have been mapped in with an ELF_C_RDWR
* command and the application could have added new content or
* re-arranged its sections before calling elf_update(). Consequently
* its not safe to work `in place' on the original file. So we
* malloc() the required space for the updated ELF object and build
* the object there and write it out to the underlying file at the
* end. Note that the application may have opened the underlying file
* in ELF_C_RDWR and only retrieved/modified a few sections. We take
* care to avoid translating file sections unnecessarily.
*
* Gaps in the coverage of the file by the file's sections will be
* filled with the fill character set by elf_fill(3).
*/
static off_t
_libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents)
{
off_t nrc, rc;
Elf_Scn *scn, *tscn;
struct _Elf_Extent *ex;
unsigned char *newfile;
assert(e->e_kind == ELF_K_ELF);
assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE);
assert(e->e_fd >= 0);
if ((newfile = malloc((size_t) newsize)) == NULL) {
LIBELF_SET_ERROR(RESOURCE, errno);
return ((off_t) -1);
}
nrc = rc = 0;
SLIST_FOREACH(ex, extents, ex_next) {
/* Fill inter-extent gaps. */
if (ex->ex_start > (size_t) rc)
(void) memset(newfile + rc, LIBELF_PRIVATE(fillchar),
(size_t) (ex->ex_start - (uint64_t) rc));
switch (ex->ex_type) {
case ELF_EXTENT_EHDR:
if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0)
goto error;
break;
case ELF_EXTENT_PHDR:
if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0)
goto error;
break;
case ELF_EXTENT_SECTION:
if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0)
goto error;
break;
case ELF_EXTENT_SHDR:
if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0)
goto error;
break;
default:
assert(0);
break;
}
assert(ex->ex_start + ex->ex_size == (size_t) nrc);
assert(rc < nrc);
rc = nrc;
}
assert(rc == newsize);
/*
* For regular files, throw away existing file content and
* unmap any existing mappings.
*/
if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) {
if (ftruncate(e->e_fd, (off_t) 0) < 0 ||
lseek(e->e_fd, (off_t) 0, SEEK_SET)) {
LIBELF_SET_ERROR(IO, errno);
goto error;
}
#if ELFTC_HAVE_MMAP
if (e->e_flags & LIBELF_F_RAWFILE_MMAP) {
assert(e->e_rawfile != NULL);
assert(e->e_cmd == ELF_C_RDWR);
if (munmap(e->e_rawfile, (size_t) e->e_rawsize) < 0) {
LIBELF_SET_ERROR(IO, errno);
goto error;
}
}
#endif
}
/*
* Write out the new contents.
*/
if (write(e->e_fd, newfile, (size_t) newsize) != newsize) {
LIBELF_SET_ERROR(IO, errno);
goto error;
}
/*
* For files opened in ELF_C_RDWR mode, set up the new 'raw'
* contents.
*/
if (e->e_cmd == ELF_C_RDWR) {
assert(e->e_rawfile != NULL);
assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) ||
(e->e_flags & LIBELF_F_RAWFILE_MMAP));
if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) {
assert((e->e_flags & LIBELF_F_RAWFILE_MMAP) == 0);
free(e->e_rawfile);
e->e_rawfile = newfile;
newfile = NULL;
}
#if ELFTC_HAVE_MMAP
else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) {
assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) == 0);
if ((e->e_rawfile = mmap(NULL, (size_t) newsize,
PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) ==
MAP_FAILED) {
LIBELF_SET_ERROR(IO, errno);
goto error;
}
}
#endif /* ELFTC_HAVE_MMAP */
/* Record the new size of the file. */
e->e_rawsize = newsize;
} else {
/* File opened in ELF_C_WRITE mode. */
assert(e->e_rawfile == NULL);
}
/*
* Reset flags, remove existing section descriptors and
* {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr()
* and elf_getscn() will function correctly.
*/
e->e_flags &= ~ELF_F_DIRTY;
STAILQ_FOREACH_SAFE(scn, &e->e_u.e_elf.e_scn, s_next, tscn)
_libelf_release_scn(scn);
if (e->e_class == ELFCLASS32) {
free(e->e_u.e_elf.e_ehdr.e_ehdr32);
if (e->e_u.e_elf.e_phdr.e_phdr32)
free(e->e_u.e_elf.e_phdr.e_phdr32);
e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL;
e->e_u.e_elf.e_phdr.e_phdr32 = NULL;
} else {
free(e->e_u.e_elf.e_ehdr.e_ehdr64);
if (e->e_u.e_elf.e_phdr.e_phdr64)
free(e->e_u.e_elf.e_phdr.e_phdr64);
e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL;
e->e_u.e_elf.e_phdr.e_phdr64 = NULL;
}
/* Free the temporary buffer. */
if (newfile)
free(newfile);
return (rc);
error:
free(newfile);
return ((off_t) -1);
}
/*
* Update an ELF object.
*/
off_t
elf_update(Elf *e, Elf_Cmd c)
{
int ec;
off_t rc;
struct _Elf_Extent_List extents;
rc = (off_t) -1;
if (e == NULL || e->e_kind != ELF_K_ELF ||
(c != ELF_C_NULL && c != ELF_C_WRITE)) {
LIBELF_SET_ERROR(ARGUMENT, 0);
return (rc);
}
if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
LIBELF_SET_ERROR(CLASS, 0);
return (rc);
}
if (e->e_version == EV_NONE)
e->e_version = EV_CURRENT;
if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) {
LIBELF_SET_ERROR(MODE, 0);
return (rc);
}
SLIST_INIT(&extents);
if ((rc = _libelf_resync_elf(e, &extents)) < 0)
goto done;
if (c == ELF_C_NULL)
goto done;
if (e->e_fd < 0) {
rc = (off_t) -1;
LIBELF_SET_ERROR(SEQUENCE, 0);
goto done;
}
rc = _libelf_write_elf(e, rc, &extents);
done:
_libelf_release_extents(&extents);
return (rc);
}
