/*- * 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. */ #include #include #include #include #include #include #include #include #include "_libelf.h" #if ELFTC_HAVE_MMAP #include #endif ELFTC_VCSID("$Id: elf_update.c,v 1.4 2021/09/02 21:12:25 deraadt Exp $"); /* * 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 (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); assert(em >= EM_NONE && em < EM__LAST__); /* * 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); }