a607e5d7f8
PT_INTERP program header entry, to ensure that gdb always finds the right dynamic linker. Use obj->relocbase to simplify a few calculations where appropriate.
310 lines
8.9 KiB
C
310 lines
8.9 KiB
C
/*-
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* Copyright 1996-1998 John D. Polstra.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <errno.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "rtld.h"
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static int protflags(int); /* Elf flags -> mmap protection */
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/*
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* Map a shared object into memory. The "fd" argument is a file descriptor,
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* which must be open on the object and positioned at its beginning.
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* The "path" argument is a pathname that is used only for error messages.
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*
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* The return value is a pointer to a newly-allocated Obj_Entry structure
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* for the shared object. Returns NULL on failure.
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*/
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Obj_Entry *
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map_object(int fd, const char *path, const struct stat *sb)
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{
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Obj_Entry *obj;
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union {
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Elf_Ehdr hdr;
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char buf[PAGE_SIZE];
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} u;
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int nbytes;
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Elf_Phdr *phdr;
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Elf_Phdr *phlimit;
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Elf_Phdr *segs[2];
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int nsegs;
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Elf_Phdr *phdyn;
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Elf_Phdr *phphdr;
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Elf_Phdr *phinterp;
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caddr_t mapbase;
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size_t mapsize;
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Elf_Off base_offset;
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Elf_Addr base_vaddr;
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Elf_Addr base_vlimit;
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caddr_t base_addr;
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Elf_Off data_offset;
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Elf_Addr data_vaddr;
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Elf_Addr data_vlimit;
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caddr_t data_addr;
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Elf_Addr clear_vaddr;
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caddr_t clear_addr;
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size_t nclear;
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Elf_Addr bss_vaddr;
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Elf_Addr bss_vlimit;
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caddr_t bss_addr;
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if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) {
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_rtld_error("%s: read error: %s", path, strerror(errno));
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return NULL;
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}
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/* Make sure the file is valid */
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if (nbytes < sizeof(Elf_Ehdr)
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|| u.hdr.e_ident[EI_MAG0] != ELFMAG0
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|| u.hdr.e_ident[EI_MAG1] != ELFMAG1
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|| u.hdr.e_ident[EI_MAG2] != ELFMAG2
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|| u.hdr.e_ident[EI_MAG3] != ELFMAG3) {
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_rtld_error("%s: invalid file format", path);
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return NULL;
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}
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if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS
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|| u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) {
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_rtld_error("%s: unsupported file layout", path);
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return NULL;
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}
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if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT
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|| u.hdr.e_version != EV_CURRENT) {
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_rtld_error("%s: unsupported file version", path);
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return NULL;
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}
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if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) {
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_rtld_error("%s: unsupported file type", path);
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return NULL;
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}
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if (u.hdr.e_machine != ELF_TARG_MACH) {
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_rtld_error("%s: unsupported machine", path);
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return NULL;
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}
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/*
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* We rely on the program header being in the first page. This is
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* not strictly required by the ABI specification, but it seems to
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* always true in practice. And, it simplifies things considerably.
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*/
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if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) {
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_rtld_error(
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"%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
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return NULL;
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}
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if (u.hdr.e_phoff + u.hdr.e_phnum*sizeof(Elf_Phdr) > nbytes) {
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_rtld_error("%s: program header too large", path);
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return NULL;
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}
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/*
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* Scan the program header entries, and save key information.
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*
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* We rely on there being exactly two load segments, text and data,
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* in that order.
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*/
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phdr = (Elf_Phdr *) (u.buf + u.hdr.e_phoff);
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phlimit = phdr + u.hdr.e_phnum;
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nsegs = 0;
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phdyn = phphdr = phinterp = NULL;
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while (phdr < phlimit) {
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switch (phdr->p_type) {
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case PT_INTERP:
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phinterp = phdr;
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break;
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case PT_LOAD:
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if (nsegs >= 2) {
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_rtld_error("%s: too many PT_LOAD segments", path);
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return NULL;
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}
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segs[nsegs] = phdr;
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++nsegs;
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break;
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case PT_PHDR:
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phphdr = phdr;
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break;
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case PT_DYNAMIC:
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phdyn = phdr;
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break;
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}
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++phdr;
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}
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if (phdyn == NULL) {
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_rtld_error("%s: object is not dynamically-linked", path);
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return NULL;
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}
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if (nsegs < 2) {
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_rtld_error("%s: too few PT_LOAD segments", path);
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return NULL;
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}
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if (segs[0]->p_align < PAGE_SIZE || segs[1]->p_align < PAGE_SIZE) {
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_rtld_error("%s: PT_LOAD segments not page-aligned", path);
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return NULL;
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}
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/*
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* Map the entire address space of the object, to stake out our
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* contiguous region, and to establish the base address for relocation.
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*/
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base_offset = trunc_page(segs[0]->p_offset);
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base_vaddr = trunc_page(segs[0]->p_vaddr);
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base_vlimit = round_page(segs[1]->p_vaddr + segs[1]->p_memsz);
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mapsize = base_vlimit - base_vaddr;
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base_addr = u.hdr.e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL;
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mapbase = mmap(base_addr, mapsize, protflags(segs[0]->p_flags),
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MAP_PRIVATE, fd, base_offset);
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if (mapbase == (caddr_t) -1) {
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_rtld_error("%s: mmap of entire address space failed: %s",
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path, strerror(errno));
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return NULL;
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}
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if (base_addr != NULL && mapbase != base_addr) {
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_rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
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path, base_addr, mapbase);
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munmap(mapbase, mapsize);
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return NULL;
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}
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/* Overlay the data segment onto the proper region. */
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data_offset = trunc_page(segs[1]->p_offset);
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data_vaddr = trunc_page(segs[1]->p_vaddr);
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data_vlimit = round_page(segs[1]->p_vaddr + segs[1]->p_filesz);
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data_addr = mapbase + (data_vaddr - base_vaddr);
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if (mmap(data_addr, data_vlimit - data_vaddr, protflags(segs[1]->p_flags),
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MAP_PRIVATE|MAP_FIXED, fd, data_offset) == (caddr_t) -1) {
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_rtld_error("%s: mmap of data failed: %s", path, strerror(errno));
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return NULL;
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}
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/* Clear any BSS in the last page of the data segment. */
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clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz;
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clear_addr = mapbase + (clear_vaddr - base_vaddr);
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if ((nclear = data_vlimit - clear_vaddr) > 0)
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memset(clear_addr, 0, nclear);
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/* Overlay the BSS segment onto the proper region. */
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bss_vaddr = data_vlimit;
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bss_vlimit = round_page(segs[1]->p_vaddr + segs[1]->p_memsz);
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bss_addr = mapbase + (bss_vaddr - base_vaddr);
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if (bss_vlimit > bss_vaddr) { /* There is something to do */
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if (mmap(bss_addr, bss_vlimit - bss_vaddr, protflags(segs[1]->p_flags),
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MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) {
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_rtld_error("%s: mmap of bss failed: %s", path, strerror(errno));
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return NULL;
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}
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}
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obj = obj_new();
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if (sb != NULL) {
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obj->dev = sb->st_dev;
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obj->ino = sb->st_ino;
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}
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obj->mapbase = mapbase;
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obj->mapsize = mapsize;
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obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
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base_vaddr;
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obj->vaddrbase = base_vaddr;
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obj->relocbase = mapbase - base_vaddr;
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obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
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if (u.hdr.e_entry != 0)
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obj->entry = (caddr_t) (obj->relocbase + u.hdr.e_entry);
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if (phphdr != NULL) {
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obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr);
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obj->phsize = phphdr->p_memsz;
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}
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if (phinterp != NULL)
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obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
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return obj;
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}
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void
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obj_free(Obj_Entry *obj)
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{
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Objlist_Entry *elm;
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free(obj->path);
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while (obj->needed != NULL) {
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Needed_Entry *needed = obj->needed;
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obj->needed = needed->next;
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free(needed);
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}
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while (!STAILQ_EMPTY(&obj->dldags)) {
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elm = STAILQ_FIRST(&obj->dldags);
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STAILQ_REMOVE_HEAD(&obj->dldags, link);
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free(elm);
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}
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while (!STAILQ_EMPTY(&obj->dagmembers)) {
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elm = STAILQ_FIRST(&obj->dagmembers);
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STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
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free(elm);
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}
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free(obj);
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}
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Obj_Entry *
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obj_new(void)
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{
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Obj_Entry *obj;
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obj = CNEW(Obj_Entry);
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STAILQ_INIT(&obj->dldags);
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STAILQ_INIT(&obj->dagmembers);
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return obj;
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}
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/*
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* Given a set of ELF protection flags, return the corresponding protection
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* flags for MMAP.
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*/
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static int
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protflags(int elfflags)
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{
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int prot = 0;
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if (elfflags & PF_R)
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prot |= PROT_READ;
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if (elfflags & PF_W)
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prot |= PROT_WRITE;
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if (elfflags & PF_X)
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prot |= PROT_EXEC;
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return prot;
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}
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