/* $NetBSD: map_object.c,v 1.13 2002/06/01 23:50:53 lukem Exp $ */ /* * Copyright 1996 John D. Polstra. * Copyright 1996 Matt Thomas * 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 #include #include #include #include #include #include #include #include "rtld.h" static int protflags __P((int)); /* Elf flags -> mmap protection */ /* * 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(path, fd, sb) const char *path; int fd; const struct stat *sb; { Obj_Entry *obj; union { Elf_Ehdr hdr; char buf[PAGESIZE]; } u; int nbytes; Elf_Phdr *phdr; Elf_Phdr *phlimit; Elf_Phdr *segs[2]; int nsegs; Elf_Phdr *phdyn; Elf_Phdr *phphdr; Elf_Phdr *phinterp; caddr_t mapbase; size_t mapsize; Elf_Off base_offset; Elf_Addr base_vaddr; Elf_Addr base_vlimit; Elf_Addr text_vlimit; caddr_t base_addr; Elf_Off data_offset; Elf_Addr data_vaddr; Elf_Addr data_vlimit; caddr_t data_addr; caddr_t gap_addr; size_t gap_size; #ifdef RTLD_LOADER Elf_Addr clear_vaddr; caddr_t clear_addr; size_t nclear; #endif if ((nbytes = read(fd, u.buf, PAGESIZE)) == -1) { _rtld_error("%s: read error: %s", path, xstrerror(errno)); return NULL; } /* Make sure the file is valid */ if (nbytes < sizeof(Elf_Ehdr) || memcmp(ELFMAG, u.hdr.e_ident, SELFMAG) != 0 || u.hdr.e_ident[EI_CLASS] != ELFCLASS) { _rtld_error("%s: unrecognized file format", path); return NULL; } /* Elf_e_ident includes class */ if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT || u.hdr.e_version != EV_CURRENT || u.hdr.e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { _rtld_error("%s: Unsupported file version", path); return NULL; } if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { _rtld_error("%s: Unsupported file type", path); return NULL; } switch (u.hdr.e_machine) { ELFDEFNNAME(MACHDEP_ID_CASES) default: _rtld_error("%s: Unsupported machine", path); return NULL; } /* * 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(u.hdr.e_phentsize == sizeof(Elf_Phdr)); assert(u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) <= PAGESIZE); assert(u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) <= nbytes); /* * 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 *) (u.buf + u.hdr.e_phoff); phlimit = phdr + u.hdr.e_phnum; nsegs = 0; phdyn = phphdr = phinterp = NULL; while (phdr < phlimit) { switch (phdr->p_type) { case PT_INTERP: phinterp = phdr; break; case PT_LOAD: if (nsegs < 2) segs[nsegs] = phdr; ++nsegs; break; case PT_PHDR: phphdr = phdr; break; case PT_DYNAMIC: phdyn = phdr; break; } ++phdr; } if (phdyn == NULL) { _rtld_error("%s: not dynamically linked", path); return NULL; } if (nsegs != 2) { _rtld_error("%s: wrong number of segments (%d != 2)", path, nsegs); return NULL; } #ifdef __i386__ assert(segs[0]->p_align <= PAGESIZE); assert(segs[1]->p_align <= PAGESIZE); #endif /* * 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. */ 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); mapsize = base_vlimit - base_vaddr; #ifdef RTLD_LOADER base_addr = u.hdr.e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; #else base_addr = NULL; #endif mapbase = mmap(base_addr, mapsize, protflags(segs[0]->p_flags), MAP_FILE | MAP_PRIVATE, fd, base_offset); if (mapbase == MAP_FAILED) { _rtld_error("mmap of entire address space failed: %s", xstrerror(errno)); return NULL; } base_addr = mapbase; /* Overlay the data segment onto the proper region. */ 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_addr = mapbase + (data_vaddr - base_vaddr); if (mmap(data_addr, data_vlimit - data_vaddr, protflags(segs[1]->p_flags), MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == MAP_FAILED) { _rtld_error("mmap of data failed: %s", xstrerror(errno)); munmap(mapbase, mapsize); return NULL; } /* Overlay the bss segment onto the proper region. */ if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, protflags(segs[1]->p_flags), MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == MAP_FAILED) { _rtld_error("mmap of bss failed: %s", xstrerror(errno)); munmap(mapbase, mapsize); return NULL; } /* Unmap the gap between the text and data. */ gap_addr = base_addr + round_up(text_vlimit - base_vaddr); gap_size = data_addr - gap_addr; if (gap_size != 0 && munmap(gap_addr, gap_size) == -1) { _rtld_error("munmap of text -> data gap failed: %s", xstrerror(errno)); munmap(mapbase, mapsize); return NULL; } #ifdef RTLD_LOADER /* Clear any BSS in the last page of the data segment. */ clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; clear_addr = mapbase + (clear_vaddr - base_vaddr); if ((nclear = data_vlimit - clear_vaddr) > 0) memset(clear_addr, 0, nclear); /* Non-file portion of BSS mapped above. */ #endif obj = _rtld_obj_new(); if (sb != NULL) { obj->dev = sb->st_dev; obj->ino = sb->st_ino; } obj->mapbase = mapbase; obj->mapsize = mapsize; obj->textsize = round_up(segs[0]->p_vaddr + segs[0]->p_memsz) - base_vaddr; obj->vaddrbase = base_vaddr; obj->relocbase = mapbase - base_vaddr; obj->dynamic = (Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); if (u.hdr.e_entry != 0) obj->entry = (caddr_t)(obj->relocbase + u.hdr.e_entry); if (phphdr != NULL) { obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr); obj->phsize = phphdr->p_memsz; } if (phinterp != NULL) obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); return obj; } void _rtld_obj_free(obj) Obj_Entry *obj; { Objlist_Entry *elm; free(obj->path); while (obj->needed != NULL) { Needed_Entry *needed = obj->needed; obj->needed = needed->next; free(needed); } while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); free(elm); } while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); free(elm); } free(obj); } Obj_Entry * _rtld_obj_new(void) { Obj_Entry *obj; obj = CNEW(Obj_Entry); SIMPLEQ_INIT(&obj->dldags); SIMPLEQ_INIT(&obj->dagmembers); return obj; } /* * Given a set of ELF protection flags, return the corresponding protection * flags for MMAP. */ static int protflags(elfflags) int elfflags; { int prot = 0; if (elfflags & PF_R) prot |= PROT_READ; #ifdef RTLD_LOADER if (elfflags & PF_W) prot |= PROT_WRITE; #endif if (elfflags & PF_X) prot |= PROT_EXEC; return prot; }