/* $NetBSD: map_object.c,v 1.60.2.2 2023/08/04 12:55:45 martin Exp $ */ /* * Copyright 1996 John D. Polstra. * Copyright 1996 Matt Thomas * Copyright 2002 Charles M. Hannum * 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 #ifndef lint __RCSID("$NetBSD: map_object.c,v 1.60.2.2 2023/08/04 12:55:45 martin Exp $"); #endif /* not lint */ #include #include #include #include #include #include #include #include #include "debug.h" #include "rtld.h" 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; Elf_Addr base_alignment; Elf_Addr base_vaddr; Elf_Addr base_vlimit; Elf_Addr text_vlimit; int text_flags; void *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; caddr_t gap_addr; size_t gap_size; int i; #ifdef RTLD_LOADER Elf_Addr clear_vaddr; caddr_t clear_addr; size_t nclear; #endif #ifdef GNU_RELRO Elf_Addr relro_page; size_t relro_size; #endif 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) { _rtld_error("%s: read error: %s", path, xstrerror(errno)); goto bad; } /* 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; #ifdef GNU_RELRO relro_page = 0; relro_size = 0; #endif 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; #ifdef GNU_RELRO case PT_GNU_RELRO: relro_page = phdr->p_vaddr; relro_size = phdr->p_memsz; break; #endif 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. */ base_alignment = segs[0]->p_align; 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; dbg(("%s: tls index %zu size %zu align %zu initsize %zu", obj->path, obj->tlsindex, obj->tlssize, obj->tlsalign, obj->tlsinitsize)); } #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; if (base_alignment > _rtld_pagesz) { unsigned int log2 = 0; for (; base_alignment > 1; base_alignment >>= 1) log2++; mapflags = MAP_ALIGNED(log2); } base_addr = NULL; #ifdef RTLD_LOADER if (!obj->isdynamic) { mapflags |= MAP_TRYFIXED; base_addr = (void *)(uintptr_t)base_vaddr; } #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; } #ifdef RTLD_LOADER if (!obj->isdynamic && mapbase != base_addr) { _rtld_error("mmap of executable at correct address failed"); goto bad; } #endif /* 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 (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 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. */ 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; } #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; dbg(("%s: tls init = %p + %"PRImemsz" = %p", obj->path, mapbase, tls_vaddr, obj->tlsinit)); } #endif obj->mapbase = mapbase; obj->mapsize = mapsize; obj->relocbase = mapbase - base_vaddr; #ifdef GNU_RELRO /* rounding happens later. */ obj->relro_page = obj->relocbase + relro_page; obj->relro_size = relro_size; #endif 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_static) _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); } 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; return prot; }