rtld-elf/amd64/reloc.c

/*-
 * Copyright 1996, 1997, 1998, 1999 John D. Polstra.
 * 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 ``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.
 *
 * $FreeBSD: stable/10/libexec/rtld-elf/amd64/reloc.c 281453 2015-04-12 06:45:40Z kib $
 */

/*
 * Dynamic linker for ELF.
 *
 * John Polstra <jdp@polstra.com>.
 */

#include <sys/param.h>
#include <sys/mman.h>
#include <machine/sysarch.h>

#include <dlfcn.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "debug.h"
#include "rtld.h"
#include "rtld_tls.h"

/*
 * Process the special R_X86_64_COPY relocations in the main program.  These
 * copy data from a shared object into a region in the main program's BSS
 * segment.
 *
 * Returns 0 on success, -1 on failure.
 */
int
do_copy_relocations(Obj_Entry *dstobj)
{
    const Elf_Rela *relalim;
    const Elf_Rela *rela;

    assert(dstobj->mainprog);	/* COPY relocations are invalid elsewhere */

    relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize);
    for (rela = dstobj->rela;  rela < relalim;  rela++) {
	if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) {
	    void *dstaddr;
	    const Elf_Sym *dstsym;
	    const char *name;
	    size_t size;
	    const void *srcaddr;
	    const Elf_Sym *srcsym;
	    const Obj_Entry *srcobj, *defobj;
	    SymLook req;
	    int res;

	    dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
	    dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
	    name = dstobj->strtab + dstsym->st_name;
	    size = dstsym->st_size;
	    symlook_init(&req, name);
	    req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info));
	    req.flags = SYMLOOK_EARLY;

	    for (srcobj = dstobj->next;  srcobj != NULL;  srcobj = srcobj->next) {
		res = symlook_obj(&req, srcobj);
		if (res == 0) {
		    srcsym = req.sym_out;
		    defobj = req.defobj_out;
		    break;
		}
	    }

	    if (srcobj == NULL) {
		_rtld_error("Undefined symbol \"%s\" referenced from COPY"
		  " relocation in %s", name, dstobj->path);
		return -1;
	    }

	    srcaddr = (const void *) (defobj->relocbase + srcsym->st_value);
	    memcpy(dstaddr, srcaddr, size);
	}
    }

    return 0;
}

/* Initialize the special GOT entries. */
void
init_pltgot(Obj_Entry *obj)
{
    if (obj->pltgot != NULL) {
	obj->pltgot[1] = (Elf_Addr) obj;
	obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
    }
}

/* Process the non-PLT relocations. */
int
reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
    RtldLockState *lockstate)
{
	const Elf_Rela *relalim;
	const Elf_Rela *rela;
	SymCache *cache;
	const Elf_Sym *def;
	const Obj_Entry *defobj;
	Elf_Addr *where, symval;
	Elf32_Addr *where32;
	int r;

	r = -1;
	/*
	 * The dynamic loader may be called from a thread, we have
	 * limited amounts of stack available so we cannot use alloca().
	 */
	if (obj != obj_rtld) {
		cache = calloc(obj->dynsymcount, sizeof(SymCache));
		/* No need to check for NULL here */
	} else
		cache = NULL;

	relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize);
	for (rela = obj->rela;  rela < relalim;  rela++) {
		/*
		 * First, resolve symbol for relocations which
		 * reference symbols.
		 */
		switch (ELF_R_TYPE(rela->r_info)) {
		case R_X86_64_64:
		case R_X86_64_PC32:
		case R_X86_64_GLOB_DAT:
		case R_X86_64_TPOFF64:
		case R_X86_64_TPOFF32:
		case R_X86_64_DTPMOD64:
		case R_X86_64_DTPOFF64:
		case R_X86_64_DTPOFF32:
			def = find_symdef(ELF_R_SYM(rela->r_info), obj,
			    &defobj, flags, cache, lockstate);
			if (def == NULL)
				goto done;
			/*
			 * If symbol is IFUNC, only perform relocation
			 * when caller allowed it by passing
			 * SYMLOOK_IFUNC flag.  Skip the relocations
			 * otherwise.
			 *
			 * Also error out in case IFUNC relocations
			 * are specified for TLS, which cannot be
			 * usefully interpreted.
			 */
			if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
				switch (ELF_R_TYPE(rela->r_info)) {
				case R_X86_64_64:
				case R_X86_64_PC32:
				case R_X86_64_GLOB_DAT:
					if ((flags & SYMLOOK_IFUNC) == 0) {
						obj->non_plt_gnu_ifunc = true;
						continue;
					}
					symval = (Elf_Addr)rtld_resolve_ifunc(
					    defobj, def);
					break;
				case R_X86_64_TPOFF64:
				case R_X86_64_TPOFF32:
				case R_X86_64_DTPMOD64:
				case R_X86_64_DTPOFF64:
				case R_X86_64_DTPOFF32:
					_rtld_error("%s: IFUNC for TLS reloc",
					    obj->path);
					goto done;
				}
			} else {
				if ((flags & SYMLOOK_IFUNC) != 0)
					continue;
				symval = (Elf_Addr)defobj->relocbase +
				    def->st_value;
			}
			break;
		default:
			if ((flags & SYMLOOK_IFUNC) != 0)
				continue;
			break;
		}
		where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
		where32 = (Elf32_Addr *)where;

		switch (ELF_R_TYPE(rela->r_info)) {
		case R_X86_64_NONE:
			break;
		case R_X86_64_64:
			*where = symval + rela->r_addend;
			break;
		case R_X86_64_PC32:
			/*
			 * I don't think the dynamic linker should
			 * ever see this type of relocation.  But the
			 * binutils-2.6 tools sometimes generate it.
			 */
			*where32 = (Elf32_Addr)(unsigned long)(symval +
		            rela->r_addend - (Elf_Addr)where);
			break;
		/* missing: R_X86_64_GOT32 R_X86_64_PLT32 */
		case R_X86_64_COPY:
			/*
			 * These are deferred until all other relocations have
			 * been done.  All we do here is make sure that the COPY
			 * relocation is not in a shared library.  They are allowed
			 * only in executable files.
			 */
			if (!obj->mainprog) {
				_rtld_error("%s: Unexpected R_X86_64_COPY "
				    "relocation in shared library", obj->path);
				goto done;
			}
			break;
		case R_X86_64_GLOB_DAT:
			*where = symval;
			break;
		case R_X86_64_TPOFF64:
			/*
			 * We lazily allocate offsets for static TLS
			 * as we see the first relocation that
			 * references the TLS block. This allows us to
			 * support (small amounts of) static TLS in
			 * dynamically loaded modules. If we run out
			 * of space, we generate an error.
			 */
			if (!defobj->tls_done) {
				if (!allocate_tls_offset((Obj_Entry*) defobj)) {
					_rtld_error("%s: No space available "
					    "for static Thread Local Storage",
					    obj->path);
					goto done;
				}
			}
			*where = (Elf_Addr)(def->st_value - defobj->tlsoffset +
			    rela->r_addend);
			break;
		case R_X86_64_TPOFF32:
			/*
			 * We lazily allocate offsets for static TLS
			 * as we see the first relocation that
			 * references the TLS block. This allows us to
			 * support (small amounts of) static TLS in
			 * dynamically loaded modules. If we run out
			 * of space, we generate an error.
			 */
			if (!defobj->tls_done) {
				if (!allocate_tls_offset((Obj_Entry*) defobj)) {
					_rtld_error("%s: No space available "
					    "for static Thread Local Storage",
					    obj->path);
					goto done;
				}
			}
			*where32 = (Elf32_Addr)(def->st_value -
			    defobj->tlsoffset + rela->r_addend);
			break;
		case R_X86_64_DTPMOD64:
			*where += (Elf_Addr)defobj->tlsindex;
			break;
		case R_X86_64_DTPOFF64:
			*where += (Elf_Addr)(def->st_value + rela->r_addend);
			break;
		case R_X86_64_DTPOFF32:
			*where32 += (Elf32_Addr)(def->st_value +
			    rela->r_addend);
			break;
		case R_X86_64_RELATIVE:
			*where = (Elf_Addr)(obj->relocbase + rela->r_addend);
			break;
		/*
		 * missing:
		 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16,
		 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8
		 */
		default:
			_rtld_error("%s: Unsupported relocation type %u"
			    " in non-PLT relocations\n", obj->path,
			    (unsigned int)ELF_R_TYPE(rela->r_info));
			goto done;
		}
	}
	r = 0;
done:
	free(cache);
	return (r);
}

/* Process the PLT relocations. */
int
reloc_plt(Obj_Entry *obj)
{
    const Elf_Rela *relalim;
    const Elf_Rela *rela;

    relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
    for (rela = obj->pltrela;  rela < relalim;  rela++) {
	Elf_Addr *where;

	switch(ELF_R_TYPE(rela->r_info)) {
	case R_X86_64_JMP_SLOT:
	  /* Relocate the GOT slot pointing into the PLT. */
	  where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
	  *where += (Elf_Addr)obj->relocbase;
	  break;

	case R_X86_64_IRELATIVE:
	  obj->irelative = true;
	  break;

	default:
	  _rtld_error("Unknown relocation type %x in PLT",
	    (unsigned int)ELF_R_TYPE(rela->r_info));
	  return (-1);
	}
    }
    return 0;
}

/* Relocate the jump slots in an object. */
int
reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate)
{
    const Elf_Rela *relalim;
    const Elf_Rela *rela;

    if (obj->jmpslots_done)
	return 0;
    relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
    for (rela = obj->pltrela;  rela < relalim;  rela++) {
	Elf_Addr *where, target;
	const Elf_Sym *def;
	const Obj_Entry *defobj;

	switch (ELF_R_TYPE(rela->r_info)) {
	case R_X86_64_JMP_SLOT:
	  where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
	  def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
		SYMLOOK_IN_PLT | flags, NULL, lockstate);
	  if (def == NULL)
	      return (-1);
	  if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
	      obj->gnu_ifunc = true;
	      continue;
	  }
	  target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend);
	  reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela);
	  break;

	case R_X86_64_IRELATIVE:
	  break;

	default:
	  _rtld_error("Unknown relocation type %x in PLT",
	    (unsigned int)ELF_R_TYPE(rela->r_info));
	  return (-1);
	}
    }
    obj->jmpslots_done = true;
    return 0;
}

int
reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate)
{
    const Elf_Rela *relalim;
    const Elf_Rela *rela;

    if (!obj->irelative)
	return (0);
    relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
    for (rela = obj->pltrela;  rela < relalim;  rela++) {
	Elf_Addr *where, target, *ptr;

	switch (ELF_R_TYPE(rela->r_info)) {
	case R_X86_64_JMP_SLOT:
	  break;

	case R_X86_64_IRELATIVE:
	  ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend);
	  where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
	  lock_release(rtld_bind_lock, lockstate);
	  target = ((Elf_Addr (*)(void))ptr)();
	  wlock_acquire(rtld_bind_lock, lockstate);
	  *where = target;
	  break;
	}
    }
    obj->irelative = false;
    return (0);
}

int
reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate)
{
    const Elf_Rela *relalim;
    const Elf_Rela *rela;

    if (!obj->gnu_ifunc)
	return (0);
    relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
    for (rela = obj->pltrela;  rela < relalim;  rela++) {
	Elf_Addr *where, target;
	const Elf_Sym *def;
	const Obj_Entry *defobj;

	switch (ELF_R_TYPE(rela->r_info)) {
	case R_X86_64_JMP_SLOT:
	  where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
	  def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
		SYMLOOK_IN_PLT | flags, NULL, lockstate);
	  if (def == NULL)
	      return (-1);
	  if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC)
	      continue;
	  lock_release(rtld_bind_lock, lockstate);
	  target = (Elf_Addr)rtld_resolve_ifunc(defobj, def);
	  wlock_acquire(rtld_bind_lock, lockstate);
	  reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela);
	  break;
	}
    }
    obj->gnu_ifunc = false;
    return (0);
}

void
allocate_initial_tls(Obj_Entry *objs)
{
    /*
     * Fix the size of the static TLS block by using the maximum
     * offset allocated so far and adding a bit for dynamic modules to
     * use.
     */
    tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
    amd64_set_fsbase(allocate_tls(objs, 0,
				  3*sizeof(Elf_Addr), sizeof(Elf_Addr)));
}

void *__tls_get_addr(tls_index *ti)
{
    Elf_Addr** segbase;

    __asm __volatile("movq %%fs:0, %0" : "=r" (segbase));

    return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset);
}