reloc.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * 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.
 */

/*
 * Dynamic linker for ELF.
 *
 * John Polstra <[email protected]>.
 */

#define _WANT_P_OSREL
#include <sys/param.h>
#include <sys/mman.h>

#include <machine/cpufunc.h>
#include <machine/specialreg.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 *)((const char *)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 = globallist_next(dstobj); srcobj != NULL;
			    srcobj = globallist_next(srcobj)) {
				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;
	symval = 0;
	def = NULL;

	/*
	 * 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 *)((const char *)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_static) {
				if (!allocate_tls_offset(__DECONST(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_static) {
				if (!allocate_tls_offset(__DECONST(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;
		case R_X86_64_IRELATIVE:
			obj->irelative_nonplt = true;
			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",
			    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, int flags __unused, RtldLockState *lockstate __unused)
{
	const Elf_Rela *relalim;
	const Elf_Rela *rela;

	relalim = (const Elf_Rela *)((const 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 *)((const 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);
}

/* Fixup the jump slot at "where" to transfer control to "target". */
Elf_Addr
reloc_jmpslot(Elf_Addr *where, Elf_Addr target,
    const struct Struct_Obj_Entry *obj __unused,
    const struct Struct_Obj_Entry *refobj __unused, const Elf_Rel *rel __unused)
{
	dbg("reloc_jmpslot: *%p = %p", where, (void *)target);
	if (!ld_bind_not)
		*where = target;
	return (target);
}

static void
reloc_iresolve_one(Obj_Entry *obj, const Elf_Rela *rela,
    RtldLockState *lockstate)
{
	Elf_Addr *where, target, *ptr;

	ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend);
	where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
	lock_release(rtld_bind_lock, lockstate);
	target = call_ifunc_resolver(ptr);
	wlock_acquire(rtld_bind_lock, lockstate);
	*where = target;
}

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

	if (!obj->irelative)
		return (0);
	obj->irelative = false;
	relalim = (const Elf_Rela *)((const char *)obj->pltrela +
	    obj->pltrelasize);
	for (rela = obj->pltrela; rela < relalim; rela++) {
		if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE)
			reloc_iresolve_one(obj, rela, lockstate);
	}
	return (0);
}

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

	if (!obj->irelative_nonplt)
		return (0);
	obj->irelative_nonplt = false;
	relalim = (const Elf_Rela *)((const char *)obj->rela + obj->relasize);
	for (rela = obj->rela; rela < relalim; rela++) {
		if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE)
			reloc_iresolve_one(obj, rela, lockstate);
	}
	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 *)((const 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);
}

uint32_t cpu_feature, cpu_feature2, cpu_stdext_feature, cpu_stdext_feature2;

void
ifunc_init(Elf_Auxinfo *aux_info[__min_size(AT_COUNT)] __unused)
{
	u_int p[4], cpu_high;

	do_cpuid(1, p);
	cpu_feature = p[3];
	cpu_feature2 = p[2];
	do_cpuid(0, p);
	cpu_high = p[0];
	if (cpu_high >= 7) {
		cpuid_count(7, 0, p);
		cpu_stdext_feature = p[1];
		cpu_stdext_feature2 = p[2];
	}
}

int __getosreldate(void);

void
allocate_initial_tls(Obj_Entry *objs)
{
	void *addr;

	/*
	 * 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 + ld_static_tls_extra;

	addr = allocate_tls(objs, 0, TLS_TCB_SIZE, TLS_TCB_ALIGN);

	/*
	 * This does not use _tcb_set() as it calls amd64_set_tlsbase()
	 * which is an ifunc and rtld must not use ifuncs.
	 */
	if (__getosreldate() >= P_OSREL_TLSBASE)
		sysarch(AMD64_SET_TLSBASE, &addr);
	else if ((cpu_stdext_feature & CPUID_STDEXT_FSGSBASE) != 0)
		wrfsbase((uintptr_t)addr);
	else
		sysarch(AMD64_SET_FSBASE, &addr);
}

void *
__tls_get_addr(tls_index *ti)
{
	return (tls_get_addr_common(_tcb_get(), ti->ti_module, ti->ti_offset));
}

size_t
calculate_tls_offset(size_t prev_offset, size_t prev_size __unused, size_t size,
    size_t align, size_t offset)
{
	size_t res;

	/*
	 * res is the smallest integer satisfying res - prev_offset >= size
	 * and (-res) % p_align = p_vaddr % p_align (= p_offset % p_align).
	 */
	res = prev_offset + size + align - 1;
	res -= (res + offset) & (align - 1);
	return (res);
}

size_t
calculate_first_tls_offset(size_t size, size_t align, size_t offset)
{
	return (calculate_tls_offset(0, 0, size, align, offset));
}