xref: /freebsd/libexec/rtld-elf/powerpc/reloc.c (revision 4b2eaea43fec8e8792be611dea204071a10b655a)

/*      $NetBSD: ppc_reloc.c,v 1.10 2001/09/10 06:09:41 mycroft Exp $   */

/*-
 * Copyright (C) 1998   Tsubai Masanari
 * 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. 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.
 *
 * $FreeBSD$
 */

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

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <machine/cpu.h>

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

#define _ppc_ha(x) ((((u_int32_t)(x) & 0x8000) ? \
                        ((u_int32_t)(x) + 0x10000) : (u_int32_t)(x)) >> 16)
#define _ppc_la(x) ((u_int32_t)(x) & 0xffff)

/*
 * Process the R_PPC_COPY relocations
 */
int
do_copy_relocations(Obj_Entry *dstobj)
{
	const Elf_Rela *relalim;
	const Elf_Rela *rela;

	/*
	 * COPY relocs are invalid outside of the main program
	 */
	assert(dstobj->mainprog);

	relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela +
	    dstobj->relasize);
	for (rela = dstobj->rela;  rela < relalim;  rela++) {
		void *dstaddr;
		const Elf_Sym *dstsym;
		const char *name;
		unsigned long hash;
		size_t size;
		const void *srcaddr;
		const Elf_Sym *srcsym = NULL;
		Obj_Entry *srcobj;

		if (ELF_R_TYPE(rela->r_info) != R_PPC_COPY) {
			continue;
		}

		dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
		dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
		name = dstobj->strtab + dstsym->st_name;
		hash = elf_hash(name);
		size = dstsym->st_size;

		for (srcobj = dstobj->next;  srcobj != NULL;
		     srcobj = srcobj->next) {
			if ((srcsym = symlook_obj(name, hash, srcobj, false))
			    != NULL) {
				break;
			}
		}

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

		srcaddr = (const void *) (srcobj->relocbase+srcsym->st_value);
		memcpy(dstaddr, srcaddr, size);
		dbg("copy_reloc: src=%p,dst=%p,size=%d\n",srcaddr,dstaddr,size);
	}

	return (0);
}


/*
 * Perform early relocation of the run-time linker image
 */
void
reloc_non_plt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
{
	const Elf_Rela *rela = 0, *relalim;
	Elf_Addr relasz = 0;
	Elf_Addr *where;

	/*
	 * Extract the rela/relasz values from the dynamic section
	 */
	for (; dynp->d_tag != DT_NULL; dynp++) {
		switch (dynp->d_tag) {
		case DT_RELA:
			rela = (const Elf_Rela *)(relocbase+dynp->d_un.d_ptr);
			break;
		case DT_RELASZ:
			relasz = dynp->d_un.d_val;
			break;
		}
	}

	/*
	 * Relocate these values
	 */
	relalim = (const Elf_Rela *)((caddr_t)rela + relasz);
	for (; rela < relalim; rela++) {
		where = (Elf_Addr *)(relocbase + rela->r_offset);
		*where = (Elf_Addr)(relocbase + rela->r_addend);
	}
}


/*
 * Relocate a non-PLT object with addend.
 */
static int
reloc_nonplt_object(Obj_Entry *obj_rtld, Obj_Entry *obj, const Elf_Rela *rela,
		    SymCache *cache)
{
	Elf_Addr        *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
	const Elf_Sym   *def;
	const Obj_Entry *defobj;
	Elf_Addr         tmp;

	switch (ELF_R_TYPE(rela->r_info)) {

	case R_PPC_NONE:
		break;

        case R_PPC_ADDR32:    /* word32 S + A */
        case R_PPC_GLOB_DAT:  /* word32 S + A */
		def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
				  false, cache);
		if (def == NULL) {
			return (-1);
		}

                tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
                    rela->r_addend);

		/* Don't issue write if unnecessary; avoid COW page fault */
                if (*where != tmp) {
                        *where = tmp;
		}
                break;

        case R_PPC_RELATIVE:  /* word32 B + A */
		tmp = (Elf_Addr)(obj->relocbase + rela->r_addend);

		/* As above, don't issue write unnecessarily */
		if (*where != tmp) {
			*where = tmp;
		}
		break;

	case R_PPC_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_COPY "
				    " relocation in shared library",
				    obj->path);
			return (-1);
		}
		break;

	case R_PPC_JMP_SLOT:
		/*
		 * These will be handled by the plt/jmpslot routines
		 */
		break;

	default:
		_rtld_error("%s: Unsupported relocation type %d"
			    " in non-PLT relocations\n", obj->path,
			    ELF_R_TYPE(rela->r_info));
		return (-1);
        }
	return (0);
}


/*
 * Process non-PLT relocations
 */
int
reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
{
	const Elf_Rela *relalim;
	const Elf_Rela *rela;
	SymCache *cache;
	int bytes = obj->nchains * sizeof(SymCache);
	int r = -1;

	/*
	 * The dynamic loader may be called from a thread, we have
	 * limited amounts of stack available so we cannot use alloca().
	 */
	cache = mmap(NULL, bytes, PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
	if (cache == MAP_FAILED) {
		cache = NULL;
	}
	if (cache != NULL) {
		memset(cache, 0, obj->nchains * sizeof(SymCache));
	}

	/*
	 * From the SVR4 PPC ABI:
	 * "The PowerPC family uses only the Elf32_Rela relocation
	 *  entries with explicit addends."
	 */
	relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize);
	for (rela = obj->rela; rela < relalim; rela++) {
		if (reloc_nonplt_object(obj_rtld, obj, rela, cache) < 0)
			goto done;
	}
	r = 0;
done:
	if (cache) {
		munmap(cache, bytes);
	}
	return (r);
}


/*
 * Initialise a PLT slot to the resolving trampoline
 */
static int
reloc_plt_object(Obj_Entry *obj, const Elf_Rela *rela)
{
	Elf_Word *where = (Elf_Word *)(obj->relocbase + rela->r_offset);
	Elf_Addr *pltresolve;
	Elf_Addr distance;
	int reloff;

	reloff = rela - obj->pltrela;

	if ((reloff < 0) || (reloff >= 0x8000)) {
		return (-1);
	}

	pltresolve = obj->pltgot + 8;

	distance = (Elf_Addr)pltresolve - (Elf_Addr)(where + 1);

	dbg(" reloc_plt_object: where=%p,pltres=%p,reloff=%x,distance=%x",
	    (void *)where, (void *)pltresolve, reloff, distance);

	/* li   r11,reloff  */
	/* b    pltresolve  */
	where[0] = 0x39600000 | reloff;
	where[1] = 0x48000000 | (distance & 0x03fffffc);

	/*
	 * The icache will be sync'd in init_pltgot, which is called
	 * after all the slots have been updated
	 */

	return (0);
}


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

	if (obj->pltrelasize != 0) {

		relalim = (const Elf_Rela *)((char *)obj->pltrela +
		    obj->pltrelasize);
		for (rela = obj->pltrela;  rela < relalim;  rela++) {
			assert(ELF_R_TYPE(rela->r_info) == R_PPC_JMP_SLOT);

			if (reloc_plt_object(obj, rela) < 0) {
				return (-1);
			}
		}
	}

	return (0);
}


/*
 * LD_BIND_NOW was set - force relocation for all jump slots
 */
int
reloc_jmpslots(Obj_Entry *obj)
{
	const Obj_Entry *defobj;
	const Elf_Rela *relalim;
	const Elf_Rela *rela;
	const Elf_Sym *def;
	Elf_Addr *where;
	Elf_Addr target;

	relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
	for (rela = obj->pltrela; rela < relalim; rela++) {
		assert(ELF_R_TYPE(rela->r_info) == R_PPC_JMP_SLOT);
		where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
		def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
		   true, NULL);
		if (def == NULL) {
			dbg("reloc_jmpslots: sym not found");
			return (-1);
		}

		target = (Elf_Addr)(defobj->relocbase + def->st_value);

#if 0
		/* PG XXX */
		dbg("\"%s\" in \"%s\" --> %p in \"%s\"",
		    defobj->strtab + def->st_name, basename(obj->path),
		    (void *)target, basename(defobj->path));
#endif

		reloc_jmpslot(where, target, defobj, obj,
		    (const Elf_Rel *) rela);
	}

	obj->jmpslots_done = true;

	return (0);
}


/*
 * Update the value of a PLT jump slot. Branch directly to the target if
 * it is within +/- 32Mb, otherwise go indirectly via the pltcall
 * trampoline call and jump table.
 */
Elf_Addr
reloc_jmpslot(Elf_Addr *wherep, Elf_Addr target, const Obj_Entry *defobj,
	      const Obj_Entry *obj, const Elf_Rel *rel)
{
	Elf_Addr offset;
	const Elf_Rela *rela = (const Elf_Rela *) rel;

	dbg(" reloc_jmpslot: where=%p, target=%p",
	    (void *)wherep, (void *)target);

	/*
	 * At the PLT entry pointed at by `wherep', construct
	 * a direct transfer to the now fully resolved function
	 * address.
	 */
	offset = target - (Elf_Addr)wherep;

	if (abs(offset) < 32*1024*1024) {     /* inside 32MB? */
		/* b    value   # branch directly */
		*wherep = 0x48000000 | (offset & 0x03fffffc);
		__syncicache(wherep, 4);
	} else {
		Elf_Addr *pltcall, *jmptab;
		int distance;
		int N = obj->pltrelasize / sizeof(Elf_Rela);
		int reloff = rela - obj->pltrela;

		if ((reloff < 0) || (reloff >= 0x8000)) {
			return (-1);
		}

		pltcall = obj->pltgot;

		dbg(" reloc_jmpslot: indir, reloff=%d, N=%d\n",
		    reloff, N);

		jmptab = obj->pltgot + 18 + N * 2;
		jmptab[reloff] = target;

		distance = (Elf_Addr)pltcall - (Elf_Addr)(wherep + 1);

		/* li   r11,reloff */
		/* b    pltcall  # use indirect pltcall routine */
		wherep[0] = 0x39600000 | reloff;
		wherep[1] = 0x48000000 | (distance & 0x03fffffc);
		__syncicache(wherep, 8);
	}

	return (target);
}


/*
 * Setup the plt glue routines.
 */
#define PLTCALL_SIZE    20
#define PLTRESOLVE_SIZE 24

void
init_pltgot(Obj_Entry *obj)
{
	Elf_Word *pltcall, *pltresolve;
	Elf_Word *jmptab;
	int N = obj->pltrelasize / sizeof(Elf_Rela);

	pltcall = obj->pltgot;

	if (pltcall == NULL) {
		return;
	}

	/*
	 * From the SVR4 PPC ABI:
	 *
	 * 'The first 18 words (72 bytes) of the PLT are reserved for
	 * use by the dynamic linker.
	 *   ...
	 * 'If the executable or shared object requires N procedure
	 *  linkage table entries, the link editor shall reserve 3*N
	 *  words (12*N bytes) following the 18 reserved words. The
	 *  first 2*N of these words are the procedure linkage table
	 *  entries themselves. The static linker directs calls to bytes
	 *  (72 + (i-1)*8), for i between 1 and N inclusive. The remaining
	 *  N words (4*N bytes) are reserved for use by the dynamic linker.'
	 */

	/*
	 * Copy the absolute-call assembler stub into the first part of
	 * the reserved PLT area.
	 */
	memcpy(pltcall, _rtld_powerpc_pltcall, PLTCALL_SIZE);

	/*
	 * Determine the address of the jumptable, which is the dyn-linker
	 * reserved area after the call cells. Write the absolute address
	 * of the jumptable into the absolute-call assembler code so it
	 * can determine this address.
	 */
	jmptab = pltcall + 18 + N * 2;
	pltcall[1] |= _ppc_ha(jmptab);	   /* addis 11,11,jmptab@ha */
	pltcall[2] |= _ppc_la(jmptab);     /* lwz   11,jmptab@l(11) */

	/*
	 * Skip down 32 bytes into the initial reserved area and copy
	 * in the standard resolving assembler call. Into this assembler,
	 * insert the absolute address of the _rtld_bind_start routine
	 * and the address of the relocation object.
	 */
	pltresolve = obj->pltgot + 8;

	memcpy(pltresolve, _rtld_powerpc_pltresolve, PLTRESOLVE_SIZE);
	pltresolve[0] |= _ppc_ha(_rtld_bind_start);
	pltresolve[1] |= _ppc_la(_rtld_bind_start);
	pltresolve[3] |= _ppc_ha(obj);
	pltresolve[4] |= _ppc_la(obj);

	/*
	 * Sync the icache for the byte range represented by the
	 * trampoline routines and call slots.
	 */
	__syncicache(pltcall, 72 + N * 8);
}