xref: /src/libexec/ld.elf_so/arch/hppa/hppa_reloc.c

/*	$NetBSD: hppa_reloc.c,v 1.29 2009/08/29 13:46:54 jmmv Exp $	*/

/*-
 * Copyright (c) 2002, 2004 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Matt Fredette and Nick Hudson.
 *
 * 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``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 FOUNDATION OR CONTRIBUTORS
 * 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 <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: hppa_reloc.c,v 1.29 2009/08/29 13:46:54 jmmv Exp $");
#endif /* not lint */

#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/queue.h>

#include <string.h>

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

#ifdef RTLD_DEBUG_HPPA
#define	hdbg(x)		xprintf x
#else
#define	hdbg(x)		/* nothing */
#endif

caddr_t _rtld_bind(const Obj_Entry *, const Elf_Addr);
void _rtld_bind_start(void);
void __rtld_setup_hppa_pltgot(const Obj_Entry *, Elf_Addr *);

/*
 * It is possible for the compiler to emit relocations for unaligned data.
 * We handle this situation with these inlines.
 */
#define	RELOC_ALIGNED_P(x) \
	(((uintptr_t)(x) & (sizeof(void *) - 1)) == 0)

static inline Elf_Addr
load_ptr(void *where)
{
	if (__predict_true(RELOC_ALIGNED_P(where)))
		return *(Elf_Addr *)where;
	else {
		Elf_Addr res;

		(void)memcpy(&res, where, sizeof(res));
		return res;
	}
}

static inline void
store_ptr(void *where, Elf_Addr val)
{
	if (__predict_true(RELOC_ALIGNED_P(where)))
		*(Elf_Addr *)where = val;
	else
		(void)memcpy(where, &val, sizeof(val));
}

/*
 * In the runtime architecture (ABI), PLABEL function
 * pointers are distinguished from normal function
 * pointers by having the next-least-significant bit
 * set.  (This bit is referred to as the L field in
 * HP documentation).  The $$dyncall millicode is
 * aware of this.
 */
#define	RTLD_MAKE_PLABEL(plabel)	(((Elf_Addr)(plabel)) | (1 << 1))
#define RTLD_IS_PLABEL(addr)		(((Elf_Addr)(addr)) & (1 << 1))
#define	RTLD_GET_PLABEL(addr)	((hppa_plabel *) (((Elf_Addr)addr) & ~3))

/*
 * This is the PLABEL structure.  The function PC and
 * shared linkage members must come first, as they are
 * the actual PLABEL.
 */
typedef struct _hppa_plabel {
	Elf_Addr	hppa_plabel_pc;
	Elf_Addr	hppa_plabel_sl;
	SLIST_ENTRY(_hppa_plabel)	hppa_plabel_next;
} hppa_plabel;

/*
 * For now allocated PLABEL structures are tracked on a
 * singly linked list.  This maybe should be revisited.
 */
static SLIST_HEAD(hppa_plabel_head, _hppa_plabel) hppa_plabel_list
    = SLIST_HEAD_INITIALIZER(hppa_plabel_list);

/*
 * Because I'm hesitant to use NEW while relocating self,
 * this is a small pool of preallocated PLABELs.
 */
#define	HPPA_PLABEL_PRE	(12)
static hppa_plabel hppa_plabel_pre[HPPA_PLABEL_PRE];
static int hppa_plabel_pre_next = 0;

void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
int _rtld_relocate_plt_objects(const Obj_Entry *);
static inline int _rtld_relocate_plt_object(const Obj_Entry *,
    const Elf_Rela *, Elf_Addr *);

/*
 * This bootstraps the dynamic linker by relocating its GOT.
 * On the hppa, unlike on other architectures, static strings
 * are found through the GOT.  Static strings are essential
 * for RTLD_DEBUG, and I suspect they're used early even when
 * !defined(RTLD_DEBUG), making relocating the GOT essential.
 *
 * It gets worse.  Relocating the GOT doesn't mean just walking
 * it and adding the relocbase to all of the entries.  You must
 * find and use the GOT relocations, since those RELA relocations
 * have the necessary addends - the GOT comes initialized as
 * zeroes.
 */
void
_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
{
	const Elf_Rela	*relafirst, *rela, *relalim;
	Elf_Addr        relasz;
	void		*where;
	Elf_Addr	*pltgot;
	const Elf_Rela	*plabel_relocs[HPPA_PLABEL_PRE];
	int		nplabel_relocs = 0;
	int		i;
	const Elf_Sym	*symtab, *sym;
	unsigned long	symnum;
	hppa_plabel	*plabel;

	/*
	 * Process the DYNAMIC section, looking for the non-PLT relocations.
	 */
	relafirst = NULL;
	relasz = 0;
	symtab = NULL;
	pltgot = NULL;
	for (; dynp->d_tag != DT_NULL; ++dynp) {
		switch (dynp->d_tag) {

		case DT_RELA:
			relafirst = (const Elf_Rela *)
			    (relocbase + dynp->d_un.d_ptr);
			break;

		case DT_RELASZ:
			relasz = dynp->d_un.d_val;
			break;

		case DT_SYMTAB:
			symtab = (const Elf_Sym *)
			    (relocbase + dynp->d_un.d_ptr);
			break;

		case DT_PLTGOT:
			pltgot = (Elf_Addr *)
			    (relocbase + dynp->d_un.d_ptr);
                        break;
		}
	}
	relalim = (const Elf_Rela *)((const char *)relafirst + relasz);

	for (rela = relafirst; rela < relalim; rela++) {
		symnum = ELF_R_SYM(rela->r_info);
		where = (void *)(relocbase + rela->r_offset);

		switch (ELF_R_TYPE(rela->r_info)) {
		case R_TYPE(DIR32):
			if (symnum == 0)
				store_ptr(where,
				    relocbase + rela->r_addend);
			else {
				sym = symtab + symnum;
				store_ptr(where,
				    relocbase + rela->r_addend + sym->st_value);
			}
			break;

		case R_TYPE(PLABEL32):
			/*
			 * PLABEL32 relocation processing is done in two phases
			 *
			 *  i) local function relocations (symbol number == 0)
			 *     can be resolved immediately.
			 *
			 * ii) external function relocations are deferred until
			 *     we finish all other relocations so that global
			 *     data isn't accessed until all other non-PLT
			 *     relocations have been done.
			 */
			if (symnum == 0)
				*((Elf_Addr *)where) =
				    relocbase + rela->r_addend;
			else
				plabel_relocs[nplabel_relocs++] = rela;
			break;

		default:
			break;
		}
	}

	assert(nplabel_relocs < HPPA_PLABEL_PRE);
	for (i = 0; i < nplabel_relocs; i++) {
		rela = plabel_relocs[i];
		where = (void *)(relocbase + rela->r_offset);
		sym = symtab + ELF_R_SYM(rela->r_info);

		plabel = &hppa_plabel_pre[hppa_plabel_pre_next++];

        	plabel->hppa_plabel_pc = (Elf_Addr)
		    (relocbase + sym->st_value + rela->r_addend);
        	plabel->hppa_plabel_sl = (Elf_Addr)pltgot;

        	SLIST_INSERT_HEAD(&hppa_plabel_list, plabel, hppa_plabel_next);
		*((Elf_Addr *)where) = (Elf_Addr)(RTLD_MAKE_PLABEL(plabel));
	}

#if defined(RTLD_DEBUG_HPPA)
	for (rela = relafirst; rela < relalim; rela++) {
		where = (void *)(relocbase + rela->r_offset);

		switch (ELF_R_TYPE(rela->r_info)) {
		case R_TYPE(DIR32):
			hdbg(("DIR32 rela @%p(%p) -> %p(%p)\n",
			    (void *)rela->r_offset,
			    (void *)where,
			    (void *)rela->r_addend,
			    (void *)*((Elf_Addr *)where) ));
			break;

		case R_TYPE(PLABEL32):
			symnum = ELF_R_SYM(rela->r_info);
			if (symnum == 0) {
				hdbg(("PLABEL rela @%p(%p) -> %p(%p)\n",
		    		    (void *)rela->r_offset,
		    		    (void *)where,
		    		    (void *)rela->r_addend,
		    		    (void *)*((Elf_Addr *)where) ));
			} else {
				sym = symtab + symnum;

				hdbg(("PLABEL32 rela @%p(%p), symnum=%ld(%p) -> %p(%p)\n",
			    	    (void *)rela->r_offset,
				    (void *)where,
				    symnum,
				    (void *)sym->st_value,
			    	    (void *)rela->r_addend,
				    (void *)*((Elf_Addr *)where) ));
			}
			break;
		default:
			hdbg(("rela XXX reloc\n"));
			break;
		}
	}
#endif /* RTLD_DEBUG_HPPA */
}

/*
 * This allocates a PLABEL.  If called with a non-NULL def, the
 * plabel is for the function associated with that definition
 * in the defining object defobj, plus the given addend.  If
 * called with a NULL def, the plabel is for the function at
 * the (unrelocated) address in addend in the object defobj.
 */
Elf_Addr
_rtld_function_descriptor_alloc(const Obj_Entry *defobj, const Elf_Sym *def,
    Elf_Addr addend)
{
	Elf_Addr	func_pc, func_sl;
	hppa_plabel	*plabel;

	if (def != NULL) {

		/*
		 * We assume that symbols of type STT_NOTYPE
		 * are undefined.  Return NULL for these.
		 */
		if (ELF_ST_TYPE(def->st_info) == STT_NOTYPE)
			return (Elf_Addr)NULL;

		/* Otherwise assert that this symbol must be a function. */
		assert(ELF_ST_TYPE(def->st_info) == STT_FUNC);

		func_pc = (Elf_Addr)(defobj->relocbase + def->st_value +
		    addend);
	} else
		func_pc = (Elf_Addr)(defobj->relocbase + addend);

	/*
	 * Search the existing PLABELs for one matching
	 * this function.  If there is one, return it.
	 */
	func_sl = (Elf_Addr)(defobj->pltgot);
	SLIST_FOREACH(plabel, &hppa_plabel_list, hppa_plabel_next)
		if (plabel->hppa_plabel_pc == func_pc &&
		    plabel->hppa_plabel_sl == func_sl)
			return RTLD_MAKE_PLABEL(plabel);

	/*
	 * Once we've used up the preallocated set, we start
	 * using NEW to allocate plabels.
	 */
	if (hppa_plabel_pre_next < HPPA_PLABEL_PRE)
		plabel = &hppa_plabel_pre[hppa_plabel_pre_next++];
	else {
		plabel = NEW(hppa_plabel);
		if (plabel == NULL)
			return (Elf_Addr)-1;
	}

	/* Fill the new entry and insert it on the list. */
	plabel->hppa_plabel_pc = func_pc;
	plabel->hppa_plabel_sl = func_sl;
	SLIST_INSERT_HEAD(&hppa_plabel_list, plabel, hppa_plabel_next);

	return RTLD_MAKE_PLABEL(plabel);
}

/*
 * If a pointer is a PLABEL, this unwraps it.
 */
const void *
_rtld_function_descriptor_function(const void *addr)
{
	return (RTLD_IS_PLABEL(addr) ?
	    (const void *) RTLD_GET_PLABEL(addr)->hppa_plabel_pc :
	    addr);
}

/* This sets up an object's GOT. */
void
_rtld_setup_pltgot(const Obj_Entry *obj)
{
	__rtld_setup_hppa_pltgot(obj, obj->pltgot);
}

int
_rtld_relocate_nonplt_objects(const Obj_Entry *obj)
{
	const Elf_Rela *rela;

	for (rela = obj->rela; rela < obj->relalim; rela++) {
		Elf_Addr        *where;
		const Elf_Sym   *def;
		const Obj_Entry *defobj;
		Elf_Addr         tmp;
		unsigned long	 symnum;

		where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
		symnum = ELF_R_SYM(rela->r_info);

		switch (ELF_R_TYPE(rela->r_info)) {
		case R_TYPE(NONE):
			break;

		case R_TYPE(DIR32):
			if (symnum) {
				/*
				 * This is either a DIR32 against a symbol
				 * (def->st_name != 0), or against a local
				 * section (def->st_name == 0).
				 */
				def = obj->symtab + symnum;
				defobj = obj;
				if (def->st_name != 0)
					def = _rtld_find_symdef(symnum, obj,
					    &defobj, false);
				if (def == NULL)
					return -1;

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

				if (load_ptr(where) != tmp)
					store_ptr(where, tmp);
				rdbg(("DIR32 %s in %s --> %p in %s",
				    obj->strtab + obj->symtab[symnum].st_name,
				    obj->path, (void *)load_ptr(where), defobj->path));
			} else {
				tmp = (Elf_Addr)(obj->relocbase +
				    rela->r_addend);

				if (load_ptr(where) != tmp)
					store_ptr(where, tmp);
				rdbg(("DIR32 in %s --> %p", obj->path,
					    (void *)load_ptr(where)));
			}
			break;

		case R_TYPE(PLABEL32):
			if (symnum) {
				def = _rtld_find_symdef(symnum, obj, &defobj,
				    false);
				if (def == NULL)
					return -1;

				tmp = _rtld_function_descriptor_alloc(defobj,
				    def, rela->r_addend);
				if (tmp == (Elf_Addr)-1)
					return -1;

				if (*where != tmp)
					*where = tmp;
				rdbg(("PLABEL32 %s in %s --> %p in %s",
				    obj->strtab + obj->symtab[symnum].st_name,
				    obj->path, (void *)*where, defobj->path));
			} else {
				/*
				 * This is a PLABEL for a static function, and
				 * the dynamic linker has both allocated a PLT
				 * entry for this function and told us where it
				 * is.  We can safely use the PLT entry as the
				 * PLABEL because there should be no other
				 * PLABEL reloc referencing this function.
				 * This object should also have an IPLT
				 * relocation to initialize the PLT entry.
				 *
				 * The dynamic linker should also have ensured
				 * that the addend has the
				 * next-least-significant bit set; the
				 * $$dyncall millicode uses this to distinguish
				 * a PLABEL pointer from a plain function
				 * pointer.
				 */
				tmp = (Elf_Addr)
				    (obj->relocbase + rela->r_addend);

				if (*where != tmp)
					*where = tmp;
				rdbg(("PLABEL32 in %s --> %p", obj->path,
				    (void *)*where));
			}
			break;

		case R_TYPE(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->isdynamic) {
				_rtld_error(
			"%s: Unexpected R_COPY relocation in shared library",
				    obj->path);
				return -1;
			}
			rdbg(("COPY (avoid in main)"));
			break;

		default:
			rdbg(("sym = %lu, type = %lu, offset = %p, "
			    "addend = %p, contents = %p, symbol = %s",
			    symnum, (u_long)ELF_R_TYPE(rela->r_info),
			    (void *)rela->r_offset, (void *)rela->r_addend,
			    (void *)load_ptr(where),
			    obj->strtab + obj->symtab[symnum].st_name));
			_rtld_error("%s: Unsupported relocation type %ld "
			    "in non-PLT relocations",
			    obj->path, (u_long) ELF_R_TYPE(rela->r_info));
			return -1;
		}
	}
	return 0;
}

int
_rtld_relocate_plt_lazy(const Obj_Entry *obj)
{
	const Elf_Rela *rela;

	for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) {
		Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
		Elf_Addr func_pc, func_sl;

		assert(ELF_R_TYPE(rela->r_info) == R_TYPE(IPLT));

		/*
		 * If this is an IPLT reloc for a static function,
		 * fully resolve the PLT entry now.
		 */
		if (ELF_R_SYM(rela->r_info) == 0) {
			func_pc = (Elf_Addr)(obj->relocbase + rela->r_addend);
			func_sl = (Elf_Addr)(obj->pltgot);
		}

		/*
		 * Otherwise set up for lazy binding.
		 */
		else {
			/*
			 * This function pointer points to the PLT
			 * stub added by the linker, and instead of
			 * a shared linkage value, we stash this
			 * relocation's offset.  The PLT stub has
			 * already been set up to transfer to
			 * _rtld_bind_start.
			 */
			func_pc = ((Elf_Addr)(obj->pltgot)) - 16;
			func_sl = (Elf_Addr)
			    ((const char *)rela - (const char *)(obj->pltrela));
		}
		rdbg(("lazy bind %s(%p) --> old=(%p,%p) new=(%p,%p)",
		    obj->path,
		    (void *)where,
		    (void *)where[0], (void *)where[1],
		    (void *)func_pc, (void *)func_sl));

		/*
		 * Fill this PLT entry and return.
		 */
		where[0] = func_pc;
		where[1] = func_sl;
	}
	return 0;
}

static inline int
_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp)
{
	Elf_Word *where = (Elf_Word *)(obj->relocbase + rela->r_offset);
	const Elf_Sym *def;
	const Obj_Entry *defobj;
	Elf_Addr	func_pc, func_sl;

	assert(ELF_R_TYPE(rela->r_info) == R_TYPE(IPLT));

	if (ELF_R_SYM(rela->r_info) == 0) {
		func_pc = (Elf_Addr)(obj->relocbase + rela->r_addend);
		func_sl = (Elf_Addr)(obj->pltgot);
	} else {
		def = _rtld_find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true);
		if (def == NULL)
			return -1;

		func_pc = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend);
		func_sl = (Elf_Addr)(defobj->pltgot);

		rdbg(("bind now/fixup in %s --> old=(%p,%p) new=(%p,%p)",
		    defobj->strtab + def->st_name,
		    (void *)where[0], (void *)where[1],
		    (void *)func_pc, (void *)func_sl));
	}
	/*
	 * Fill this PLT entry and return.
	 */
	if (where[0] != func_pc)
		where[0] = func_pc;
	if (where[1] != func_sl)
		where[1] = func_sl;

	if (tp)
		*tp = (Elf_Addr)where;

	return 0;
}

caddr_t
_rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
{
	const Elf_Rela *rela;
	Elf_Addr new_value;
	int err;

	rela = (const Elf_Rela *)((const char *)obj->pltrela + reloff);

	assert(ELF_R_SYM(rela->r_info) != 0);

	err = _rtld_relocate_plt_object(obj, rela, &new_value);
	if (err || new_value == 0)
		_rtld_die();

	return (caddr_t)new_value;
}

int
_rtld_relocate_plt_objects(const Obj_Entry *obj)
{
	const Elf_Rela *rela = obj->pltrela;

	for (; rela < obj->pltrelalim; rela++) {
		if (_rtld_relocate_plt_object(obj, rela, NULL) < 0)
			return -1;
	}
	return 0;
}