xref: /src/libexec/ld.elf_so/arch/powerpc/ppc_reloc.c

/*	$NetBSD: ppc_reloc.c,v 1.65 2024/08/03 21:59:58 riastradh Exp $	*/

/*-
 * Copyright (C) 1998	Tsubai Masanari
 * Portions copyright 2002 Charles M. Hannum <root (at) ihack.net>
 * 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.
 */

/*
 * Power ELF relocations.
 *
 * Reference:
 *
 *	Power Architecture(R) 32-bit
 *	Application Binary Interface Supplement 1.0 - Linux(R)
 *	http://web.archive.org/web/20120608163845/https://www.power.org/resources/downloads/Power-Arch-32-bit-ABI-supp-1.0-Linux.pdf
 *
 *	64-bit PowerPC ELF Application Binary Interface Supplement 1.9
 *	https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.pdf
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: ppc_reloc.c,v 1.65 2024/08/03 21:59:58 riastradh Exp $");
#endif /* not lint */

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <machine/cpu.h>

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

void _rtld_powerpc_pltcall(Elf_Word);
void _rtld_powerpc_pltresolve(Elf_Word, Elf_Word);

#define __u64(x)	((uint64_t)(x))
#define __u32(x)	((uint32_t)(x))
#define __ha48		__u64(0xffffffff8000)
#define __ha32		__u64(0xffff8000)
#define __ha16		__u32(0x8000)
#define __ha(x,n) ((((x) >> (n)) + (((x) & __ha##n) == __ha##n)) & 0xffff)
#define __hi(x,n) (((x) >> (n)) & 0xffff)
#ifdef __LP64
#define highesta(x)	__ha(__u64(x), 48)
#define highest(x)	__hi(__u64(x), 48)
#define higher(x)	__ha(__u64(x), 32)
#define higher(x)	__hi(__u64(x), 32)
#endif
#define ha(x)		__ha(__u32(x), 16)
#define hi(x)		__hi(__u32(x), 16)
#define lo(x)		(__u32(x) & 0xffff)

#ifdef _LP64
/* function descriptor for _rtld_bind_start */
extern const uint64_t _rtld_bind_start[3];
#else
void _rtld_bind_bssplt_start(void);
void _rtld_bind_secureplt_start(void);
#endif
Elf_Addr _rtld_bind(const Obj_Entry *, Elf_Word);
void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
static int _rtld_relocate_plt_object(const Obj_Entry *,
    const Elf_Rela *, int, Elf_Addr *);

/*
 * The PPC32 PLT format consists of three sections:
 * (1) The "pltcall" and "pltresolve" glue code.  This is always 18 words.
 * (2) The code part of the PLT entries.  There are 2 words per entry for
 *     up to 8192 entries, then 4 words per entry for any additional entries.
 * (3) The data part of the PLT entries, comprising a jump table.
 *     This section is half the size of the second section (ie. 1 or 2 words
 *     per entry).
 */

void
_rtld_setup_pltgot(const Obj_Entry *obj)
{
#ifdef _LP64
	/*
	 * For powerpc64, just copy the function descriptor to pltgot[0].
	 */
	if (obj->pltgot != NULL) {
		obj->pltgot[0] = (Elf_Addr) _rtld_bind_start[0];
		obj->pltgot[1] = (Elf_Addr) _rtld_bind_start[1];
		obj->pltgot[2] = (Elf_Addr) obj;
	}
#else
	/*
	 * Secure-PLT is much more sane.
	 */
	if (obj->gotptr != NULL) {
		obj->gotptr[1] = (Elf_Addr) _rtld_bind_secureplt_start;
		obj->gotptr[2] = (Elf_Addr) obj;
		dbg(("obj %s secure-plt gotptr=%p start=%p obj=%p",
		    obj->path, obj->gotptr,
		    (void *) obj->gotptr[1], (void *) obj->gotptr[2]));
	} else {
/*
 * Setup the plt glue routines (for bss-plt).
 */
#define BSSPLTCALL_SIZE		20
#define BSSPLTRESOLVE_SIZE	24

		Elf_Word *pltcall, *pltresolve;
		Elf_Word *jmptab;
		int N = obj->pltrelalim - obj->pltrela;

		/* Entries beyond 8192 take twice as much space. */
		if (N > 8192)
			N += N-8192;

		dbg(("obj %s bss-plt pltgot=%p jmptab=%u start=%p obj=%p",
		    obj->path, obj->pltgot, 18 + N * 2,
		    _rtld_bind_bssplt_start, obj));

		pltcall = obj->pltgot;
		jmptab = pltcall + 18 + N * 2;

		memcpy(pltcall, _rtld_powerpc_pltcall, BSSPLTCALL_SIZE);
		pltcall[1] |= ha(jmptab);
		pltcall[2] |= lo(jmptab);

		pltresolve = obj->pltgot + 8;

		memcpy(pltresolve, _rtld_powerpc_pltresolve, BSSPLTRESOLVE_SIZE);
		pltresolve[0] |= ha(_rtld_bind_bssplt_start);
		pltresolve[1] |= lo(_rtld_bind_bssplt_start);
		pltresolve[3] |= ha(obj);
		pltresolve[4] |= lo(obj);

		/*
		 * Invalidate the icache for only the code part of the PLT
		 * (and not the jump table at the end).
		 */
		__syncicache(pltcall, (char *)jmptab - (char *)pltcall);
	}
#endif
}

void
_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
{
	const Elf_Rela *rela = 0, *relalim;
	Elf_Addr relasz = 0;
	Elf_Addr *where;

	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;
		}
	}
	relalim = (const Elf_Rela *)((const uint8_t *)rela + relasz);
	for (; rela < relalim; rela++) {
		where = (Elf_Addr *)(relocbase + rela->r_offset);
		*where = (Elf_Addr)(relocbase + rela->r_addend);
	}
}

int
_rtld_relocate_nonplt_objects(Obj_Entry *obj)
{
	const Elf_Rela *rela;
	const Elf_Sym *def = NULL;
	const Obj_Entry *defobj = NULL;
	unsigned long last_symnum = ULONG_MAX;

	for (rela = obj->rela; rela < obj->relalim; rela++) {
		Elf_Addr        *where;
		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)) {
#ifdef _LP64
		case R_TYPE(ADDR64):	/* <address> S + A */
#else
		case R_TYPE(ADDR32):	/* <address> S + A */
		case R_TYPE(UADDR32):	/* <address> S + A */
#endif
		case R_TYPE(GLOB_DAT):	/* <address> S + A */
		case R_TYPE(ADDR16_LO):
		case R_TYPE(ADDR16_HI):
		case R_TYPE(ADDR16_HA):
		case R_TYPE(DTPMOD):
		case R_TYPE(DTPREL):
		case R_TYPE(TPREL):
			if (last_symnum != symnum) {
				last_symnum = symnum;
				def = _rtld_find_symdef(symnum, obj, &defobj,
				    false);
				if (def == NULL)
					return -1;
			}
			break;
		default:
			break;
		}

		switch (ELF_R_TYPE(rela->r_info)) {
#if 1 /* XXX Should not be necessary. */
		case R_TYPE(JMP_SLOT):
#endif
		case R_TYPE(NONE):
			break;

#ifdef _LP64
		case R_TYPE(ADDR64):	/* <address> S + A */
#else
		case R_TYPE(ADDR32):	/* <address> S + A */
		case R_TYPE(UADDR32):	/* <address> S + A */
#endif
		case R_TYPE(GLOB_DAT):	/* <address> S + A */
			tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
			    rela->r_addend);
			if (*where != tmp)
				*where = tmp;
			rdbg(("32/GLOB_DAT %s in %s --> %p in %s",
			    obj->strtab + obj->symtab[symnum].st_name,
			    obj->path, (void *)*where, defobj->path));
			break;

		/*
		 * Recent GNU ld does not resolve ADDR16_{LO,HI,HA} if
		 * the reloc is in a writable section and the symbol
		 * is not already referenced from text.
		 */
		case R_TYPE(ADDR16_LO): {
			tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
			    rela->r_addend);

			uint16_t tmp16 = lo(tmp);

			uint16_t *where16 = (uint16_t *)where;
			if (*where16 != tmp16)
				*where16 = tmp16;
			rdbg(("ADDR16_LO %s in %s --> #lo(%p) = 0x%x in %s",
			    obj->strtab + obj->symtab[symnum].st_name,
			      obj->path, (void *)tmp, tmp16, defobj->path));
			break;
		}

		case R_TYPE(ADDR16_HI):
		case R_TYPE(ADDR16_HA): {
			tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
			    rela->r_addend);

			uint16_t tmp16 = hi(tmp);
			if (ELF_R_TYPE(rela->r_info) == R_TYPE(ADDR16_HA)
			    && (tmp & __ha16))
				++tmp16; /* adjust to ha(tmp) */

			uint16_t *where16 = (uint16_t *)where;
			if (*where16 != tmp16)
				*where16 = tmp16;
			rdbg(("ADDR16_H%c %s in %s --> #h%c(%p) = 0x%x in %s",
			      (ELF_R_TYPE(rela->r_info) == R_TYPE(ADDR16_HI)
			           ? 'I' : 'A'),
			      obj->strtab + obj->symtab[symnum].st_name,
			      obj->path,
			      (ELF_R_TYPE(rela->r_info) == R_TYPE(ADDR16_HI)
			           ? 'i' : 'a'),
			      (void *)tmp, tmp16, defobj->path));
			break;
		}

		case R_TYPE(RELATIVE):	/* <address> B + A */
			*where = (Elf_Addr)(obj->relocbase + rela->r_addend);
			rdbg(("RELATIVE 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;

		case R_TYPE(DTPMOD):
			*where = (Elf_Addr)defobj->tlsindex;
			rdbg(("DTPMOD32 %s in %s --> %p in %s",
			    obj->strtab + obj->symtab[symnum].st_name,
			    obj->path, (void *)*where, defobj->path));
			break;

		case R_TYPE(DTPREL):
			*where = (Elf_Addr)(def->st_value + rela->r_addend
			    - TLS_DTV_OFFSET);
			rdbg(("DTPREL32 %s in %s --> %p in %s",
			    obj->strtab + obj->symtab[symnum].st_name,
			    obj->path, (void *)*where, defobj->path));
			break;

		case R_TYPE(TPREL):
			if (!defobj->tls_static &&
			    _rtld_tls_offset_allocate(__UNCONST(defobj)))
				return -1;

			*where = (Elf_Addr)(def->st_value + rela->r_addend
			    + defobj->tlsoffset - TLS_TP_OFFSET);
			rdbg(("TPREL32 %s in %s --> %p in %s",
			    obj->strtab + obj->symtab[symnum].st_name,
			    obj->path, (void *)*where, defobj->path));
			break;

		case R_TYPE(IRELATIVE):
			/* IFUNC relocations are handled in _rtld_call_ifunc */
			if (obj->ifunc_remaining_nonplt == 0) {
				obj->ifunc_remaining_nonplt =
				    obj->relalim - rela;
			}
			break;

		default:
			rdbg(("sym = %lu, type = %lu, offset = %p, "
			    "addend = %p, contents = %p, symbol = %s",
			    (u_long)ELF_R_SYM(rela->r_info),
			    (u_long)ELF_R_TYPE(rela->r_info),
			    (void *)rela->r_offset, (void *)rela->r_addend,
			    (void *)*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(Obj_Entry *obj)
{
#ifdef _LP64
	/*
	 * For PowerPC64, the plt stubs handle an empty function descriptor
	 * so there's nothing to do.
	 */
	/* XXX ifunc support */
#else
	Elf_Addr * const pltresolve = obj->pltgot + 8;
	const Elf_Rela *rela;

	for (rela = obj->pltrelalim; rela-- > obj->pltrela;) {
		size_t reloff = rela - obj->pltrela;
		Elf_Word *where = (Elf_Word *)(obj->relocbase + rela->r_offset);

		assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT) ||
		       ELF_R_TYPE(rela->r_info) == R_TYPE(IRELATIVE));

		if (ELF_R_TYPE(rela->r_info) == R_TYPE(IRELATIVE)) {
			/* No ifunc support for old-style insecure PLT. */
			assert(obj->gotptr != NULL);
			obj->ifunc_remaining = obj->pltrelalim - rela;
		}

		if (obj->gotptr != NULL) {
			/*
			 * For now, simply treat then as relative.
			 */
			*where += (Elf_Addr)obj->relocbase;
		} else {
			int distance;

			if (reloff < 32768) {
				/* li	r11,reloff */
				*where++ = 0x39600000 | reloff;
			} else {
				/* lis  r11,ha(reloff) */
				/* addi	r11,lo(reloff) */
				*where++ = 0x3d600000 | ha(reloff);
				*where++ = 0x396b0000 | lo(reloff);
			}
			/* b	pltresolve */
			distance = (Elf_Addr)pltresolve - (Elf_Addr)where;
			*where++ = 0x48000000 | (distance & 0x03fffffc);

			/*
			 * Icache invalidation is not done for each entry here
			 * because we sync the entire code part of the PLT once
			 * in _rtld_setup_pltgot() after all the entries have been
			 * initialized.
			 */
			/* __syncicache(where - 3, 12); */
		}
	}
#endif /* !_LP64 */

	return 0;
}

static int
_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, int reloff, Elf_Addr *tp)
{
	Elf_Word *where = (Elf_Word *)(obj->relocbase + rela->r_offset);
	Elf_Addr value;
	const Elf_Sym *def;
	const Obj_Entry *defobj;
	unsigned long info = rela->r_info;

	assert(ELF_R_TYPE(info) == R_TYPE(JMP_SLOT));

	def = _rtld_find_plt_symdef(ELF_R_SYM(info), obj, &defobj, tp != NULL);
	if (__predict_false(def == NULL))
		return -1;
	if (__predict_false(def == &_rtld_sym_zero))
		return 0;

	if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
		if (tp == NULL)
			return 0;
		value = _rtld_resolve_ifunc(defobj, def);
	} else {
		value = (Elf_Addr)(defobj->relocbase + def->st_value);
	}
	rdbg(("bind now/fixup in %s --> new=%p",
	    defobj->strtab + def->st_name, (void *)value));

#ifdef _LP64
	/*
	 * For PowerPC64 we simply replace the function descriptor in the
	 * PLTGOT with the one from source object.
	 */
	assert(where >= (Elf_Word *)obj->pltgot);
	assert(where < (Elf_Word *)obj->pltgot + (obj->pltrelalim - obj->pltrela));
	const Elf_Addr * const fdesc = (Elf_Addr *) value;
	where[0] = fdesc[0];
	where[1] = fdesc[1];
	where[2] = fdesc[2];
#else
	ptrdiff_t distance = value - (Elf_Addr)where;
	if (obj->gotptr != NULL) {
		/*
		 * For Secure-PLT we simply replace the entry in GOT with the
		 * address of the routine.
		 */
		assert(where >= (Elf_Word *)obj->pltgot);
		assert(where < (Elf_Word *)obj->pltgot + (obj->pltrelalim - obj->pltrela));
		*where = value;
	} else if (labs(distance) < 32*1024*1024) {	/* inside 32MB? */
		/* b	value	# branch directly */
		*where = 0x48000000 | (distance & 0x03fffffc);
		__syncicache(where, 4);
	} else {
		Elf_Addr *pltcall, *jmptab;
		int N = obj->pltrelalim - obj->pltrela;

		/* Entries beyond 8192 take twice as much space. */
		if (N > 8192)
			N += N-8192;

		pltcall = obj->pltgot;
		jmptab = pltcall + 18 + N * 2;

		jmptab[reloff] = value;

		if (reloff < 32768) {
			/* li	r11,reloff */
			*where++ = 0x39600000 | reloff;
		} else {
#ifdef notyet
			/* lis  r11,ha(value) */
			/* addi	r11,lo(value) */
			/* mtctr r11 */
			/* bctr */
			*where++ = 0x3d600000 | ha(value);
			*where++ = 0x396b0000 | lo(value);
			*where++ = 0x7d6903a6;
			*where++ = 0x4e800420;
#else
			/* lis  r11,ha(reloff) */
			/* addi	r11,lo(reloff) */
			*where++ = 0x3d600000 | ha(reloff);
			*where++ = 0x396b0000 | lo(reloff);
#endif
		}
		/* b	pltcall	*/
		distance = (Elf_Addr)pltcall - (Elf_Addr)where;
		*where++ = 0x48000000 | (distance & 0x03fffffc);
		__syncicache(where - 3, 12);
	}
#endif /* _LP64 */

	if (tp)
		*tp = value;
	return 0;
}

Elf_Addr
_rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
{
	const Elf_Rela *rela = obj->pltrela + reloff;
	Elf_Addr new_value;
	int err;

	new_value = 0;	/* XXX gcc */

	_rtld_shared_enter();
	err = _rtld_relocate_plt_object(obj, rela, reloff, &new_value);
	if (err)
		_rtld_die();
	_rtld_shared_exit();

#ifdef _LP64
	return obj->glink;
#else
	return new_value;
#endif
}

int
_rtld_relocate_plt_objects(const Obj_Entry *obj)
{
	const Elf_Rela *rela;
	int reloff;

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