/*      $NetBSD: mdreloc.c,v 1.48 2025/04/16 17:37:48 riastradh Exp $   */

/*
 * Copyright 1996 John D. Polstra.
 * Copyright 1996 Matt Thomas <matt@3am-software.com>
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by John Polstra.
 * 4. 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.
 */

/*
 * i386 ELF relocations.
 *
 * References:
 *
 *      [ABI386-4] System V Application Binary Interface: Intel386
 *      Architecture Processor Supplement, Fourth Edition, 1997-03-19,
 *      The Santa Cruz Operation, Inc.
 *      https://www.sco.com/developers/devspecs/abi386-4.pdf
 *      https://web.archive.org/web/20250329184450/https://www.sco.com/developers/devspecs/abi386-4.pdf
 *
 * Note: Intel and SuSE have published an update to the i386 ELF
 * supplement, but it is not entirely compatible (e.g., it requires
 * 16-byte alignment for the stack pointer, not just 4-byte alignment),
 * so it is not reliable as a normative reference:
 *
 *      [ABI386-2015] System V Application Binary Interface: Intel386
 *      Architecture Processor Supplement, Version 1.0, 2015-02-03.
 *      https://uclibc.org/docs/psABI-i386.pdf
 *      https://web.archive.org/web/20250118211449/https://uclibc.org/docs/psABI-i386.pdf
 *      https://gitlab.com/x86-psABIs/i386-ABI
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: mdreloc.c,v 1.48 2025/04/16 17:37:48 riastradh Exp $");
#endif /* not lint */

#include <sys/types.h>
#include <machine/lwp_private.h>

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

void _rtld_bind_start(void);
void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
caddr_t _rtld_bind(const Obj_Entry *, Elf_Word);

#define rdbg_symname(obj, rela) \
        ((obj)->strtab + (obj)->symtab[ELF_R_SYM((rela)->r_info)].st_name)

void
_rtld_setup_pltgot(const Obj_Entry *obj)
{
        obj->pltgot[1] = (Elf_Addr) obj;
        obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
}

void
_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
{
        const Elf_Rel *rel = 0, *rellim;
        Elf_Addr relsz = 0;
        Elf_Addr *where;

        for (; dynp->d_tag != DT_NULL; dynp++) {
                switch (dynp->d_tag) {
                case DT_REL:
                        rel = (const Elf_Rel *)(relocbase + dynp->d_un.d_ptr);
                        break;
                case DT_RELSZ:
                        relsz = dynp->d_un.d_val;
                        break;
                }
        }
        if (rel == 0 || relsz == 0)
                return;
        rellim = (const Elf_Rel *)((const uint8_t *)rel + relsz);
        for (; rel < rellim; rel++) {
                where = (Elf_Addr *)(relocbase + rel->r_offset);
                *where += (Elf_Addr)relocbase;
        }
}

int
_rtld_relocate_nonplt_objects(Obj_Entry *obj)
{
        const Elf_Rel *rel;
        Elf_Addr target = 0;
        const Elf_Sym   *def = NULL;
        const Obj_Entry *defobj = NULL;
        unsigned long last_symnum = ULONG_MAX;

        for (rel = obj->rel; rel < obj->rellim; rel++) {
                Elf_Addr        *where;
                Elf_Addr         tmp;
                unsigned long    symnum;

                where = (Elf_Addr *)(obj->relocbase + rel->r_offset);

                switch (ELF_R_TYPE(rel->r_info)) {
                case R_TYPE(PC32):
                case R_TYPE(GOT32):
                case R_TYPE(32):
                case R_TYPE(GLOB_DAT):
                case R_TYPE(TLS_TPOFF):
                case R_TYPE(TLS_TPOFF32):
                case R_TYPE(TLS_DTPMOD32):
                case R_TYPE(TLS_DTPOFF32):
                        symnum = ELF_R_SYM(rel->r_info);
                        if (symnum != last_symnum) {
                                last_symnum = symnum;
                                def = _rtld_find_symdef(symnum, obj, &defobj,
                                    false);
                                if (def == NULL)
                                        return -1;
                        }
                        break;
                default:
                        break;
                }


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

#if 1 /* XXX should not occur */
                case R_TYPE(PC32):
                        target = (Elf_Addr)(defobj->relocbase + def->st_value);

                        *where += target - (Elf_Addr)where;
                        rdbg(("PC32 %s in %s --> %p in %s",
                            rdbg_symname(obj, rel),
                            obj->path, (void *)*where, defobj->path));
                        break;

                case R_TYPE(GOT32):
#endif
                case R_TYPE(32):
                case R_TYPE(GLOB_DAT):
                        target = (Elf_Addr)(defobj->relocbase + def->st_value);

                        tmp = target + *where;
                        if (*where != tmp)
                                *where = tmp;
                        rdbg(("32/GLOB_DAT %s in %s --> %p in %s",
                            rdbg_symname(obj, rel),
                            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->rellim - rel;
                        }
                        /* FALL-THROUGH */

                case R_TYPE(RELATIVE):
                        *where += (Elf_Addr)obj->relocbase;
                        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(TLS_TPOFF):
                        if (!defobj->tls_static &&
                            _rtld_tls_offset_allocate(__UNCONST(defobj)))
                                return -1;

                        *where += (Elf_Addr)(def->st_value - defobj->tlsoffset);

                        rdbg(("TLS_TPOFF %s in %s --> %p",
                            rdbg_symname(obj, rel),
                            obj->path, (void *)*where));
                        break;

                case R_TYPE(TLS_TPOFF32):
                        if (!defobj->tls_static &&
                            _rtld_tls_offset_allocate(__UNCONST(defobj)))
                                return -1;

                        *where += (Elf_Addr)(defobj->tlsoffset - def->st_value);
                        rdbg(("TLS_TPOFF32 %s in %s --> %p",
                            rdbg_symname(obj, rel),
                            obj->path, (void *)*where));
                        break;

                case R_TYPE(TLS_DTPMOD32):
                        *where = (Elf_Addr)(defobj->tlsindex);

                        rdbg(("TLS_DTPMOD32 %s in %s --> %p",
                            rdbg_symname(obj, rel),
                            obj->path, (void *)*where));
                        break;

                case R_TYPE(TLS_DTPOFF32):
                        *where = (Elf_Addr)(def->st_value);

                        rdbg(("TLS_DTPOFF32 %s in %s --> %p",
                            rdbg_symname(obj, rel),
                            obj->path, (void *)*where));

                        break;

                default:
                        rdbg(("sym = %lu, type = %lu, offset = %p, "
                            "contents = %p, symbol = %s",
                            (u_long)ELF_R_SYM(rel->r_info),
                            (u_long)ELF_R_TYPE(rel->r_info),
                            (void *)rel->r_offset, (void *)*where,
                            rdbg_symname(obj, rel)));
                        _rtld_error("%s: Unsupported relocation type %ld "
                            "in non-PLT relocations",
                            obj->path, (u_long) ELF_R_TYPE(rel->r_info));
                        return -1;
                }
        }
        return 0;
}

int
_rtld_relocate_plt_lazy(Obj_Entry *obj)
{
        const Elf_Rel *rel;

        for (rel = obj->pltrellim; rel-- > obj->pltrel; ) {
                Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rel->r_offset);

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

                if (ELF_R_TYPE(rel->r_info) == R_TYPE(IRELATIVE))
                        obj->ifunc_remaining = obj->pltrellim - rel;

                /* Just relocate the GOT slots pointing into the PLT */
                *where += (Elf_Addr)obj->relocbase;
                rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where));
        }

        return 0;
}

static inline int
_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rel *rel,
        Elf_Addr *tp)
{
        Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
        Elf_Addr target;
        const Elf_Sym *def;
        const Obj_Entry *defobj;
        unsigned long info = rel->r_info;

        if (ELF_R_TYPE(info) == R_TYPE(IRELATIVE))
                return 0;

        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;
                target = _rtld_resolve_ifunc(defobj, def);
        } else {
                target = (Elf_Addr)(defobj->relocbase + def->st_value);
        }

        rdbg(("bind now/fixup in %s --> old=%p new=%p",
            defobj->strtab + def->st_name, (void *)*where,
            (void *)target));
        if (*where != target)
                *where = target;
        if (tp)
                *tp = target;
        return 0;
}

caddr_t
_rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
{
        const Elf_Rel *rel = (const Elf_Rel *)((const uint8_t *)obj->pltrel
            + reloff);
        Elf_Addr new_value;
        int err;

        new_value = 0;  /* XXX gcc */

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

        return (caddr_t)new_value;
}

int
_rtld_relocate_plt_objects(const Obj_Entry *obj)
{
        const Elf_Rel *rel;
        int err = 0;

        for (rel = obj->pltrel; rel < obj->pltrellim; rel++) {
                err = _rtld_relocate_plt_object(obj, rel, NULL);
                if (err)
                        break;
        }
        return err;
}

/*
 * i386 specific GNU variant of __tls_get_addr using register based
 * argument passing.
 */
#define DTV_MAX_INDEX(dtv)      ((size_t)((dtv)[-1]))

__dso_public __attribute__((__regparm__(1))) void *
___tls_get_addr(void *arg_)
{
        size_t *arg = (size_t *)arg_;
        void **dtv;
        struct tls_tcb *tcb = __lwp_getprivate_fast();
        size_t idx = arg[0], offset = arg[1];

        dtv = tcb->tcb_dtv;

        if (__predict_true(idx < DTV_MAX_INDEX(dtv) && dtv[idx] != NULL))
                return (uint8_t *)dtv[idx] + offset;

        return _rtld_tls_get_addr(tcb, idx, offset);
}