/*      $NetBSD: alpha_reloc.c,v 1.47 2025/04/18 19:11:44 riastradh Exp $       */

/*
 * Copyright (c) 2001 Wasabi Systems, Inc.
 * All rights reserved.
 *
 * Written by Jason R. Thorpe for Wasabi Systems, Inc.
 *
 * 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 for the NetBSD Project by
 *      Wasabi Systems, Inc.
 * 4. The name of Wasabi Systems, Inc. may not be used to endorse
 *    or promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``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 WASABI SYSTEMS, INC
 * 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.
 */

/*
 * 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.
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: alpha_reloc.c,v 1.47 2025/04/18 19:11:44 riastradh Exp $");
#endif /* not lint */

#include <sys/types.h>
#include <sys/tls.h>
#include <string.h>

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

#ifdef RTLD_DEBUG_ALPHA
#define adbg(x)         xprintf x
#else
#define adbg(x)         /* nothing */
#endif

void _rtld_bind_start_secureplt(void);
void _rtld_bind_start(void);
void _rtld_bind_start_old(void);
void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
caddr_t _rtld_bind(const Obj_Entry *, Elf_Addr);
static inline int _rtld_relocate_plt_object(const Obj_Entry *,
    const Elf_Rela *, Elf_Addr *);

void
_rtld_setup_pltgot(const Obj_Entry *obj)
{
        uint32_t word0;

        /*
         * If we're using Alpha secureplt, the PLTGOT points to the
         * .got.plt section.  Just fill in the rtld binding stub and
         * we're done -- we're not writing to instruction memory, so no
         * imb needed.
         */
        if (obj->secureplt) {
                obj->pltgot[0] = (Elf_Addr) _rtld_bind_start_secureplt;
                obj->pltgot[1] = (Elf_Addr) obj;
                return;
        }

        /*
         * The non-secureplt PLTGOT on the Alpha looks like this:
         *
         *      PLT HEADER
         *      .
         *      . 32 bytes
         *      .
         *      PLT ENTRY #0
         *      .
         *      . 12 bytes
         *      .
         *      PLT ENTRY #1
         *      .
         *      . 12 bytes
         *      .
         *      etc.
         *
         * The old-format entries look like (displacements filled in
         * by the linker):
         *
         *      ldah    $28, 0($31)             # 0x279f0000
         *      lda     $28, 0($28)             # 0x239c0000
         *      br      $31, plt0               # 0xc3e00000
         *
         * The new-format entries look like:
         *
         *      br      $28, plt0               # 0xc3800000
         *                                      # 0x00000000
         *                                      # 0x00000000
         *
         * What we do is fetch the first PLT entry and check to
         * see the first word of it matches the first word of the
         * old format.  If so, we use a binding routine that can
         * handle the old format, otherwise we use a binding routine
         * that handles the new format.
         *
         * Note that this is done on a per-object basis, we can mix
         * and match shared objects build with both the old and new
         * linker.
         */
        word0 = *(uint32_t *)(((char *) obj->pltgot) + 32);
        if ((word0 & 0xffff0000) == 0x279f0000) {
                /* Old PLT entry format. */
                adbg(("ALPHA: object %p has old PLT format\n", obj));
                obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old;
                obj->pltgot[3] = (Elf_Addr) obj;
        } else {
                /* New PLT entry format. */
                adbg(("ALPHA: object %p has new PLT format\n", obj));
                obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
                obj->pltgot[3] = (Elf_Addr) obj;
        }

        __asm volatile("imb");
}

/*
 * 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)
{
        Elf_Addr res;

        memcpy(&res, where, sizeof(res));

        return (res);
}

static inline void
store_ptr(void *where, Elf_Addr val)
{

        memcpy(where, &val, sizeof(val));
}

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);
                /* XXX For some reason I see a few GLOB_DAT relocs here. */
                *where += (Elf_Addr)relocbase;
        }
}

int
_rtld_relocate_nonplt_objects(Obj_Entry *obj)
{
        const Elf_Rela *rela;
        Elf_Addr target = -1;
        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 = ELF_R_SYM(rela->r_info);

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

                switch (ELF_R_TYPE(rela->r_info)) {
                case R_TYPE(REFQUAD):
                case R_TYPE(GLOB_DAT):
                case R_TYPE(TPREL64):
                case R_TYPE(DTPMOD64):
                case R_TYPE(DTPREL64):
                        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)) {
                case R_TYPE(NONE):
                        break;

                case R_TYPE(REFQUAD):
                case R_TYPE(GLOB_DAT):
                        target = (Elf_Addr)(defobj->relocbase +
                            def->st_value);

                        tmp = target + rela->r_addend;
                        if (__predict_true(RELOC_ALIGNED_P(where))) {
                                if (*where != tmp)
                                        *where = tmp;
                        } else {
                                if (load_ptr(where) != tmp)
                                        store_ptr(where, tmp);
                        }
                        rdbg(("REFQUAD/GLOB_DAT %s in %s --> %p in %s",
                            obj->strtab + obj->symtab[symnum].st_name,
                            obj->path, (void *)tmp, defobj->path));
                        break;

                case R_TYPE(RELATIVE):
                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where += (Elf_Addr)obj->relocbase;
                        else
                                store_ptr(where,
                                    load_ptr(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(TPREL64):
                        if (!defobj->tls_static &&
                            _rtld_tls_offset_allocate(__UNCONST(defobj)))
                                return -1;

                        tmp = (Elf64_Addr)(def->st_value +
                            sizeof(struct tls_tcb) + defobj->tlsoffset +
                            rela->r_addend);

                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where = tmp;
                        else
                                store_ptr(where, tmp);

                        rdbg(("TPREL64 %s in %s --> %p",
                            obj->strtab + obj->symtab[symnum].st_name,
                            obj->path, (void *)*where));

                        break;

                case R_TYPE(DTPMOD64):
                        tmp = (Elf64_Addr)defobj->tlsindex;
                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where = tmp;
                        else
                                store_ptr(where, tmp);

                        rdbg(("DTPMOD64 %s in %s --> %p",
                            obj->strtab + obj->symtab[symnum].st_name,
                            obj->path, (void *)*where));

                        break;

                case R_TYPE(DTPREL64):
                        tmp = (Elf64_Addr)(def->st_value + rela->r_addend);
                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where = tmp;
                        else
                                store_ptr(where, tmp);

                        rdbg(("DTPREL64 %s in %s --> %p",
                            obj->strtab + obj->symtab[symnum].st_name,
                            obj->path, (void *)*where));

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

        if (!obj->relocbase)
                return 0;

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

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

                /* 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_Rela *rela,
    Elf_Addr *tp)
{
        Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
        Elf_Addr new_value;
        const Elf_Sym *def;
        const Obj_Entry *defobj;
        Elf_Addr stubaddr;
        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;
                new_value = _rtld_resolve_ifunc(defobj, def);
        } else {
                new_value = (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 *)new_value));

        if ((stubaddr = *where) != new_value) {
                int64_t delta, idisp;
                uint32_t insn[3], *stubptr;
                int insncnt;
                Elf_Addr pc;

                /* Point this GOT entry at the target. */
                *where = new_value;

                /*
                 * Alpha shared objects may have multiple GOTs, each
                 * of which may point to this entry in the PLT.  But,
                 * we only have a reference to the first GOT entry which
                 * points to this PLT entry.  In order to avoid having to
                 * re-bind this call every time a non-first GOT entry is
                 * used, we will attempt to patch up the PLT entry to
                 * reference the target, rather than the binder.
                 *
                 * When the PLT stub gets control, PV contains the address
                 * of the PLT entry.  Each PLT entry has room for 3 insns.
                 * If the displacement of the target from PV fits in a signed
                 * 32-bit integer, we can simply add it to PV.  Otherwise,
                 * we must load the GOT entry itself into PV.
                 *
                 * Note if the shared object uses the old PLT format, then
                 * we cannot patch up the PLT safely, and so we skip it
                 * in that case[*].  And if the shared object has a read-only
                 * secureplt, then we also skip it.
                 *
                 * [*] Actually, if we're not doing lazy-binding, then
                 * we *can* (and do) patch up this PLT entry; the PLTGOT
                 * thunk won't yet point to any binder entry point, and
                 * so this test will fail as it would for the new PLT
                 * entry format.
                 */
                if (obj->secureplt) {
                        rdbg(("  secureplt format"));
                        goto out;
                }
                if (obj->pltgot[2] == (Elf_Addr) &_rtld_bind_start_old) {
                        rdbg(("  old PLT format"));
                        goto out;
                }

                delta = new_value - stubaddr;
                rdbg(("  stubaddr=%p, where-stubaddr=%ld, delta=%ld",
                    (void *)stubaddr, (long)where - (long)stubaddr,
                    (long)delta));
                insncnt = 0;
                if ((int32_t)delta == delta) {
                        /*
                         * We can adjust PV with an LDA, LDAH sequence.
                         *
                         * First, build an LDA insn to adjust the low 16
                         * bits.
                         */
                        insn[insncnt++] = 0x08 << 26 | 27 << 21 | 27 << 16 |
                            (delta & 0xffff);
                        rdbg(("  LDA  $27,%d($27)", (int16_t)delta));
                        /*
                         * Adjust the delta to account for the effects of
                         * the LDA, including sign-extension.
                         */
                        delta -= (int16_t)delta;
                        if (delta != 0) {
                                /*
                                 * Build an LDAH instruction to adjust the
                                 * high 16 bits.
                                 */
                                insn[insncnt++] = 0x09 << 26 | 27 << 21 |
                                    27 << 16 | ((delta >> 16) & 0xffff);
                                rdbg(("  LDAH $27,%d($27)",
                                    (int16_t)(delta >> 16)));
                        }
                } else {
                        int64_t dhigh;

                        /* We must load the GOT entry. */
                        delta = (Elf_Addr)where - stubaddr;

                        /*
                         * If the GOT entry is too far away from the PLT
                         * entry, then we can't patch up the PLT entry.
                         * This PLT entry will have to be bound for each
                         * GOT entry except for the first one.  This program
                         * will still run, albeit very slowly.  It is very
                         * unlikely that this case will ever happen in
                         * practice.
                         */
                        if ((int32_t)delta != delta) {
                                rdbg(("  PLT stub too far from GOT to relocate"));
                                goto out;
                        }
                        dhigh = delta - (int16_t)delta;
                        if (dhigh != 0) {
                                /*
                                 * Build an LDAH instruction to adjust the
                                 * high 16 bits.
                                 */
                                insn[insncnt++] = 0x09 << 26 | 27 << 21 |
                                    27 << 16 | ((dhigh >> 16) & 0xffff);
                                rdbg(("  LDAH $27,%d($27)",
                                    (int16_t)(dhigh >> 16)));
                        }
                        /* Build an LDQ to load the GOT entry. */
                        insn[insncnt++] = 0x29 << 26 | 27 << 21 |
                            27 << 16 | (delta & 0xffff);
                        rdbg(("  LDQ  $27,%d($27)",
                            (int16_t)delta));
                }

                /*
                 * Now, build a JMP or BR insn to jump to the target.  If
                 * the displacement fits in a sign-extended 21-bit field,
                 * we can use the more efficient BR insn.  Otherwise, we
                 * have to jump indirect through PV.
                 */
                pc = stubaddr + (4 * (insncnt + 1));
                idisp = (int64_t)(new_value - pc) >> 2;
                if (-0x100000 <= idisp && idisp < 0x100000) {
                        insn[insncnt++] = 0x30 << 26 | 31 << 21 |
                            (idisp & 0x1fffff);
                        rdbg(("  BR   $31,%p", (void *)new_value));
                } else {
                        insn[insncnt++] = 0x1a << 26 | 31 << 21 |
                            27 << 16 | (idisp & 0x3fff);
                        rdbg(("  JMP  $31,($27),%d",
                            (int)(idisp & 0x3fff)));
                }

                /*
                 * Fill in the tail of the PLT entry first, for reentrancy.
                 * Until we have overwritten the first insn (an unconditional
                 * branch), the remaining insns have no effect.
                 */
                stubptr = (uint32_t *)stubaddr;
                while (insncnt > 1) {
                        insncnt--;
                        stubptr[insncnt] = insn[insncnt];
                }
                /*
                 * Commit the tail of the insn sequence to memory
                 * before overwriting the first insn.
                 */
                __asm volatile("wmb" ::: "memory");
                stubptr[0] = insn[0];
                /*
                 * I-stream will be sync'd when we either return from
                 * the binder (lazy bind case) or when the PLTGOT thunk
                 * is patched up (bind-now case).
                 */
        }
out:
        if (tp)
                *tp = new_value;

        return 0;
}

caddr_t
_rtld_bind(const Obj_Entry *obj, Elf_Addr reloff)
{
        const Elf_Rela *rela =
            (const Elf_Rela *)((const uint8_t *)obj->pltrela + reloff);
        Elf_Addr result = 0; /* XXX gcc */
        int err;

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

        return (caddr_t)result;
}

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

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

        return 0;
}