/*      $NetBSD: mdreloc.c,v 1.48 2024/08/03 21:59:58 riastradh Exp $   */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: mdreloc.c,v 1.48 2024/08/03 21:59:58 riastradh Exp $");
#endif /* not lint */

/*
 * Arm (32-bit) ELF relocations.
 *
 * Reference:
 *
 *      [AAELF32] ELF for the Arm Architecture, 2022Q3.  Arm Ltd.
 *      https://github.com/ARM-software/abi-aa/blob/2982a9f3b512a5bfdc9e3fea5d3b298f9165c36b/aaelf32/aaelf32.rst
 */

#include <sys/types.h>
#include <string.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);

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;
                }
        }
        rellim = (const Elf_Rel *)((const uint8_t *)rel + relsz);
        for (; rel < rellim; rel++) {
                where = (Elf_Addr *)(relocbase + rel->r_offset);
                *where += (Elf_Addr)relocbase;
        }
}

/*
 * 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));
}

int
_rtld_relocate_nonplt_objects(Obj_Entry *obj)
{
        const Elf_Rel *rel;
        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(PC24):      /* word32 S - P + A */
                case R_TYPE(ABS32):     /* word32 B + S + A */
                case R_TYPE(GLOB_DAT):  /* word32 B + S */
                case R_TYPE(TLS_DTPOFF32):
                case R_TYPE(TLS_DTPMOD32):
                case R_TYPE(TLS_TPOFF32):
                        symnum = ELF_R_SYM(rel->r_info);
                        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(rel->r_info)) {
                case R_TYPE(NONE):
                        break;

#if 1 /* XXX should not occur */
                case R_TYPE(PC24): {    /* word32 S - P + A */
                        Elf32_Sword addend;

                        /*
                         * Extract addend and sign-extend if needed.
                         */
                        addend = *where;
                        if (addend & 0x00800000)
                                addend |= 0xff000000;
                        tmp = (Elf_Addr)obj->relocbase + def->st_value
                            - (Elf_Addr)where + (addend << 2);
                        if ((tmp & 0xfe000000) != 0xfe000000 &&
                            (tmp & 0xfe000000) != 0) {
                                _rtld_error(
                                "%s: R_ARM_PC24 relocation @ %p to %s failed "
                                "(displacement %ld (%#lx) out of range)",
                                    obj->path, where,
                                    obj->strtab + obj->symtab[
                                        ELF_R_SYM(rel->r_info)].st_name,
                                    (long) tmp, (long) tmp);
                                return -1;
                        }
                        tmp >>= 2;
                        *where = (*where & 0xff000000) | (tmp & 0x00ffffff);
                        rdbg(("PC24 %s in %s --> %p @ %p in %s",
                            obj->strtab + obj->symtab[ELF_R_SYM(rel->r_info)]
                            .st_name, obj->path, (void *)*where, where,
                            defobj->path));
                        break;
                }
#endif

                case R_TYPE(ABS32):     /* word32 B + S + A */
                case R_TYPE(GLOB_DAT):  /* word32 B + S */
                        if (__predict_true(RELOC_ALIGNED_P(where))) {
                                tmp = *where + (Elf_Addr)defobj->relocbase +
                                    def->st_value;
                                /* Set the Thumb bit, if needed.  */
                                if (ELF_ST_TYPE(def->st_info) == STT_ARM_TFUNC)
                                    tmp |= 1;
                                *where = tmp;
                        } else {
                                tmp = load_ptr(where) +
                                    (Elf_Addr)defobj->relocbase +
                                    def->st_value;
                                /* Set the Thumb bit, if needed.  */
                                if (ELF_ST_TYPE(def->st_info) == STT_ARM_TFUNC)
                                    tmp |= 1;
                                store_ptr(where, tmp);
                        }
                        rdbg(("ABS32/GLOB_DAT %s in %s --> %p @ %p in %s",
                            obj->strtab + obj->symtab[ELF_R_SYM(rel->r_info)]
                            .st_name, obj->path, (void *)tmp, 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):  /* word32 B + A */
                        if (__predict_true(RELOC_ALIGNED_P(where))) {
                                tmp = *where + (Elf_Addr)obj->relocbase;
                                *where = tmp;
                        } else {
                                tmp = load_ptr(where) +
                                    (Elf_Addr)obj->relocbase;
                                store_ptr(where, tmp);
                        }
                        rdbg(("RELATIVE in %s --> %p", obj->path,
                            (void *)tmp));
                        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_DTPOFF32):
                        tmp = (Elf_Addr)(def->st_value);
                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where = tmp;
                        else
                                store_ptr(where, tmp);

                        rdbg(("TLS_DTPOFF32 %s in %s --> %p",
                            obj->strtab + obj->symtab[ELF_R_SYM(rel->r_info)]
                            .st_name, obj->path, (void *)tmp));

                        break;
                case R_TYPE(TLS_DTPMOD32):
                        tmp = (Elf_Addr)(defobj->tlsindex);
                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where = tmp;
                        else
                                store_ptr(where, tmp);

                        rdbg(("TLS_DTPMOD32 %s in %s --> %p",
                            obj->strtab + obj->symtab[ELF_R_SYM(rel->r_info)]
                            .st_name, obj->path, (void *)tmp));

                        break;

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

                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                tmp = *where;
                        else
                                tmp = load_ptr(where);
                        tmp += (Elf_Addr)def->st_value + defobj->tlsoffset + sizeof(struct tls_tcb);
                        if (__predict_true(RELOC_ALIGNED_P(where)))
                                *where = tmp;
                        else
                                store_ptr(where, tmp);
                        rdbg(("TLS_TPOFF32 %s in %s --> %p",
                            obj->strtab + obj->symtab[ELF_R_SYM(rel->r_info)]
                            .st_name, obj->path, (void *)tmp));
                        break;

                default:
                        rdbg(("sym = %lu, type = %lu, offset = %p, "
                            "contents = %p",
                            (u_long)ELF_R_SYM(rel->r_info),
                            (u_long)ELF_R_TYPE(rel->r_info),
                            (void *)rel->r_offset, (void *)load_ptr(where)));
                        _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(JUMP_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 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 new_value;
        const Elf_Sym  *def;
        const Obj_Entry *defobj;
        unsigned long info = rel->r_info;

        assert(ELF_R_TYPE(info) == R_TYPE(JUMP_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);
        }
        /* Set the Thumb bit, if needed.  */
        if (ELF_ST_TYPE(def->st_info) == STT_ARM_TFUNC)
                new_value |= 1;
        rdbg(("bind now/fixup in %s --> old=%p new=%p",
            defobj->strtab + def->st_name, (void *)*where, (void *)new_value));
        if (*where != new_value)
                *where = new_value;
        if (tp)
                *tp = new_value;

        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 = 0; /* XXX gcc */
        int err;

        _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;
}