/* $NetBSD: alpha_reloc.c,v 1.43.14.1 2023/08/01 16:35:00 martin 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 #ifndef lint __RCSID("$NetBSD: alpha_reloc.c,v 1.43.14.1 2023/08/01 16:35:00 martin Exp $"); #endif /* not lint */ #include #include #include #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(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; /* * The 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; 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): symnum = ELF_R_SYM(rela->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(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[*]. * * [*] 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->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; }