/* $OpenBSD: rtld_machine.c,v 1.69 2022/01/08 06:49:42 guenther Exp $ */ /* * Copyright (c) 1999 Dale Rahn * Copyright (c) 2001 Niklas Hallqvist * Copyright (c) 2001 Artur Grabowski * * 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. */ /*- * Copyright (c) 2000 Eduardo Horvath. * Copyright (c) 1999 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Paul Kranenburg. * * 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 the NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``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 FOUNDATION OR CONTRIBUTORS * 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. */ #define _DYN_LOADER #include #include #include #include #include #include /* for ST_SYSCALL */ #include "util.h" #include "resolve.h" int64_t pcookie __attribute__((section(".openbsd.randomdata"))) __dso_hidden; /* * The following table holds for each relocation type: * - the width in bits of the memory location the relocation * applies to (not currently used) * - the number of bits the relocation value must be shifted to the * right (i.e. discard least significant bits) to fit into * the appropriate field in the instruction word. * - flags indicating whether * * the relocation involves a symbol * * the relocation is relative to the current position * * the relocation is for a GOT entry * * the relocation is relative to the load address * */ #define _RF_S 0x80000000 /* Resolve symbol */ #define _RF_A 0x40000000 /* Use addend */ #define _RF_P 0x20000000 /* Location relative */ #define _RF_G 0x10000000 /* GOT offset */ #define _RF_B 0x08000000 /* Load address relative */ #define _RF_U 0x04000000 /* Unaligned */ #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ #define _RF_RS(s) ((s) & 0xff) /* right shift */ static const int reloc_target_flags[] = { 0, /* NONE */ _RF_S|_RF_A| _RF_SZ(8) | _RF_RS(0), /* RELOC_8 */ _RF_S|_RF_A| _RF_SZ(16) | _RF_RS(0), /* RELOC_16 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* RELOC_32 */ _RF_S|_RF_A|_RF_P| _RF_SZ(8) | _RF_RS(0), /* DISP_8 */ _RF_S|_RF_A|_RF_P| _RF_SZ(16) | _RF_RS(0), /* DISP_16 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* DISP_32 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP_30 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP_22 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(10), /* HI22 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 22 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 13 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* LO10 */ _RF_G| _RF_SZ(32) | _RF_RS(0), /* GOT10 */ _RF_G| _RF_SZ(32) | _RF_RS(0), /* GOT13 */ _RF_G| _RF_SZ(32) | _RF_RS(10), /* GOT22 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PC10 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(10), /* PC22 */ _RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WPLT30 */ _RF_S| _RF_SZ(32) | _RF_RS(0), /* COPY */ _RF_S|_RF_A| _RF_SZ(64) | _RF_RS(0), /* GLOB_DAT */ _RF_S| _RF_SZ(32) | _RF_RS(0), /* JMP_SLOT */ _RF_A| _RF_B| _RF_SZ(64) | _RF_RS(0), /* RELATIVE */ _RF_S|_RF_A| _RF_U| _RF_SZ(32) | _RF_RS(0), /* UA_32 */ _RF_A| _RF_SZ(32) | _RF_RS(0), /* PLT32 */ _RF_A| _RF_SZ(32) | _RF_RS(10), /* HIPLT22 */ _RF_A| _RF_SZ(32) | _RF_RS(0), /* LOPLT10 */ _RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PCPLT32 */ _RF_A|_RF_P| _RF_SZ(32) | _RF_RS(10), /* PCPLT22 */ _RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PCPLT10 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 10 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 11 */ _RF_S|_RF_A| _RF_SZ(64) | _RF_RS(0), /* 64 */ _RF_S|_RF_A|/*extra*/ _RF_SZ(32) | _RF_RS(0), /* OLO10 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(42), /* HH22 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(32), /* HM10 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(10), /* LM22 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(42), /* PC_HH22 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(32), /* PC_HM10 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(10), /* PC_LM22 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP16 */ _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP19 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_JMP */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 7 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 5 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 6 */ _RF_S|_RF_A|_RF_P| _RF_SZ(64) | _RF_RS(0), /* DISP64 */ _RF_A| _RF_SZ(64) | _RF_RS(0), /* PLT64 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(10), /* HIX22 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* LOX10 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(22), /* H44 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(12), /* M44 */ _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* L44 */ _RF_S|_RF_A| _RF_SZ(64) | _RF_RS(0), /* REGISTER */ _RF_S|_RF_A| _RF_U| _RF_SZ(64) | _RF_RS(0), /* UA64 */ _RF_S|_RF_A| _RF_U| _RF_SZ(16) | _RF_RS(0), /* UA16 */ }; #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) #define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) static const long reloc_target_bitmask[] = { #define _BM(x) (~(-(1ULL << (x)))) 0, /* NONE */ _BM(8), _BM(16), _BM(32), /* RELOC_8, _16, _32 */ _BM(8), _BM(16), _BM(32), /* DISP8, DISP16, DISP32 */ _BM(30), _BM(22), /* WDISP30, WDISP22 */ _BM(22), _BM(22), /* HI22, _22 */ _BM(13), _BM(10), /* RELOC_13, _LO10 */ _BM(10), _BM(13), _BM(22), /* GOT10, GOT13, GOT22 */ _BM(10), _BM(22), /* _PC10, _PC22 */ _BM(30), 0, /* _WPLT30, _COPY */ -1, _BM(32), -1, /* _GLOB_DAT, JMP_SLOT, _RELATIVE */ _BM(32), _BM(32), /* _UA32, PLT32 */ _BM(22), _BM(10), /* _HIPLT22, LOPLT10 */ _BM(32), _BM(22), _BM(10), /* _PCPLT32, _PCPLT22, _PCPLT10 */ _BM(10), _BM(11), -1, /* _10, _11, _64 */ _BM(10), _BM(22), /* _OLO10, _HH22 */ _BM(10), _BM(22), /* _HM10, _LM22 */ _BM(22), _BM(10), _BM(22), /* _PC_HH22, _PC_HM10, _PC_LM22 */ _BM(16), _BM(19), /* _WDISP16, _WDISP19 */ -1, /* GLOB_JMP */ _BM(7), _BM(5), _BM(6) /* _7, _5, _6 */ -1, -1, /* DISP64, PLT64 */ _BM(22), _BM(13), /* HIX22, LOX10 */ _BM(22), _BM(10), _BM(13), /* H44, M44, L44 */ -1, -1, _BM(16), /* REGISTER, UA64, UA16 */ #undef _BM }; #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) int _dl_reloc_plt(Elf_Word *where1, Elf_Word *where2, Elf_Word *pltaddr, Elf_Addr value); void _dl_install_plt(Elf_Word *pltgot, Elf_Addr proc); int _dl_md_reloc(elf_object_t *object, int rel, int relasz) { long i; long numrela; long relrel; int fails = 0; Elf_Addr loff; Elf_Addr prev_value = 0; const Elf_Sym *prev_sym = NULL; Elf_RelA *relas; loff = object->obj_base; numrela = object->Dyn.info[relasz] / sizeof(Elf_RelA); relrel = rel == DT_RELA ? object->relacount : 0; relas = (Elf_RelA *)(object->Dyn.info[rel]); if (relas == NULL) return 0; if (relrel > numrela) _dl_die("relacount > numrel: %ld > %ld", relrel, numrela); /* tight loop for leading RELATIVE relocs */ for (i = 0; i < relrel; i++, relas++) { Elf_Addr *where; where = (Elf_Addr *)(relas->r_offset + loff); *where = relas->r_addend + loff; } for (; i < numrela; i++, relas++) { Elf_Addr *where, value, mask; Elf_Word type; const Elf_Sym *sym; const char *symn; type = ELF_R_TYPE(relas->r_info); if (type == R_TYPE(NONE) || type == R_TYPE(JMP_SLOT)) continue; where = (Elf_Addr *)(relas->r_offset + loff); if (RELOC_USE_ADDEND(type)) value = relas->r_addend; else value = 0; sym = NULL; symn = NULL; if (RELOC_RESOLVE_SYMBOL(type)) { sym = object->dyn.symtab; sym += ELF_R_SYM(relas->r_info); symn = object->dyn.strtab + sym->st_name; if (sym->st_shndx != SHN_UNDEF && ELF_ST_BIND(sym->st_info) == STB_LOCAL) { value += loff; } else if (sym == prev_sym) { value += prev_value; } else { struct sym_res sr; sr = _dl_find_symbol(symn, SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_NOTPLT, sym, object); if (sr.sym == NULL) { resolve_failed: if (ELF_ST_BIND(sym->st_info) != STB_WEAK) fails++; continue; } prev_sym = sym; prev_value = (Elf_Addr)(sr.obj->obj_base + sr.sym->st_value); value += prev_value; } } if (type == R_TYPE(COPY)) { void *dstaddr = where; const void *srcaddr; const Elf_Sym *dstsym = sym; struct sym_res sr; sr = _dl_find_symbol(symn, SYM_SEARCH_OTHER|SYM_WARNNOTFOUND|SYM_NOTPLT, dstsym, object); if (sr.sym == NULL) goto resolve_failed; srcaddr = (void *)(sr.obj->obj_base + sr.sym->st_value); _dl_bcopy(srcaddr, dstaddr, dstsym->st_size); continue; } if (RELOC_PC_RELATIVE(type)) value -= (Elf_Addr)where; if (RELOC_BASE_RELATIVE(type)) value += loff; mask = RELOC_VALUE_BITMASK(type); value >>= RELOC_VALUE_RIGHTSHIFT(type); value &= mask; if (RELOC_UNALIGNED(type)) { /* Handle unaligned relocations. */ Elf_Addr tmp = 0; char *ptr = (char *)where; int i, size = RELOC_TARGET_SIZE(type)/8; /* Read it in one byte at a time. */ for (i=0; i> (8*i)) & 0xff); } else if (RELOC_TARGET_SIZE(type) > 32) { *where &= ~mask; *where |= value; } else { Elf32_Addr *where32 = (Elf32_Addr *)where; *where32 &= ~mask; *where32 |= value; } } return fails; } /* * Instruction templates: */ #define BAA 0x30680000 /* ba,a %xcc, 0 */ #define SETHI 0x03000000 /* sethi %hi(0), %g1 */ #define JMP 0x81c06000 /* jmpl %g1+%lo(0), %g0 <-- simm13 */ #define NOP 0x01000000 /* sethi %hi(0), %g0 */ #define OR 0x82106000 /* or %g1, 0, %g1 */ #define ORG5 0x8a116000 /* or %g5, 0, %g5 */ #define XOR 0x82186000 /* xor %g1, 0, %g1 */ #define MOV71 0x8210000f /* or %o7, 0, %g1 */ #define MOV17 0x9e100001 /* or %g1, 0, %o7 */ #define CALL 0x40000000 /* call 0 <-- disp30 */ #define SLLX 0x83287000 /* sllx %g1, 0, %g1 */ #define SLLXG5 0x8b297000 /* sllx %g5, 0, %g5 */ #define SRAX 0x83387000 /* srax %g1, 0, %g1 */ #define SETHIG5 0x0b000000 /* sethi %hi(0), %g5 */ #define ORG15 0x82804005 /* or %g1, %g5, %g1 */ /* %hi(v) with variable shift */ #define HIVAL(v, s) (((v) >> (s)) & 0x003fffff) #define LOVAL(v) ((v) & 0x000003ff) int _dl_reloc_plt(Elf_Word *where1, Elf_Word *where2, Elf_Word *pltaddr, Elf_Addr value) { Elf_Addr offset; /* * At the PLT entry pointed at by `where', we now construct * a direct transfer to the now fully resolved function * address. * * A PLT entry is supposed to start by looking like this: * * sethi %hi(. - .PLT0), %g1 * ba,a,pt %xcc, .PLT1 * nop * nop * nop * nop * nop * nop * * When we replace these entries we either (a) only replace * the second word (the ba,a,pt), or (b) replace multiple * words: one or more nops, then finally the ba,a,pt. By * replacing the ba,a,pt last, we guarantee that the PLT can * be used by other threads even while it's being updated. * This is made slightly more complicated by kbind, for which * we need to pass them to the kernel in the order they get * written. To that end, we store the word to overwrite the * ba,a,pt at *where1, and the words to overwrite the nops at * where2[0], where2[1], ... * * We now need to find out how far we need to jump. We * have a choice of several different relocation techniques * which are increasingly expensive. */ offset = value - ((Elf_Addr)pltaddr); if ((int64_t)(offset-4) <= (1L<<20) && (int64_t)(offset-4) >= -(1L<<20)) { /* * We're within 1MB -- we can use a direct branch insn. * * We can generate this pattern: * * sethi %hi(. - .PLT0), %g1 * ba,a,pt %xcc, addr * nop * nop * nop * nop * nop * nop * */ *where1 = BAA | (((offset-4) >> 2) &0x7ffff); return 0; } else if (value < (1UL<<32)) { /* * We're within 32-bits of address zero. * * The resulting code in the jump slot is: * * sethi %hi(. - .PLT0), %g1 * sethi %hi(addr), %g1 * jmp %g1+%lo(addr) * nop * nop * nop * nop * nop * */ *where1 = SETHI | HIVAL(value, 10); where2[0] = JMP | LOVAL(value); return 1; } else if (value > -(1UL<<32)) { /* * We're within 32-bits of address -1. * * The resulting code in the jump slot is: * * sethi %hi(. - .PLT0), %g1 * sethi %hix(~addr), %g1 * xor %g1, %lox(~addr), %g1 * jmp %g1 * nop * nop * nop * nop * */ *where1 = SETHI | HIVAL(~value, 10); where2[0] = XOR | ((~value) & 0x00001fff); where2[1] = JMP; return 2; } else if ((int64_t)(offset-8) <= (1L<<31) && (int64_t)(offset-8) >= -((1L<<31) - 4)) { /* * We're within 32-bits -- we can use a direct call insn * * The resulting code in the jump slot is: * * sethi %hi(. - .PLT0), %g1 * mov %o7, %g1 * call (.+offset) * mov %g1, %o7 * nop * nop * nop * nop * */ *where1 = MOV71; where2[0] = CALL | (((offset-8) >> 2) & 0x3fffffff); where2[1] = MOV17; return 2; } else if (value < (1L<<42)) { /* * Target 42bits or smaller. * We can generate this pattern: * * The resulting code in the jump slot is: * * sethi %hi(. - .PLT0), %g1 * sethi %hi(addr >> 20), %g1 * or %g1, %lo(addr >> 10), %g1 * sllx %g1, 10, %g1 * jmp %g1+%lo(addr) * nop * nop * nop * * this can handle addresses 0 - 0x3fffffffffc */ *where1 = SETHI | HIVAL(value, 20); where2[0] = OR | LOVAL(value >> 10); where2[1] = SLLX | 10; where2[2] = JMP | LOVAL(value); return 3; } else if (value > -(1UL<<41)) { /* * Large target >= 0xfffffe0000000000UL * We can generate this pattern: * * The resulting code in the jump slot is: * * sethi %hi(. - .PLT0), %g1 * sethi %hi(addr >> 20), %g1 * or %g1, %lo(addr >> 10), %g1 * sllx %g1, 32, %g1 * srax %g1, 22, %g1 * jmp %g1+%lo(addr) * nop * nop * nop * */ *where1 = SETHI | HIVAL(value, 20); where2[0] = OR | LOVAL(value >> 10); where2[1] = SLLX | 32; where2[2] = SRAX | 22; where2[3] = JMP | LOVAL(value); return 4; } else { /* * We need to load all 64-bits * * The resulting code in the jump slot is: * * sethi %hi(. - .PLT0), %g1 * sethi %hi(addr >> 42), %g5 * sethi %hi(addr >> 10), %g1 * or %g1, %lo(addr >> 32), %g5 * sllx %g5, 32, %g5 * or %g1, %g5, %g1 * jmp %g1+%lo(addr) * nop * */ *where1 = SETHIG5 | HIVAL(value, 42); where2[0] = SETHI | HIVAL(value, 10); where2[1] = ORG5 | LOVAL(value >> 32); where2[2] = SLLXG5 | 32; where2[3] = ORG15; where2[4] = JMP | LOVAL(value); return 5; } } /* * Resolve a symbol at run-time. */ Elf_Addr _dl_bind(elf_object_t *object, int index) { Elf_RelA *rela; Elf_Word *addr; Elf_Addr newvalue; struct sym_res sr; const Elf_Sym *sym; const char *symn; int64_t cookie = pcookie; struct { struct __kbind param[2]; Elf_Word newval[6]; } buf; struct __kbind *param; size_t psize; int i; rela = (Elf_RelA *)(object->Dyn.info[DT_JMPREL]); if (ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)) { /* * XXXX * * The first four PLT entries are reserved. There * is some disagreement whether they should have * associated relocation entries. Both the SPARC * 32-bit and 64-bit ELF specifications say that * they should have relocation entries, but the * 32-bit SPARC binutils do not generate them, * and now the 64-bit SPARC binutils have stopped * generating them too. * * So, to provide binary compatibility, we will * check the first entry, if it is reserved it * should not be of the type JMP_SLOT. If it * is JMP_SLOT, then the 4 reserved entries were * not generated and our index is 4 entries too far. */ rela += index - 4; } else rela += index; sym = object->dyn.symtab; sym += ELF_R_SYM(rela->r_info); symn = object->dyn.strtab + sym->st_name; sr = _dl_find_symbol(symn, SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object); if (sr.sym == NULL) _dl_die("lazy binding failed!"); newvalue = sr.obj->obj_base + sr.sym->st_value; if (__predict_false(sr.obj->traced) && _dl_trace_plt(sr.obj, symn)) return newvalue; /* * While some relocations just need to write one word and * can do that with kbind() with just one block, many * require two blocks to be written: all but first word, * then the first word. So, if we want to write 5 words * in total, then the layout of the buffer we pass to * kbind() needs to be one of these: * +------------+ * | kbind.addr | * | """ | * | kbind.size | * | """ | +------------+ * | kbind.addr | | kbind.addr | * | """ | | """ | * | kbind.size | | kbind.size | * | """ | | """ | * | word 2 | | word | * | word 3 | +------------+ * | word 4 | * | word 5 | * | word 1 | * +------------+ * * We first handle the special case of relocations with a * non-zero r_addend, which have one block to update whose * address is the relocation address itself. This is only * used for PLT entries after the 2^15th, i.e., truly monstrous * programs, thus the __predict_false(). */ addr = (Elf_Word *)(object->obj_base + rela->r_offset); _dl_memset(&buf, 0, sizeof(buf)); if (__predict_false(rela->r_addend)) { /* * This entry is >32768. The relocation points to a * PC-relative pointer to the _dl_bind_start_0 stub at * the top of the PLT section. Update it to point to * the target function. */ buf.newval[0] = rela->r_addend + newvalue - object->Dyn.info[DT_PLTGOT]; buf.param[1].kb_addr = addr; buf.param[1].kb_size = sizeof(buf.newval[0]); param = &buf.param[1]; psize = sizeof(struct __kbind) + sizeof(buf.newval[0]); } else { Elf_Word first; /* * For the other relocations, the word at the relocation * address will be left unchanged. Assume _dl_reloc_plt() * will tell us to update multiple words, so save the first * word to the side. */ i = _dl_reloc_plt(&first, &buf.newval[0], addr, newvalue); /* * _dl_reloc_plt() returns the number of words that must be * written after the first word in location, but before it * in time. If it returns zero, then only a single block * with one word is needed, so we just put it in place per * the right-hand diagram and just use param[1] and newval[0] */ if (i == 0) { /* fill in the __kbind structure */ buf.param[1].kb_addr = &addr[1]; buf.param[1].kb_size = sizeof(Elf_Word); buf.newval[0] = first; param = &buf.param[1]; psize = sizeof(struct __kbind) + sizeof(buf.newval[0]); } else { /* * Two blocks are necessary. Save the first word * after the other words. */ buf.param[0].kb_addr = &addr[2]; buf.param[0].kb_size = i * sizeof(Elf_Word); buf.param[1].kb_addr = &addr[1]; buf.param[1].kb_size = sizeof(Elf_Word); buf.newval[i] = first; param = &buf.param[0]; psize = 2 * sizeof(struct __kbind) + (i + 1) * sizeof(buf.newval[0]); } } /* directly code the syscall, so that it's actually inline here */ { register long syscall_num __asm("g1") = SYS_kbind; register void *arg1 __asm("o0") = param; register long arg2 __asm("o1") = psize; register long arg3 __asm("o2") = cookie; __asm volatile("t %2" : "+r" (arg1), "+r" (arg2) : "i" (ST_SYSCALL), "r" (syscall_num), "r" (arg3) : "cc", "memory"); } return newvalue; } /* * Install rtld function call into this PLT slot. */ #define SAVE 0x9de3bf50 #define SETHI_l0 0x21000000 #define SETHI_l1 0x23000000 #define OR_l0_l0 0xa0142000 #define SLLX_l0_32_l0 0xa12c3020 #define OR_l0_l1_l0 0xa0140011 #define JMPL_l0_o1 0x93c42000 #define MOV_g1_o0 0x90100001 void _dl_install_plt(Elf_Word *pltgot, Elf_Addr proc) { pltgot[0] = SAVE; pltgot[1] = SETHI_l0 | HIVAL(proc, 42); pltgot[2] = SETHI_l1 | HIVAL(proc, 10); pltgot[3] = OR_l0_l0 | LOVAL((proc) >> 32); pltgot[4] = SLLX_l0_32_l0; pltgot[5] = OR_l0_l1_l0; pltgot[6] = JMPL_l0_o1 | LOVAL(proc); pltgot[7] = MOV_g1_o0; } void _dl_bind_start_0(long, long); void _dl_bind_start_1(long, long); static int _dl_md_reloc_all_plt(elf_object_t *object) { long i; long numrela; int fails = 0; Elf_Addr loff; Elf_RelA *relas; loff = object->obj_base; numrela = object->Dyn.info[DT_PLTRELSZ] / sizeof(Elf_RelA); relas = (Elf_RelA *)(object->Dyn.info[DT_JMPREL]); if (relas == NULL) return 0; for (i = 0; i < numrela; i++, relas++) { Elf_Addr value; Elf_Word *where; struct sym_res sr; const Elf_Sym *sym; if (ELF_R_TYPE(relas->r_info) != R_TYPE(JMP_SLOT)) continue; sym = object->dyn.symtab + ELF_R_SYM(relas->r_info); sr = _dl_find_symbol(object->dyn.strtab + sym->st_name, SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object); if (sr.sym == NULL) { if (ELF_ST_BIND(sym->st_info) != STB_WEAK) fails++; continue; } where = (Elf_Word *)(relas->r_offset + loff); value = sr.obj->obj_base + sr.sym->st_value; if (__predict_false(relas->r_addend)) { /* * This entry is >32768. The relocation points to a * PC-relative pointer to the _dl_bind_start_0 stub at * the top of the PLT section. Update it to point to * the target function. */ *(Elf_Addr *)where = relas->r_addend + value - object->Dyn.info[DT_PLTGOT]; } else _dl_reloc_plt(&where[1], &where[2], where, value); } return fails; } /* * Relocate the Global Offset Table (GOT). */ int _dl_md_reloc_got(elf_object_t *object, int lazy) { int fails = 0; Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT]; Elf_Word *entry = (Elf_Word *)pltgot; if (object->Dyn.info[DT_PLTREL] != DT_RELA) return 0; if (!lazy) { fails = _dl_md_reloc_all_plt(object); } else { _dl_install_plt(&entry[0], (Elf_Addr)&_dl_bind_start_0); _dl_install_plt(&entry[8], (Elf_Addr)&_dl_bind_start_1); pltgot[8] = (Elf_Addr)object; } return fails; }