1/* $NetBSD: rtld_start.S,v 1.4 2001/09/26 04:06:43 mycroft Exp $ */ 2 3/*- 4 * Copyright (C) 1998 Tsubai Masanari 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 * 29 * $FreeBSD$ 30 */ 31 32#include <machine/asm.h> 33 34.extern _GLOBAL_OFFSET_TABLE_ 35.extern _DYNAMIC 36 37_ENTRY(.rtld_start) 38 stwu %r1,-48(%r1) /* 16-byte aligned stack for reg saves + 39 exit_proc & obj _rtld args + 40 backchain & lrsave stack frame */ 41 stw %r3,16(%r1) /* argc */ 42 stw %r4,20(%r1) /* argv */ 43 stw %r5,24(%r1) /* envp */ 44/* stw %r6,28(%r1) *//* obj (always 0) */ 45/* stw %r7,32(%r1) *//* cleanup (always 0) */ 46 stw %r8,36(%r1) /* ps_strings */ 47 48 /* 49 * Perform initial relocation of ld-elf.so. Not as easy as it 50 * sounds. 51 * - perform small forward branch to put PC into link reg 52 * - use link-time constants to determine offset to the 53 * _DYNAMIC section and the GOT. Add these to the PC to 54 * convert to absolute addresses. 55 * - read GOT[0], which is the SVR4 ABI-specified link-time 56 * value of _DYNAMIC. Subtract this value from the absolute 57 * value to determine the load address 58 * - call reloc_non_plt_self() to fix up ld-elf.so's relocations 59 */ 60 bcl 20,31,1f 611: mflr %r30 62 mr %r3,%r30 # save for _DYNAMIC 63 addis %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@ha 64 addi %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@l 65 addis %r3,%r3,_DYNAMIC-1b@ha # get _DYNAMIC actual address 66 addi %r3,%r3,_DYNAMIC-1b@l 67 lwz %r28,0(%r30) # get base-relative &_DYNAMIC 68 sub %r28,%r3,%r28 # r28 = relocbase 69 mr %r4,%r28 # r4 = relocbase 70 bl reloc_non_plt_self /* reloc_non_plt_self(&_DYNAMIC,base) */ 71 72 /* 73 * The _rtld() function likes to see a stack layout containing 74 * { argc, argv[0], argv[1] ... argv[N], 0, env[0], ... , env[N] } 75 * Since the PowerPC stack was 16-byte aligned at exec time, the 76 * original stack layout has to be found by moving back a word 77 * from the argv pointer. 78 */ 79 lwz %r4,20(%r1) /* restore argv */ 80 addi %r3,%r4,-4 /* locate argc ptr, &argv[-1] */ 81 82 addi %r4,%r1,8 /* &exit_proc on stack */ 83 addi %r5,%r1,12 /* &obj_main on stack */ 84 85 bl _rtld /* &_start = _rtld(sp, &exit_proc, &obj_main)*/ 86 mtlr %r3 87 88 /* 89 * Restore args, with new obj/exit proc 90 */ 91 lwz %r3,16(%r1) /* argc */ 92 lwz %r4,20(%r1) /* argv */ 93 lwz %r5,24(%r1) /* envp */ 94 lwz %r6,12(%r1) /* obj */ 95 lwz %r7,8(%r1) /* exit proc */ 96 lwz %r8,36(%r1) /* ps_strings */ 97 addi %r1,%r1,48 /* restore original stackptr */ 98 99 blrl /* _start(argc, argv, envp, obj, cleanup, ps_strings) */ 100 101 li %r0,1 /* _exit() */ 102 sc 103 104/* 105 * _rtld_bind_secureplt_start() 106 * 107 * Call into the MI binder (Secure-PLT stub). 108 * secure-plt expects %r11 to be the offset to the rela entry. 109 * bss-plt expects %r11 to be index of the rela entry. 110 * So for bss-plt, we multiply the index by 12 to get the offset. 111 */ 112_ENTRY(_rtld_bind_secureplt_start) 113 stwu %r1,-160(%r1) # stack space for 29 regs + r0/lr/cr 114 stw %r0,20(%r1) # save r0 115 116 /* 117 * Instead of division which is costly we will use multiplicative 118 * inverse. a / n = ((a * inv(n)) >> 32) 119 * where inv(n) = (0x100000000 + n - 1) / n 120 */ 121 mr %r0,%r11 122 lis %r11,0x15555556@h # load multiplicative inverse of 12 123 ori %r11,%r11,0x15555556@l 124 mulhwu %r11,%r11,%r0 # get high half of multiplication 125 b 1f 126 127/* 128 * _rtld_bind_start() 129 * 130 * Call into the MI binder. This routine is reached via the PLT call cell, 131 * and then _rtld_powerpc_pltresolve(). 132 * On entry, %r11 contains the index of the PLT cell, and %r12 contains 133 * a pointer to the ELF object for the file. 134 * Save all registers, call into the binder to resolve and fixup the external 135 * routine, and then transfer to the external routine on return. 136 */ 137 .globl _rtld_bind 138 139_ENTRY(_rtld_bind_start) 140 stwu %r1,-160(%r1) # stack space for 29 regs + r0/lr/cr 141 stw %r0,20(%r1) # save r0 1421: 143 mflr %r0 144 stw %r0,16(%r1) # save lr 145 mfcr %r0 146 stw %r0,12(%r1) # save cr 147 stmw %r3,24(%r1) # save r3-r31 148 149 mr %r3,%r12 # obj 150 mulli %r4,%r11,12 # rela index * sizeof(Elf_Rela) 151 bl _rtld_bind # target addr = _rtld_bind(obj, reloff) 152 mtctr %r3 # move absolute target addr into ctr 153 154 lmw %r3,24(%r1) # restore r3-r31 155 lwz %r0,12(%r1) # restore cr 156 mtcr %r0 157 lwz %r0,16(%r1) # restore lr 158 mtlr %r0 159 lwz %r0,20(%r1) # restore r0 160 161 addi %r1,%r1,160 # restore stack 162 bctr # jump to target 163 164 165/* 166 * _rtld_powerpc_pltresolve() 167 * 168 * This routine is copied into the latter part of the 72-byte reserved 169 * area at the start of the PLT. The absolute address of the _rtld_bind_start 170 * routine, and the ELF object for the loaded file, are inserted into 171 * the code by the reloc.c:init_pltgot() routine. 172 * The first time an external routine is called, the PLT slot will 173 * set up %r11 to the offset of the slot, and will jump to this routine. 174 * The ELF object is shifted into %r11, and _rtld_bind_start is called 175 * to complete the binding. 176 */ 177_ENTRY(_rtld_powerpc_pltlongresolve) 178 lis %r12,0 # lis 12,jmptab@ha 179 addi %r12,%r12,0 # addi 12,12,jmptab@l 180 subf %r11,%r12,%r11 # reloff 181 li %r12,2 182 srw %r11,%r11,%r12 # index = reloff/sizeof(Elf_Addr) 183_ENTRY(_rtld_powerpc_pltresolve) 184 lis %r12,0 # lis 12,_rtld_bind_start@ha 185 addi %r12,%r12,0 # addi 12,12,_rtld_bind_start@l 186 mtctr %r12 187 lis %r12,0 # lis 12,obj@ha 188 addi %r12,%r12,0 # addi 12,12,obj@l 189 bctr 190 191/* 192 * _rtld_powerpc_pltcall() 193 * 194 * This routine is copied into the 72-byte reserved area at the 195 * start of the PLT. The reloc.c:init_pltgot() routine inserts 196 * the absolute address of the jumptable. 197 * Control is transferred to this routine when the binder has 198 * located the external routine, but determined that it is > 32Mb 199 * from the PLT slot. Code is inserted into the PLT slot to set up 200 * %r11 with the jumptable index, and jump to here, where the 201 * absolute address of the external routine is loaded from the 202 * jumptable and transferred to 203 */ 204_ENTRY(_rtld_powerpc_pltcall) 205 slwi %r11,%r11,2 # jmptab offset = index * 4 206 addis %r11,%r11,0 # addis 11,11,jmptab@ha 207 lwz %r11,0(%r11) # lwz 11,jmptab@l(11) 208 mtctr %r11 209 bctr # (*jmptab[index])() 210 211 .section .note.GNU-stack,"",%progbits 212