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 30#include <machine/asm.h> 31#include <machine/spr.h> /* For SPR_SPEFSCR if needed. */ 32 33.extern _GLOBAL_OFFSET_TABLE_ 34.extern _DYNAMIC 35 36_ENTRY(.rtld_start) 37 stwu %r1,-48(%r1) /* 16-byte aligned stack for reg saves + 38 exit_proc & obj _rtld args + 39 backchain & lrsave stack frame */ 40 stw %r3,16(%r1) /* argc */ 41 stw %r4,20(%r1) /* argv */ 42 stw %r5,24(%r1) /* envp */ 43/* stw %r6,28(%r1) *//* obj (always 0) */ 44/* stw %r7,32(%r1) *//* cleanup (always 0) */ 45 stw %r8,36(%r1) /* ps_strings */ 46 47 /* 48 * Perform initial relocation of ld-elf.so. Not as easy as it 49 * sounds. 50 * - perform small forward branch to put PC into link reg 51 * - use link-time constants to determine offset to the 52 * _DYNAMIC section and the GOT. Add these to the PC to 53 * convert to absolute addresses. 54 * - read GOT[0], which is the SVR4 ABI-specified link-time 55 * value of _DYNAMIC. Subtract this value from the absolute 56 * value to determine the load address 57 * - call reloc_non_plt_self() to fix up ld-elf.so's relocations 58 */ 59 bcl 20,31,1f 601: mflr %r30 61 mr %r3,%r30 # save for _DYNAMIC 62 addis %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@ha 63 addi %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@l 64 addis %r3,%r3,_DYNAMIC-1b@ha # get _DYNAMIC actual address 65 addi %r3,%r3,_DYNAMIC-1b@l 66 lwz %r28,0(%r30) # get base-relative &_DYNAMIC 67 sub %r28,%r3,%r28 # r28 = relocbase 68 mr %r4,%r28 # r4 = relocbase 69 bl reloc_non_plt_self /* reloc_non_plt_self(&_DYNAMIC,base) */ 70 71 /* 72 * The _rtld() function likes to see a stack layout containing 73 * { argc, argv[0], argv[1] ... argv[N], 0, env[0], ... , env[N] } 74 * Since the PowerPC stack was 16-byte aligned at exec time, the 75 * original stack layout has to be found by moving back a word 76 * from the argv pointer. 77 */ 78 lwz %r4,20(%r1) /* restore argv */ 79 addi %r3,%r4,-4 /* locate argc ptr, &argv[-1] */ 80 81 addi %r4,%r1,8 /* &exit_proc on stack */ 82 addi %r5,%r1,12 /* &obj_main on stack */ 83 84 bl _rtld /* &_start = _rtld(sp, &exit_proc, &obj_main)*/ 85 mtlr %r3 86 87 /* 88 * Restore args, with new obj/exit proc 89 */ 90 lwz %r3,16(%r1) /* argc */ 91 lwz %r4,20(%r1) /* argv */ 92 lwz %r5,24(%r1) /* envp */ 93 lwz %r6,12(%r1) /* obj */ 94 lwz %r7,8(%r1) /* exit proc */ 95 lwz %r8,36(%r1) /* ps_strings */ 96 addi %r1,%r1,48 /* restore original stackptr */ 97 98 blrl /* _start(argc, argv, envp, obj, cleanup, ps_strings) */ 99 100 li %r0,1 /* _exit() */ 101 sc 102_END(.rtld_start) 103 104/* stack space for 30 GPRs + lr/cr */ 105#define NREGS 30 106#define GPRWIDTH 4 107#define FUDGE 4 108/* Stack frame needs the 12-byte ABI frame plus fudge factor. */ 109#define STACK_SIZE (NREGS * GPRWIDTH + 4 * 2 + 12 + FUDGE) 110 111/* 112 * _rtld_bind_secureplt_start() 113 * 114 * Call into the MI binder (Secure-PLT stub). 115 * secure-plt expects %r11 to be the offset to the rela entry. 116 * bss-plt expects %r11 to be index of the rela entry. 117 * So for bss-plt, we multiply the index by 12 to get the offset. 118 */ 119_ENTRY(_rtld_bind_secureplt_start) 120 stwu %r1,-STACK_SIZE(%r1) 121 stw %r0,20(%r1) # save r0 122 123 /* 124 * Instead of division which is costly we will use multiplicative 125 * inverse. a / n = ((a * inv(n)) >> 32) 126 * where inv(n) = (0x100000000 + n - 1) / n 127 */ 128 mr %r0,%r11 129 lis %r11,0x15555556@h # load multiplicative inverse of 12 130 ori %r11,%r11,0x15555556@l 131 mulhwu %r11,%r11,%r0 # get high half of multiplication 132 b 1f 133_END(_rtld_bind_secureplt_start) 134 135/* 136 * _rtld_bind_start() 137 * 138 * Call into the MI binder. This routine is reached via the PLT call cell, 139 * and then _rtld_powerpc_pltresolve(). 140 * On entry, %r11 contains the index of the PLT cell, and %r12 contains 141 * a pointer to the ELF object for the file. 142 * Save all registers, call into the binder to resolve and fixup the external 143 * routine, and then transfer to the external routine on return. 144 */ 145 .globl _rtld_bind 146 147_ENTRY(_rtld_bind_start) 148 stwu %r1,-STACK_SIZE(%r1) 149 stw %r0,20(%r1) # save r0 1501: 151 mflr %r0 152 stw %r0,16(%r1) # save lr 153 mfcr %r0 154 stw %r0,12(%r1) # save cr 155 stmw %r3,24(%r1) # save r3-r31 156 157 mr %r3,%r12 # obj 158 mulli %r4,%r11,12 # rela index * sizeof(Elf_Rela) 159 bl _rtld_bind # target addr = _rtld_bind(obj, reloff) 160 mtctr %r3 # move absolute target addr into ctr 161 162 lmw %r3,24(%r1) # restore r3-r31 163 lwz %r0,12(%r1) # restore cr 164 mtcr %r0 165 lwz %r0,16(%r1) # restore lr 166 mtlr %r0 167 lwz %r0,20(%r1) # restore r0 168 169 addi %r1,%r1,STACK_SIZE # restore stack 170 bctr # jump to target 171_END(_rtld_bind_start) 172 173 174/* 175 * _rtld_powerpc_pltresolve() 176 * 177 * This routine is copied into the latter part of the 72-byte reserved 178 * area at the start of the PLT. The absolute address of the _rtld_bind_start 179 * routine, and the ELF object for the loaded file, are inserted into 180 * the code by the reloc.c:init_pltgot() routine. 181 * The first time an external routine is called, the PLT slot will 182 * set up %r11 to the offset of the slot, and will jump to this routine. 183 * The ELF object is shifted into %r11, and _rtld_bind_start is called 184 * to complete the binding. 185 */ 186_ENTRY(_rtld_powerpc_pltlongresolve) 187 lis %r12,0 # lis 12,jmptab@ha 188 addi %r12,%r12,0 # addi 12,12,jmptab@l 189 subf %r11,%r12,%r11 # reloff 190 li %r12,2 191 srw %r11,%r11,%r12 # index = reloff/sizeof(Elf_Addr) 192_END(_rtld_powerpc_pltlongresolve) 193_ENTRY(_rtld_powerpc_pltresolve) 194 lis %r12,0 # lis 12,_rtld_bind_start@ha 195 addi %r12,%r12,0 # addi 12,12,_rtld_bind_start@l 196 mtctr %r12 197 lis %r12,0 # lis 12,obj@ha 198 addi %r12,%r12,0 # addi 12,12,obj@l 199 bctr 200_END(_rtld_powerpc_pltresolve) 201 202/* 203 * _rtld_powerpc_pltcall() 204 * 205 * This routine is copied into the 72-byte reserved area at the 206 * start of the PLT. The reloc.c:init_pltgot() routine inserts 207 * the absolute address of the jumptable. 208 * Control is transferred to this routine when the binder has 209 * located the external routine, but determined that it is > 32Mb 210 * from the PLT slot. Code is inserted into the PLT slot to set up 211 * %r11 with the jumptable index, and jump to here, where the 212 * absolute address of the external routine is loaded from the 213 * jumptable and transferred to 214 */ 215_ENTRY(_rtld_powerpc_pltcall) 216 slwi %r11,%r11,2 # jmptab offset = index * 4 217 addis %r11,%r11,0 # addis 11,11,jmptab@ha 218 lwz %r11,0(%r11) # lwz 11,jmptab@l(11) 219 mtctr %r11 220 bctr # (*jmptab[index])() 221_END(_rtld_powerpc_pltcall) 222 223 .section .note.GNU-stack,"",%progbits 224