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 32.extern _GLOBAL_OFFSET_TABLE_ 33.extern _DYNAMIC 34 35_ENTRY(_rtld_start) 36 stdu %r1,-144(%r1) /* 16-byte aligned stack for reg saves + 37 exit_proc & obj _rtld args + 38 backchain & lrsave stack frame */ 39 40 /* Save and restore only initial argv, because _rtld will modify 41 * argv and envp if invoked explicitly, making it necessary to 42 * load the (possibly) adjusted values from the stack. 43 */ 44 std %r4,104(%r1) /* argv */ 45/* std %r6,120(%r1) *//* obj (always 0) */ 46/* std %r7,128(%r1) *//* cleanup (always 0) */ 47 std %r8,136(%r1) /* ps_strings */ 48 49 /* 50 * Perform initial relocation of ld-elf.so. Not as easy as it 51 * sounds. 52 * - perform small forward branch to put PC into link reg 53 * - use link-time constants to determine offset to the 54 * _DYNAMIC section and the GOT. Add these to the PC to 55 * convert to absolute addresses. 56 * - call reloc_non_plt_self() to fix up ld-elf.so's relocations 57 */ 58 59 bl 1f 60 .llong _DYNAMIC-. 611: 62 mflr %r3 /* PC value at .llong */ 63 ld %r4,0(%r3) /* offset to _DYNAMIC */ 64 add %r3,%r4,%r3 /* r3 = &_DYNAMIC, absolute value */ 65 66 ld %r4,-0x8000(%r2) /* First TOC entry is TOC base */ 67 subf %r4,%r4,%r2 /* Subtract from real TOC base to get base */ 68 69 bl reloc_non_plt_self /* reloc_non_plt_self(&_DYNAMIC,base) */ 70 nop 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 ld %r4,104(%r1) 80 addi %r3,%r4,-8 /* locate argc ptr, &argv[-1] */ 81 addi %r4,%r1,128 /* &exit_proc on stack */ 82 addi %r5,%r1,120 /* &obj_main on stack */ 83 84 bl _rtld /* &_start = _rtld(sp, &exit_proc, &obj_main)*/ 85 nop 86#if !defined(_CALL_ELF) || _CALL_ELF == 1 87 ld %r2,8(%r3) 88 ld %r11,16(%r3) 89 ld %r3,0(%r3) 90#else 91 mr %r12,%r3 92#endif 93 mtlr %r3 94 95 /* 96 * Restore args, with new obj/exit proc 97 */ 98 ld %r4,104(%r1) /* argv */ 99 ld %r3,-8(%r4) /* argc */ 100 101 /* envp = argv + argc + 1 */ 102 addi %r5,%r3,1 103 sldi %r5,%r5,3 /* x8 */ 104 add %r5,%r4,%r5 105 106 ld %r6,120(%r1) /* obj */ 107 ld %r7,128(%r1) /* exit proc */ 108 ld %r8,136(%r1) /* ps_strings */ 109 110 blrl /* _start(argc, argv, envp, obj, cleanup, ps_strings) */ 111 112 li %r0,1 /* _exit() */ 113 sc 114_END(_rtld_start) 115 116/* 117 * _rtld_bind_start() 118 * 119 * Call into the MI binder. This routine is reached via the PLT call cell 120 * 121 * On entry, %r11 contains an object pointer and %r0 contains the PLT index. 122 * 123 * Save all registers, call into the binder to resolve and fixup the external 124 * routine, and then transfer to the external routine on return. 125 */ 126 .globl _rtld_bind 127 128_ENTRY(_rtld_bind_start) 129 mr %r12,%r0 # save r0 (index) immediately to r12 130 mflr %r0 131 std %r0,16(%r1) # save lr 132 mfcr %r0 133 std %r0,8(%r1) # save cr 134 135 stdu %r1,-48-12*8(%r1) # stack space for 8 regs + header 136 # + 2 save regs 137 std %r3,64+0*8(%r1) # save r3-r10 (arguments) 138 std %r4,64+1*8(%r1) 139 std %r5,64+2*8(%r1) 140 std %r6,64+3*8(%r1) 141 std %r7,64+4*8(%r1) 142 std %r8,64+5*8(%r1) 143 std %r9,64+6*8(%r1) 144 std %r10,64+7*8(%r1) 145 146 mr %r3,%r11 147 mulli %r4,%r12,24 # Multiply index by sizeof(Elf_Rela) 148 149 bl _rtld_bind # target addr = _rtld_bind(obj, reloff) 150 nop 151 152#if !defined(_CALL_ELF) || _CALL_ELF == 1 153 ld %r2,8(%r3) 154 ld %r11,16(%r3) 155 ld %r3,0(%r3) 156#else 157 mr %r12,%r3 158#endif 159 mtctr %r3 # move absolute target addr into ctr 160 161 ld %r3,64+0*8(%r1) # restore r3-r10 162 ld %r4,64+1*8(%r1) 163 ld %r5,64+2*8(%r1) 164 ld %r6,64+3*8(%r1) 165 ld %r7,64+4*8(%r1) 166 ld %r8,64+5*8(%r1) 167 ld %r9,64+6*8(%r1) 168 ld %r10,64+7*8(%r1) 169 170 ld %r1,0(%r1) # restore stack 171 ld %r0,8(%r1) # restore cr 172 mtcr %r0 173 ld %r0,16(%r1) # restore lr 174 mtlr %r0 175 176 bctr # jump to target 177_END(_rtld_bind_start) 178 179 .section .note.GNU-stack,"",%progbits 180