rtld_start.S revision 281453
1/*- 2 * Copyright 1996-1998 John D. Polstra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $FreeBSD: stable/10/libexec/rtld-elf/amd64/rtld_start.S 281453 2015-04-12 06:45:40Z kib $ 26 */ 27 28 .text 29 .align 4 30 .globl .rtld_start 31 .type .rtld_start,@function 32.rtld_start: 33 xorq %rbp,%rbp # Clear frame pointer for good form 34 subq $24,%rsp # A place to store exit procedure addr 35 movq %rdi,%r12 36 movq %rsp,%rsi # save address of exit proc 37 movq %rsp,%rdx # construct address of obj_main 38 addq $8,%rdx 39 call _rtld # Call rtld(sp); returns entry point 40 popq %rsi # Get exit procedure address 41 movq %r12,%rdi # *ap 42/* 43 * At this point, %rax contains the entry point of the main program, and 44 * %rdx contains a pointer to a termination function that should be 45 * registered with atexit(). (crt1.o registers it.) 46 */ 47.globl .rtld_goto_main 48.rtld_goto_main: # This symbol exists just to make debugging easier. 49 jmp *%rax # Enter main program 50 51 52/* 53 * Binder entry point. Control is transferred to here by code in the PLT. 54 * On entry, there are two arguments on the stack. In ascending address 55 * order, they are (1) "obj", a pointer to the calling object's Obj_Entry, 56 * and (2) "reloff", the byte offset of the appropriate relocation entry 57 * in the PLT relocation table. 58 * 59 * We are careful to preserve all registers, even the caller-save 60 * registers. That is because this code may be invoked by low-level 61 * assembly-language code that is not ABI-compliant. 62 * 63 * Stack map: 64 * reloff 0x60 65 * obj 0x58 66 * spare 0x50 67 * rflags 0x48 68 * rax 0x40 69 * rdx 0x38 70 * rcx 0x30 71 * rsi 0x28 72 * rdi 0x20 73 * r8 0x18 74 * r9 0x10 75 * r10 0x8 76 * r11 0x0 77 */ 78 .align 4 79 .globl _rtld_bind_start 80 .type _rtld_bind_start,@function 81_rtld_bind_start: 82 .cfi_startproc 83 .cfi_adjust_cfa_offset 16 84 subq $8,%rsp 85 .cfi_adjust_cfa_offset 8 86 pushfq # Save rflags 87 .cfi_adjust_cfa_offset 8 88 pushq %rax # Save %rax 89 .cfi_adjust_cfa_offset 8 90 .cfi_offset %rax,-32 91 pushq %rdx # Save %rdx 92 .cfi_adjust_cfa_offset 8 93 .cfi_offset %rdx,-40 94 pushq %rcx # Save %rcx 95 .cfi_adjust_cfa_offset 8 96 .cfi_offset %rcx,-48 97 pushq %rsi # Save %rsi 98 .cfi_adjust_cfa_offset 8 99 .cfi_offset %rsi,-56 100 pushq %rdi # Save %rdi 101 .cfi_adjust_cfa_offset 8 102 .cfi_offset %rdi,-64 103 pushq %r8 # Save %r8 104 .cfi_adjust_cfa_offset 8 105 .cfi_offset %r8,-72 106 pushq %r9 # Save %r9 107 .cfi_adjust_cfa_offset 8 108 .cfi_offset %r9,-80 109 pushq %r10 # Save %r10 110 .cfi_adjust_cfa_offset 8 111 .cfi_offset %r10,-88 112 pushq %r11 # Save %r11 113 .cfi_adjust_cfa_offset 8 114 .cfi_offset %r11,-96 115 116 movq 0x58(%rsp),%rdi # Fetch obj argument 117 movq 0x60(%rsp),%rsi # Fetch reloff argument 118 leaq (%rsi,%rsi,2),%rsi # multiply by 3 119 leaq (,%rsi,8),%rsi # now 8, for 24 (sizeof Elf_Rela) 120 121 call _rtld_bind # Transfer control to the binder 122 /* Now %rax contains the entry point of the function being called. */ 123 124 movq %rax,0x60(%rsp) # Store target over reloff argument 125 popq %r11 # Restore %r11 126 .cfi_adjust_cfa_offset -8 127 .cfi_restore %r11 128 popq %r10 # Restore %r10 129 .cfi_adjust_cfa_offset -8 130 .cfi_restore %r10 131 popq %r9 # Restore %r9 132 .cfi_adjust_cfa_offset -8 133 .cfi_restore %r9 134 popq %r8 # Restore %r8 135 .cfi_adjust_cfa_offset -8 136 .cfi_restore %r8 137 popq %rdi # Restore %rdi 138 .cfi_adjust_cfa_offset -8 139 .cfi_restore %rdi 140 popq %rsi # Restore %rsi 141 .cfi_adjust_cfa_offset -8 142 .cfi_restore %rsi 143 popq %rcx # Restore %rcx 144 .cfi_adjust_cfa_offset -8 145 .cfi_restore %rcx 146 popq %rdx # Restore %rdx 147 .cfi_adjust_cfa_offset -8 148 .cfi_restore %rdx 149 popq %rax # Restore %rax 150 .cfi_adjust_cfa_offset -8 151 .cfi_restore %rax 152 popfq # Restore rflags 153 .cfi_adjust_cfa_offset -8 154 leaq 16(%rsp),%rsp # Discard spare, obj, do not change rflags 155 ret # "Return" to target address 156 .cfi_endproc 157 .size _rtld_bind_start, . - _rtld_bind_start 158 159 .section .note.GNU-stack,"",%progbits 160