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 * $Id: rtld_start.S,v 1.1.1.1 1998/03/07 19:24:35 jdp Exp $ 26 */ 27 28 .text 29 .align 4 30 .globl .rtld_start 31 .type .rtld_start,@function 32.rtld_start: 33 xorl %ebp,%ebp # Clear frame pointer for good form 34 movl %esp,%eax # Save initial stack pointer 35 subl $8,%esp # A place to store exit procedure addr 36 movl %esp,%ebx # save address of exit proc 37 movl %esp,%ecx # construct address of obj_main 38 addl $4,%ecx 39 pushl %ecx # Pass address of obj_main 40 pushl %ebx # Pass address of exit proc 41 pushl %eax # Pass initial stack pointer to rtld 42 call _rtld@PLT # Call rtld(sp); returns entry point 43 addl $12,%esp # Remove arguments from stack 44 popl %edx # Get exit procedure address 45 addl $4,%esp # Ignore obj_main 46/* 47 * At this point, %eax contains the entry point of the main program, and 48 * %edx contains a pointer to a termination function that should be 49 * registered with atexit(). (crt1.o registers it.) 50 */ 51.globl .rtld_goto_main 52.rtld_goto_main: # This symbol exists just to make debugging easier. 53 jmp *%eax # Enter main program 54 55 56/* 57 * Binder entry point. Control is transferred to here by code in the PLT. 58 * On entry, there are two arguments on the stack. In ascending address 59 * order, they are (1) "obj", a pointer to the calling object's Obj_Entry, 60 * and (2) "reloff", the byte offset of the appropriate relocation entry 61 * in the PLT relocation table. 62 * 63 * We are careful to preserve all registers, even the the caller-save 64 * registers. That is because this code may be invoked by low-level 65 * assembly-language code that is not ABI-compliant. 66 */ 67 .align 4 68 .globl _rtld_bind_start 69 .type _rtld_bind_start,@function 70_rtld_bind_start: 71 pushf # Save eflags 72 pushl %eax # Save %eax 73 pushl %edx # Save %edx 74 pushl %ecx # Save %ecx 75 pushl 20(%esp) # Copy reloff argument 76 pushl 20(%esp) # Copy obj argument 77 78 call _rtld_bind@PLT # Transfer control to the binder 79 /* Now %eax contains the entry point of the function being called. */ 80 81 addl $8,%esp # Discard binder arguments 82 movl %eax,20(%esp) # Store target over obj argument 83 popl %ecx # Restore %ecx 84 popl %edx # Restore %edx 85 popl %eax # Restore %eax 86 popf # Restore eflags 87 leal 4(%esp),%esp # Discard reloff, do not change eflags 88 ret # "Return" to target address 89