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 1.6 1998/03/05 21:05:53 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 $4,%esp # A place to store exit procedure addr 36 pushl %esp # Pass its address to rtld 37 pushl %eax # Pass initial stack pointer to rtld 38 call _rtld@PLT # Call rtld(sp); returns entry point 39 addl $8,%esp # Remove arguments from stack 40 popl %edx # Get exit procedure address 41/* 42 * At this point, %eax contains the entry point of the main program, and 43 * %edx contains a pointer to a termination function that should be 44 * registered with atexit(). (crt1.o registers it.) 45 */ 46.globl .rtld_goto_main 47.rtld_goto_main: # This symbol exists just to make debugging easier. 48 jmp *%eax # Enter main program 49 50 51/* 52 * Binder entry point. Control is transferred to here by code in the PLT. 53 * On entry, there are two arguments on the stack. In ascending address 54 * order, they are (1) "obj", a pointer to the calling object's Obj_Entry, 55 * and (2) "reloff", the byte offset of the appropriate relocation entry 56 * in the PLT relocation table. 57 * 58 * We are careful to preserve all registers, even the the caller-save 59 * registers. That is because this code may be invoked by low-level 60 * assembly-language code that is not ABI-compliant. 61 */ 62 .align 4 63 .globl _rtld_bind_start 64 .type _rtld_bind_start,@function 65_rtld_bind_start: 66 pushf # Save eflags 67 pushl %eax # Save %eax 68 pushl %edx # Save %edx 69 pushl %ecx # Save %ecx 70 pushl 20(%esp) # Copy reloff argument 71 pushl 20(%esp) # Copy obj argument 72 73 call _rtld_bind@PLT # Transfer control to the binder 74 /* Now %eax contains the entry point of the function being called. */ 75 76 addl $8,%esp # Discard binder arguments 77 movl %eax,20(%esp) # Store target over obj argument 78 popl %ecx # Restore %ecx 79 popl %edx # Restore %edx 80 popl %eax # Restore %eax 81 popf # Restore eflags 82 leal 4(%esp),%esp # Discard reloff, do not change eflags 83 ret # "Return" to target address 84