2 * Copyright 1996-1998 John D. Polstra.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
25 * $FreeBSD: src/libexec/rtld-elf/amd64/rtld_start.S,v 1.5 2004/03/21 01:43:39 peter Exp $
26 * $DragonFly: src/libexec/rtld-elf/amd64/rtld_start.S,v 1.1 2006/07/27 00:40:35 corecode Exp $
33 .type .rtld_start,@function
36 xorq %rbp,%rbp # Clear frame pointer for good form
37 subq $24,%rsp # A place to store exit procedure addr
39 movq %rsp,%rsi # save address of exit proc
40 movq %rsp,%rdx # construct address of obj_main
42 call _rtld@PLT # Call rtld(sp); returns entry point
43 popq %rsi # Get exit procedure address
46 * At this point, %rax contains the entry point of the main program, and
47 * %rdx contains a pointer to a termination function that should be
48 * registered with atexit(). (crt1.o registers it.)
50 .globl .rtld_goto_main
51 .rtld_goto_main: # This symbol exists just to make debugging easier.
52 jmp *%rax # Enter main program
56 * Binder entry point. Control is transferred to here by code in the PLT.
57 * On entry, there are two arguments on the stack. In ascending address
58 * order, they are (1) "obj", a pointer to the calling object's Obj_Entry,
59 * and (2) "reloff", the byte offset of the appropriate relocation entry
60 * in the PLT relocation table.
62 * We are careful to preserve all registers, even the the caller-save
63 * registers. That is because this code may be invoked by low-level
64 * assembly-language code that is not ABI-compliant.
82 .globl _rtld_bind_start
83 .type _rtld_bind_start,@function
87 pushq %rax # Save %rax
88 pushq %rdx # Save %rdx
89 pushq %rcx # Save %rcx
90 pushq %rsi # Save %rsi
91 pushq %rdi # Save %rdi
94 pushq %r10 # Save %r10
95 pushq %r11 # Save %r11
97 movq 0x58(%rsp),%rdi # Fetch obj argument
98 movq 0x60(%rsp),%rsi # Fetch reloff argument
99 leaq (%rsi,%rsi,2),%rsi # multiply by 3
100 leaq (,%rsi,8),%rsi # now 8, for 24 (sizeof Elf_Rela)
102 call _rtld_bind@PLT # Transfer control to the binder
103 /* Now %rax contains the entry point of the function being called. */
105 movq %rax,0x60(%rsp) # Store target over reloff argument
106 popq %r11 # Restore %r11
107 popq %r10 # Restore %r10
108 popq %r9 # Restore %r9
109 popq %r8 # Restore %r8
110 popq %rdi # Restore %rdi
111 popq %rsi # Restore %rsi
112 popq %rcx # Restore %rcx
113 popq %rdx # Restore %rdx
114 popq %rax # Restore %rax
115 popfq # Restore rflags
116 leaq 16(%rsp),%rsp # Discard spare, obj, do not change rflags
117 ret # "Return" to target address