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 $
29 * Dynamic program start. argv pointer is in %rdi.
35 .type .rtld_start,@function
38 xorq %rbp,%rbp # Clear frame pointer for good form
39 subq $24,%rsp # A place to store exit procedure addr
41 movq %rsp,%rsi # save address of exit proc
42 movq %rsp,%rdx # construct address of obj_main
44 call _rtld@PLT # Call rtld(sp); returns entry point
45 popq %rsi # Get exit procedure address
48 * At this point, %rax contains the entry point of the main program, and
49 * %rdx contains a pointer to a termination function that should be
50 * registered with atexit(). (crt1.o registers it.)
52 .globl .rtld_goto_main
53 .rtld_goto_main: # This symbol exists just to make debugging easier.
54 jmp *%rax # Enter main program
58 * Binder entry point. Control is transferred to here by code in the PLT.
59 * On entry, there are two arguments on the stack. In ascending address
60 * order, they are (1) "obj", a pointer to the calling object's Obj_Entry,
61 * and (2) "reloff", the byte offset of the appropriate relocation entry
62 * in the PLT relocation table.
64 * We are careful to preserve all registers, even the the caller-save
65 * registers. That is because this code may be invoked by low-level
66 * assembly-language code that is not ABI-compliant.
84 .globl _rtld_bind_start
85 .type _rtld_bind_start,@function
89 pushq %rax # Save %rax
90 pushq %rdx # Save %rdx
91 pushq %rcx # Save %rcx
92 pushq %rsi # Save %rsi
93 pushq %rdi # Save %rdi
96 pushq %r10 # Save %r10
97 pushq %r11 # Save %r11
98 movq 0x58(%rsp),%rdi # Fetch obj argument (arg 1)
99 movq 0x60(%rsp),%rsi # Fetch reloff argument (arg 2)
100 leaq 0x68(%rsp),%rdx # Fetch original stack pointer (arg 3)
101 leaq (%rsi,%rsi,2),%rsi # multiply by 3
102 leaq (,%rsi,8),%rsi # now 8, for 24 (sizeof Elf_Rela)
104 call _rtld_bind@PLT # Transfer control to the binder
105 /* Now %rax contains the entry point of the function being called. */
107 movq %rax,0x60(%rsp) # Store target over reloff argument
108 popq %r11 # Restore %r11
109 popq %r10 # Restore %r10
110 popq %r9 # Restore %r9
111 popq %r8 # Restore %r8
112 popq %rdi # Restore %rdi
113 popq %rsi # Restore %rsi
114 popq %rcx # Restore %rcx
115 popq %rdx # Restore %rdx
116 popq %rax # Restore %rax
117 popfq # Restore rflags
118 leaq 16(%rsp),%rsp # Discard spare, obj, do not change rflags
119 ret # "Return" to target address