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: src/libexec/rtld-elf/amd64/rtld_start.S,v 1.5 2004/03/21 01:43:39 peter Exp $
26 */
27
28/*
29 * Dynamic program start.  argv pointer is in %rdi.
30 */
31	.text
32	.align	4
33	.globl	resident_start
34	.globl	.rtld_start
35	.type	.rtld_start,@function
36resident_start:
37.rtld_start:
38	xorq	%rbp,%rbp		# Clear frame pointer for good form
39	subq	$24,%rsp		# A place to store exit procedure addr
40	movq	%rdi,%r12
41	movq	%rsp,%rsi		# save address of exit proc
42	movq	%rsp,%rdx		# construct address of obj_main
43	addq	$8,%rdx
44	call	_rtld@PLT		# Call rtld(sp); returns entry point
45	popq	%rsi			# Get exit procedure address
46	movq	%r12,%rdi		# *ap
47/*
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.)
51 */
52.globl .rtld_goto_main
53.rtld_goto_main:	# This symbol exists just to make debugging easier.
54	jmp	*%rax			# Enter main program
55
56
57/*
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.
63 *
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.
67 *
68 * Stack map:
69 * reloff       0x60
70 * obj          0x58
71 * spare	0x50
72 * rflags       0x48
73 * rax          0x40
74 * rdx          0x38
75 * rcx          0x30
76 * rsi          0x28
77 * rdi          0x20
78 * r8           0x18
79 * r9           0x10
80 * r10          0x8
81 * r11          0x0
82 */
83	.align	4
84	.globl	_rtld_bind_start
85	.type	_rtld_bind_start,@function
86_rtld_bind_start:
87	subq	$8,%rsp
88	pushfq				# Save rflags
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
94	pushq	%r8			# Save %r8
95	pushq	%r9			# Save %r9
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)
103
104	call	_rtld_bind@PLT		# Transfer control to the binder
105	/* Now %rax contains the entry point of the function being called. */
106
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
120