1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/* $OpenBSD: ldasm.S,v 1.5 2002/07/07 08:54:50 jufi Exp $ */
/*
* Copyright (c) 1999 Dale Rahn
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed under OpenBSD by
* Dale Rahn.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
/*
* #ifdef blrl_never_causes_illegal_access
* background for the else of this define
* On the machine this code is being written, on a large portion
* of the tims this code is executed the blrl instruct causes an
* illegal instruction, hopefully by touching the page with a load
* will prevent the execute access from faulting.
*/
#define AUX_entry 9
#include <machine/asm.h>
ENTRY(_dl_start)
mr 19, 1
stwu 1, (-16 -((AUX_entry+3)*4))(1) # Some space.
mflr 27 /* save off old link register */
stw 27, 4(19) /* save in normal location */
# squirrel away the arguments for main
mr 20, 3 #argc
mr 21, 4 #argv
mr 22, 5 #envp
mr 23, 6 # ???
.local .L___offset_sym
.type .L___offset_sym,@function
bl 1f
.L___offset_sym:
# this instruction never gets executed but can be used
# to find the virtual address where the page is loaded.
bl _GLOBAL_OFFSET_TABLE_@local-4
bl _DYNAMIC@local
1:
mflr 5 # this stores where we are (+4)
lwz 18, 0(5) # load the instruction at offset_sym
# it contains an offset to the location
# of the GOT.
rlwinm 18,18,0,8,30 # mask off the offset portion of the instr.
/*
* these adds effectively calculate the value the
* bl _GLOBAL_OFFSET_TABLE_@local-4
* operation that would be below would calulate.
*/
add 28, 18, 5
li 0, 0
dcbf 5, 18
sync
isync
icbi 5, 18 # make certain that the got table addr is
# not in the icache
sync
isync
addi 28, 28, 4
mr 29, 28
lwz 30, 0(28) # this loads the first entry of the GOT
# thus forcing it to be paged in when
# we jump to it below.
# calculate where we want to be (via the got)
bl _GLOBAL_OFFSET_TABLE_@local-4
mflr 28
lwz 4, .L___offset_sym@got(28)
mr 6, 4 # make copy of register for debugging
/* This cheats and calculates the address of _DYNAMIC
* the same way that the GLOBAL_OFFSET_TABLE was calcuated
*/
lwz 18, 4(5)
rlwinm 18,18,0,8,30 # mask off the offset portion of the instr.
add 8, 18, 5 # address of _DYNAMIC (arg6 for _dl_boot)
addi 18, 8, 4 # correction.
sub 4, 5, 4 # calculate offset (arg1 for _dl_boot)
mr 17, 4
subi 3, 21, 4 # Get stack pointer (arg0 for _dl_boot).
mr 4, 17 # loff
mr 5, 18 # dynamicp
addi 6, 1, 8 # dl_data
bl _dl_boot_bind@local
mr 3, 21 # argv
mr 4, 22 # envp
mr 5, 17 # loff
mr 6, 18 # dynamicp
addi 7, 1, 8 # dl_data
bl _dl_boot@local
mtctr 3 # put return value into ctr to execute
# get back the squirreled away the arguments for main
mr 3, 20
mr 4, 21
mr 5, 22
mr 6, 23
mtlr 27
lwz 1, 0(1) # Restore stack pointer.
bctr # Go execute the 'real' program.
.globl _dl_rt_resolve
.data
_dl_rt_resolve:
.long 0
|
