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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
/* plugin_new_section_layout.c -- Simple plugin to reorder function sections in
plugin-generated objects
Copyright (C) 2017-2018 Free Software Foundation, Inc.
Written by Stephen Crane <sjc@immunant.com>.
This file is part of gold.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
MA 02110-1301, USA. */
/* This plugin tests the new_input API of the linker plugin interface that
* allows plugins to modify section layout and assign sections to segments for
* sections in plugin-generated object files. It assumes that another plugin is
* also in use which will add new files. In practice a plugin is likely to
* generate new input files itself in all_symbols_read and want to
* reorder/assign sections for these files in the new_input_hook callback. */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "plugin-api.h"
#include "elf/common.h"
static ld_plugin_get_input_section_count get_input_section_count = NULL;
static ld_plugin_get_input_section_type get_input_section_type = NULL;
static ld_plugin_get_input_section_name get_input_section_name = NULL;
static ld_plugin_update_section_order update_section_order = NULL;
static ld_plugin_allow_section_ordering allow_section_ordering = NULL;
static ld_plugin_allow_unique_segment_for_sections
allow_unique_segment_for_sections = NULL;
static ld_plugin_unique_segment_for_sections unique_segment_for_sections = NULL;
enum ld_plugin_status onload(struct ld_plugin_tv *tv);
enum ld_plugin_status new_input_hook(const struct ld_plugin_input_file *file);
/* Plugin entry point. */
enum ld_plugin_status
onload(struct ld_plugin_tv *tv)
{
struct ld_plugin_tv *entry;
for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
{
switch (entry->tv_tag)
{
case LDPT_GET_INPUT_SECTION_COUNT:
get_input_section_count = *entry->tv_u.tv_get_input_section_count;
break;
case LDPT_GET_INPUT_SECTION_TYPE:
get_input_section_type = *entry->tv_u.tv_get_input_section_type;
break;
case LDPT_GET_INPUT_SECTION_NAME:
get_input_section_name = *entry->tv_u.tv_get_input_section_name;
break;
case LDPT_UPDATE_SECTION_ORDER:
update_section_order = *entry->tv_u.tv_update_section_order;
break;
case LDPT_ALLOW_SECTION_ORDERING:
allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
break;
case LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS:
allow_unique_segment_for_sections
= *entry->tv_u.tv_allow_unique_segment_for_sections;
break;
case LDPT_UNIQUE_SEGMENT_FOR_SECTIONS:
unique_segment_for_sections
= *entry->tv_u.tv_unique_segment_for_sections;
break;
case LDPT_REGISTER_NEW_INPUT_HOOK:
assert((*entry->tv_u.tv_register_new_input) (new_input_hook)
== LDPS_OK);
break;
default:
break;
}
}
if (get_input_section_count == NULL
|| get_input_section_type == NULL
|| get_input_section_name == NULL
|| update_section_order == NULL
|| allow_section_ordering == NULL
|| allow_unique_segment_for_sections == NULL
|| unique_segment_for_sections == NULL)
{
fprintf(stderr, "Some interfaces are missing\n");
return LDPS_ERR;
}
/* Inform the linker to prepare for section reordering. */
(*allow_section_ordering)();
/* Inform the linker to prepare to map some sections to unique
segments. */
(*allow_unique_segment_for_sections)();
return LDPS_OK;
}
inline static int is_prefix_of(const char *prefix, const char *str)
{
return strncmp(prefix, str, strlen (prefix)) == 0;
}
/* This function is called by the linker when new files are added by a plugin.
We can now tell the linker the desired function order since we have a file
handle for the newly added file. */
enum ld_plugin_status
new_input_hook(const struct ld_plugin_input_file *file)
{
struct ld_plugin_section section_list[3];
int num_entries = 0;
unsigned int count;
if (get_input_section_count(file->handle, &count) != LDPS_OK)
return LDPS_ERR;
unsigned int i;
for (i = 0; i < count; ++i)
{
struct ld_plugin_section section;
unsigned int type = 0;
char *name = NULL;
int position = 3;
section.handle = file->handle;
section.shndx = i;
if (get_input_section_type(section, &type) != LDPS_OK)
return LDPL_FATAL;
if (type != SHT_PROGBITS)
continue;
if (get_input_section_name(section, &name))
return LDPL_FATAL;
/* As in plugin_section_order.c, order is foo() followed by bar()
followed by baz() */
if (is_prefix_of(".text.", name))
{
if (strstr(name, "_Z3foov") != NULL)
position = 0;
else if (strstr(name, "_Z3barv") != NULL)
position = 1;
else if (strstr(name, "_Z3bazv") != NULL)
position = 2;
else
position = 3;
}
if (position < 3)
{
section_list[position] = section;
num_entries++;
}
}
if (num_entries != 3)
return LDPL_FATAL;
update_section_order(section_list, num_entries);
unique_segment_for_sections (".text.plugin_created_unique", 0, 0x1000,
section_list, num_entries);
return LDPS_OK;
}
|
GitWeb