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c4e64843 SC |
1 | /* plugin_new_section_layout.c -- Simple plugin to reorder function sections in |
2 | plugin-generated objects | |
3 | ||
82704155 | 4 | Copyright (C) 2017-2019 Free Software Foundation, Inc. |
c4e64843 SC |
5 | Written by Stephen Crane <sjc@immunant.com>. |
6 | ||
7 | This file is part of gold. | |
8 | ||
9 | This program is free software; you can redistribute it and/or modify | |
10 | it under the terms of the GNU General Public License as published by | |
11 | the Free Software Foundation; either version 3 of the License, or | |
12 | (at your option) any later version. | |
13 | ||
14 | This program is distributed in the hope that it will be useful, | |
15 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
17 | GNU General Public License for more details. | |
18 | ||
19 | You should have received a copy of the GNU General Public License | |
20 | along with this program; if not, write to the Free Software | |
21 | Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, | |
22 | MA 02110-1301, USA. */ | |
23 | ||
24 | /* This plugin tests the new_input API of the linker plugin interface that | |
25 | * allows plugins to modify section layout and assign sections to segments for | |
26 | * sections in plugin-generated object files. It assumes that another plugin is | |
27 | * also in use which will add new files. In practice a plugin is likely to | |
28 | * generate new input files itself in all_symbols_read and want to | |
29 | * reorder/assign sections for these files in the new_input_hook callback. */ | |
30 | ||
31 | #ifdef HAVE_CONFIG_H | |
32 | #include "config.h" | |
33 | #endif | |
34 | ||
35 | #include <stdio.h> | |
36 | #include <stdlib.h> | |
37 | #include <string.h> | |
38 | #include <assert.h> | |
39 | #include "plugin-api.h" | |
40 | #include "elf/common.h" | |
41 | ||
42 | static ld_plugin_get_input_section_count get_input_section_count = NULL; | |
43 | static ld_plugin_get_input_section_type get_input_section_type = NULL; | |
44 | static ld_plugin_get_input_section_name get_input_section_name = NULL; | |
45 | static ld_plugin_update_section_order update_section_order = NULL; | |
46 | static ld_plugin_allow_section_ordering allow_section_ordering = NULL; | |
47 | static ld_plugin_allow_unique_segment_for_sections | |
48 | allow_unique_segment_for_sections = NULL; | |
49 | static ld_plugin_unique_segment_for_sections unique_segment_for_sections = NULL; | |
50 | ||
51 | enum ld_plugin_status onload(struct ld_plugin_tv *tv); | |
52 | enum ld_plugin_status new_input_hook(const struct ld_plugin_input_file *file); | |
53 | ||
54 | /* Plugin entry point. */ | |
55 | enum ld_plugin_status | |
56 | onload(struct ld_plugin_tv *tv) | |
57 | { | |
58 | struct ld_plugin_tv *entry; | |
59 | for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry) | |
60 | { | |
61 | switch (entry->tv_tag) | |
62 | { | |
63 | case LDPT_GET_INPUT_SECTION_COUNT: | |
64 | get_input_section_count = *entry->tv_u.tv_get_input_section_count; | |
65 | break; | |
66 | case LDPT_GET_INPUT_SECTION_TYPE: | |
67 | get_input_section_type = *entry->tv_u.tv_get_input_section_type; | |
68 | break; | |
69 | case LDPT_GET_INPUT_SECTION_NAME: | |
70 | get_input_section_name = *entry->tv_u.tv_get_input_section_name; | |
71 | break; | |
72 | case LDPT_UPDATE_SECTION_ORDER: | |
73 | update_section_order = *entry->tv_u.tv_update_section_order; | |
74 | break; | |
75 | case LDPT_ALLOW_SECTION_ORDERING: | |
76 | allow_section_ordering = *entry->tv_u.tv_allow_section_ordering; | |
77 | break; | |
78 | case LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS: | |
79 | allow_unique_segment_for_sections | |
80 | = *entry->tv_u.tv_allow_unique_segment_for_sections; | |
81 | break; | |
82 | case LDPT_UNIQUE_SEGMENT_FOR_SECTIONS: | |
83 | unique_segment_for_sections | |
84 | = *entry->tv_u.tv_unique_segment_for_sections; | |
85 | break; | |
86 | case LDPT_REGISTER_NEW_INPUT_HOOK: | |
87 | assert((*entry->tv_u.tv_register_new_input) (new_input_hook) | |
88 | == LDPS_OK); | |
89 | break; | |
90 | default: | |
91 | break; | |
92 | } | |
93 | } | |
94 | ||
95 | if (get_input_section_count == NULL | |
96 | || get_input_section_type == NULL | |
97 | || get_input_section_name == NULL | |
98 | || update_section_order == NULL | |
99 | || allow_section_ordering == NULL | |
100 | || allow_unique_segment_for_sections == NULL | |
101 | || unique_segment_for_sections == NULL) | |
102 | { | |
103 | fprintf(stderr, "Some interfaces are missing\n"); | |
104 | return LDPS_ERR; | |
105 | } | |
106 | ||
107 | /* Inform the linker to prepare for section reordering. */ | |
108 | (*allow_section_ordering)(); | |
109 | /* Inform the linker to prepare to map some sections to unique | |
110 | segments. */ | |
111 | (*allow_unique_segment_for_sections)(); | |
112 | ||
113 | return LDPS_OK; | |
114 | } | |
115 | ||
116 | inline static int is_prefix_of(const char *prefix, const char *str) | |
117 | { | |
118 | return strncmp(prefix, str, strlen (prefix)) == 0; | |
119 | } | |
120 | ||
121 | /* This function is called by the linker when new files are added by a plugin. | |
122 | We can now tell the linker the desired function order since we have a file | |
123 | handle for the newly added file. */ | |
124 | ||
125 | enum ld_plugin_status | |
126 | new_input_hook(const struct ld_plugin_input_file *file) | |
127 | { | |
128 | struct ld_plugin_section section_list[3]; | |
129 | int num_entries = 0; | |
130 | unsigned int count; | |
131 | ||
132 | if (get_input_section_count(file->handle, &count) != LDPS_OK) | |
133 | return LDPS_ERR; | |
134 | ||
135 | unsigned int i; | |
136 | for (i = 0; i < count; ++i) | |
137 | { | |
138 | struct ld_plugin_section section; | |
139 | unsigned int type = 0; | |
140 | char *name = NULL; | |
141 | int position = 3; | |
142 | ||
143 | section.handle = file->handle; | |
144 | section.shndx = i; | |
145 | ||
146 | if (get_input_section_type(section, &type) != LDPS_OK) | |
147 | return LDPL_FATAL; | |
148 | if (type != SHT_PROGBITS) | |
149 | continue; | |
150 | ||
151 | if (get_input_section_name(section, &name)) | |
152 | return LDPL_FATAL; | |
153 | ||
154 | /* As in plugin_section_order.c, order is foo() followed by bar() | |
155 | followed by baz() */ | |
156 | if (is_prefix_of(".text.", name)) | |
157 | { | |
158 | if (strstr(name, "_Z3foov") != NULL) | |
159 | position = 0; | |
160 | else if (strstr(name, "_Z3barv") != NULL) | |
161 | position = 1; | |
162 | else if (strstr(name, "_Z3bazv") != NULL) | |
163 | position = 2; | |
164 | else | |
165 | position = 3; | |
166 | } | |
167 | if (position < 3) | |
168 | { | |
169 | section_list[position] = section; | |
170 | num_entries++; | |
171 | } | |
172 | } | |
173 | ||
174 | if (num_entries != 3) | |
175 | return LDPL_FATAL; | |
176 | ||
177 | update_section_order(section_list, num_entries); | |
178 | unique_segment_for_sections (".text.plugin_created_unique", 0, 0x1000, | |
179 | section_list, num_entries); | |
180 | ||
181 | return LDPS_OK; | |
182 | } |