1 // plugin_section_alignment.cc -- plugins to test ordering with {size,alignment}
3 // Copyright (C) 2016-2017 Free Software Foundation, Inc.
4 // Written by Than McIntosh <thanm@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
37 #include "plugin-api.h"
39 static ld_plugin_get_input_section_count get_input_section_count = NULL;
40 static ld_plugin_get_input_section_alignment get_input_section_alignment = NULL;
41 static ld_plugin_get_input_section_size get_input_section_size = NULL;
42 static ld_plugin_get_input_section_name get_input_section_name = NULL;
43 static ld_plugin_update_section_order update_section_order = NULL;
44 static ld_plugin_allow_section_ordering allow_section_ordering = NULL;
47 enum ld_plugin_status onload(struct ld_plugin_tv *tv);
48 enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
50 enum ld_plugin_status all_symbols_read_hook(void);
53 typedef enum { FL_BSS, FL_DATA, FL_RODATA, FL_UNKNOWN } sec_flavor;
55 inline static int is_prefix_of(const char *prefix, const char *str)
57 return strncmp(prefix, str, strlen(prefix)) == 0;
60 inline static sec_flavor flavor_from_name(const char *secname)
62 if (is_prefix_of(".data.v", secname)) {
64 } else if (is_prefix_of(".bss.v", secname)) {
66 } else if (is_prefix_of(".rodata.v", secname)) {
74 ld_plugin_section plugin_section;
80 static bool SectionInfoLt(const SectionInfo &i1,
81 const SectionInfo &i2)
83 if (i1.flavor != i2.flavor) {
84 return ((unsigned) i1.flavor) < ((unsigned) i2.flavor);
88 // Sort data items by increasing alignment then increasing size
89 if (i1.align != i2.align) {
90 return ((unsigned) i1.align) < ((unsigned) i2.align);
92 if (i1.size != i2.size) {
93 return ((unsigned) i1.size) < ((unsigned) i2.size);
97 // Sort bss items by decreasing alignment then decreasing size
98 if (i1.align != i2.align) {
99 return ((unsigned) i2.align) < ((unsigned) i1.align);
101 if (i1.size != i2.size) {
102 return ((unsigned) i2.size) < ((unsigned) i1.size);
106 // Sort rodata items by decreasing alignment then increasing size
107 if (i1.align != i2.align) {
108 return ((unsigned) i2.align) < ((unsigned) i1.align);
110 if (i1.size != i2.size) {
111 return ((unsigned) i1.size) < ((unsigned) i2.size);
117 // Break ties by name
118 return i1.name.compare(i2.name) < 0;
122 typedef std::vector<SectionInfo> section_info_vector;
123 section_info_vector raw_sections;
125 // Set to 1 for debugging output
130 // Plugin entry point.
131 enum ld_plugin_status onload(struct ld_plugin_tv *tv)
133 struct ld_plugin_tv *entry;
134 for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
136 switch (entry->tv_tag)
139 if (!strcmp(entry->tv_u.tv_string,"-trace")) {
140 fprintf(stderr, "enabling tracing\n");
143 fprintf(stderr, "unknown plugin option %s", entry->tv_u.tv_string);
146 case LDPT_REGISTER_CLAIM_FILE_HOOK:
147 assert((*entry->tv_u.tv_register_claim_file)(claim_file_hook) ==
150 case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
151 assert((*entry->tv_u.tv_register_all_symbols_read)(
152 all_symbols_read_hook) == LDPS_OK);
154 case LDPT_GET_INPUT_SECTION_COUNT:
155 get_input_section_count = *entry->tv_u.tv_get_input_section_count;
157 case LDPT_GET_INPUT_SECTION_NAME:
158 get_input_section_name = *entry->tv_u.tv_get_input_section_name;
160 case LDPT_GET_INPUT_SECTION_ALIGNMENT:
161 get_input_section_alignment =
162 *entry->tv_u.tv_get_input_section_alignment;
164 case LDPT_GET_INPUT_SECTION_SIZE:
165 get_input_section_size = *entry->tv_u.tv_get_input_section_size;
167 case LDPT_UPDATE_SECTION_ORDER:
168 update_section_order = *entry->tv_u.tv_update_section_order;
170 case LDPT_ALLOW_SECTION_ORDERING:
171 allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
178 if (get_input_section_count == NULL || get_input_section_alignment == NULL ||
179 get_input_section_size == NULL || get_input_section_name == NULL ||
180 update_section_order == NULL || allow_section_ordering == NULL) {
181 fprintf(stderr, "Some interfaces are missing\n");
188 // This function is called by the linker for every new object it encounters.
189 enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
192 static bool is_ordering_specified = false;
193 struct ld_plugin_section section;
198 if (!is_ordering_specified) {
199 // Inform the linker to prepare for section reordering.
200 (*allow_section_ordering)();
201 is_ordering_specified = true;
204 (*get_input_section_count)(file->handle, &count);
206 for (shndx = 0; shndx < count; ++shndx) {
209 section.handle = file->handle;
210 section.shndx = shndx;
211 (*get_input_section_name)(section, &name);
212 if (is_prefix_of(".data.v", name) ||
213 is_prefix_of(".bss.v", name) ||
214 is_prefix_of(".rodata.v", name)) {
216 si.plugin_section.handle = file->handle;
217 si.plugin_section.shndx = shndx;
218 (*get_input_section_size)(section, &si.size);
219 (*get_input_section_alignment)(section, &si.align);
221 si.flavor = flavor_from_name(name);
222 raw_sections.push_back(si);
229 // This function is called by the linker after all the symbols have been read.
230 // At this stage, it is fine to tell the linker the desired function order.
232 enum ld_plugin_status all_symbols_read_hook(void)
234 // We expect to see a total of twelve sections -- if this is not the case
235 // then something went wrong somewhere along the way.
236 if (raw_sections.size() != 12) {
237 fprintf(stderr, "Expected 12 sections, found %u sections",
238 (unsigned) raw_sections.size());
242 std::sort(raw_sections.begin(), raw_sections.end(),
243 SectionInfo::SectionInfoLt);
245 struct ld_plugin_section section_list[12];
246 for (unsigned ii = 0; ii < 12; ++ii) {
247 section_list[ii] = raw_sections[ii].plugin_section;
251 fprintf(stderr, "Specified section order is:\n");
252 for (section_info_vector::iterator it = raw_sections.begin();
253 it != raw_sections.end();
255 const SectionInfo &si = (*it);
256 fprintf(stderr, "Idx=%u Name=%s Align=%u Size=%u\n",
257 si.plugin_section.shndx, si.name.c_str(), si.align,
262 update_section_order(section_list, 12);