| 1 | // plugin_section_alignment.cc -- plugins to test ordering with {size,alignment} |
| 2 | // |
| 3 | // Copyright (C) 2016-2020 Free Software Foundation, Inc. |
| 4 | // Written by Than McIntosh <thanm@google.com>. |
| 5 | // |
| 6 | // This file is part of gold. |
| 7 | // |
| 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. |
| 12 | // |
| 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. |
| 17 | // |
| 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. |
| 22 | // |
| 23 | |
| 24 | #ifdef HAVE_CONFIG_H |
| 25 | #include "config.h" |
| 26 | #endif |
| 27 | |
| 28 | #include <assert.h> |
| 29 | #include <stdio.h> |
| 30 | #include <stdlib.h> |
| 31 | #include <string.h> |
| 32 | |
| 33 | #include <string> |
| 34 | #include <vector> |
| 35 | #include <algorithm> |
| 36 | |
| 37 | #include "plugin-api.h" |
| 38 | |
| 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; |
| 45 | |
| 46 | extern "C" { |
| 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, |
| 49 | int *claimed); |
| 50 | enum ld_plugin_status all_symbols_read_hook(void); |
| 51 | } |
| 52 | |
| 53 | typedef enum { FL_BSS, FL_DATA, FL_RODATA, FL_UNKNOWN } sec_flavor; |
| 54 | |
| 55 | inline static int is_prefix_of(const char *prefix, const char *str) |
| 56 | { |
| 57 | return strncmp(prefix, str, strlen(prefix)) == 0; |
| 58 | } |
| 59 | |
| 60 | inline static sec_flavor flavor_from_name(const char *secname) |
| 61 | { |
| 62 | if (is_prefix_of(".data.v", secname)) { |
| 63 | return FL_DATA; |
| 64 | } else if (is_prefix_of(".bss.v", secname)) { |
| 65 | return FL_BSS; |
| 66 | } else if (is_prefix_of(".rodata.v", secname)) { |
| 67 | return FL_RODATA; |
| 68 | } else { |
| 69 | return FL_UNKNOWN; |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | struct SectionInfo { |
| 74 | ld_plugin_section plugin_section; |
| 75 | std::string name; |
| 76 | uint64_t size; |
| 77 | sec_flavor flavor; |
| 78 | unsigned align; |
| 79 | |
| 80 | static bool SectionInfoLt(const SectionInfo &i1, |
| 81 | const SectionInfo &i2) |
| 82 | { |
| 83 | if (i1.flavor != i2.flavor) { |
| 84 | return ((unsigned) i1.flavor) < ((unsigned) i2.flavor); |
| 85 | } |
| 86 | switch (i1.flavor) { |
| 87 | case FL_DATA: |
| 88 | // Sort data items by increasing alignment then increasing size |
| 89 | if (i1.align != i2.align) { |
| 90 | return ((unsigned) i1.align) < ((unsigned) i2.align); |
| 91 | } |
| 92 | if (i1.size != i2.size) { |
| 93 | return ((unsigned) i1.size) < ((unsigned) i2.size); |
| 94 | } |
| 95 | break; |
| 96 | case FL_BSS: |
| 97 | // Sort bss items by decreasing alignment then decreasing size |
| 98 | if (i1.align != i2.align) { |
| 99 | return ((unsigned) i2.align) < ((unsigned) i1.align); |
| 100 | } |
| 101 | if (i1.size != i2.size) { |
| 102 | return ((unsigned) i2.size) < ((unsigned) i1.size); |
| 103 | } |
| 104 | break; |
| 105 | case FL_RODATA: |
| 106 | // Sort rodata items by decreasing alignment then increasing size |
| 107 | if (i1.align != i2.align) { |
| 108 | return ((unsigned) i2.align) < ((unsigned) i1.align); |
| 109 | } |
| 110 | if (i1.size != i2.size) { |
| 111 | return ((unsigned) i1.size) < ((unsigned) i2.size); |
| 112 | } |
| 113 | default: |
| 114 | break; |
| 115 | } |
| 116 | |
| 117 | // Break ties by name |
| 118 | return i1.name.compare(i2.name) < 0; |
| 119 | } |
| 120 | |
| 121 | }; |
| 122 | typedef std::vector<SectionInfo> section_info_vector; |
| 123 | section_info_vector raw_sections; |
| 124 | |
| 125 | // Set to 1 for debugging output |
| 126 | unsigned trace = 0; |
| 127 | |
| 128 | extern "C" { |
| 129 | |
| 130 | // Plugin entry point. |
| 131 | enum ld_plugin_status onload(struct ld_plugin_tv *tv) |
| 132 | { |
| 133 | struct ld_plugin_tv *entry; |
| 134 | for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry) |
| 135 | { |
| 136 | switch (entry->tv_tag) |
| 137 | { |
| 138 | case LDPT_OPTION: |
| 139 | if (!strcmp(entry->tv_u.tv_string,"-trace")) { |
| 140 | fprintf(stderr, "enabling tracing\n"); |
| 141 | trace += 1; |
| 142 | } else { |
| 143 | fprintf(stderr, "unknown plugin option %s", entry->tv_u.tv_string); |
| 144 | } |
| 145 | break; |
| 146 | case LDPT_REGISTER_CLAIM_FILE_HOOK: |
| 147 | assert((*entry->tv_u.tv_register_claim_file)(claim_file_hook) == |
| 148 | LDPS_OK); |
| 149 | break; |
| 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); |
| 153 | break; |
| 154 | case LDPT_GET_INPUT_SECTION_COUNT: |
| 155 | get_input_section_count = *entry->tv_u.tv_get_input_section_count; |
| 156 | break; |
| 157 | case LDPT_GET_INPUT_SECTION_NAME: |
| 158 | get_input_section_name = *entry->tv_u.tv_get_input_section_name; |
| 159 | break; |
| 160 | case LDPT_GET_INPUT_SECTION_ALIGNMENT: |
| 161 | get_input_section_alignment = |
| 162 | *entry->tv_u.tv_get_input_section_alignment; |
| 163 | break; |
| 164 | case LDPT_GET_INPUT_SECTION_SIZE: |
| 165 | get_input_section_size = *entry->tv_u.tv_get_input_section_size; |
| 166 | break; |
| 167 | case LDPT_UPDATE_SECTION_ORDER: |
| 168 | update_section_order = *entry->tv_u.tv_update_section_order; |
| 169 | break; |
| 170 | case LDPT_ALLOW_SECTION_ORDERING: |
| 171 | allow_section_ordering = *entry->tv_u.tv_allow_section_ordering; |
| 172 | break; |
| 173 | default: |
| 174 | break; |
| 175 | } |
| 176 | } |
| 177 | |
| 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"); |
| 182 | return LDPS_ERR; |
| 183 | } |
| 184 | |
| 185 | return LDPS_OK; |
| 186 | } |
| 187 | |
| 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, |
| 190 | int *claimed) |
| 191 | { |
| 192 | static bool is_ordering_specified = false; |
| 193 | struct ld_plugin_section section; |
| 194 | unsigned count = 0; |
| 195 | unsigned shndx; |
| 196 | |
| 197 | *claimed = 0; |
| 198 | if (!is_ordering_specified) { |
| 199 | // Inform the linker to prepare for section reordering. |
| 200 | (*allow_section_ordering)(); |
| 201 | is_ordering_specified = true; |
| 202 | } |
| 203 | |
| 204 | (*get_input_section_count)(file->handle, &count); |
| 205 | |
| 206 | for (shndx = 0; shndx < count; ++shndx) { |
| 207 | char *name = NULL; |
| 208 | |
| 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)) { |
| 215 | SectionInfo si; |
| 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); |
| 220 | si.name = name; |
| 221 | si.flavor = flavor_from_name(name); |
| 222 | raw_sections.push_back(si); |
| 223 | } |
| 224 | } |
| 225 | |
| 226 | return LDPS_OK; |
| 227 | } |
| 228 | |
| 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. |
| 231 | |
| 232 | enum ld_plugin_status all_symbols_read_hook(void) |
| 233 | { |
| 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()); |
| 239 | return LDPS_ERR; |
| 240 | } |
| 241 | |
| 242 | std::sort(raw_sections.begin(), raw_sections.end(), |
| 243 | SectionInfo::SectionInfoLt); |
| 244 | |
| 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; |
| 248 | } |
| 249 | |
| 250 | if (trace) { |
| 251 | fprintf(stderr, "Specified section order is:\n"); |
| 252 | for (section_info_vector::iterator it = raw_sections.begin(); |
| 253 | it != raw_sections.end(); |
| 254 | ++it) { |
| 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, |
| 258 | (unsigned) si.size); |
| 259 | } |
| 260 | } |
| 261 | |
| 262 | update_section_order(section_list, 12); |
| 263 | |
| 264 | return LDPS_OK; |
| 265 | } |
| 266 | |
| 267 | } // end extern "C" |