gold/testsuite/plugin_section_order.c

   1 /* plugin_section_reorder.c -- Simple plugin to reorder function sections
   2
   3    Copyright (C) 2011-2025 Free Software Foundation, Inc.
   4    Written by Sriraman Tallam <tmsriram@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 #ifdef HAVE_CONFIG_H
  24 #include "config.h"
  25 #endif
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <assert.h>
  31 #include "plugin-api.h"
  32
  33 static ld_plugin_get_input_section_count get_input_section_count = NULL;
  34 static ld_plugin_get_input_section_type get_input_section_type = NULL;
  35 static ld_plugin_get_input_section_name get_input_section_name = NULL;
  36 static ld_plugin_get_input_section_contents get_input_section_contents = NULL;
  37 static ld_plugin_update_section_order update_section_order = NULL;
  38 static ld_plugin_allow_section_ordering allow_section_ordering = NULL;
  39 static ld_plugin_allow_unique_segment_for_sections
  40     allow_unique_segment_for_sections = NULL;
  41 static ld_plugin_unique_segment_for_sections unique_segment_for_sections = NULL;
  42
  43 enum ld_plugin_status onload(struct ld_plugin_tv *tv);
  44 enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
  45                                       int *claimed);
  46 enum ld_plugin_status all_symbols_read_hook(void);
  47
  48 /* Plugin entry point.  */
  49 enum ld_plugin_status
  50 onload(struct ld_plugin_tv *tv)
  51 {
  52   struct ld_plugin_tv *entry;
  53   for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
  54     {
  55       switch (entry->tv_tag)
  56         {
  57         case LDPT_REGISTER_CLAIM_FILE_HOOK:
  58           assert((*entry->tv_u.tv_register_claim_file) (claim_file_hook)
  59                  == LDPS_OK);
  60           break;
  61         case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
  62           assert((*entry->tv_u.tv_register_all_symbols_read)
  63                      (all_symbols_read_hook)
  64                  == LDPS_OK);
  65           break;
  66         case LDPT_GET_INPUT_SECTION_COUNT:
  67           get_input_section_count = *entry->tv_u.tv_get_input_section_count;
  68           break;
  69         case LDPT_GET_INPUT_SECTION_TYPE:
  70           get_input_section_type = *entry->tv_u.tv_get_input_section_type;
  71           break;
  72         case LDPT_GET_INPUT_SECTION_NAME:
  73           get_input_section_name = *entry->tv_u.tv_get_input_section_name;
  74           break;
  75         case LDPT_GET_INPUT_SECTION_CONTENTS:
  76           get_input_section_contents
  77               = *entry->tv_u.tv_get_input_section_contents;
  78           break;
  79         case LDPT_UPDATE_SECTION_ORDER:
  80           update_section_order = *entry->tv_u.tv_update_section_order;
  81           break;
  82         case LDPT_ALLOW_SECTION_ORDERING:
  83           allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
  84           break;
  85         case LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS:
  86           allow_unique_segment_for_sections
  87               = *entry->tv_u.tv_allow_unique_segment_for_sections;
  88           break;
  89         case LDPT_UNIQUE_SEGMENT_FOR_SECTIONS:
  90           unique_segment_for_sections
  91               = *entry->tv_u.tv_unique_segment_for_sections;
  92           break;
  93         default:
  94           break;
  95         }
  96     }
  97
  98   if (get_input_section_count == NULL
  99       || get_input_section_type == NULL
 100       || get_input_section_name == NULL
 101       || get_input_section_contents == NULL
 102       || update_section_order == NULL
 103       || allow_section_ordering == NULL
 104       || allow_unique_segment_for_sections == NULL
 105       || unique_segment_for_sections == NULL)
 106     {
 107       fprintf(stderr, "Some interfaces are missing\n");
 108       return LDPS_ERR;
 109     }
 110
 111   return LDPS_OK;
 112 }
 113
 114 inline static int is_prefix_of(const char *prefix, const char *str)
 115 {
 116   return strncmp(prefix, str, strlen (prefix)) == 0;
 117 }
 118
 119 struct ld_plugin_section section_list[3];
 120 int num_entries = 0;
 121
 122 /* This function is called by the linker for every new object it encounters.  */
 123 enum ld_plugin_status
 124 claim_file_hook(const struct ld_plugin_input_file *file, int *claimed)
 125 {
 126   static int is_ordering_specified = 0;
 127   struct ld_plugin_section section;
 128   unsigned int count = 0;
 129   unsigned int shndx;
 130
 131   *claimed = 0;
 132   if (is_ordering_specified == 0)
 133     {
 134       /* Inform the linker to prepare for section reordering.  */
 135       (*allow_section_ordering)();
 136       /* Inform the linker to prepare to map some sections to unique
 137          segments.  */
 138       (*allow_unique_segment_for_sections)();
 139       is_ordering_specified = 1;
 140     }
 141
 142   (*get_input_section_count)(file->handle, &count);
 143
 144   for (shndx = 0; shndx < count; ++shndx)
 145     {
 146       char *name = NULL;
 147       int position = 3;
 148
 149       section.handle = file->handle;
 150       section.shndx = shndx;
 151       (*get_input_section_name)(section, &name);
 152
 153       /* Order is foo() followed by bar() followed by baz()  */
 154       if (is_prefix_of(".text.", name))
 155         {
 156           if (strstr(name, "_Z3foov") != NULL)
 157             position = 0;
 158           else if (strstr(name, "_Z3barv") != NULL)
 159             position = 1;
 160           else if (strstr(name, "_Z3bazv") != NULL)
 161             position = 2;
 162           else
 163             position = 3;
 164         }
 165       if (position < 3)
 166         {
 167           section_list[position].handle = file->handle;
 168           section_list[position].shndx = shndx;
 169           num_entries++;
 170         }
 171     }
 172   return LDPS_OK;
 173 }
 174
 175 /* This function is called by the linker after all the symbols have been read.
 176    At this stage, it is fine to tell the linker the desired function order.  */
 177
 178 enum ld_plugin_status
 179 all_symbols_read_hook(void)
 180 {
 181   if (num_entries == 3)
 182     {
 183       update_section_order(section_list, num_entries);
 184       unique_segment_for_sections (".text.plugin_created_unique", 0, 0x1000,
 185                                    section_list, num_entries);
 186     }
 187
 188   return LDPS_OK;
 189 }