gold/testsuite/plugin_section_order.c

   1 /* plugin_section_reorder.c -- Simple plugin to reorder function sections
   2
   3    Copyright 2011 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
  40 enum ld_plugin_status onload(struct ld_plugin_tv *tv);
  41 enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
  42                                       int *claimed);
  43 enum ld_plugin_status all_symbols_read_hook(void);
  44
  45 /* Plugin entry point.  */
  46 enum ld_plugin_status
  47 onload(struct ld_plugin_tv *tv)
  48 {
  49   struct ld_plugin_tv *entry;
  50   for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
  51     {
  52       switch (entry->tv_tag)
  53         {
  54         case LDPT_REGISTER_CLAIM_FILE_HOOK:
  55           assert((*entry->tv_u.tv_register_claim_file) (claim_file_hook) == LDPS_OK);
  56           break;
  57         case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
  58           assert((*entry->tv_u.tv_register_all_symbols_read) (all_symbols_read_hook)
  59                   == LDPS_OK);
  60           break;
  61         case LDPT_GET_INPUT_SECTION_COUNT:
  62           get_input_section_count = *entry->tv_u.tv_get_input_section_count;
  63           break;
  64         case LDPT_GET_INPUT_SECTION_TYPE:
  65           get_input_section_type = *entry->tv_u.tv_get_input_section_type;
  66           break;
  67         case LDPT_GET_INPUT_SECTION_NAME:
  68           get_input_section_name = *entry->tv_u.tv_get_input_section_name;
  69           break;
  70         case LDPT_GET_INPUT_SECTION_CONTENTS:
  71           get_input_section_contents = *entry->tv_u.tv_get_input_section_contents;
  72           break;
  73         case LDPT_UPDATE_SECTION_ORDER:
  74           update_section_order = *entry->tv_u.tv_update_section_order;
  75           break;
  76         case LDPT_ALLOW_SECTION_ORDERING:
  77           allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
  78           break;
  79         default:
  80           break;
  81         }
  82     }
  83
  84   if (get_input_section_count == NULL
  85       || get_input_section_type == NULL
  86       || get_input_section_name == NULL
  87       || get_input_section_contents == NULL
  88       || update_section_order == NULL
  89       || allow_section_ordering == NULL)
  90     {
  91       fprintf(stderr, "Some interfaces are missing\n");
  92       return LDPS_ERR;
  93     }
  94
  95   return LDPS_OK;
  96 }
  97
  98 inline static int is_prefix_of(const char *prefix, const char *str)
  99 {
 100   return strncmp(prefix, str, strlen (prefix)) == 0;
 101 }
 102
 103 struct ld_plugin_section section_list[3];
 104 int num_entries = 0;
 105
 106 /* This function is called by the linker for every new object it encounters.  */
 107 enum ld_plugin_status
 108 claim_file_hook(const struct ld_plugin_input_file *file, int *claimed)
 109 {
 110   static int is_ordering_specified = 0;
 111   struct ld_plugin_section section;
 112   unsigned int count = 0;
 113   unsigned int shndx;
 114
 115   *claimed = 0;
 116   if (is_ordering_specified == 0)
 117     {
 118       /* Inform the linker to prepare for section reordering.  */
 119       (*allow_section_ordering)();
 120       is_ordering_specified = 1;
 121     }
 122
 123   (*get_input_section_count)(file->handle, &count);
 124
 125   for (shndx = 0; shndx < count; ++shndx)
 126     {
 127       char *name = NULL;
 128       int position = 3;
 129
 130       section.handle = file->handle;
 131       section.shndx = shndx;
 132       (*get_input_section_name)(section, &name);
 133
 134       /* Order is foo() followed by bar() followed by baz()  */
 135       if (is_prefix_of(".text.", name))
 136         {
 137           if (strstr(name, "_Z3foov") != NULL)
 138             position = 0;
 139           else if (strstr(name, "_Z3barv") != NULL)
 140             position = 1;
 141           else if (strstr(name, "_Z3bazv") != NULL)
 142             position = 2;
 143           else
 144             position = 3;
 145         }
 146       if (position < 3)
 147         {
 148           section_list[position].handle = file->handle;
 149           section_list[position].shndx = shndx;
 150           num_entries++;
 151         }
 152     }
 153   return LDPS_OK;
 154 }
 155
 156 /* This function is called by the linker after all the symbols have been read.
 157    At this stage, it is fine to tell the linker the desired function order.  */
 158
 159 enum ld_plugin_status
 160 all_symbols_read_hook(void)
 161 {
 162   if (num_entries == 3)
 163     update_section_order(section_list, num_entries);
 164
 165   return LDPS_OK;
 166 }
 167