267 lines
8.2 KiB
C++
267 lines
8.2 KiB
C++
// plugin_section_alignment.cc -- plugins to test ordering with {size,alignment}
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//
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// Copyright (C) 2016-2022 Free Software Foundation, Inc.
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// Written by Than McIntosh <thanm@google.com>.
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//
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// This file is part of gold.
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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//
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <string>
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#include <vector>
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#include <algorithm>
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#include "plugin-api.h"
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static ld_plugin_get_input_section_count get_input_section_count = NULL;
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static ld_plugin_get_input_section_alignment get_input_section_alignment = NULL;
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static ld_plugin_get_input_section_size get_input_section_size = NULL;
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static ld_plugin_get_input_section_name get_input_section_name = NULL;
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static ld_plugin_update_section_order update_section_order = NULL;
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static ld_plugin_allow_section_ordering allow_section_ordering = NULL;
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extern "C" {
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enum ld_plugin_status onload(struct ld_plugin_tv *tv);
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enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
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int *claimed);
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enum ld_plugin_status all_symbols_read_hook(void);
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}
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typedef enum { FL_BSS, FL_DATA, FL_RODATA, FL_UNKNOWN } sec_flavor;
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inline static int is_prefix_of(const char *prefix, const char *str)
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{
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return strncmp(prefix, str, strlen(prefix)) == 0;
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}
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inline static sec_flavor flavor_from_name(const char *secname)
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{
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if (is_prefix_of(".data.v", secname)) {
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return FL_DATA;
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} else if (is_prefix_of(".bss.v", secname)) {
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return FL_BSS;
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} else if (is_prefix_of(".rodata.v", secname)) {
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return FL_RODATA;
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} else {
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return FL_UNKNOWN;
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}
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}
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struct SectionInfo {
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ld_plugin_section plugin_section;
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std::string name;
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uint64_t size;
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sec_flavor flavor;
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unsigned align;
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static bool SectionInfoLt(const SectionInfo &i1,
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const SectionInfo &i2)
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{
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if (i1.flavor != i2.flavor) {
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return ((unsigned) i1.flavor) < ((unsigned) i2.flavor);
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}
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switch (i1.flavor) {
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case FL_DATA:
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// Sort data items by increasing alignment then increasing size
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if (i1.align != i2.align) {
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return ((unsigned) i1.align) < ((unsigned) i2.align);
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}
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if (i1.size != i2.size) {
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return ((unsigned) i1.size) < ((unsigned) i2.size);
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}
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break;
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case FL_BSS:
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// Sort bss items by decreasing alignment then decreasing size
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if (i1.align != i2.align) {
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return ((unsigned) i2.align) < ((unsigned) i1.align);
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}
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if (i1.size != i2.size) {
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return ((unsigned) i2.size) < ((unsigned) i1.size);
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}
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break;
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case FL_RODATA:
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// Sort rodata items by decreasing alignment then increasing size
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if (i1.align != i2.align) {
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return ((unsigned) i2.align) < ((unsigned) i1.align);
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}
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if (i1.size != i2.size) {
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return ((unsigned) i1.size) < ((unsigned) i2.size);
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}
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default:
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break;
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}
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// Break ties by name
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return i1.name.compare(i2.name) < 0;
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}
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};
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typedef std::vector<SectionInfo> section_info_vector;
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section_info_vector raw_sections;
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// Set to 1 for debugging output
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unsigned trace = 0;
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extern "C" {
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// Plugin entry point.
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enum ld_plugin_status onload(struct ld_plugin_tv *tv)
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{
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struct ld_plugin_tv *entry;
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for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
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{
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switch (entry->tv_tag)
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{
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case LDPT_OPTION:
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if (!strcmp(entry->tv_u.tv_string,"-trace")) {
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fprintf(stderr, "enabling tracing\n");
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trace += 1;
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} else {
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fprintf(stderr, "unknown plugin option %s", entry->tv_u.tv_string);
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}
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break;
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case LDPT_REGISTER_CLAIM_FILE_HOOK:
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assert((*entry->tv_u.tv_register_claim_file)(claim_file_hook) ==
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LDPS_OK);
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break;
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case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
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assert((*entry->tv_u.tv_register_all_symbols_read)(
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all_symbols_read_hook) == LDPS_OK);
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break;
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case LDPT_GET_INPUT_SECTION_COUNT:
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get_input_section_count = *entry->tv_u.tv_get_input_section_count;
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break;
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case LDPT_GET_INPUT_SECTION_NAME:
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get_input_section_name = *entry->tv_u.tv_get_input_section_name;
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break;
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case LDPT_GET_INPUT_SECTION_ALIGNMENT:
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get_input_section_alignment =
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*entry->tv_u.tv_get_input_section_alignment;
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break;
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case LDPT_GET_INPUT_SECTION_SIZE:
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get_input_section_size = *entry->tv_u.tv_get_input_section_size;
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break;
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case LDPT_UPDATE_SECTION_ORDER:
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update_section_order = *entry->tv_u.tv_update_section_order;
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break;
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case LDPT_ALLOW_SECTION_ORDERING:
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allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
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break;
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default:
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break;
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}
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}
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if (get_input_section_count == NULL || get_input_section_alignment == NULL ||
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get_input_section_size == NULL || get_input_section_name == NULL ||
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update_section_order == NULL || allow_section_ordering == NULL) {
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fprintf(stderr, "Some interfaces are missing\n");
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return LDPS_ERR;
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}
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return LDPS_OK;
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}
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// This function is called by the linker for every new object it encounters.
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enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
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int *claimed)
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{
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static bool is_ordering_specified = false;
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struct ld_plugin_section section;
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unsigned count = 0;
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unsigned shndx;
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*claimed = 0;
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if (!is_ordering_specified) {
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// Inform the linker to prepare for section reordering.
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(*allow_section_ordering)();
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is_ordering_specified = true;
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}
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(*get_input_section_count)(file->handle, &count);
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for (shndx = 0; shndx < count; ++shndx) {
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char *name = NULL;
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section.handle = file->handle;
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section.shndx = shndx;
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(*get_input_section_name)(section, &name);
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if (is_prefix_of(".data.v", name) ||
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is_prefix_of(".bss.v", name) ||
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is_prefix_of(".rodata.v", name)) {
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SectionInfo si;
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si.plugin_section.handle = file->handle;
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si.plugin_section.shndx = shndx;
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(*get_input_section_size)(section, &si.size);
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(*get_input_section_alignment)(section, &si.align);
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si.name = name;
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si.flavor = flavor_from_name(name);
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raw_sections.push_back(si);
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}
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}
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return LDPS_OK;
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}
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// This function is called by the linker after all the symbols have been read.
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// At this stage, it is fine to tell the linker the desired function order.
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enum ld_plugin_status all_symbols_read_hook(void)
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{
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// We expect to see a total of twelve sections -- if this is not the case
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// then something went wrong somewhere along the way.
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if (raw_sections.size() != 12) {
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fprintf(stderr, "Expected 12 sections, found %u sections",
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(unsigned) raw_sections.size());
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return LDPS_ERR;
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}
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std::sort(raw_sections.begin(), raw_sections.end(),
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SectionInfo::SectionInfoLt);
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struct ld_plugin_section section_list[12];
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for (unsigned ii = 0; ii < 12; ++ii) {
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section_list[ii] = raw_sections[ii].plugin_section;
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}
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if (trace) {
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fprintf(stderr, "Specified section order is:\n");
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for (section_info_vector::iterator it = raw_sections.begin();
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it != raw_sections.end();
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++it) {
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const SectionInfo &si = (*it);
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fprintf(stderr, "Idx=%u Name=%s Align=%u Size=%u\n",
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si.plugin_section.shndx, si.name.c_str(), si.align,
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(unsigned) si.size);
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}
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}
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update_section_order(section_list, 12);
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return LDPS_OK;
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}
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} // end extern "C"
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