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// plugin_section_alignment.cc -- plugins to test ordering with {size,alignment}
//
// Copyright (C) 2016-2020 Free Software Foundation, Inc.
// Written by Than McIntosh <thanm@google.com>.
//
// This file is part of gold.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
//
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <vector>
#include <algorithm>
#include "plugin-api.h"
static ld_plugin_get_input_section_count get_input_section_count = NULL;
static ld_plugin_get_input_section_alignment get_input_section_alignment = NULL;
static ld_plugin_get_input_section_size get_input_section_size = NULL;
static ld_plugin_get_input_section_name get_input_section_name = NULL;
static ld_plugin_update_section_order update_section_order = NULL;
static ld_plugin_allow_section_ordering allow_section_ordering = NULL;
extern "C" {
enum ld_plugin_status onload(struct ld_plugin_tv *tv);
enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
int *claimed);
enum ld_plugin_status all_symbols_read_hook(void);
}
typedef enum { FL_BSS, FL_DATA, FL_RODATA, FL_UNKNOWN } sec_flavor;
inline static int is_prefix_of(const char *prefix, const char *str)
{
return strncmp(prefix, str, strlen(prefix)) == 0;
}
inline static sec_flavor flavor_from_name(const char *secname)
{
if (is_prefix_of(".data.v", secname)) {
return FL_DATA;
} else if (is_prefix_of(".bss.v", secname)) {
return FL_BSS;
} else if (is_prefix_of(".rodata.v", secname)) {
return FL_RODATA;
} else {
return FL_UNKNOWN;
}
}
struct SectionInfo {
ld_plugin_section plugin_section;
std::string name;
uint64_t size;
sec_flavor flavor;
unsigned align;
static bool SectionInfoLt(const SectionInfo &i1,
const SectionInfo &i2)
{
if (i1.flavor != i2.flavor) {
return ((unsigned) i1.flavor) < ((unsigned) i2.flavor);
}
switch (i1.flavor) {
case FL_DATA:
// Sort data items by increasing alignment then increasing size
if (i1.align != i2.align) {
return ((unsigned) i1.align) < ((unsigned) i2.align);
}
if (i1.size != i2.size) {
return ((unsigned) i1.size) < ((unsigned) i2.size);
}
break;
case FL_BSS:
// Sort bss items by decreasing alignment then decreasing size
if (i1.align != i2.align) {
return ((unsigned) i2.align) < ((unsigned) i1.align);
}
if (i1.size != i2.size) {
return ((unsigned) i2.size) < ((unsigned) i1.size);
}
break;
case FL_RODATA:
// Sort rodata items by decreasing alignment then increasing size
if (i1.align != i2.align) {
return ((unsigned) i2.align) < ((unsigned) i1.align);
}
if (i1.size != i2.size) {
return ((unsigned) i1.size) < ((unsigned) i2.size);
}
default:
break;
}
// Break ties by name
return i1.name.compare(i2.name) < 0;
}
};
typedef std::vector<SectionInfo> section_info_vector;
section_info_vector raw_sections;
// Set to 1 for debugging output
unsigned trace = 0;
extern "C" {
// Plugin entry point.
enum ld_plugin_status onload(struct ld_plugin_tv *tv)
{
struct ld_plugin_tv *entry;
for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
{
switch (entry->tv_tag)
{
case LDPT_OPTION:
if (!strcmp(entry->tv_u.tv_string,"-trace")) {
fprintf(stderr, "enabling tracing\n");
trace += 1;
} else {
fprintf(stderr, "unknown plugin option %s", entry->tv_u.tv_string);
}
break;
case LDPT_REGISTER_CLAIM_FILE_HOOK:
assert((*entry->tv_u.tv_register_claim_file)(claim_file_hook) ==
LDPS_OK);
break;
case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
assert((*entry->tv_u.tv_register_all_symbols_read)(
all_symbols_read_hook) == LDPS_OK);
break;
case LDPT_GET_INPUT_SECTION_COUNT:
get_input_section_count = *entry->tv_u.tv_get_input_section_count;
break;
case LDPT_GET_INPUT_SECTION_NAME:
get_input_section_name = *entry->tv_u.tv_get_input_section_name;
break;
case LDPT_GET_INPUT_SECTION_ALIGNMENT:
get_input_section_alignment =
*entry->tv_u.tv_get_input_section_alignment;
break;
case LDPT_GET_INPUT_SECTION_SIZE:
get_input_section_size = *entry->tv_u.tv_get_input_section_size;
break;
case LDPT_UPDATE_SECTION_ORDER:
update_section_order = *entry->tv_u.tv_update_section_order;
break;
case LDPT_ALLOW_SECTION_ORDERING:
allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
break;
default:
break;
}
}
if (get_input_section_count == NULL || get_input_section_alignment == NULL ||
get_input_section_size == NULL || get_input_section_name == NULL ||
update_section_order == NULL || allow_section_ordering == NULL) {
fprintf(stderr, "Some interfaces are missing\n");
return LDPS_ERR;
}
return LDPS_OK;
}
// This function is called by the linker for every new object it encounters.
enum ld_plugin_status claim_file_hook(const struct ld_plugin_input_file *file,
int *claimed)
{
static bool is_ordering_specified = false;
struct ld_plugin_section section;
unsigned count = 0;
unsigned shndx;
*claimed = 0;
if (!is_ordering_specified) {
// Inform the linker to prepare for section reordering.
(*allow_section_ordering)();
is_ordering_specified = true;
}
(*get_input_section_count)(file->handle, &count);
for (shndx = 0; shndx < count; ++shndx) {
char *name = NULL;
section.handle = file->handle;
section.shndx = shndx;
(*get_input_section_name)(section, &name);
if (is_prefix_of(".data.v", name) ||
is_prefix_of(".bss.v", name) ||
is_prefix_of(".rodata.v", name)) {
SectionInfo si;
si.plugin_section.handle = file->handle;
si.plugin_section.shndx = shndx;
(*get_input_section_size)(section, &si.size);
(*get_input_section_alignment)(section, &si.align);
si.name = name;
si.flavor = flavor_from_name(name);
raw_sections.push_back(si);
}
}
return LDPS_OK;
}
// This function is called by the linker after all the symbols have been read.
// At this stage, it is fine to tell the linker the desired function order.
enum ld_plugin_status all_symbols_read_hook(void)
{
// We expect to see a total of twelve sections -- if this is not the case
// then something went wrong somewhere along the way.
if (raw_sections.size() != 12) {
fprintf(stderr, "Expected 12 sections, found %u sections",
(unsigned) raw_sections.size());
return LDPS_ERR;
}
std::sort(raw_sections.begin(), raw_sections.end(),
SectionInfo::SectionInfoLt);
struct ld_plugin_section section_list[12];
for (unsigned ii = 0; ii < 12; ++ii) {
section_list[ii] = raw_sections[ii].plugin_section;
}
if (trace) {
fprintf(stderr, "Specified section order is:\n");
for (section_info_vector::iterator it = raw_sections.begin();
it != raw_sections.end();
++it) {
const SectionInfo &si = (*it);
fprintf(stderr, "Idx=%u Name=%s Align=%u Size=%u\n",
si.plugin_section.shndx, si.name.c_str(), si.align,
(unsigned) si.size);
}
}
update_section_order(section_list, 12);
return LDPS_OK;
}
} // end extern "C"
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