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// script.h -- handle linker scripts for gold -*- C++ -*-
// Copyright (C) 2006-2024 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@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.
// We implement a subset of the original GNU ld linker script language
// for compatibility. The goal is not to implement the entire
// language. It is merely to implement enough to handle common uses.
// In particular we need to handle /usr/lib/libc.so on a typical
// GNU/Linux system, and we want to handle linker scripts used by the
// Linux kernel build.
#ifndef GOLD_SCRIPT_H
#define GOLD_SCRIPT_H
#include <cstdio>
#include <string>
#include <vector>
#include "elfcpp.h"
#include "script-sections.h"
namespace gold
{
class General_options;
class Command_line;
class Symbol_table;
class Layout;
class Mapfile;
class Input_argument;
class Input_arguments;
class Input_objects;
class Input_group;
class Input_file;
class Output_segment;
class Task_token;
class Workqueue;
struct Version_dependency_list;
struct Version_expression_list;
struct Version_tree;
struct Version_expression;
class Lazy_demangler;
class Incremental_script_entry;
// This class represents an expression in a linker script.
class Expression
{
protected:
// These should only be created by child classes.
Expression()
{ }
public:
virtual ~Expression()
{ }
// Return the value of the expression which is not permitted to
// refer to the dot symbol. CHECK_ASSERTIONS is true if we should
// check whether assertions are true.
uint64_t
eval(const Symbol_table*, const Layout*, bool check_assertions);
// Return the value of an expression which is permitted to refer to
// the dot symbol. DOT_VALUE is the absolute value of the dot
// symbol. DOT_SECTION is the section in which dot is defined; it
// should be NULL if the dot symbol has an absolute value (e.g., is
// defined in a SECTIONS clause outside of any output section
// definition). This sets *RESULT_SECTION to indicate where the
// value is defined. If the value is absolute *RESULT_SECTION will
// be NULL. Note that the returned value is still an absolute
// value; to get a section relative value the caller must subtract
// the section address. If RESULT_ALIGNMENT is not NULL, this sets
// *RESULT_ALIGNMENT to the alignment of the value of that alignment
// is larger than *RESULT_ALIGNMENT; this will only be non-zero if
// this is an ALIGN expression. If IS_SECTION_DOT_ASSIGMENT is true,
// we are evaluating an assignment to dot within an output section,
// and an absolute value should be interpreted as an offset within
// the section.
uint64_t
eval_with_dot(const Symbol_table*, const Layout*, bool check_assertions,
uint64_t dot_value, Output_section* dot_section,
Output_section** result_section, uint64_t* result_alignment,
bool is_section_dot_assignment);
// Return the value of an expression which may or may not be
// permitted to refer to the dot symbol, depending on
// is_dot_available. If IS_SECTION_DOT_ASSIGMENT is true,
// we are evaluating an assignment to dot within an output section,
// and an absolute value should be interpreted as an offset within
// the section.
uint64_t
eval_maybe_dot(const Symbol_table*, const Layout*, bool check_assertions,
bool is_dot_available, uint64_t dot_value,
Output_section* dot_section,
Output_section** result_section, uint64_t* result_alignment,
elfcpp::STT* type, elfcpp::STV* vis, unsigned char* nonvis,
bool is_section_dot_assignment, bool* is_valid_pointer);
// Print the expression to the FILE. This is for debugging.
virtual void
print(FILE*) const = 0;
protected:
struct Expression_eval_info;
public:
// Compute the value of the expression (implemented by child class).
// This is public rather than protected because it is called
// directly by children of Expression on other Expression objects.
virtual uint64_t
value(const Expression_eval_info*) = 0;
// Sets all symbols used in expressions as seen in a real ELF object.
virtual void
set_expr_sym_in_real_elf(Symbol_table*) const
{ return; }
private:
// May not be copied.
Expression(const Expression&);
Expression& operator=(const Expression&);
};
// Version_script_info stores information parsed from the version
// script, either provided by --version-script or as part of a linker
// script. A single Version_script_info object per target is owned by
// Script_options.
class Version_script_info
{
public:
// The languages which can be specified in a versionn script.
enum Language
{
LANGUAGE_C, // No demangling.
LANGUAGE_CXX, // C++ demangling.
LANGUAGE_JAVA, // Java demangling.
LANGUAGE_COUNT
};
Version_script_info();
~Version_script_info();
// Clear everything.
void
clear();
// Finalize the version control information.
void
finalize();
// Return whether the information is finalized.
bool
is_finalized() const
{ return this->is_finalized_; }
// Return whether any version were defined in the version script.
bool
empty() const
{ return this->version_trees_.empty(); }
// If there is a version associated with SYMBOL, return true, and
// set *VERSION to the version, and *IS_GLOBAL to whether the symbol
// should be global. Otherwise, return false.
bool
get_symbol_version(const char* symbol, std::string* version,
bool* is_global) const;
// Return whether this symbol matches the local: section of some
// version.
bool
symbol_is_local(const char* symbol) const
{
bool is_global;
return (this->get_symbol_version(symbol, NULL, &is_global)
&& !is_global);
}
// Return the names of versions defined in the version script.
std::vector<std::string>
get_versions() const;
// Return the list of dependencies for this version.
std::vector<std::string>
get_dependencies(const char* version) const;
// The following functions should only be used by the bison helper
// functions. They allocate new structs whose memory belongs to
// Version_script_info. The bison functions copy the information
// from the version script into these structs.
struct Version_dependency_list*
allocate_dependency_list();
struct Version_expression_list*
allocate_expression_list();
struct Version_tree*
allocate_version_tree();
// Build the lookup tables after all data have been read.
void
build_lookup_tables();
// Give an error if there are any unmatched names in the version
// script.
void
check_unmatched_names(const Symbol_table*) const;
// Print contents to the FILE. This is for debugging.
void
print(FILE*) const;
private:
void
print_expression_list(FILE* f, const Version_expression_list*) const;
bool
get_symbol_version_helper(const char* symbol,
bool check_global,
std::string* pversion) const;
// Fast lookup information for a given language.
// We map from exact match strings to Version_tree's. Historically
// version scripts sometimes have the same symbol multiple times,
// which is ambiguous. We warn about that case by storing the
// second Version_tree we see.
struct Version_tree_match
{
Version_tree_match(const Version_tree* r, bool ig,
const Version_expression* e)
: real(r), is_global(ig), expression(e), ambiguous(NULL)
{ }
// The Version_tree that we return.
const Version_tree* real;
// True if this is a global match for the REAL member, false if it
// is a local match.
bool is_global;
// Point back to the Version_expression for which we created this
// match.
const Version_expression* expression;
// If not NULL, another Version_tree that defines the symbol.
const Version_tree* ambiguous;
};
// Map from an exact match string to a Version_tree.
typedef Unordered_map<std::string, Version_tree_match> Exact;
// Fast lookup information for a glob pattern.
struct Glob
{
Glob()
: expression(NULL), version(NULL), is_global(false)
{ }
Glob(const Version_expression* e, const Version_tree* v, bool ig)
: expression(e), version(v), is_global(ig)
{ }
// A pointer to the version expression holding the pattern to
// match and the language to use for demangling the symbol before
// doing the match.
const Version_expression* expression;
// The Version_tree we use if this pattern matches.
const Version_tree* version;
// True if this is a global symbol.
bool is_global;
};
typedef std::vector<Glob> Globs;
bool
unquote(std::string*) const;
void
add_exact_match(const std::string&, const Version_tree*, bool is_global,
const Version_expression*, Exact*);
void
build_expression_list_lookup(const Version_expression_list*,
const Version_tree*, bool);
const char*
get_name_to_match(const char*, int,
Lazy_demangler*, Lazy_demangler*) const;
// All the version dependencies we allocate.
std::vector<Version_dependency_list*> dependency_lists_;
// All the version expressions we allocate.
std::vector<Version_expression_list*> expression_lists_;
// The list of versions.
std::vector<Version_tree*> version_trees_;
// Exact matches for global symbols, by language.
Exact* exact_[LANGUAGE_COUNT];
// A vector of glob patterns mapping to Version_trees.
Globs globs_;
// The default version to use, if there is one. This is from a
// pattern of "*".
const Version_tree* default_version_;
// True if the default version is global.
bool default_is_global_;
// Whether this has been finalized.
bool is_finalized_;
};
// This class manages assignments to symbols. These can appear in
// three different locations in scripts: outside of a SECTIONS clause,
// within a SECTIONS clause, and within an output section definition
// within a SECTIONS clause. This can also appear on the command line
// via the --defsym command line option.
class Symbol_assignment
{
public:
Symbol_assignment(const char* name, size_t namelen, bool is_defsym,
Expression* val, bool provide, bool hidden)
: name_(name, namelen), val_(val), is_defsym_(is_defsym),
provide_(provide), hidden_(hidden), sym_(NULL)
{ }
// Add the symbol to the symbol table.
void
add_to_table(Symbol_table*);
// Finalize the symbol value.
void
finalize(Symbol_table*, const Layout*);
bool
is_defsym() const
{ return is_defsym_; }
Expression *
value() const
{ return val_; }
// Finalize the symbol value when it can refer to the dot symbol.
void
finalize_with_dot(Symbol_table*, const Layout*, uint64_t dot_value,
Output_section* dot_section);
// Set the symbol value, but only if the value is absolute or relative to
// DOT_SECTION. This is used while processing a SECTIONS clause.
// We assume that dot is an absolute value here. We do not check assertions.
void
set_if_absolute(Symbol_table*, const Layout*, bool is_dot_available,
uint64_t dot_value, Output_section* dot_section);
const std::string&
name() const
{ return this->name_; }
// Print the assignment to the FILE. This is for debugging.
void
print(FILE*) const;
private:
// Shared by finalize and finalize_with_dot.
void
finalize_maybe_dot(Symbol_table*, const Layout*, bool is_dot_available,
uint64_t dot_value, Output_section* dot_section);
// Sized version of finalize.
template<int size>
void
sized_finalize(Symbol_table*, const Layout*, bool is_dot_available,
uint64_t dot_value, Output_section*);
// Symbol name.
std::string name_;
// Expression to assign to symbol.
Expression* val_;
// True if this symbol is defined by a --defsym, false if it is
// defined in a linker script.
bool is_defsym_;
// Whether the assignment should be provided (only set if there is
// an undefined reference to the symbol.
bool provide_;
// Whether the assignment should be hidden.
bool hidden_;
// The entry in the symbol table.
Symbol* sym_;
};
// This class manages assertions in linker scripts. These can appear
// in all the places where a Symbol_assignment can appear.
class Script_assertion
{
public:
Script_assertion(Expression* check, const char* message,
size_t messagelen)
: check_(check), message_(message, messagelen)
{ }
// Check the assertion.
void
check(const Symbol_table*, const Layout*);
// Print the assertion to the FILE. This is for debugging.
void
print(FILE*) const;
private:
// The expression to check.
Expression* check_;
// The message to issue if the expression fails.
std::string message_;
};
// We can read a linker script in two different contexts: when
// initially parsing the command line, and when we find an input file
// which is actually a linker script. Also some of the data which can
// be set by a linker script can also be set via command line options
// like -e and --defsym. This means that we have a type of data which
// can be set both during command line option parsing and while
// reading input files. We store that data in an instance of this
// object. We will keep pointers to that instance in both the
// Command_line and Layout objects.
class Script_options
{
public:
Script_options();
// Add a symbol to be defined.
void
add_symbol_assignment(const char* name, size_t length, bool is_defsym,
Expression* value, bool provide, bool hidden);
// Look for an assigned symbol.
bool
is_pending_assignment(const char* name);
// Add a reference to a symbol.
void
add_symbol_reference(const char* name, size_t length);
// Add an assertion.
void
add_assertion(Expression* check, const char* message, size_t messagelen);
// Define a symbol from the command line.
bool
define_symbol(const char* definition);
// Populates the set with symbol names used in LHS of defsym.
void
find_defsym_defs(Unordered_set<std::string>&);
// Set symbols used in defsym expressions as seen in a real ELF object.
void set_defsym_uses_in_real_elf(Symbol_table*) const;
// Create sections required by any linker scripts.
void
create_script_sections(Layout*);
// Add all symbol definitions to the symbol table.
void
add_symbols_to_table(Symbol_table*);
// Used to iterate over symbols which are referenced in expressions
// but not defined.
typedef Unordered_set<std::string>::const_iterator referenced_const_iterator;
referenced_const_iterator
referenced_begin() const
{ return this->symbol_references_.begin(); }
referenced_const_iterator
referenced_end() const
{ return this->symbol_references_.end(); }
// Return whether a symbol is referenced but not defined.
bool
is_referenced(const std::string& name) const
{
return (this->symbol_references_.find(name)
!= this->symbol_references_.end());
}
// Return whether there are any symbols which were referenced but
// not defined.
bool
any_unreferenced() const
{ return !this->symbol_references_.empty(); }
// Finalize the symbol values. Also check assertions.
void
finalize_symbols(Symbol_table*, const Layout*);
// Version information parsed from a version script. Everything
// else has a pointer to this object.
Version_script_info*
version_script_info()
{ return &this->version_script_info_; }
const Version_script_info*
version_script_info() const
{ return &this->version_script_info_; }
// A SECTIONS clause parsed from a linker script. Everything else
// has a pointer to this object.
Script_sections*
script_sections()
{ return &this->script_sections_; }
const Script_sections*
script_sections() const
{ return &this->script_sections_; }
// Whether we saw a SECTIONS clause.
bool
saw_sections_clause() const
{ return this->script_sections_.saw_sections_clause(); }
// Whether we saw a PHDRS clause.
bool
saw_phdrs_clause() const
{ return this->script_sections_.saw_phdrs_clause(); }
// Set section addresses using a SECTIONS clause. Return the
// segment which should hold the file header and segment headers;
// this may return NULL, in which case the headers are not in a
// loadable segment.
Output_segment*
set_section_addresses(Symbol_table*, Layout*);
// Print the script to the FILE. This is for debugging.
void
print(FILE*) const;
private:
// We keep a list of symbol assignments which occur outside of a
// SECTIONS clause.
typedef std::vector<Symbol_assignment*> Symbol_assignments;
// We keep a list of all assertions which occur outside of a
// SECTIONS clause.
typedef std::vector<Script_assertion*> Assertions;
// The entry address. This will be empty if not set.
std::string entry_;
// Symbols to set.
Symbol_assignments symbol_assignments_;
// Symbols defined in an expression, for faster lookup.
Unordered_set<std::string> symbol_definitions_;
// Symbols referenced in an expression.
Unordered_set<std::string> symbol_references_;
// Assertions to check.
Assertions assertions_;
// Version information parsed from a version script.
Version_script_info version_script_info_;
// Information from any SECTIONS clauses.
Script_sections script_sections_;
};
// FILE was found as an argument on the command line, but was not
// recognized as an ELF file. Try to read it as a script. Return
// true if the file was handled. This has to handle /usr/lib/libc.so
// on a GNU/Linux system. *USED_NEXT_BLOCKER is set to indicate
// whether the function took over NEXT_BLOCKER.
bool
read_input_script(Workqueue*, Symbol_table*, Layout*, Dirsearch*, int,
Input_objects*, Mapfile*, Input_group*,
const Input_argument*, Input_file*,
Task_token* next_blocker, bool* used_next_blocker);
// FILE was found as an argument to --script (-T).
// Read it as a script, and execute its contents immediately.
bool
read_commandline_script(const char* filename, Command_line* cmdline);
// FILE was found as an argument to --version-script. Read it as a
// version script, and store its contents in
// cmdline->script_options()->version_script_info().
bool
read_version_script(const char* filename, Command_line* cmdline);
// FILENAME was found as an argument to --dynamic-list. Read it as a
// version script (actually, a versym_node from a version script), and
// store its contents in DYNAMIC_LIST.
bool
read_dynamic_list(const char* filename, Command_line* cmdline,
Script_options* dynamic_list);
} // End namespace gold.
#endif // !defined(GOLD_SCRIPT_H)