396 lines
12 KiB
C++
396 lines
12 KiB
C++
// script.h -- handle linker scripts for gold -*- C++ -*-
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// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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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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// 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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// 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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// We implement a subset of the original GNU ld linker script language
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// for compatibility. The goal is not to implement the entire
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// language. It is merely to implement enough to handle common uses.
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// In particular we need to handle /usr/lib/libc.so on a typical
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// GNU/Linux system, and we want to handle linker scripts used by the
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// Linux kernel build.
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#ifndef GOLD_SCRIPT_H
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#define GOLD_SCRIPT_H
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#include <cstdio>
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#include <vector>
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#include "script-sections.h"
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namespace gold
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{
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class General_options;
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class Command_line;
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class Symbol_table;
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class Layout;
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class Input_argument;
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class Input_objects;
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class Input_group;
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class Input_file;
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class Output_segment;
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class Task_token;
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class Workqueue;
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struct Version_dependency_list;
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struct Version_expression_list;
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struct Version_tree;
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// This class represents an expression in a linker script.
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class Expression
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{
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protected:
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// These should only be created by child classes.
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Expression()
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{ }
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public:
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virtual ~Expression()
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{ }
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// Return the value of the expression which is not permitted to
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// refer to the dot symbol.
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uint64_t
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eval(const Symbol_table*, const Layout*);
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// Return the value of an expression which is permitted to refer to
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// the dot symbol. This sets *IS_ABSOLUTE to indicate whether this
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// is an absolute value; it will be false if a non-absolute symbol
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// was referenced in the expression; this is used to detect invalid
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// uses when setting a section address.
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uint64_t
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eval_with_dot(const Symbol_table*, const Layout*, bool dot_has_value,
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uint64_t dot_value, bool* is_absolute);
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// Return the value of an expression which may or may not be
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// permitted to refer to the dot symbol, depending on
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// is_dot_available.
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uint64_t
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eval_maybe_dot(const Symbol_table*, const Layout*, bool is_dot_available,
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bool dot_has_value, uint64_t dot_value, bool* is_absolute);
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// Print the expression to the FILE. This is for debugging.
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virtual void
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print(FILE*) const = 0;
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protected:
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struct Expression_eval_info;
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public:
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// Compute the value of the expression (implemented by child class).
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// This is public rather than protected because it is called
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// directly by children of Expression on other Expression objects.
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virtual uint64_t
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value(const Expression_eval_info*) = 0;
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private:
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// May not be copied.
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Expression(const Expression&);
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Expression& operator=(const Expression&);
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};
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// Version_script_info stores information parsed from the version
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// script, either provided by --version-script or as part of a linker
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// script. A single Version_script_info object per target is owned by
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// Script_options.
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class Version_script_info
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{
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public:
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~Version_script_info();
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// Return whether any version were defined in the version script.
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bool
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empty() const
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{ return this->version_trees_.empty(); }
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// Return the version associated with the given symbol name.
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// Strings are allocated out of the stringpool given in the
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// constructor. Strings are allocated out of the stringpool given
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// in the constructor.
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const std::string&
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get_symbol_version(const char* symbol) const
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{ return get_symbol_version_helper(symbol, true); }
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// Return whether this symbol matches the local: section of a
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// version script (it doesn't matter which).
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bool
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symbol_is_local(const char* symbol) const
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{
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return (get_symbol_version(symbol).empty()
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&& !get_symbol_version_helper(symbol, false).empty());
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}
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// Return the names of versions defined in the version script.
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// Strings are allocated out of the stringpool given in the
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// constructor.
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std::vector<std::string>
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get_versions() const;
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// Return the list of dependencies for this version.
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std::vector<std::string>
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get_dependencies(const char* version) const;
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// The following functions should only be used by the bison helper
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// functions. They allocate new structs whose memory belongs to
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// Version_script_info. The bison functions copy the information
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// from the version script into these structs.
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struct Version_dependency_list*
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allocate_dependency_list();
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struct Version_expression_list*
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allocate_expression_list();
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struct Version_tree*
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allocate_version_tree();
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// Print contents to the FILE. This is for debugging.
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void
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print(FILE*) const;
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private:
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void
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print_expression_list(FILE* f, const Version_expression_list*) const;
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const std::string& get_symbol_version_helper(const char* symbol,
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bool check_global) const;
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std::vector<struct Version_dependency_list*> dependency_lists_;
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std::vector<struct Version_expression_list*> expression_lists_;
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std::vector<struct Version_tree*> version_trees_;
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};
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// This class manages assignments to symbols. These can appear in
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// three different locations in scripts: outside of a SECTIONS clause,
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// within a SECTIONS clause, and within an output section definition
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// within a SECTIONS clause. This can also appear on the command line
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// via the --defsym command line option.
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class Symbol_assignment
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{
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public:
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Symbol_assignment(const char* name, size_t namelen, Expression* val,
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bool provide, bool hidden)
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: name_(name, namelen), val_(val), provide_(provide), hidden_(hidden),
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sym_(NULL)
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{ }
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// Add the symbol to the symbol table.
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void
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add_to_table(Symbol_table*);
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// Finalize the symbol value.
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void
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finalize(Symbol_table*, const Layout*);
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// Finalize the symbol value when it can refer to the dot symbol.
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void
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finalize_with_dot(Symbol_table*, const Layout*, bool dot_has_value,
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uint64_t dot_value);
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// Set the symbol value, but only if the value is absolute. This is
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// used while processing a SECTIONS clause.
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void
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set_if_absolute(Symbol_table*, const Layout*, bool is_dot_available,
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bool dot_has_value, uint64_t dot_value);
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// Print the assignment to the FILE. This is for debugging.
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void
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print(FILE*) const;
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private:
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// Shared by finalize and finalize_with_dot.
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void
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finalize_maybe_dot(Symbol_table*, const Layout*, bool is_dot_available,
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bool dot_has_value, uint64_t dot_value);
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// Sized version of finalize.
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template<int size>
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void
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sized_finalize(Symbol_table*, const Layout*, bool is_dot_available,
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bool dot_has_value, uint64_t dot_value);
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// Symbol name.
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std::string name_;
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// Expression to assign to symbol.
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Expression* val_;
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// Whether the assignment should be provided (only set if there is
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// an undefined reference to the symbol.
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bool provide_;
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// Whether the assignment should be hidden.
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bool hidden_;
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// The entry in the symbol table.
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Symbol* sym_;
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};
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// This class manages assertions in linker scripts. These can appear
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// in all the places where a Symbol_assignment can appear.
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class Script_assertion
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{
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public:
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Script_assertion(Expression* check, const char* message,
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size_t messagelen)
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: check_(check), message_(message, messagelen)
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{ }
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// Check the assertion.
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void
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check(const Symbol_table*, const Layout*);
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// Print the assertion to the FILE. This is for debugging.
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void
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print(FILE*) const;
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private:
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// The expression to check.
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Expression* check_;
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// The message to issue if the expression fails.
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std::string message_;
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};
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// We can read a linker script in two different contexts: when
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// initially parsing the command line, and when we find an input file
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// which is actually a linker script. Also some of the data which can
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// be set by a linker script can also be set via command line options
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// like -e and --defsym. This means that we have a type of data which
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// can be set both during command line option parsing and while
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// reading input files. We store that data in an instance of this
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// object. We will keep pointers to that instance in both the
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// Command_line and Layout objects.
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class Script_options
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{
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public:
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Script_options();
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// The entry address.
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const char*
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entry() const
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{ return this->entry_.empty() ? NULL : this->entry_.c_str(); }
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// Set the entry address.
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void
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set_entry(const char* entry, size_t length)
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{ this->entry_.assign(entry, length); }
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// Add a symbol to be defined.
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void
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add_symbol_assignment(const char* name, size_t length, Expression* value,
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bool provide, bool hidden);
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// Add an assertion.
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void
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add_assertion(Expression* check, const char* message, size_t messagelen);
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// Define a symbol from the command line.
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bool
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define_symbol(const char* definition);
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// Add all symbol definitions to the symbol table.
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void
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add_symbols_to_table(Symbol_table*);
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// Finalize the symbol values. Also check assertions.
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void
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finalize_symbols(Symbol_table*, const Layout*);
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// Version information parsed from a version script. Everything
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// else has a pointer to this object.
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Version_script_info*
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version_script_info()
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{ return &this->version_script_info_; }
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// A SECTIONS clause parsed from a linker script. Everything else
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// has a pointer to this object.
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Script_sections*
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script_sections()
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{ return &this->script_sections_; }
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// Whether we saw a SECTIONS clause.
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bool
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saw_sections_clause() const
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{ return this->script_sections_.saw_sections_clause(); }
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// Set section addresses using a SECTIONS clause. Return the
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// segment which should hold the file header and segment headers;
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// this may return NULL, in which case the headers are not in a
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// loadable segment.
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Output_segment*
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set_section_addresses(Symbol_table*, Layout*);
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// Print the script to the FILE. This is for debugging.
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void
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print(FILE*) const;
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private:
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// We keep a list of symbol assignments which occur outside of a
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// SECTIONS clause.
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typedef std::vector<Symbol_assignment*> Symbol_assignments;
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// We keep a list of all assertions whcih occur outside of a
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// SECTIONS clause.
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typedef std::vector<Script_assertion*> Assertions;
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// The entry address. This will be empty if not set.
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std::string entry_;
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// Symbols to set.
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Symbol_assignments symbol_assignments_;
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// Assertions to check.
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Assertions assertions_;
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// Version information parsed from a version script.
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Version_script_info version_script_info_;
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// Information from any SECTIONS clauses.
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Script_sections script_sections_;
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};
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// FILE was found as an argument on the command line, but was not
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// recognized as an ELF file. Try to read it as a script. We've
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// already read BYTES of data into P. Return true if the file was
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// handled. This has to handle /usr/lib/libc.so on a GNU/Linux
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// system.
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bool
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read_input_script(Workqueue*, const General_options&, Symbol_table*, Layout*,
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Dirsearch*, Input_objects*, Input_group*,
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const Input_argument*, Input_file*, const unsigned char* p,
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off_t bytes, Task_token* this_blocker,
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Task_token* next_blocker);
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// FILE was found as an argument to --script (-T).
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// Read it as a script, and execute its contents immediately.
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bool
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read_commandline_script(const char* filename, Command_line*);
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// FILE was found as an argument to --version-script. Read it as a
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// version script, and store its contents in
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// cmdline->script_options()->version_script_info().
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bool
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read_version_script(const char* filename, Command_line* cmdline);
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} // End namespace gold.
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#endif // !defined(GOLD_SCRIPT_H)
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