[llvm.py] Implement interface to object files

It is now possible to load object files and scan over sections, symbols,
and relocations! Includes test code with partial coverage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152482 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 374 insertions, 99 deletions

diff --git a/bindings/python/llvm/object.py b/bindings/python/llvm/object.py
index f633f60..473aa3a 100644
--- a/bindings/python/llvm/object.py
+++ b/bindings/python/llvm/object.py
@@ -7,11 +7,82 @@
 #
 #===------------------------------------------------------------------------===#
 
+r"""
+Object File Interface
+=====================
+
+This module provides an interface for reading information from object files
+(e.g. binary executables and libraries).
+
+Using this module, you can obtain information about an object file's sections,
+symbols, and relocations. These are represented by the classes ObjectFile,
+Section, Symbol, and Relocation, respectively.
+
+Usage
+-----
+
+The only way to use this module is to start by creating an ObjectFile. You can
+create an ObjectFile by loading a file (specified by its path) or by creating a
+llvm.core.MemoryBuffer and loading that.
+
+Once you have an object file, you can inspect its sections and symbols directly
+by calling get_sections() and get_symbols() respectively. To inspect
+relocations, call get_relocations() on a Section instance.
+
+Iterator Interface
+------------------
+
+The LLVM bindings expose iteration over sections, symbols, and relocations in a
+way that only allows one instance to be operated on at a single time. This is
+slightly annoying from a Python perspective, as it isn't very Pythonic to have
+objects that "expire" but are still active from a dynamic language.
+
+To aid working around this limitation, each Section, Symbol, and Relocation
+instance caches its properties after first access. So, if the underlying
+iterator is advanced, the properties can still be obtained provided they have
+already been retrieved.
+
+In addition, we also provide a "cache" method on each class to cache all
+available data. You can call this on each obtained instance. Or, you can pass
+cache=True to the appropriate get_XXX() method to have this done for you.
+
+Here are some examples on how to perform iteration:
+
+    obj = ObjectFile(filename='/bin/ls')
+
+    # This is OK. Each Section is only accessed inside its own iteration slot.
+    section_names = []
+    for section in obj.get_sections():
+        section_names.append(section.name)
+
+    # This is NOT OK. You perform a lookup after the object has expired.
+    symbols = list(obj.get_symbols())
+    for symbol in symbols:
+        print symbol.name # This raises because the object has expired.
+
+    # In this example, we mix a working and failing scenario.
+    symbols = []
+    for symbol in obj.get_symbols():
+        symbols.append(symbol)
+        print symbol.name
+
+    for symbol in symbols:
+        print symbol.name # OK
+        print symbol.address # NOT OK. We didn't look up this property before.
+
+    # Cache everything up front.
+    symbols = list(obj.get_symbols(cache=True))
+    for symbol in symbols:
+        print symbol.name # OK
+
+"""
+
 from ctypes import c_char_p
 from ctypes import c_uint64
-from ctypes import c_void_p
 
+from .common import CachedProperty
 from .common import LLVMObject
+from .common import c_object_p
 from .common import get_library
 from .core import MemoryBuffer
 
@@ -23,7 +94,7 @@ __all__ = [
     "Symbol",
 ]
 
-class ObjectFile(object):
+class ObjectFile(LLVMObject):
     """Represents an object/binary file."""
 
     def __init__(self, filename=None, contents=None):
@@ -39,209 +110,413 @@ class ObjectFile(object):
         if filename is not None:
             contents = MemoryBuffer(filename=filename)
 
-        self._memory = contents
-        self._obj = lib.LLVMCreateObjectFile(contents)
-        contents.release_ownership()
-        self._as_parameter_ = self._obj
-
-    def __del__(self):
-        lib.LLVMDisposeObjectFile(self)
+        if contents is None:
+            raise Exception('No input found.')
 
-    def from_param(self):
-        return self._as_parameter_
+        ptr = lib.LLVMCreateObjectFile(contents)
+        LLVMObject.__init__(self, ptr, disposer=lib.LLVMDisposeObjectFile)
+        self.take_ownership(contents)
 
-    def get_sections(self):
+    def get_sections(self, cache=False):
         """Obtain the sections in this object file.
 
-        This is an iterator for llvm.object.Section instances.
+        This is a generator for llvm.object.Section instances.
+
+        Sections are exposed as limited-use objects. See the module's
+        documentation on iterators for more.
         """
-        pass
+        sections = lib.LLVMGetSections(self)
+        last = None
+        while True:
+            if lib.LLVMIsSectionIteratorAtEnd(self, sections):
+                break
+
+            last = Section(sections)
+            if cache:
+                last.cache()
 
-    def get_symbols(self):
+            yield last
+
+            lib.LLVMMoveToNextSection(sections)
+            last.expire()
+
+        if last is not None:
+            last.expire()
+
+        lib.LLVMDisposeSectionIterator(sections)
+
+    def get_symbols(self, cache=False):
         """Obtain the symbols in this object file.
 
-        This is an iterator for llvm.object.Symbol instances.
+        This is a generator for llvm.object.Symbol instances.
+
+        Each Symbol instance is a limited-use object. See this module's
+        documentation on iterators for more.
         """
+        symbols = lib.LLVMGetSymbols(self)
+        last = None
+        while True:
+            if lib.LLVMIsSymbolIteratorAtEnd(self, symbols):
+                break
+
+            last = Symbol(symbols, self)
+            if cache:
+                last.cache()
+
+            yield last
+
+            lib.LLVMMoveToNextSymbol(symbols)
+            last.expire()
+
+        if last is not None:
+            last.expire()
+
+        lib.LLVMDisposeSymbolIterator(symbols)
 
-class Section(object):
+class Section(LLVMObject):
     """Represents a section in an object file."""
 
-    def __init__(self, obj=None):
+    def __init__(self, ptr):
         """Construct a new section instance.
 
         Section instances can currently only be created from an ObjectFile
         instance. Therefore, this constructor should not be used outside of
         this module.
         """
-        pass
+        LLVMObject.__init__(self, ptr)
 
-    def __del__(self):
-        pass
+        self.expired = False
 
-    @property
+    @CachedProperty
     def name(self):
-        pass
+        """Obtain the string name of the section.
 
-    @property
+        This is typically something like '.dynsym' or '.rodata'.
+        """
+        if self.expired:
+            raise Exception('Section instance has expired.')
+
+        return lib.LLVMGetSectionName(self)
+
+    @CachedProperty
     def size(self):
-        pass
+        """The size of the section, in long bytes."""
+        if self.expired:
+            raise Exception('Section instance has expired.')
 
-    @property
+        return lib.LLVMGetSectionSize(self)
+
+    @CachedProperty
     def contents(self):
-        pass
+        if self.expired:
+            raise Exception('Section instance has expired.')
+
+        return lib.LLVMGetSectionContents(self)
 
-    @property
+    @CachedProperty
     def address(self):
-        pass
+        """The address of this section, in long bytes."""
+        if self.expired:
+            raise Exception('Section instance has expired.')
+
+        return lib.LLVMGetSectionAddress(self)
 
-    # TODO consider exposing more Pythonic interface, like __contains__
     def has_symbol(self, symbol):
-        pass
+        """Returns whether a Symbol instance is present in this Section."""
+        if self.expired:
+            raise Exception('Section instance has expired.')
+
+        assert isinstance(symbol, Symbol)
+        return lib.LLVMGetSectionContainsSymbol(self, symbol)
+
+    def get_relocations(self, cache=False):
+        """Obtain the relocations in this Section.
 
-    def get_relocations(self):
-        pass
+        This is a generator for llvm.object.Relocation instances.
+
+        Each instance is a limited used object. See this module's documentation
+        on iterators for more.
+        """
+        if self.expired:
+            raise Exception('Section instance has expired.')
 
-class Symbol(object):
-    def __init__(self):
-        pass
+        relocations = lib.LLVMGetRelocations(self)
+        last = None
+        while True:
+            if lib.LLVMIsRelocationIteratorAtEnd(self, relocations):
+                break
 
-    @property
+            last = Relocation(relocations)
+            if cache:
+                last.cache()
+
+            yield last
+
+            lib.LLVMMoveToNextRelocation(relocations)
+            last.expire()
+
+        if last is not None:
+            last.expire()
+
+        lib.LLVMDisposeRelocationIterator(relocations)
+
+    def cache(self):
+        """Cache properties of this Section.
+
+        This can be called as a workaround to the single active Section
+        limitation. When called, the properties of the Section are fetched so
+        they are still available after the Section has been marked inactive.
+        """
+        getattr(self, 'name')
+        getattr(self, 'size')
+        getattr(self, 'contents')
+        getattr(self, 'address')
+
+    def expire(self):
+        """Expire the section.
+
+        This is called internally by the section iterator.
+        """
+        self.expired = True
+
+class Symbol(LLVMObject):
+    """Represents a symbol in an object file."""
+    def __init__(self, ptr, object_file):
+        assert isinstance(ptr, c_object_p)
+        assert isinstance(object_file, ObjectFile)
+
+        LLVMObject.__init__(self, ptr)
+
+        self.expired = False
+        self._object_file = object_file
+
+    @CachedProperty
     def name(self):
-        pass
+        """The str name of the symbol.
+
+        This is often a function or variable name. Keep in mind that name
+        mangling could be in effect.
+        """
+        if self.expired:
+            raise Exception('Symbol instance has expired.')
+
+        return lib.LLVMGetSymbolName(self)
 
-    @property
+    @CachedProperty
     def address(self):
-        pass
+        """The address of this symbol, in long bytes."""
+        if self.expired:
+            raise Exception('Symbol instance has expired.')
+
+        return lib.LLVMGetSymbolAddress(self)
 
-    @property
+    @CachedProperty
     def file_offset(self):
-        pass
+        """The offset of this symbol in the file, in long bytes."""
+        if self.expired:
+            raise Exception('Symbol instance has expired.')
 
-    @property
+        return lib.LLVMGetSymbolFileOffset(self)
+
+    @CachedProperty
     def size(self):
-        pass
+        """The size of the symbol, in long bytes."""
+        if self.expired:
+            raise Exception('Symbol instance has expired.')
+
+        return lib.LLVMGetSymbolSize(self)
 
-class Relocation(object):
-    def __init__(self):
-        pass
+    @CachedProperty
+    def section(self):
+        """The Section to which this Symbol belongs.
 
-    @property
+        The returned Section instance does not expire, unlike Sections that are
+        commonly obtained through iteration.
+
+        Because this obtains a new section iterator each time it is accessed,
+        calling this on a number of Symbol instances could be expensive.
+        """
+        sections = lib.LLVMGetSections(self._object_file)
+        lib.LLVMMoveToContainingSection(sections, self)
+
+        return Section(sections)
+
+    def cache(self):
+        """Cache all cacheable properties."""
+        getattr(self, 'name')
+        getattr(self, 'address')
+        getattr(self, 'file_offset')
+        getattr(self, 'size')
+
+    def expire(self):
+        """Mark the object as expired to prevent future API accesses.
+
+        This is called internally by this module and it is unlikely that
+        external callers have a legitimate reason for using it.
+        """
+        self.expired = True
+
+class Relocation(LLVMObject):
+    """Represents a relocation definition."""
+    def __init__(self, ptr):
+        """Create a new relocation instance.
+
+        Relocations are created from objects derived from Section instances.
+        Therefore, this constructor should not be called outside of this
+        module. See Section.get_relocations() for the proper method to obtain
+        a Relocation instance.
+        """
+        assert isinstance(ptr, c_object_p)
+
+        LLVMObject.__init__(self, ptr)
+
+        self.expired = False
+
+    @CachedProperty
     def address(self):
-        pass
+        """The address of this relocation, in long bytes."""
+        if self.expired:
+            raise Exception('Relocation instance has expired.')
 
-    @property
+        return lib.LLVMGetRelocationAddress(self)
+
+    @CachedProperty
     def offset(self):
-        pass
+        """The offset of this relocation, in long bytes."""
+        if self.expired:
+            raise Exception('Relocation instance has expired.')
+
+        return lib.LLVMGetRelocationOffset(self)
 
-    @property
+    @CachedProperty
     def symbol(self):
-        pass
+        """The Symbol corresponding to this Relocation."""
+        if self.expired:
+            raise Exception('Relocation instance has expired.')
 
-    @property
-    def type(self):
-        pass
+        ptr = lib.LLVMGetRelocationSymbol(self)
+        return Symbol(ptr)
 
-    @property
+    @CachedProperty
+    def type_number(self):
+        """The relocation type, as a long."""
+        if self.expired:
+            raise Exception('Relocation instance has expired.')
+
+        return lib.LLVMGetRelocationType(self)
+
+    @CachedProperty
     def type_name(self):
-        pass
+        """The relocation type's name, as a str."""
+        if self.expired:
+            raise Exception('Relocation instance has expired.')
+
+        return lib.LLVMGetRelocationTypeName(self)
 
-    @property
+    @CachedProperty
     def value_string(self):
-        pass
+        if self.expired:
+            raise Exception('Relocation instance has expired.')
+
+        return lib.LLVMGetRelocationValueString(self)
+
+    def expire(self):
+        """Expire this instance, making future API accesses fail."""
+        self.expired = True
 
-SectionIteratorRef = c_void_p
-SymbolIteratorRef = c_void_p
-RelocationIteratorRef = c_void_p
+    def cache(self):
+        """Cache all cacheable properties on this instance."""
+        getattr(self, 'address')
+        getattr(self, 'offset')
+        getattr(self, 'symbol')
+        getattr(self, 'type')
+        getattr(self, 'type_name')
+        getattr(self, 'value_string')
 
 def register_library(library):
     """Register function prototypes with LLVM library instance."""
 
     # Object.h functions
     library.LLVMCreateObjectFile.argtypes = [MemoryBuffer]
-    library.LLVMCreateObjectFile.restype = LLVMObject
+    library.LLVMCreateObjectFile.restype = c_object_p
 
     library.LLVMDisposeObjectFile.argtypes = [ObjectFile]
 
     library.LLVMGetSections.argtypes = [ObjectFile]
-    library.LLVMGetSections.restype = SectionIteratorRef
+    library.LLVMGetSections.restype = c_object_p
 
-    library.LLVMDisposeSectionIterator.argtypes = [SectionIteratorRef]
+    library.LLVMDisposeSectionIterator.argtypes = [c_object_p]
 
-    library.LLVMIsSectionIteratorAtEnd.argtypes = [ObjectFile,
-            SectionIteratorRef]
+    library.LLVMIsSectionIteratorAtEnd.argtypes = [ObjectFile, c_object_p]
     library.LLVMIsSectionIteratorAtEnd.restype = bool
 
-    library.LLVMMoveToNextSection.argtypes = [SectionIteratorRef]
+    library.LLVMMoveToNextSection.argtypes = [c_object_p]
 
-    library.LLVMMoveToContainingSection.argtypes = [SectionIteratorRef,
-            SymbolIteratorRef]
+    library.LLVMMoveToContainingSection.argtypes = [c_object_p, c_object_p]
 
     library.LLVMGetSymbols.argtypes = [ObjectFile]
-    library.LLVMGetSymbols.restype = SymbolIteratorRef
+    library.LLVMGetSymbols.restype = c_object_p
 
-    library.LLVMDisposeSymbolIterator.argtypes = [SymbolIteratorRef]
+    library.LLVMDisposeSymbolIterator.argtypes = [c_object_p]
 
-    library.LLVMIsSymbolIteratorAtEnd.argtypes = [ObjectFile,
-            SymbolIteratorRef]
+    library.LLVMIsSymbolIteratorAtEnd.argtypes = [ObjectFile, c_object_p]
     library.LLVMIsSymbolIteratorAtEnd.restype = bool
 
-    library.LLVMMoveToNextSymbol.argtypes = [SymbolIteratorRef]
+    library.LLVMMoveToNextSymbol.argtypes = [c_object_p]
 
-    library.LLVMGetSectionName.argtypes = [SectionIteratorRef]
+    library.LLVMGetSectionName.argtypes = [c_object_p]
     library.LLVMGetSectionName.restype = c_char_p
 
-    library.LLVMGetSectionSize.argtypes = [SectionIteratorRef]
+    library.LLVMGetSectionSize.argtypes = [c_object_p]
     library.LLVMGetSectionSize.restype = c_uint64
 
-    library.LLVMGetSectionContents.argtypes = [SectionIteratorRef]
+    library.LLVMGetSectionContents.argtypes = [c_object_p]
     library.LLVMGetSectionContents.restype = c_char_p
 
-    library.LLVMGetSectionAddress.argtypes = [SectionIteratorRef]
+    library.LLVMGetSectionAddress.argtypes = [c_object_p]
     library.LLVMGetSectionAddress.restype = c_uint64
 
-    library.LLVMGetSectionContainsSymbol.argtypes = [SectionIteratorRef,
-            SymbolIteratorRef]
+    library.LLVMGetSectionContainsSymbol.argtypes = [c_object_p, c_object_p]
     library.LLVMGetSectionContainsSymbol.restype = bool
 
-    library.LLVMGetRelocations.argtypes = [SectionIteratorRef]
-    library.LLVMGetRelocations.restype = RelocationIteratorRef
+    library.LLVMGetRelocations.argtypes = [c_object_p]
+    library.LLVMGetRelocations.restype = c_object_p
 
-    library.LLVMDisposeRelocationIterator.argtypes = [RelocationIteratorRef]
+    library.LLVMDisposeRelocationIterator.argtypes = [c_object_p]
 
-    library.LLVMIsRelocationIteratorAtEnd.argtypes = [SectionIteratorRef,
-            RelocationIteratorRef]
+    library.LLVMIsRelocationIteratorAtEnd.argtypes = [c_object_p, c_object_p]
     library.LLVMIsRelocationIteratorAtEnd.restype = bool
 
-    library.LLVMMoveToNextRelocation.argtypes = [RelocationIteratorRef]
+    library.LLVMMoveToNextRelocation.argtypes = [c_object_p]
 
-    library.LLVMGetSymbolName.argtypes = [SymbolIteratorRef]
+    library.LLVMGetSymbolName.argtypes = [Symbol]
     library.LLVMGetSymbolName.restype = c_char_p
 
-    library.LLVMGetSymbolAddress.argtypes = [SymbolIteratorRef]
+    library.LLVMGetSymbolAddress.argtypes = [Symbol]
     library.LLVMGetSymbolAddress.restype = c_uint64
 
-    library.LLVMGetSymbolFileOffset.argtypes = [SymbolIteratorRef]
+    library.LLVMGetSymbolFileOffset.argtypes = [Symbol]
     library.LLVMGetSymbolFileOffset.restype = c_uint64
 
-    library.LLVMGetSymbolSize.argtypes = [SymbolIteratorRef]
+    library.LLVMGetSymbolSize.argtypes = [Symbol]
     library.LLVMGetSymbolSize.restype = c_uint64
 
-    library.LLVMGetRelocationAddress.argtypes = [SymbolIteratorRef]
+    library.LLVMGetRelocationAddress.argtypes = [c_object_p]
     library.LLVMGetRelocationAddress.restype = c_uint64
 
-    library.LLVMGetRelocationOffset.argtypes = [RelocationIteratorRef]
+    library.LLVMGetRelocationOffset.argtypes = [c_object_p]
     library.LLVMGetRelocationOffset.restype = c_uint64
 
-    library.LLVMGetRelocationSymbol.argtypes = [RelocationIteratorRef]
-    library.LLVMGetRelocationSymbol.restype = SymbolIteratorRef
+    library.LLVMGetRelocationSymbol.argtypes = [c_object_p]
+    library.LLVMGetRelocationSymbol.restype = c_object_p
 
-    library.LLVMGetRelocationType.argtypes = [RelocationIteratorRef]
+    library.LLVMGetRelocationType.argtypes = [c_object_p]
     library.LLVMGetRelocationType.restype = c_uint64
 
-    library.LLVMGetRelocationTypeName.argtypes = [RelocationIteratorRef]
+    library.LLVMGetRelocationTypeName.argtypes = [c_object_p]
     library.LLVMGetRelocationTypeName.restype = c_char_p
 
-    library.LLVMGetRelocationValueString.argtypes = [RelocationIteratorRef]
+    library.LLVMGetRelocationValueString.argtypes = [c_object_p]
     library.LLVMGetRelocationValueString.restype = c_char_p
 
 lib = get_library()