Add support for -fsanitize-blacklist and default blacklists for DFSan.
Also add some documentation.
Differential Revision: http://llvm-reviews.chandlerc.com/D1346
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188403 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/DataFlowSanitizer.rst b/docs/DataFlowSanitizer.rst
index 4260990..e0e9d74 100644
--- a/docs/DataFlowSanitizer.rst
+++ b/docs/DataFlowSanitizer.rst
@@ -2,6 +2,11 @@
DataFlowSanitizer
=================
+.. toctree::
+ :hidden:
+
+ DataFlowSanitizerDesign
+
.. contents::
:local:
@@ -28,6 +33,82 @@
For further information about each function, please refer to the header
file.
+ABI List
+--------
+
+DataFlowSanitizer uses a list of functions known as an ABI list to decide
+whether a call to a specific function should use the operating system's native
+ABI or whether it should use a variant of this ABI that also propagates labels
+through function parameters and return values. The ABI list file also controls
+how labels are propagated in the former case. DataFlowSanitizer comes with a
+default ABI list which is intended to eventually cover the glibc library on
+Linux but it may become necessary for users to extend the ABI list in cases
+where a particular library or function cannot be instrumented (e.g. because
+it is implemented in assembly or another language which DataFlowSanitizer does
+not support) or a function is called from a library or function which cannot
+be instrumented.
+
+DataFlowSanitizer's ABI list file is a :doc:`SanitizerSpecialCaseList`.
+The pass treats every function in the ``uninstrumented`` category in the
+ABI list file as conforming to the native ABI. Unless the ABI list contains
+additional categories for those functions, a call to one of those functions
+will produce a warning message, as the labelling behavior of the function
+is unknown. The other supported categories are ``discard``, ``functional``
+and ``custom``.
+
+* ``discard`` -- To the extent that this function writes to (user-accessible)
+ memory, it also updates labels in shadow memory (this condition is trivially
+ satisfied for functions which do not write to user-accessible memory). Its
+ return value is unlabelled.
+* ``functional`` -- Like ``discard``, except that the label of its return value
+ is the union of the label of its arguments.
+* ``custom`` -- Instead of calling the function, a custom wrapper ``__dfsw_F``
+ is called, where ``F`` is the name of the function. This function may wrap
+ the original function or provide its own implementation. This category is
+ generally used for uninstrumentable functions which write to user-accessible
+ memory or which have more complex label propagation behavior. The signature
+ of ``__dfsw_F`` is based on that of ``F`` with each argument having a
+ label of type ``dfsan_label`` appended to the argument list. If ``F``
+ is of non-void return type a final argument of type ``dfsan_label *``
+ is appended to which the custom function can store the label for the
+ return value. For example:
+
+.. code-block:: c++
+
+ void f(int x);
+ void __dfsw_f(int x, dfsan_label x_label);
+
+ void *memcpy(void *dest, const void *src, size_t n);
+ void *__dfsw_memcpy(void *dest, const void *src, size_t n,
+ dfsan_label dest_label, dfsan_label src_label,
+ dfsan_label n_label, dfsan_label *ret_label);
+
+If a function defined in the translation unit being compiled belongs to the
+``uninstrumented`` category, it will be compiled so as to conform to the
+native ABI. Its arguments will be assumed to be unlabelled, but it will
+propagate labels in shadow memory.
+
+For example:
+
+.. code-block:: none
+
+ # main is called by the C runtime using the native ABI.
+ fun:main=uninstrumented
+ fun:main=discard
+
+ # malloc only writes to its internal data structures, not user-accessible memory.
+ fun:malloc=uninstrumented
+ fun:malloc=discard
+
+ # tolower is a pure function.
+ fun:tolower=uninstrumented
+ fun:tolower=functional
+
+ # memcpy needs to copy the shadow from the source to the destination region.
+ # This is done in a custom function.
+ fun:memcpy=uninstrumented
+ fun:memcpy=custom
+
Example
=======