зеркало из https://github.com/microsoft/clang-1.git
154 строки
5.2 KiB
ReStructuredText
154 строки
5.2 KiB
ReStructuredText
================
|
|
AddressSanitizer
|
|
================
|
|
|
|
.. contents::
|
|
:local:
|
|
|
|
Introduction
|
|
============
|
|
|
|
AddressSanitizer is a fast memory error detector. It consists of a compiler
|
|
instrumentation module and a run-time library. The tool can detect the
|
|
following types of bugs:
|
|
|
|
* Out-of-bounds accesses to heap, stack and globals
|
|
* Use-after-free
|
|
* Use-after-return (to some extent)
|
|
* Double-free, invalid free
|
|
|
|
Typical slowdown introduced by AddressSanitizer is **2x**.
|
|
|
|
How to build
|
|
============
|
|
|
|
Follow the `clang build instructions <../get_started.html>`_. CMake build is
|
|
supported.
|
|
|
|
Usage
|
|
=====
|
|
|
|
Simply compile and link your program with ``-fsanitize=address`` flag. The
|
|
AddressSanitizer run-time library should be linked to the final executable, so
|
|
make sure to use ``clang`` (not ``ld``) for the final link step. When linking
|
|
shared libraries, the AddressSanitizer run-time is not linked, so
|
|
``-Wl,-z,defs`` may cause link errors (don't use it with AddressSanitizer). To
|
|
get a reasonable performance add ``-O1`` or higher. To get nicer stack traces
|
|
in error messages add ``-fno-omit-frame-pointer``. To get perfect stack traces
|
|
you may need to disable inlining (just use ``-O1``) and tail call elimination
|
|
(``-fno-optimize-sibling-calls``).
|
|
|
|
.. code-block:: console
|
|
|
|
% cat example_UseAfterFree.cc
|
|
int main(int argc, char **argv) {
|
|
int *array = new int[100];
|
|
delete [] array;
|
|
return array[argc]; // BOOM
|
|
}
|
|
|
|
# Compile and link
|
|
% clang -O1 -g -fsanitize=address -fno-omit-frame-pointer example_UseAfterFree.cc
|
|
|
|
or:
|
|
|
|
.. code-block:: console
|
|
|
|
# Compile
|
|
% clang -O1 -g -fsanitize=address -fno-omit-frame-pointer -c example_UseAfterFree.cc
|
|
# Link
|
|
% clang -g -fsanitize=address example_UseAfterFree.o
|
|
|
|
If a bug is detected, the program will print an error message to stderr and
|
|
exit with a non-zero exit code. Currently, AddressSanitizer does not symbolize
|
|
its output, so you may need to use a separate script to symbolize the result
|
|
offline (this will be fixed in future).
|
|
|
|
.. code-block:: console
|
|
|
|
% ./a.out 2> log
|
|
% projects/compiler-rt/lib/asan/scripts/asan_symbolize.py / < log | c++filt
|
|
==9442== ERROR: AddressSanitizer heap-use-after-free on address 0x7f7ddab8c084 at pc 0x403c8c bp 0x7fff87fb82d0 sp 0x7fff87fb82c8
|
|
READ of size 4 at 0x7f7ddab8c084 thread T0
|
|
#0 0x403c8c in main example_UseAfterFree.cc:4
|
|
#1 0x7f7ddabcac4d in __libc_start_main ??:0
|
|
0x7f7ddab8c084 is located 4 bytes inside of 400-byte region [0x7f7ddab8c080,0x7f7ddab8c210)
|
|
freed by thread T0 here:
|
|
#0 0x404704 in operator delete[](void*) ??:0
|
|
#1 0x403c53 in main example_UseAfterFree.cc:4
|
|
#2 0x7f7ddabcac4d in __libc_start_main ??:0
|
|
previously allocated by thread T0 here:
|
|
#0 0x404544 in operator new[](unsigned long) ??:0
|
|
#1 0x403c43 in main example_UseAfterFree.cc:2
|
|
#2 0x7f7ddabcac4d in __libc_start_main ??:0
|
|
==9442== ABORTING
|
|
|
|
AddressSanitizer exits on the first detected error. This is by design.
|
|
One reason: it makes the generated code smaller and faster (both by
|
|
~5%). Another reason: this makes fixing bugs unavoidable. With Valgrind,
|
|
it is often the case that users treat Valgrind warnings as false
|
|
positives (which they are not) and don't fix them.
|
|
|
|
``__has_feature(address_sanitizer)``
|
|
------------------------------------
|
|
|
|
In some cases one may need to execute different code depending on whether
|
|
AddressSanitizer is enabled.
|
|
:ref:`\_\_has\_feature <langext-__has_feature-__has_extension>` can be used for
|
|
this purpose.
|
|
|
|
.. code-block:: c
|
|
|
|
#if defined(__has_feature)
|
|
# if __has_feature(address_sanitizer)
|
|
// code that builds only under AddressSanitizer
|
|
# endif
|
|
#endif
|
|
|
|
``__attribute__((no_address_safety_analysis))``
|
|
-----------------------------------------------
|
|
|
|
Some code should not be instrumented by AddressSanitizer. One may use the
|
|
function attribute
|
|
:ref:`no_address_safety_analysis <langext-address_sanitizer>`
|
|
to disable instrumentation of a particular function. This attribute may not be
|
|
supported by other compilers, so we suggest to use it together with
|
|
``__has_feature(address_sanitizer)``. Note: currently, this attribute will be
|
|
lost if the function is inlined.
|
|
|
|
Supported Platforms
|
|
===================
|
|
|
|
AddressSanitizer is supported on
|
|
|
|
* Linux i386/x86\_64 (tested on Ubuntu 10.04 and 12.04);
|
|
* MacOS 10.6, 10.7 and 10.8 (i386/x86\_64).
|
|
|
|
Support for Linux ARM (and Android ARM) is in progress (it may work, but
|
|
is not guaranteed too).
|
|
|
|
Limitations
|
|
===========
|
|
|
|
* AddressSanitizer uses more real memory than a native run. Exact overhead
|
|
depends on the allocations sizes. The smaller the allocations you make the
|
|
bigger the overhead is.
|
|
* AddressSanitizer uses more stack memory. We have seen up to 3x increase.
|
|
* On 64-bit platforms AddressSanitizer maps (but not reserves) 16+ Terabytes of
|
|
virtual address space. This means that tools like ``ulimit`` may not work as
|
|
usually expected.
|
|
* Static linking is not supported.
|
|
|
|
Current Status
|
|
==============
|
|
|
|
AddressSanitizer is fully functional on supported platforms starting from LLVM
|
|
3.1. The test suite is integrated into CMake build and can be run with ``make
|
|
check-asan`` command.
|
|
|
|
More Information
|
|
================
|
|
|
|
`http://code.google.com/p/address-sanitizer <http://code.google.com/p/address-sanitizer/>`_
|
|
|