2011-11-29 00:51:02 +04:00
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<title>AddressSanitizer, a fast memory error detector</title>
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2011-11-29 02:34:10 +04:00
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<div id="content">
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2011-11-29 00:51:02 +04:00
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<h1>AddressSanitizer</h1>
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<ul>
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2012-04-23 13:05:50 +04:00
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<li> <a href="#intro">Introduction</a>
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<li> <a href="#howtobuild">How to Build</a>
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<li> <a href="#usage">Usage</a>
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<ul><li> <a href="#has_feature">__has_feature(address_sanitizer)</a></ul>
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<ul><li> <a href="#no_address_safety_analysis">
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__attribute__((no_address_safety_analysis))</a></ul>
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<li> <a href="#platforms">Supported Platforms</a>
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<li> <a href="#limitations">Limitations</a>
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<li> <a href="#status">Current Status</a>
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<li> <a href="#moreinfo">More Information</a>
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2011-11-29 00:51:02 +04:00
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</ul>
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<h2 id="intro">Introduction</h2>
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AddressSanitizer is a fast memory error detector.
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It consists of a compiler instrumentation module and a run-time library.
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The tool can detect the following types of bugs:
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2011-12-13 03:22:31 +04:00
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<ul> <li> Out-of-bounds accesses to heap, stack and globals
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2011-11-29 00:51:02 +04:00
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<li> Use-after-free
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<li> Use-after-return (to some extent)
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2011-12-13 03:22:31 +04:00
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<li> Double-free, invalid free
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2011-11-29 00:51:02 +04:00
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</ul>
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Typical slowdown introduced by AddressSanitizer is <b>2x</b>.
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2011-12-13 03:22:31 +04:00
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<h2 id="howtobuild">How to build</h2>
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2012-03-15 20:20:29 +04:00
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Follow the <a href="../get_started.html">clang build instructions</a>. <BR>
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Note: CMake build does not work yet.
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2012-03-15 20:22:06 +04:00
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See <a href="http://llvm.org/bugs/show_bug.cgi?id=12272">bug 12272</a>.
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2011-12-13 03:22:31 +04:00
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2012-01-15 19:26:07 +04:00
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<h2 id="usage">Usage</h2>
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2011-12-13 03:22:31 +04:00
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Simply compile and link your program with <tt>-faddress-sanitizer</tt> flag. <BR>
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To get a reasonable performance add <tt>-O1</tt> or higher. <BR>
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2012-01-06 21:35:27 +04:00
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To get nicer stack traces in error messages add
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<tt>-fno-omit-frame-pointer</tt>. <BR>
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2012-01-23 22:50:23 +04:00
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To get perfect stack traces you may need to disable inlining (just use <tt>-O1</tt>) and tail call
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elimination (</tt>-fno-optimize-sibling-calls</tt>).
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2011-12-13 03:22:31 +04:00
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<pre>
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% cat example_UseAfterFree.cc
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int main(int argc, char **argv) {
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int *array = new int[100];
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delete [] array;
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return array[argc]; // BOOM
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}
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</pre>
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<pre>
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2012-01-06 21:35:27 +04:00
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% clang -O1 -g -faddress-sanitizer -fno-omit-frame-pointer example_UseAfterFree.cc
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2011-12-13 03:22:31 +04:00
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</pre>
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If a bug is detected, the program will print an error message to stderr and exit with a
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2011-12-02 04:24:42 +04:00
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non-zero exit code.
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2011-12-13 03:22:31 +04:00
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Currently, AddressSanitizer does not symbolize its output, so you may need to use a
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separate script to symbolize the result offline (this will be fixed in future).
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<pre>
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% ./a.out 2> log
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% projects/compiler-rt/lib/asan/scripts/asan_symbolize.py / < log | c++filt
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==9442== ERROR: AddressSanitizer heap-use-after-free on address 0x7f7ddab8c084 at pc 0x403c8c bp 0x7fff87fb82d0 sp 0x7fff87fb82c8
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READ of size 4 at 0x7f7ddab8c084 thread T0
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#0 0x403c8c in main example_UseAfterFree.cc:4
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#1 0x7f7ddabcac4d in __libc_start_main ??:0
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0x7f7ddab8c084 is located 4 bytes inside of 400-byte region [0x7f7ddab8c080,0x7f7ddab8c210)
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freed by thread T0 here:
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#0 0x404704 in operator delete[](void*) ??:0
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#1 0x403c53 in main example_UseAfterFree.cc:4
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#2 0x7f7ddabcac4d in __libc_start_main ??:0
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previously allocated by thread T0 here:
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#0 0x404544 in operator new[](unsigned long) ??:0
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#1 0x403c43 in main example_UseAfterFree.cc:2
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#2 0x7f7ddabcac4d in __libc_start_main ??:0
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==9442== ABORTING
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</pre>
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2011-11-29 00:51:02 +04:00
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<h3 id="has_feature">__has_feature(address_sanitizer)</h3>
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In some cases one may need to execute different code depending on whether
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AddressSanitizer is enabled.
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<a href="LanguageExtensions.html#__has_feature_extension">__has_feature</a>
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can be used for this purpose.
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<pre>
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2012-07-02 15:00:33 +04:00
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#if defined(__has_feature)
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# if __has_feature(address_sanitizer)
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code that builds only under AddressSanitizer
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# endif
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2011-11-29 00:51:02 +04:00
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#endif
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</pre>
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2012-04-23 13:05:50 +04:00
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<h3 id="no_address_safety_analysis">__attribute__((no_address_safety_analysis))</h3>
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Some code should not be instrumentated by AddressSanitizer.
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One may use the function attribute
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<a href="LanguageExtensions.html#address_sanitizer">
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<tt>no_address_safety_analysis</tt></a>
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to disable instrumentation of a particular function.
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2012-07-02 15:00:33 +04:00
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This attribute may not be supported by other compilers, so we suggest to
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use it together with <tt>__has_feature(address_sanitizer)</tt>.
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2012-04-23 13:05:50 +04:00
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Note: currently, this attribute will be lost if the function is inlined.
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2011-11-29 00:51:02 +04:00
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<h2 id="platforms">Supported Platforms</h2>
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2011-12-13 03:22:31 +04:00
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AddressSanitizer is supported on
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<ul><li>Linux x86_64 (tested on Ubuntu 10.04).
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2012-07-02 15:00:33 +04:00
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<li>MacOS 10.6 and 10.7 (i386/x86_64).
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2011-11-29 00:51:02 +04:00
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</ul>
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2012-07-02 15:00:33 +04:00
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Support for Linux i386/ARM is in progress
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2012-03-15 20:20:29 +04:00
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(it may work, but is not guaranteed too).
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2011-11-29 00:51:02 +04:00
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<h2 id="limitations">Limitations</h2>
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<ul>
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2012-04-23 13:05:50 +04:00
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<li> AddressSanitizer uses more real memory than a native run.
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How much -- depends on the allocations sizes. The smaller the
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allocations you make the bigger the overhead.
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<li> AddressSanitizer uses more stack memory. We have seen up to 3x increase.
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<li> On 64-bit platforms AddressSanitizer maps (but not reserves)
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16+ Terabytes of virtual address space.
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This means that tools like <tt>ulimit</tt> may not work as usually expected.
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<li> Static linking is not supported.
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2011-11-29 00:51:02 +04:00
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</ul>
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<h2 id="status">Current Status</h2>
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2012-04-23 14:15:18 +04:00
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AddressSanitizer is fully functional on supported platforms starting from LLVM 3.1.
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2011-12-13 03:22:31 +04:00
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However, the test suite is not fully integrated yet and we lack the testing
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process (buildbots).
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<h2 id="moreinfo">More Information</h2>
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2011-11-29 00:51:02 +04:00
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<a href="http://code.google.com/p/address-sanitizer/">http://code.google.com/p/address-sanitizer</a>.
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2011-11-29 02:34:10 +04:00
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</div>
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2011-11-29 00:51:02 +04:00
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</body>
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</html>
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