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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [SanitizerCoverage] implement instrumentation for lowest stack pointer value"
href="https://bugs.llvm.org/show_bug.cgi?id=33857">33857</a>
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<th>Summary</th>
<td>[SanitizerCoverage] implement instrumentation for lowest stack pointer value
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>mascasa@google.com
</td>
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<th>Reporter</th>
<td>kcc@google.com
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>r308577 adds a libFuzzer logic to use recursion depth as a signal
(inspired by
<a href="https://guidovranken.wordpress.com/2017/07/08/libfuzzer-gv-new-techniques-for-dramatically-faster-fuzzing/">https://guidovranken.wordpress.com/2017/07/08/libfuzzer-gv-new-techniques-for-dramatically-faster-fuzzing/</a>,
"Stack-depth-guided fuzzing")
We need to extract the recursion depth with a dedicated inlined compiler
instrumentation.
it should be something like -fsanitize-coverage=stack-depth
that would insert this code at the beginning of every function:
uintptr_t current_stack = __builtin_frame_address(0);
if (__sanitizer_cov_lowest_stack > current_stack)
__sanitizer_cov_lowest_stack = current_stack;
// Users should declare this in their code (e.g. in libFuzzer)
thread_local uintptr __sanitizer_cov_lowest_stack;</pre>
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