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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - compiler-rt: Mark REAL(swapcontext) with indirect_return attribute on x86"
href="https://bugs.llvm.org/show_bug.cgi?id=38249">38249</a>
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<th>Summary</th>
<td>compiler-rt: Mark REAL(swapcontext) with indirect_return attribute on x86
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hjl.tools@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>kcc@google.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>When shadow stack from Intel CET is enabled, the first instruction of all
indirect branch targets must be a special instruction, ENDBR.
lib/asan/asan_interceptors.cc has
...
int res = REAL(swapcontext)(oucp, ucp);
...
REAL(swapcontext) is a function pointer to swapcontext in libc. Since
swapcontext may return via indirect branch on x86 when shadow stack is
enabled, as in this case,
int res = REAL(swapcontext)(oucp, ucp);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This function may be
returned via an indirect branch.
Here compiler must insert ENDBR after call, like
call *bar(%rip)
endbr64
I opened an LLVM bug:
<a class="bz_bug_link
bz_status_NEW "
title="NEW - Need indirect_return function attribute for CET"
href="show_bug.cgi?id=38207">https://bugs.llvm.org/show_bug.cgi?id=38207</a>
to add the indirect_return attribute so that it can be used to inform
compiler to insert ENDBR after REAL(swapcontext) call.</pre>
</div>
</p>
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