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<body><span class="vcard"><a class="email" href="mailto:emaste@freebsd.org" title="emaste@freebsd.org">emaste@freebsd.org</a>
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<a class="bz_bug_link
bz_status_NEW "
title="NEW --- - frame info lost after failed expression evaluation"
href="http://llvm.org/bugs/show_bug.cgi?id=17226">bug 17226</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Assignee</td>
<td>lldb-dev@cs.uiuc.edu
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<td>emaste@freebsd.org
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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - frame info lost after failed expression evaluation"
href="http://llvm.org/bugs/show_bug.cgi?id=17226#c3">Comment # 3</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - frame info lost after failed expression evaluation"
href="http://llvm.org/bugs/show_bug.cgi?id=17226">bug 17226</a>
from <span class="vcard"><a class="email" href="mailto:emaste@freebsd.org" title="emaste@freebsd.org">emaste@freebsd.org</a>
</span></b>
<pre>It turns out this happens because FreeBSD does not allow user processes to
change PSL_RF via ptrace(). It seems the sequence of events is
1) breakpoint or exception
2) lldb checkpoints thread state - ptrace(..., PT_GETREGS) returns rflags with
PSL_RF set
3) expression is JITted and executed, leaving PSL_RF cleared in kernel thread
state
4) lldb tries to restore checkpointed thread state via PT_SETREGS
5) ptrace() returns EINVAL due to attempt to change PSL_RF</pre>
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