Bug 85086 - _Unwind_Resume can't unwind shadow stack with thread cancellation and alternate signal stack
Summary: _Unwind_Resume can't unwind shadow stack with thread cancellation and alterna...
Status: RESOLVED INVALID
Alias: None
Product: gcc
Classification: Unclassified
Component: libgcc (show other bugs)
Version: 8.0.1
: P3 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks: 81652
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Reported: 2018-03-26 22:31 UTC by H.J. Lu
Modified: 2018-03-30 17:57 UTC (History)
2 users (show)

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Target: x86
Build:
Known to work:
Known to fail:
Last reconfirmed:

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Description H.J. Lu 2018-03-26 22:31:58 UTC 
On Linux, when alternate signal stack is used with thread cancellation,
_Unwind_Resume fails when it tries to unwind shadow stack from signal
handler on alternate signal stack.  The issue is that signal handler on
alternate signal stack uses a separate shadow stack and we must switch
to the original shadow stack to unwind it. But frame count will be wrong
in this case.  For thread cancellation, there is no need to unwind shadow
stack since it will long jump back and exit.
Comment 1 H.J. Lu 2018-03-30 17:57:32 UTC 
We changing the kernel not to use alternate shadow stack.