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    SubjectRe: [PATCH 00/10] Control Flow Enforcement - Part (3)
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    On Thu, 2018-06-14 at 07:56 -0700, Yu-cheng Yu wrote:
    > On Thu, 2018-06-14 at 11:07 +1000, Balbir Singh wrote:
    > > On Tue, 2018-06-12 at 08:03 -0700, Yu-cheng Yu wrote:
    > > > On Tue, 2018-06-12 at 20:56 +1000, Balbir Singh wrote:
    > > > >
    > > > > On 08/06/18 00:37, Yu-cheng Yu wrote:
    > > > > > This series introduces CET - Shadow stack
    > > > > >
    > > > > > At the high level, shadow stack is:
    > > > > >
    > > > > > Allocated from a task's address space with vm_flags VM_SHSTK;
    > > > > > Its PTEs must be read-only and dirty;
    > > > > > Fixed sized, but the default size can be changed by sys admin.
    > > > > >
    > > > > > For a forked child, the shadow stack is duplicated when the next
    > > > > > shadow stack access takes place.
    > > > > >
    > > > > > For a pthread child, a new shadow stack is allocated.
    > > > > >
    > > > > > The signal handler uses the same shadow stack as the main program.
    > > > > >
    > > > >
    > > > > Even with sigaltstack()?
    > > > >
    > > >
    > > > Yes.
    > >
    > > I am not convinced that it would work, as we switch stacks, oveflow might
    > > be an issue. I also forgot to bring up setcontext(2), I presume those
    > > will get new shadow stacks
    >
    > Do you mean signal stack/sigaltstack overflow or swapcontext in a signal
    > handler?
    >

    I meant any combination of that. If there is a user space threads implementation that uses sigaltstack for switching threads

    Balbir Singh.

    > Yu-cheng
    >

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