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implement shadow stacks #455

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implement shadow stacks #455

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Commits on Sep 18, 2024

  1. mm: implement VMKernelShadowStack 

    The initialization and pt_flags are a bit special for shadow stack
pages, so this warrants a new `VirtualMapping` implementations.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  2. percpu: allocate an initial shadow stack 

    This shadow stack is used when not using a task's shadow stack.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  3. percpu: setup ISST 

    The interrupt shadow stack table (ISST) is very similar to the
interrupt stack table (IST) except that it contains shadow stack
addresses instead of normal stack addresses.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  4. task: allocate shadow stacks for each task 

    Each task needs to a normal shadow stack and shadow stack used for
exception handling.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  5. idt: add shadow stack pointer to exception context 

    Some exception handlers will need to update the shadow stack, so they
need to know the shadow stack pointer at the time of the exception.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  6. idt: update return address on shadow stack 

    Whenever we update the return address on the shadow stack, we'll also
need to update the return address on the shadow stack.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  7. schedule: switch to special stack during context switches 

    We need to guard against IRQs coming in after switching to the new page tables
and before switching to the new stack.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  8. schedule: switch shadow stacks in context switch 

    Each task has separate shadow stacks, so we need to switch them when
switching tasks.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  9. svsm: enable shadow stack 

    This enables shadow stacks for the BSP.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
    Freax13 committed Sep 18, 2024
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  10. vmsa: enable shadow stacks 

    This enables shadow stacks on the secondary APs.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
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  11. idt: implement #CP handler 

    This exception handler will be executed when the CPU detects a mismatch
between the return address on the stack and the return address on the
shadow stack.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
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  12. shadow_stack: determine support at runtime 

    Trusted CPUID values are hard to come by, so let's just try to enable
CET in CR4 and handle failure gracefully.

Signed-off-by: Tom Dohrmann <erbse.13@gmx.de>
    @Freax13
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