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SubjectRe: [PATCH v2 5/7] x86/mm, tracing: Fix CR2 corruption
On Thu, Jul 4, 2019 at 1:03 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> Despire the current efforts to read CR2 before tracing happens there
> still exist a number of possible holes:
>
> idtentry page_fault do_page_fault has_error_code=1
> call error_entry
> TRACE_IRQS_OFF
> call trace_hardirqs_off*
> #PF // modifies CR2
>
> CALL_enter_from_user_mode
> __context_tracking_exit()
> trace_user_exit(0)
> #PF // modifies CR2
>
> call do_page_fault
> address = read_cr2(); /* whoopsie */
>
> And similar for i386.
>
> Fix it by pulling the CR2 read into the entry code, before any of that
> stuff gets a chance to run and ruin things.

Reviewed-by: Andy Lutomirski <luto@kernel.org>

Subject to the discussion as to whether this is the right approach at all.

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