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James Morse authored
This reverts commit a1f33941. The unsafe accessors allow the PAN enable/disable calls to be made once for a group of accesses. Adding these means we can now have sequences that look like this: | user_access_begin(); | unsafe_put_user(static-value, x, err); | unsafe_put_user(helper-that-sleeps(), x, err); | user_access_end(); Calling schedule() without taking an exception doesn't switch the PSTATE or TTBRs. We can switch out of a uaccess-enabled region, and run other code with uaccess enabled for a different thread. We can also switch from uaccess-disabled code back into this region, meaning the unsafe_put_user()s will fault. For software-PAN, threads that do this will get stuck as handle_mm_fault() will determine the page has already been mapped in, but we fault again as the page tables aren't loaded. To solve this we need code in __switch_to() that save/restores the PAN state. Acked-by: Julien Thierry <julien.thierry@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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