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fpu__clear() currently resets both register state and kernel XSAVE buffer state. It has two modes: one for all state (supervisor and user) and another for user state only. fpu__clear_all() uses the "all state" (user_only=0) mode, while a number of signal paths use the user_only=1 mode. Make fpu__clear() work only for user state (user_only=1) and remove the "all state" (user_only=0) code. Rename it to match so it can be used by the signal paths. Replace the "all state" (user_only=0) fpu__clear() functionality. Use the TIF_NEED_FPU_LOAD functionality instead of making any actual hardware registers changes in this path. Instead of invoking fpu__initialize() just memcpy() init_fpstate into the task's FPU state because that has already the correct format and in case of PKRU also contains the default PKRU value. Move the actual PKRU write out into flush_thread() where it belongs and where it will end up anyway when PKRU and XSTATE have been untangled. For bisectability a workaround is required which stores the PKRU value in the xstate memory until PKRU is untangled from XSTATE for context switching and return to user. [ Dave Hansen: Polished changelog ] [ tglx: Fixed the PKRU fallout ] Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210623121455.922729522@linutronix.de |
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