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Commit 2843ade2 authored by Will Deacon's avatar Will Deacon Committed by Greg Kroah-Hartman
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arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks 




Commit 18011eac28c7 upstream.

When unmapping the kernel at EL0, we use tpidrro_el0 as a scratch register
during exception entry from native tasks and subsequently zero it in
the kernel_ventry macro. We can therefore avoid zeroing tpidrro_el0
in the context-switch path for native tasks using the entry trampoline.

Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Tested-by: default avatarLaura Abbott <labbott@redhat.com>
Tested-by: default avatarShanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4e29f25b

arch/arm64/kernel/process.c

+5 −7
Original line number Diff line number Diff line
@@ -314,16 +314,14 @@ void tls_preserve_current_state(void) 


static void tls_thread_switch(struct task_struct *next)

{

	unsigned long tpidr, tpidrro;



	tls_preserve_current_state();



	tpidr = *task_user_tls(next);

	tpidrro = is_compat_thread(task_thread_info(next)) ?

		  next->thread.tp_value : 0;

	if (is_compat_thread(task_thread_info(next)))

		write_sysreg(next->thread.tp_value, tpidrro_el0);

	else if (!arm64_kernel_unmapped_at_el0())

		write_sysreg(0, tpidrro_el0);



	write_sysreg(tpidr, tpidr_el0);

	write_sysreg(tpidrro, tpidrro_el0);

	write_sysreg(*task_user_tls(next), tpidr_el0);

}



/* Restore the UAO state depending on next's addr_limit */