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arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks
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: Mark Rutland <mark.rutland@arm.com> Tested-by: Laura Abbott <labbott@redhat.com> Tested-by: Shanker Donthineni <shankerd@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
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@ -370,16 +370,14 @@ void tls_preserve_current_state(void)
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static void tls_thread_switch(struct task_struct *next)
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{
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unsigned long tpidr, tpidrro;
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tls_preserve_current_state();
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tpidr = *task_user_tls(next);
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tpidrro = is_compat_thread(task_thread_info(next)) ?
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next->thread.tp_value : 0;
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if (is_compat_thread(task_thread_info(next)))
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write_sysreg(next->thread.tp_value, tpidrro_el0);
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else if (!arm64_kernel_unmapped_at_el0())
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write_sysreg(0, tpidrro_el0);
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write_sysreg(tpidr, tpidr_el0);
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write_sysreg(tpidrro, tpidrro_el0);
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write_sysreg(*task_user_tls(next), tpidr_el0);
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}
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/* Restore the UAO state depending on next's addr_limit */
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