4.14-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon will.deacon@arm.com
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: 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 Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/process.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
--- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -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 */