Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 59eae0db authored by Will Deacon's avatar Will Deacon Committed by Greg Kroah-Hartman
Browse files

FROMLIST: 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: 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>
(cherry picked from git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git


 commit 18011eac28c7cb31c87b86b7d0e5b01894405c7f)

Change-Id: Ief7b4099f055420a7a23c8dcf497269192f5fb58
[ghackmann@google.com: adjust context]
Signed-off-by: default avatarGreg Hackmann <ghackmann@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@google.com>
parent c6e2ad95

arch/arm64/kernel/process.c

+6 −8
Original line number Diff line number Diff line
@@ -376,19 +376,17 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start, 


static void tls_thread_switch(struct task_struct *next)

{

	unsigned long tpidr, tpidrro;

	unsigned long tpidr;



	asm("mrs %0, tpidr_el0" : "=r" (tpidr));

	*task_user_tls(current) = tpidr;



	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);



	asm(

	"	msr	tpidr_el0, %0\n"

	"	msr	tpidrro_el0, %1"

	: : "r" (tpidr), "r" (tpidrro));

	write_sysreg(*task_user_tls(next), tpidr_el0);

}



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