diff options
| author | Will Deacon <will.deacon@arm.com> | 2017-11-14 14:33:28 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@google.com> | 2018-01-06 11:14:01 +0100 |
| commit | 59eae0dbcf6c0cfb428f2bfb167af8a281026a05 (patch) | |
| tree | ae43f9f818526f634afb3ffa3437825e761b011a /arch | |
| parent | c6e2ad951f73e59defd13ec4c8b2285557ee0193 (diff) | |
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: 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>
(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: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/kernel/process.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 5ac462f222f8..dfbabc0e274b 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -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 */ |