UPSTREAM: 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 commit 18011eac28c7cb31c87b86b7d0e5b01894405c7f)
[toddpoynor@google.com: fixup context]
Change-Id: I4a0ded2e339b0c75521bc3b5a7fbbb3e60aa8774
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Git-commit: da1016a5635158113253b3dc420c25d289193c1d
Git-repo: https://android.googlesource.com/kernel/common/
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 5fe594e..e74ec9c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -366,17 +366,17 @@ 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;
tpidr = read_sysreg(tpidr_el0);
*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);
- 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 */