[PATCH v8 10/14] arch/arm64: adopt prepare_exit_to_usermode() model from x86

Chris Metcalf
2015-10-20T20:37:26Z

This change is a prerequisite change for TASK_ISOLATION but also
stands on its own for readability and maintainability. The existing
arm64 do_notify_resume() is called in a loop from assembly on
the slow path; this change moves the loop into C code as well.
For the x86 version see commit c5c46f59e4e7 ("x86/entry: Add new,
comprehensible entry and exit handlers written in C").

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
---
arch/arm64/kernel/entry.S | 6 +++---
arch/arm64/kernel/signal.c | 32 ++++++++++++++++++++++----------
2 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 4306c937b1ff..6fcbf8ea307b 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -628,9 +628,8 @@ work_pending:
mov x0, sp // 'regs'
tst x2, #PSR_MODE_MASK // user mode regs?
b.ne no_work_pending // returning to kernel
- enable_irq // enable interrupts for do_notify_resume()
- bl do_notify_resume
- b ret_to_user
+ bl prepare_exit_to_usermode
+ b no_user_work_pending
work_resched:
bl schedule

@@ -642,6 +641,7 @@ ret_to_user:
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
+no_user_work_pending:
enable_step_tsk x1, x2
no_work_pending:
kernel_exit 0
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index e18c48cb6db1..fde59c1139a9 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -399,18 +399,30 @@ static void do_signal(struct pt_regs *regs)
restore_saved_sigmask();
}

-asmlinkage void do_notify_resume(struct pt_regs *regs,
- unsigned int thread_flags)
+asmlinkage void prepare_exit_to_usermode(struct pt_regs *regs,
+ unsigned int thread_flags)
{
- if (thread_flags & _TIF_SIGPENDING)
- do_signal(regs);
+ do {
+ local_irq_enable();

- if (thread_flags & _TIF_NOTIFY_RESUME) {
- clear_thread_flag(TIF_NOTIFY_RESUME);
- tracehook_notify_resume(regs);
- }
+ if (thread_flags & _TIF_NEED_RESCHED)
+ schedule();
+
+ if (thread_flags & _TIF_SIGPENDING)
+ do_signal(regs);
+
+ if (thread_flags & _TIF_NOTIFY_RESUME) {
+ clear_thread_flag(TIF_NOTIFY_RESUME);
+ tracehook_notify_resume(regs);
+ }
+
+ if (thread_flags & _TIF_FOREIGN_FPSTATE)
+ fpsimd_restore_current_state();
+
+ local_irq_disable();

- if (thread_flags & _TIF_FOREIGN_FPSTATE)
- fpsimd_restore_current_state();
+ thread_flags = READ_ONCE(current_thread_info()->flags) &
+ _TIF_WORK_MASK;

+ } while (thread_flags);
}
--
2.1.2