ARM: 7688/1: add support for context tracking subsystem

commit 91d1aa43 (context_tracking: New context tracking susbsystem)
generalized parts of the RCU userspace extended quiescent state into
the context tracking subsystem.  Context tracking is then used
to implement adaptive tickless (a.k.a extended nohz)

To support the new context tracking subsystem on ARM, the user/kernel
boundary transtions need to be instrumented.

For exceptions and IRQs in usermode, the existing usr_entry macro is
used to instrument the user->kernel transition.  For the return to
usermode path, the ret_to_user* path is instrumented.  Using the
usr_entry macro, this covers interrupts in userspace, data abort and
prefetch abort exceptions in userspace as well as undefined exceptions
in userspace (which is where FP emulation and VFP are handled.)

For syscalls, the slow return path is covered by instrumenting the
ret_to_user path.  In addition, the syscall entry point is
instrumented which covers the user->kernel transition for both fast
and slow syscalls, and an additional instrumentation point is added
for the fast syscall return path (ret_fast_syscall).

Cc: Mats Liljegren <mats.liljegren@enea.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

5 files changed, 34 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 5b714695b01b..7dc4cabc34d7 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -59,6 +59,7 @@ config ARM
         select CLONE_BACKWARDS
         select OLD_SIGSUSPEND3
         select OLD_SIGACTION
+        select HAVE_CONTEXT_TRACKING
         help
           The ARM series is a line of low-power-consumption RISC chip designs
           licensed by ARM Ltd and targeted at embedded applications and
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index cddda1f41f0f..1995d1a84060 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -152,6 +152,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define TIF_SYSCALL_AUDIT       9
 #define TIF_SYSCALL_TRACEPOINT  10
 #define TIF_SECCOMP             11      /* seccomp syscall filtering active */
+#define TIF_NOHZ                12      /* in adaptive nohz mode */
 #define TIF_USING_IWMMXT        17
 #define TIF_MEMDIE              18      /* is terminating due to OOM killer */
 #define TIF_RESTORE_SIGMASK     20
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 0f82098c9bfe..2b1de1b2f132 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -396,6 +396,7 @@ ENDPROC(__pabt_svc)
 #ifdef CONFIG_IRQSOFF_TRACER
         bl      trace_hardirqs_off
 #endif
+        ct_user_exit save = 0
         .endm
 
         .macro  kuser_cmpxchg_check
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 3248cde504ed..469e82b3f757 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -41,6 +41,7 @@ ret_fast_syscall:
 
         /* perform architecture specific actions before user return */
         arch_ret_to_user r1, lr
+        ct_user_enter
 
         restore_user_regs fast = 1, offset = S_OFF
  UNWIND(.fnend          )
@@ -76,6 +77,7 @@ no_work_pending:
 #endif
         /* perform architecture specific actions before user return */
         arch_ret_to_user r1, lr
+        ct_user_enter save = 0
 
         restore_user_regs fast = 0, offset = 0
 ENDPROC(ret_to_user_from_irq)
@@ -394,6 +396,7 @@ ENTRY(vector_swi)
         mcr     p15, 0, ip, c1, c0              @ update control register
 #endif
         enable_irq
+        ct_user_exit
 
         get_thread_info tsk
         adr     tbl, sys_call_table             @ load syscall table pointer
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 9a8531eadd3d..782a94956286 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -164,6 +164,34 @@
 #endif  /* !CONFIG_THUMB2_KERNEL */
 
 /*
+ * Context tracking subsystem.  Used to instrument transitions
+ * between user and kernel mode.
+ */
+        .macro ct_user_exit, save = 1
+#ifdef CONFIG_CONTEXT_TRACKING
+        .if     \save
+        stmdb   sp!, {r0-r3, ip, lr}
+        bl      user_exit
+        ldmia   sp!, {r0-r3, ip, lr}
+        .else
+        bl      user_exit
+        .endif
+#endif
+        .endm
+
+        .macro ct_user_enter, save = 1
+#ifdef CONFIG_CONTEXT_TRACKING
+        .if     \save
+        stmdb   sp!, {r0-r3, ip, lr}
+        bl      user_enter
+        ldmia   sp!, {r0-r3, ip, lr}
+        .else
+        bl      user_enter
+        .endif
+#endif
+        .endm
+
+/*
  * These are the registers used in the syscall handler, and allow us to
  * have in theory up to 7 arguments to a function - r0 to r6.
  *