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Commit b0088480 authored by Kevin Hilman's avatar Kevin Hilman Committed by Russell King
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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: default avatarKevin Hilman <khilman@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 4fd75911

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/include/asm/thread_info.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/entry-armv.S

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/entry-common.S

+3 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/entry-header.S

+28 −0
Original line number Diff line number Diff line
@@ -163,6 +163,34 @@ 
	.endm

#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.