arm64: enable context tracking

Make calls to ct_user_enter when the kernel is exited
and ct_user_exit when the kernel is entered (in el0_da,
el0_ia, el0_svc, el0_irq and all of the "error" paths).

These macros expand to function calls which will only work
properly if el0_sync and related code has been rearranged
(in a previous patch of this series).

The calls to ct_user_exit are made after hw debugging has been
enabled (enable_dbg_and_irq).

The call to ct_user_enter is made at the beginning of the
kernel_exit macro.

This patch is based on earlier work by Kevin Hilman.
Save/restore optimizations were also done by Kevin.

Acked-by: Will Deacon <[e-mail]>
Reviewed-by: Kevin Hilman <[e-mail]>
Tested-by: Kevin Hilman <[e-mail]>
Signed-off-by: Larry Bassel <[e-mail]>
Signed-off-by: Kevin Hilman <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>
Signed-off-by: Catalin Marinas <[e-mail]>

arch/arm64/Kconfig

···
 	select RTC_LIB
 	select SPARSE_IRQ
 	select SYSCTL_EXCEPTION_TRACE
+	select HAVE_CONTEXT_TRACKING
 	help
 	  ARM 64-bit (AArch64) Linux support.
 

arch/arm64/include/asm/thread_info.h

···
 #define TIF_NEED_RESCHED	1
 #define TIF_NOTIFY_RESUME	2	/* callback before returning to user */
 #define TIF_FOREIGN_FPSTATE	3	/* CPU's FP state is not current's */
+#define TIF_NOHZ		7
 #define TIF_SYSCALL_TRACE	8
 #define TIF_SYSCALL_AUDIT	9
 #define TIF_SYSCALL_TRACEPOINT	10
···
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_FOREIGN_FPSTATE	(1 << TIF_FOREIGN_FPSTATE)
+#define _TIF_NOHZ		(1 << TIF_NOHZ)
 #define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
···
 				 _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE)
 
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
-				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP)
+				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
+				 _TIF_NOHZ)
 
 #endif /* __KERNEL__ */
 #endif /* __ASM_THREAD_INFO_H */

arch/arm64/kernel/entry.S

···
 #include <asm/unistd32.h>
 
 /*
+ * Context tracking subsystem.  Used to instrument transitions
+ * between user and kernel mode.
+ */
+	.macro ct_user_exit, syscall = 0
+#ifdef CONFIG_CONTEXT_TRACKING
+	bl	context_tracking_user_exit
+	.if \syscall == 1
+	/*
+	 * Save/restore needed during syscalls.  Restore syscall arguments from
+	 * the values already saved on stack during kernel_entry.
+	 */
+	ldp	x0, x1, [sp]
+	ldp	x2, x3, [sp, #S_X2]
+	ldp	x4, x5, [sp, #S_X4]
+	ldp	x6, x7, [sp, #S_X6]
+	.endif
+#endif
+	.endm
+
+	.macro ct_user_enter
+#ifdef CONFIG_CONTEXT_TRACKING
+	bl	context_tracking_user_enter
+#endif
+	.endm
+
+/*
  * Bad Abort numbers
  *-----------------
  */
···
 	.macro	kernel_exit, el, ret = 0
 	ldp	x21, x22, [sp, #S_PC]		// load ELR, SPSR
 	.if	\el == 0
+	ct_user_enter
 	ldr	x23, [sp, #S_SP]		// load return stack pointer
 	.endif
 	.if	\ret
···
 	mrs	x26, far_el1
 	// enable interrupts before calling the main handler
 	enable_dbg_and_irq
+	ct_user_exit
 	bic	x0, x26, #(0xff << 56)
 	mov	x1, x25
 	mov	x2, sp
···
 	mrs	x26, far_el1
 	// enable interrupts before calling the main handler
 	enable_dbg_and_irq
+	ct_user_exit
 	mov	x0, x26
 	orr	x1, x25, #1 << 24		// use reserved ISS bit for instruction aborts
 	mov	x2, sp
···
 	 * Floating Point or Advanced SIMD access
 	 */
 	enable_dbg
+	ct_user_exit
 	mov	x0, x25
 	mov	x1, sp
 	adr	lr, ret_to_user
···
 	 * Floating Point or Advanced SIMD exception
 	 */
 	enable_dbg
+	ct_user_exit
 	mov	x0, x25
 	mov	x1, sp
 	adr	lr, ret_to_user
···
 	 */
 	// enable interrupts before calling the main handler
 	enable_dbg_and_irq
+	ct_user_exit
 	mov	x0, sp
 	adr	lr, ret_to_user
 	b	do_undefinstr
···
 	mov	x2, sp
 	bl	do_debug_exception
 	enable_dbg
+	ct_user_exit
 	b	ret_to_user
 el0_inv:
 	enable_dbg
+	ct_user_exit
 	mov	x0, sp
 	mov	x1, #BAD_SYNC
 	mrs	x2, esr_el1
···
 	bl	trace_hardirqs_off
 #endif
 
+	ct_user_exit
 	irq_handler
 
 #ifdef CONFIG_TRACE_IRQFLAGS
···
 el0_svc_naked:					// compat entry point
 	stp	x0, scno, [sp, #S_ORIG_X0]	// save the original x0 and syscall number
 	enable_dbg_and_irq
+	ct_user_exit 1
 
 	ldr	x16, [tsk, #TI_FLAGS]		// check for syscall hooks
 	tst	x16, #_TIF_SYSCALL_WORK