csky: Fixup add zero_fp fixup perf backtrace panic

We need set fp zero to let backtrace know the end. The patch fixup perf
callchain panic problem, because backtrace didn't know what is the end
of fp.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Reported-by: Mao Han <han_mao@c-sky.com>

arch/csky/kernel/entry.S

@@ -17,6 +17,12 @@
 #define PTE_INDX_SHIFT  10
 #define _PGDIR_SHIFT    22
 
+.macro	zero_fp
+#ifdef CONFIG_STACKTRACE
+	movi	r8, 0
+#endif
+.endm
+
 .macro tlbop_begin name, val0, val1, val2
 ENTRY(csky_\name)
 	mtcr    a3, ss2
@@ -96,6 +102,7 @@ ENTRY(csky_\name)
 	SAVE_ALL 0
 .endm
 .macro tlbop_end is_write
+	zero_fp
 	RD_MEH	a2
 	psrset  ee, ie
 	mov     a0, sp
@@ -120,6 +127,7 @@ tlbop_end 1
 
 ENTRY(csky_systemcall)
 	SAVE_ALL TRAP0_SIZE
+	zero_fp
 
 	psrset  ee, ie
 
@@ -136,9 +144,9 @@ ENTRY(csky_systemcall)
 	mov     r9, sp
 	bmaski  r10, THREAD_SHIFT
 	andn    r9, r10
-	ldw     r8, (r9, TINFO_FLAGS)
-	ANDI_R3	r8, (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
-	cmpnei	r8, 0
+	ldw     r12, (r9, TINFO_FLAGS)
+	ANDI_R3	r12, (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
+	cmpnei	r12, 0
 	bt      csky_syscall_trace
 #if defined(__CSKYABIV2__)
 	subi    sp, 8
@@ -180,7 +188,7 @@ csky_syscall_trace:
 
 ENTRY(ret_from_kernel_thread)
 	jbsr	schedule_tail
-	mov	a0, r8
+	mov	a0, r10
 	jsr	r9
 	jbsr	ret_from_exception
 
@@ -189,9 +197,9 @@ ENTRY(ret_from_fork)
 	mov	r9, sp
 	bmaski	r10, THREAD_SHIFT
 	andn	r9, r10
-	ldw	r8, (r9, TINFO_FLAGS)
-	ANDI_R3	r8, (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
-	cmpnei	r8, 0
+	ldw	r12, (r9, TINFO_FLAGS)
+	ANDI_R3	r12, (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
+	cmpnei	r12, 0
 	bf	ret_from_exception
 	mov	a0, sp			/* sp = pt_regs pointer */
 	jbsr	syscall_trace_exit
@@ -209,9 +217,9 @@ ret_from_exception:
 	bmaski	r10, THREAD_SHIFT
 	andn	r9, r10
 
-	ldw	r8, (r9, TINFO_FLAGS)
-	andi	r8, (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED)
-	cmpnei	r8, 0
+	ldw	r12, (r9, TINFO_FLAGS)
+	andi	r12, (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED)
+	cmpnei	r12, 0
 	bt	exit_work
 1:
 	RESTORE_ALL
@@ -220,18 +228,19 @@ exit_work:
 	lrw	syscallid, ret_from_exception
 	mov	lr, syscallid
 
-	btsti	r8, TIF_NEED_RESCHED
+	btsti	r12, TIF_NEED_RESCHED
 	bt	work_resched
 
 	mov	a0, sp
-	mov	a1, r8
+	mov	a1, r12
 	jmpi	do_notify_resume
 
 work_resched:
 	jmpi	schedule
 
 ENTRY(csky_trap)
 	SAVE_ALL 0
+	zero_fp
 	psrset	ee
 	mov	a0, sp                 /* Push Stack pointer arg */
 	jbsr	trap_c                 /* Call C-level trap handler */
@@ -265,6 +274,7 @@ ENTRY(csky_get_tls)
 
 ENTRY(csky_irq)
 	SAVE_ALL 0
+	zero_fp
 	psrset	ee
 
 #ifdef CONFIG_PREEMPT
@@ -276,21 +286,21 @@ ENTRY(csky_irq)
 	 * Get task_struct->stack.preempt_count for current,
 	 * and increase 1.
 	 */
-	ldw	r8, (r9, TINFO_PREEMPT)
-	addi	r8, 1
-	stw	r8, (r9, TINFO_PREEMPT)
+	ldw	r12, (r9, TINFO_PREEMPT)
+	addi	r12, 1
+	stw	r12, (r9, TINFO_PREEMPT)
 #endif
 
 	mov	a0, sp
 	jbsr	csky_do_IRQ
 
 #ifdef CONFIG_PREEMPT
-	subi	r8, 1
-	stw	r8, (r9, TINFO_PREEMPT)
-	cmpnei	r8, 0
+	subi	r12, 1
+	stw	r12, (r9, TINFO_PREEMPT)
+	cmpnei	r12, 0
 	bt	2f
-	ldw	r8, (r9, TINFO_FLAGS)
-	btsti	r8, TIF_NEED_RESCHED
+	ldw	r12, (r9, TINFO_FLAGS)
+	btsti	r12, TIF_NEED_RESCHED
 	bf	2f
 1:
 	jbsr	preempt_schedule_irq	/* irq en/disable is done inside */

arch/csky/kernel/process.c

@@ -55,7 +55,7 @@ int copy_thread(unsigned long clone_flags,
 	if (unlikely(p->flags & PF_KTHREAD)) {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childstack->r15 = (unsigned long) ret_from_kernel_thread;
-		childstack->r8 = kthread_arg;
+		childstack->r10 = kthread_arg;
 		childstack->r9 = usp;
 		childregs->sr = mfcr("psr");
 	} else {