csky: Set regs->usp to kernel sp, when the exception is from kernel

In the past, we didn't care about kernel sp when saving pt_reg. But in some
cases, we still need pt_reg->usp to represent the kernel stack before enter
exception.

For cmpxhg in atomic.S, we need save and restore usp for above.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

arch/csky/abiv1/inc/abi/entry.h

@@ -16,14 +16,16 @@
 #define LSAVE_A4	40
 #define LSAVE_A5	44
 
+#define usp ss1
+
 .macro USPTOKSP
-	mtcr	sp, ss1
+	mtcr	sp, usp
 	mfcr	sp, ss0
 .endm
 
 .macro KSPTOUSP
 	mtcr	sp, ss0
-	mfcr	sp, ss1
+	mfcr	sp, usp
 .endm
 
 .macro	SAVE_ALL epc_inc
@@ -45,7 +47,13 @@
 	add	lr, r13
 	stw     lr, (sp, 8)
 
+	mov	lr, sp
+	addi	lr, 32
+	addi	lr, 32
+	addi	lr, 16
+	bt	2f
 	mfcr	lr, ss1
+2:
 	stw     lr, (sp, 16)
 
 	stw     a0, (sp, 20)
@@ -79,9 +87,10 @@
 	ldw     a0, (sp, 12)
 	mtcr    a0, epsr
 	btsti   a0, 31
+	bt      1f
 	ldw     a0, (sp, 16)
 	mtcr	a0, ss1
-
+1:
 	ldw     a0, (sp, 24)
 	ldw     a1, (sp, 28)
 	ldw     a2, (sp, 32)
@@ -102,9 +111,9 @@
 	addi	sp, 32
 	addi	sp, 8
 
-	bt      1f
+	bt      2f
 	KSPTOUSP
-1:
+2:
 	rte
 .endm
 

arch/csky/abiv2/inc/abi/entry.h

@@ -31,7 +31,13 @@
 
 	mfcr	lr, epsr
 	stw	lr, (sp, 12)
+	btsti   lr, 31
+	bf      1f
+	addi    lr, sp, 152
+	br	2f
+1:
 	mfcr	lr, usp
+2:
 	stw	lr, (sp, 16)
 
 	stw     a0, (sp, 20)
@@ -64,8 +70,10 @@
 	mtcr	a0, epc
 	ldw	a0, (sp, 12)
 	mtcr	a0, epsr
+	btsti   a0, 31
 	ldw	a0, (sp, 16)
 	mtcr	a0, usp
+	mtcr	a0, ss0
 
 #ifdef CONFIG_CPU_HAS_HILO
 	ldw	a0, (sp, 140)
@@ -86,6 +94,9 @@
 	addi    sp, 40
 	ldm     r16-r30, (sp)
 	addi    sp, 72
+	bf	1f
+	mfcr	sp, ss0
+1:
 	rte
 .endm
 

arch/csky/kernel/atomic.S

@@ -17,10 +17,12 @@ ENTRY(csky_cmpxchg)
 	mfcr	a3, epc
 	addi	a3, TRAP0_SIZE
 
-	subi    sp, 8
+	subi    sp, 16
 	stw     a3, (sp, 0)
 	mfcr    a3, epsr
 	stw     a3, (sp, 4)
+	mfcr	a3, usp
+	stw     a3, (sp, 8)
 
 	psrset	ee
 #ifdef CONFIG_CPU_HAS_LDSTEX
@@ -47,7 +49,9 @@ ENTRY(csky_cmpxchg)
 	mtcr	a3, epc
 	ldw     a3, (sp, 4)
 	mtcr	a3, epsr
-	addi	sp, 8
+	ldw     a3, (sp, 8)
+	mtcr	a3, usp
+	addi	sp, 16
 	KSPTOUSP
 	rte
 END(csky_cmpxchg)