csky: Reconstruct signal processing

Linux kernel has provided some apis for arch signal's implementation.
For example:
	restore_saved_sigmask()
	set_current_blocked()
	restore_altstack()

But in last version of csky signal.c didn't use them and some codes are
confusing, so reconstruct signal.c with reference to riscv's code.

Now csky signal.c implementation are very close to riscv and we can
get the following benefits:
 - Clear code structure
 - The signal code of riscv and csky can be reviewed together
 - Promoting the unification of arch's signal implementation

Also modified the related code in entry.S
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Arnd Bergmann <arnd@arndb.de>

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

@@ -16,9 +16,6 @@
 #define LSAVE_A4	40
 #define LSAVE_A5	44
 
-#define EPC_INCREASE	2
-#define EPC_KEEP	0
-
 .macro USPTOKSP
 	mtcr	sp, ss1
 	mfcr	sp, ss0
@@ -29,10 +26,6 @@
 	mfcr	sp, ss1
 .endm
 
-.macro INCTRAP	rx
-	addi	\rx, EPC_INCREASE
-.endm
-
 .macro	SAVE_ALL epc_inc
 	mtcr    r13, ss2
 	mfcr    r13, epsr

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

@@ -21,4 +21,6 @@
 
 #define SYSTRACE_SAVENUM	2
 
+#define TRAP0_SIZE		2
+
 #endif /* __ASM_CSKY_REGDEF_H */

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

@@ -14,18 +14,11 @@
 #define LSAVE_A2	32
 #define LSAVE_A3	36
 
-#define EPC_INCREASE	4
-#define EPC_KEEP	0
-
 #define KSPTOUSP
 #define USPTOKSP
 
 #define usp cr<14, 1>
 
-.macro INCTRAP	rx
-	addi	\rx, EPC_INCREASE
-.endm
-
 .macro SAVE_ALL epc_inc
 	subi    sp, 152
 	stw	tls, (sp, 0)

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

@@ -21,4 +21,6 @@
 
 #define SYSTRACE_SAVENUM	5
 
+#define TRAP0_SIZE		4
+
 #endif /* __ASM_CSKY_REGDEF_H */

arch/csky/kernel/atomic.S

@@ -12,11 +12,10 @@
  * If *ptr != oldval && return 1,
  * else *ptr = newval return 0.
  */
-#ifdef CONFIG_CPU_HAS_LDSTEX
 ENTRY(csky_cmpxchg)
 	USPTOKSP
 	mfcr	a3, epc
-	INCTRAP	a3
+	addi	a3, TRAP0_SIZE
 
 	subi    sp, 8
 	stw     a3, (sp, 0)
@@ -24,6 +23,7 @@ ENTRY(csky_cmpxchg)
 	stw     a3, (sp, 4)
 
 	psrset	ee
+#ifdef CONFIG_CPU_HAS_LDSTEX
 1:
 	ldex	a3, (a2)
 	cmpne	a0, a3
@@ -33,27 +33,7 @@ ENTRY(csky_cmpxchg)
 	bez	a3, 1b
 2:
 	sync.is
-	mvc	a0
-	ldw	a3, (sp, 0)
-	mtcr	a3, epc
-	ldw     a3, (sp, 4)
-	mtcr	a3, epsr
-	addi	sp, 8
-	KSPTOUSP
-	rte
-END(csky_cmpxchg)
 #else
-ENTRY(csky_cmpxchg)
-	USPTOKSP
-	mfcr	a3, epc
-	INCTRAP	a3
-
-	subi    sp, 8
-	stw     a3, (sp, 0)
-	mfcr    a3, epsr
-	stw     a3, (sp, 4)
-
-	psrset	ee
 1:
 	ldw	a3, (a2)
 	cmpne	a0, a3
@@ -61,6 +41,7 @@ ENTRY(csky_cmpxchg)
 2:
 	stw	a1, (a2)
 3:
+#endif
 	mvc	a0
 	ldw	a3, (sp, 0)
 	mtcr	a3, epc
@@ -71,6 +52,7 @@ ENTRY(csky_cmpxchg)
 	rte
 END(csky_cmpxchg)
 
+#ifndef CONFIG_CPU_HAS_LDSTEX
 /*
  * Called from tlbmodified exception
  */

arch/csky/kernel/entry.S

@@ -91,7 +91,7 @@ ENTRY(csky_\name)
 	mfcr    a3, ss2
 	mfcr    r6, ss3
 	mfcr    a2, ss4
-	SAVE_ALL EPC_KEEP
+	SAVE_ALL 0
 .endm
 .macro tlbop_end is_write
 	RD_MEH	a2
@@ -117,7 +117,7 @@ jbsr csky_cmpxchg_fixup
 tlbop_end 1
 
 ENTRY(csky_systemcall)
-	SAVE_ALL EPC_INCREASE
+	SAVE_ALL TRAP0_SIZE
 
 	psrset  ee, ie
 
@@ -190,11 +190,9 @@ ENTRY(ret_from_fork)
 	ldw	r8, (r9, TINFO_FLAGS)
 	ANDI_R3	r8, (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
 	cmpnei	r8, 0
-	bf	3f
+	bf	ret_from_exception
 	mov	a0, sp			/* sp = pt_regs pointer */
 	jbsr	syscall_trace_exit
-3:
-	jbsr	ret_from_exception
 
 ret_from_exception:
 	ld	syscallid, (sp, LSAVE_PSR)
@@ -209,34 +207,29 @@ ret_from_exception:
 	bmaski	r10, THREAD_SHIFT
 	andn	r9, r10
 
-resume_userspace:
 	ldw	r8, (r9, TINFO_FLAGS)
 	andi	r8, (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED)
 	cmpnei	r8, 0
 	bt	exit_work
-1:  RESTORE_ALL
+1:
+	RESTORE_ALL
 
 exit_work:
+	lrw	syscallid, ret_from_exception
+	mov	lr, syscallid
+
 	btsti	r8, TIF_NEED_RESCHED
 	bt	work_resched
-	/* If thread_info->flag is empty, RESTORE_ALL */
-	cmpnei	r8, 0
-	bf	1b
-	mov	a0, r8
-	mov	a1, sp
-	jbsr	do_notify_resume	/* do signals */
-	br	resume_userspace
+
+	mov	a0, sp
+	mov	a1, r8
+	jmpi	do_notify_resume
 
 work_resched:
-	lrw	syscallid, ret_from_exception
-	mov	r15, syscallid		/* Return address in link */
 	jmpi	schedule
 
-ENTRY(sys_rt_sigreturn)
-	jmpi	do_rt_sigreturn
-
 ENTRY(csky_trap)
-	SAVE_ALL EPC_KEEP
+	SAVE_ALL 0
 	psrset	ee
 	mov	a0, sp                 /* Push Stack pointer arg */
 	jbsr	trap_c                 /* Call C-level trap handler */
@@ -252,7 +245,7 @@ ENTRY(csky_get_tls)
 
 	/* increase epc for continue */
 	mfcr	a0, epc
-	INCTRAP	a0
+	addi	a0, TRAP0_SIZE
 	mtcr	a0, epc
 
 	/* get current task thread_info with kernel 8K stack */
@@ -269,7 +262,7 @@ ENTRY(csky_get_tls)
 	rte
 
 ENTRY(csky_irq)
-	SAVE_ALL EPC_KEEP
+	SAVE_ALL 0
 	psrset	ee
 
 #ifdef CONFIG_PREEMPT