csky: Implement ftrace with regs

This patch implements FTRACE_WITH_REGS for csky, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified.

Signed-off-by: Guo Ren <[e-mail]>

arch/csky/Kconfig

···
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_COPY_THREAD_TLS
 	select HAVE_DYNAMIC_FTRACE
+	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FTRACE_MCOUNT_RECORD

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

···
 	rte
 .endm
 
+.macro SAVE_REGS_FTRACE
+	subi    sp, 152
+	stw	tls, (sp, 0)
+	stw	lr, (sp, 4)
+
+	mfcr	lr, psr
+	stw	lr, (sp, 12)
+
+	addi    lr, sp, 152
+	stw	lr, (sp, 16)
+
+	stw     a0, (sp, 20)
+	stw     a0, (sp, 24)
+	stw     a1, (sp, 28)
+	stw     a2, (sp, 32)
+	stw     a3, (sp, 36)
+
+	addi	sp, 40
+	stm	r4-r13, (sp)
+
+	addi    sp, 40
+	stm     r16-r30, (sp)
+#ifdef CONFIG_CPU_HAS_HILO
+	mfhi	lr
+	stw	lr, (sp, 60)
+	mflo	lr
+	stw	lr, (sp, 64)
+	mfcr	lr, cr14
+	stw	lr, (sp, 68)
+#endif
+	subi	sp, 80
+.endm
+
+.macro	RESTORE_REGS_FTRACE
+	ldw	tls, (sp, 0)
+	ldw	a0, (sp, 16)
+	mtcr	a0, ss0
+
+#ifdef CONFIG_CPU_HAS_HILO
+	ldw	a0, (sp, 140)
+	mthi	a0
+	ldw	a0, (sp, 144)
+	mtlo	a0
+	ldw	a0, (sp, 148)
+	mtcr	a0, cr14
+#endif
+
+	ldw     a0, (sp, 24)
+	ldw     a1, (sp, 28)
+	ldw     a2, (sp, 32)
+	ldw     a3, (sp, 36)
+
+	addi	sp, 40
+	ldm	r4-r13, (sp)
+	addi    sp, 40
+	ldm     r16-r30, (sp)
+	addi    sp, 72
+	mfcr	sp, ss0
+.endm
+
 .macro SAVE_SWITCH_STACK
 	subi    sp, 64
 	stm	r4-r11, (sp)

arch/csky/abiv2/mcount.S

···
 
 #include <linux/linkage.h>
 #include <asm/ftrace.h>
+#include <abi/entry.h>
+#include <asm/asm-offsets.h>
 
 /*
  * csky-gcc with -pg will put the following asm after prologue:
···
 	ldw	r8, (sp, 20)
 	ldw	lr, (sp, 24)
 	addi	sp, 28
+	jmp	t1
+.endm
+
+.macro mcount_enter_regs
+	subi	sp, 8
+	stw	lr, (sp, 0)
+	stw	r8, (sp, 4)
+	SAVE_REGS_FTRACE
+.endm
+
+.macro mcount_exit_regs
+	RESTORE_REGS_FTRACE
+	ldw	t1, (sp, 0)
+	ldw	r8, (sp, 4)
+	ldw	lr, (sp, 8)
+	addi	sp, 12
 	jmp	t1
 .endm
 
···
 	ldw	a0, (sp, 16)
 	subi	a0, 4
 	ldw	a1, (sp, 24)
+	lrw	a2, function_trace_op
+	ldw	a2, (a2, 0)
 
 	nop
 GLOBAL(ftrace_call)
···
 	jmp	lr
 END(return_to_handler)
 #endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ENTRY(ftrace_regs_caller)
+	mcount_enter_regs
+
+	lrw	t1, PT_FRAME_SIZE
+	add	t1, sp
+
+	ldw	a0, (t1, 0)
+	subi	a0, 4
+	ldw	a1, (t1, 8)
+	lrw	a2, function_trace_op
+	ldw	a2, (a2, 0)
+	mov	a3, sp
+
+	nop
+GLOBAL(ftrace_regs_call)
+	nop32_stub
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	nop
+GLOBAL(ftrace_graph_regs_call)
+	nop32_stub
+#endif
+
+	mcount_exit_regs
+ENDPROC(ftrace_regs_caller)
+#endif /* CONFIG_DYNAMIC_FTRACE */

arch/csky/include/asm/ftrace.h

···
 
 #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
+#define ARCH_SUPPORTS_FTRACE_OPS 1
+
 #define MCOUNT_ADDR	((unsigned long)_mcount)
 
 #ifndef __ASSEMBLY__

arch/csky/kernel/asm-offsets.c

···
 	DEFINE(PT_RLO,            offsetof(struct pt_regs, rlo));
 #endif
 	DEFINE(PT_USP,            offsetof(struct pt_regs, usp));
+	DEFINE(PT_FRAME_SIZE,     sizeof(struct pt_regs));
 
 	/* offsets into the irq_cpustat_t struct */
 	DEFINE(CPUSTAT_SOFTIRQ_PENDING, offsetof(irq_cpustat_t,

arch/csky/kernel/ftrace.c

···
 {
 	int ret = ftrace_modify_code((unsigned long)&ftrace_call,
 				(unsigned long)func, true, true);
+	if (!ret)
+		ret = ftrace_modify_code((unsigned long)&ftrace_regs_call,
+				(unsigned long)func, true, true);
 	return ret;
 }
 
···
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+		       unsigned long addr)
+{
+	return ftrace_modify_code(rec->ip, addr, true, true);
+}
+#endif
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,