1 files changed, 131 insertions, 0 deletions
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
new file mode 100644
index 0000000000..8818a8fa9f
--- /dev/null
+++ b/arch/riscv/kernel/mcount.S
@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2017 Andes Technology Corporation */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <linux/cfi_types.h>
+#include <asm/asm.h>
+#include <asm/csr.h>
+#include <asm/unistd.h>
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
+#include <asm-generic/export.h>
+#include <asm/ftrace.h>
+
+	.text
+
+	.macro SAVE_ABI_STATE
+	addi	sp, sp, -16
+	REG_S	s0, 0*SZREG(sp)
+	REG_S	ra, 1*SZREG(sp)
+	addi	s0, sp, 16
+	.endm
+
+	/*
+	 * The call to ftrace_return_to_handler would overwrite the return
+	 * register if a0 was not saved.
+	 */
+	.macro SAVE_RET_ABI_STATE
+	addi	sp, sp, -4*SZREG
+	REG_S	s0, 2*SZREG(sp)
+	REG_S	ra, 3*SZREG(sp)
+	REG_S	a0, 1*SZREG(sp)
+	REG_S	a1, 0*SZREG(sp)
+	addi	s0, sp, 4*SZREG
+	.endm
+
+	.macro RESTORE_ABI_STATE
+	REG_L	ra, 1*SZREG(sp)
+	REG_L	s0, 0*SZREG(sp)
+	addi	sp, sp, 16
+	.endm
+
+	.macro RESTORE_RET_ABI_STATE
+	REG_L	ra, 3*SZREG(sp)
+	REG_L	s0, 2*SZREG(sp)
+	REG_L	a0, 1*SZREG(sp)
+	REG_L	a1, 0*SZREG(sp)
+	addi	sp, sp, 4*SZREG
+	.endm
+
+SYM_TYPED_FUNC_START(ftrace_stub)
+#ifdef CONFIG_DYNAMIC_FTRACE
+       .global MCOUNT_NAME
+       .set    MCOUNT_NAME, ftrace_stub
+#endif
+	ret
+SYM_FUNC_END(ftrace_stub)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+SYM_TYPED_FUNC_START(ftrace_stub_graph)
+	ret
+SYM_FUNC_END(ftrace_stub_graph)
+
+ENTRY(return_to_handler)
+/*
+ * On implementing the frame point test, the ideal way is to compare the
+ * s0 (frame pointer, if enabled) on entry and the sp (stack pointer) on return.
+ * However, the psABI of variable-length-argument functions does not allow this.
+ *
+ * So alternatively we check the *old* frame pointer position, that is, the
+ * value stored in -16(s0) on entry, and the s0 on return.
+ */
+	SAVE_RET_ABI_STATE
+	mv	a0, sp
+	call	ftrace_return_to_handler
+	mv	a2, a0
+	RESTORE_RET_ABI_STATE
+	jalr	a2
+ENDPROC(return_to_handler)
+#endif
+
+#ifndef CONFIG_DYNAMIC_FTRACE
+ENTRY(MCOUNT_NAME)
+	la	t4, ftrace_stub
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	la	t0, ftrace_graph_return
+	REG_L	t1, 0(t0)
+	bne	t1, t4, do_ftrace_graph_caller
+
+	la	t3, ftrace_graph_entry
+	REG_L	t2, 0(t3)
+	la	t6, ftrace_graph_entry_stub
+	bne	t2, t6, do_ftrace_graph_caller
+#endif
+	la	t3, ftrace_trace_function
+	REG_L	t5, 0(t3)
+	bne	t5, t4, do_trace
+	ret
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * A pseudo representation for the function graph tracer:
+ * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
+ */
+do_ftrace_graph_caller:
+	addi	a0, s0, -SZREG
+	mv	a1, ra
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+	REG_L	a2, -2*SZREG(s0)
+#endif
+	SAVE_ABI_STATE
+	call	prepare_ftrace_return
+	RESTORE_ABI_STATE
+	ret
+#endif
+
+/*
+ * A pseudo representation for the function tracer:
+ * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
+ */
+do_trace:
+	REG_L	a1, -SZREG(s0)
+	mv	a0, ra
+
+	SAVE_ABI_STATE
+	jalr	t5
+	RESTORE_ABI_STATE
+	ret
+ENDPROC(MCOUNT_NAME)
+#endif
+EXPORT_SYMBOL(MCOUNT_NAME)