1/* SPDX-License-Identifier: GPL-2.0 */
  2/* Copyright (C) 2017 Andes Technology Corporation */
  3
  4#include <linux/init.h>
  5#include <linux/linkage.h>
  6#include <asm/asm.h>
  7#include <asm/csr.h>
  8#include <asm/unistd.h>
  9#include <asm/thread_info.h>
 10#include <asm/asm-offsets.h>
 11#include <asm-generic/export.h>
 12#include <asm/ftrace.h>
 13
 14	.text
 15
 16	.macro SAVE_ABI_STATE
 17	addi	sp, sp, -16
 18	sd	s0, 0(sp)
 19	sd	ra, 8(sp)
 20	addi	s0, sp, 16
 21	.endm
 22
 23	/*
 24	 * The call to ftrace_return_to_handler would overwrite the return
 25	 * register if a0 was not saved.
 26	 */
 27	.macro SAVE_RET_ABI_STATE
 28	addi	sp, sp, -32
 29	sd	s0, 16(sp)
 30	sd	ra, 24(sp)
 31	sd	a0, 8(sp)
 32	addi	s0, sp, 32
 33	.endm
 34
 35	.macro RESTORE_ABI_STATE
 36	ld	ra, 8(sp)
 37	ld	s0, 0(sp)
 38	addi	sp, sp, 16
 39	.endm
 40
 41	.macro RESTORE_RET_ABI_STATE
 42	ld	ra, 24(sp)
 43	ld	s0, 16(sp)
 44	ld	a0, 8(sp)
 45	addi	sp, sp, 32
 46	.endm
 47
 48ENTRY(ftrace_stub)
 49#ifdef CONFIG_DYNAMIC_FTRACE
 50       .global _mcount
 51       .set    _mcount, ftrace_stub
 52#endif
 53	ret
 54ENDPROC(ftrace_stub)
 55
 56#ifdef CONFIG_FUNCTION_GRAPH_TRACER
 57ENTRY(return_to_handler)
 58/*
 59 * On implementing the frame point test, the ideal way is to compare the
 60 * s0 (frame pointer, if enabled) on entry and the sp (stack pointer) on return.
 61 * However, the psABI of variable-length-argument functions does not allow this.
 62 *
 63 * So alternatively we check the *old* frame pointer position, that is, the
 64 * value stored in -16(s0) on entry, and the s0 on return.
 65 */
 66#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 67	mv	t6, s0
 68#endif
 69	SAVE_RET_ABI_STATE
 70#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 71	mv	a0, t6
 72#endif
 73	call	ftrace_return_to_handler
 74	mv	a1, a0
 75	RESTORE_RET_ABI_STATE
 76	jalr	a1
 77ENDPROC(return_to_handler)
 78#endif
 79
 80#ifndef CONFIG_DYNAMIC_FTRACE
 81ENTRY(_mcount)
 82	la	t4, ftrace_stub
 83#ifdef CONFIG_FUNCTION_GRAPH_TRACER
 84	la	t0, ftrace_graph_return
 85	ld	t1, 0(t0)
 86	bne	t1, t4, do_ftrace_graph_caller
 87
 88	la	t3, ftrace_graph_entry
 89	ld	t2, 0(t3)
 90	la	t6, ftrace_graph_entry_stub
 91	bne	t2, t6, do_ftrace_graph_caller
 92#endif
 93	la	t3, ftrace_trace_function
 94	ld	t5, 0(t3)
 95	bne	t5, t4, do_trace
 96	ret
 97
 98#ifdef CONFIG_FUNCTION_GRAPH_TRACER
 99/*
100 * A pseudo representation for the function graph tracer:
101 * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
102 */
103do_ftrace_graph_caller:
104	addi	a0, s0, -8
105	mv	a1, ra
106#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
107	ld	a2, -16(s0)
108#endif
109	SAVE_ABI_STATE
110	call	prepare_ftrace_return
111	RESTORE_ABI_STATE
112	ret
113#endif
114
115/*
116 * A pseudo representation for the function tracer:
117 * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
118 */
119do_trace:
120	ld	a1, -8(s0)
121	mv	a0, ra
122
123	SAVE_ABI_STATE
124	jalr	t5
125	RESTORE_ABI_STATE
126	ret
127ENDPROC(_mcount)
128#endif
129EXPORT_SYMBOL(_mcount)