/* 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 <linux/export.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/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, -FREGS_SIZE_ON_STACK
        REG_S   ra, FREGS_RA(sp)
        REG_S   s0, FREGS_S0(sp)
        REG_S   a0, FREGS_A0(sp)
        REG_S   a1, FREGS_A1(sp)
        addi    s0, sp, FREGS_SIZE_ON_STACK
        .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, FREGS_RA(sp)
        REG_L   s0, FREGS_S0(sp)
        REG_L   a0, FREGS_A0(sp)
        REG_L   a1, FREGS_A1(sp)
        addi    sp, sp, FREGS_SIZE_ON_STACK
        .endm

SYM_TYPED_FUNC_START(ftrace_stub)
#ifdef CONFIG_DYNAMIC_FTRACE
       .global _mcount
       .set    _mcount, 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)

SYM_FUNC_START(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
SYM_FUNC_END(return_to_handler)
#endif

#ifndef CONFIG_DYNAMIC_FTRACE
SYM_FUNC_START(_mcount)
        la      t4, ftrace_stub
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        la      t0, ftrace_graph_return
        REG_L   t1, 0(t0)
        bne     t1, t4, .Ldo_ftrace_graph_caller

        la      t3, ftrace_graph_entry
        REG_L   t2, 0(t3)
        la      t6, ftrace_graph_entry_stub
        bne     t2, t6, .Ldo_ftrace_graph_caller
#endif
        la      t3, ftrace_trace_function
        REG_L   t5, 0(t3)
        bne     t5, t4, .Ldo_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)
 */
.Ldo_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)
 */
.Ldo_trace:
        REG_L   a1, -SZREG(s0)
        mv      a0, ra

        SAVE_ABI_STATE
        jalr    t5
        RESTORE_ABI_STATE
        ret
SYM_FUNC_END(_mcount)
#endif
EXPORT_SYMBOL(_mcount)