// SPDX-License-Identifier: GPL-2.0-only
// Copyright (C) 2015-2021 ARM Limited.
// Original author: Dave Martin <Dave.Martin@arm.com>
//
// Utility functions for assembly code.

#include <asm/unistd.h>
#include "assembler.h"

// Print a single character x0 to stdout
// Clobbers x0-x2,x8
function putc
        str     x0, [sp, #-16]!

        mov     x0, #1                  // STDOUT_FILENO
        mov     x1, sp
        mov     x2, #1
        mov     x8, #__NR_write
        svc     #0

        add     sp, sp, #16
        ret
endfunction
.globl  putc
        
// Print a NUL-terminated string starting at address x0 to stdout
// Clobbers x0-x3,x8
function puts
        mov     x1, x0

        mov     x2, #0
0:      ldrb    w3, [x0], #1
        cbz     w3, 1f
        add     x2, x2, #1
        b       0b

1:      mov     w0, #1                  // STDOUT_FILENO
        mov     x8, #__NR_write
        svc     #0

        ret
endfunction
.globl  puts

// Print an unsigned decimal number x0 to stdout
// Clobbers x0-x4,x8
function putdec
        mov     x1, sp
        str     x30, [sp, #-32]!        // Result can't be > 20 digits

        mov     x2, #0
        strb    w2, [x1, #-1]!          // Write the NUL terminator

        mov     x2, #10
0:      udiv    x3, x0, x2              // div-mod loop to generate the digits
        msub    x0, x3, x2, x0
        add     w0, w0, #'0'
        strb    w0, [x1, #-1]!
        mov     x0, x3
        cbnz    x3, 0b

        ldrb    w0, [x1]
        cbnz    w0, 1f
        mov     w0, #'0'                // Print "0" for 0, not ""
        strb    w0, [x1, #-1]!

1:      mov     x0, x1
        bl      puts

        ldr     x30, [sp], #32
        ret
endfunction
.globl  putdec

// Print an unsigned decimal number x0 to stdout, followed by a newline
// Clobbers x0-x5,x8
function putdecn
        mov     x5, x30

        bl      putdec
        mov     x0, #'\n'
        bl      putc

        ret     x5
endfunction
.globl  putdecn

// Clobbers x0-x3,x8
function puthexb
        str     x30, [sp, #-0x10]!

        mov     w3, w0
        lsr     w0, w0, #4
        bl      puthexnibble
        mov     w0, w3

        ldr     x30, [sp], #0x10
        // fall through to puthexnibble
endfunction
.globl  puthexb

// Clobbers x0-x2,x8
function puthexnibble
        and     w0, w0, #0xf
        cmp     w0, #10
        blo     1f
        add     w0, w0, #'a' - ('9' + 1)
1:      add     w0, w0, #'0'
        b       putc
endfunction
.globl  puthexnibble

// x0=data in, x1=size in, clobbers x0-x5,x8
function dumphex
        str     x30, [sp, #-0x10]!

        mov     x4, x0
        mov     x5, x1

0:      subs    x5, x5, #1
        b.lo    1f
        ldrb    w0, [x4], #1
        bl      puthexb
        b       0b

1:      ldr     x30, [sp], #0x10
        ret
endfunction
.globl  dumphex

        // Trivial memory copy: copy x2 bytes, starting at address x1, to address x0.
// Clobbers x0-x3
function memcpy
        cmp     x2, #0
        b.eq    1f
0:      ldrb    w3, [x1], #1
        strb    w3, [x0], #1
        subs    x2, x2, #1
        b.ne    0b
1:      ret
endfunction
.globl  memcpy

// Fill x1 bytes starting at x0 with 0xae (for canary purposes)
// Clobbers x1, x2.
function memfill_ae
        mov     w2, #0xae
        b       memfill
endfunction
.globl  memfill_ae
        
// Fill x1 bytes starting at x0 with 0.
// Clobbers x1, x2.
function memclr
        mov     w2, #0
endfunction
.globl  memclr
        // fall through to memfill

// Trivial memory fill: fill x1 bytes starting at address x0 with byte w2
// Clobbers x1
function memfill
        cmp     x1, #0
        b.eq    1f

0:      strb    w2, [x0], #1
        subs    x1, x1, #1
        b.ne    0b

1:      ret
endfunction
.globl  memfill