// SPDX-FileCopyrightText: 2024 Tillitis AB <tillitis.se>
// SPDX-License-Identifier: BSD-2-Clause

#include "../tk1/picorv32/custom_ops.S"

	.section ".text"
	.globl syscall


syscall:
	// Save registers to stack
	addi sp, sp, -32*4
	sw x0, 0*4(sp)
	sw x1, 1*4(sp)
	// x2 (sp) is assumed to be preserved by the interrupt handler.
	sw x3, 3*4(sp)
	sw x4, 4*4(sp)
	sw x5, 5*4(sp)
	sw x6, 6*4(sp)
	sw x7, 7*4(sp)
	sw x8, 8*4(sp)
	sw x9, 9*4(sp)
	// x10 (a0) will contain syscall return value. And should not be saved.
	sw x11, 11*4(sp)
	sw x12, 12*4(sp)
	sw x13, 13*4(sp)
	sw x14, 14*4(sp)
	sw x15, 15*4(sp)
	sw x16, 16*4(sp)
	sw x17, 17*4(sp)
	sw x18, 18*4(sp)
	sw x19, 19*4(sp)
	sw x20, 20*4(sp)
	sw x21, 21*4(sp)
	sw x22, 22*4(sp)
	sw x23, 23*4(sp)
	sw x24, 24*4(sp)
	sw x25, 25*4(sp)
	sw x26, 26*4(sp)
	sw x27, 27*4(sp)
	sw x28, 28*4(sp)
	sw x29, 29*4(sp)
	sw x30, 30*4(sp)
	sw x31, 31*4(sp)

	// Trigger syscall interrupt
	li t1, 0xe1000000 // Syscall interrupt trigger address
	sw zero, 0(t1) // Trigger interrupt

	// Restore registers from stack
	lw x0, 0*4(sp)
	lw x1, 1*4(sp)
	// x2 (sp) is assumed to be preserved by the interrupt handler.
	lw x3, 3*4(sp)
	lw x4, 4*4(sp)
	lw x5, 5*4(sp)
	lw x6, 6*4(sp)
	lw x7, 7*4(sp)
	lw x8, 8*4(sp)
	lw x9, 9*4(sp)
	// x10 (a0) contains syscall return value. And should not be destroyed.
	lw x11, 11*4(sp)
	lw x12, 12*4(sp)
	lw x13, 13*4(sp)
	lw x14, 14*4(sp)
	lw x15, 15*4(sp)
	lw x16, 16*4(sp)
	lw x17, 17*4(sp)
	lw x18, 18*4(sp)
	lw x19, 19*4(sp)
	lw x20, 20*4(sp)
	lw x21, 21*4(sp)
	lw x22, 22*4(sp)
	lw x23, 23*4(sp)
	lw x24, 24*4(sp)
	lw x25, 25*4(sp)
	lw x26, 26*4(sp)
	lw x27, 27*4(sp)
	lw x28, 28*4(sp)
	lw x29, 29*4(sp)
	lw x30, 30*4(sp)
	lw x31, 31*4(sp)
	addi sp, sp, 32*4

	ret