// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

//go:build linux && loong64

package debug

// Regs holds the full general-purpose register set of a traced process
// (the Linux loong64 user_pt_regs layout).
type Regs struct {
	R0  uint64 // zero
	R1  uint64 // RA (return address)
	R2  uint64 // TP (thread pointer)
	R3  uint64 // SP (stack pointer)
	R4  uint64 // A0
	R5  uint64 // A1
	R6  uint64 // A2
	R7  uint64 // A3
	R8  uint64 // A4
	R9  uint64 // A5
	R10 uint64 // A6
	R11 uint64 // A7
	R12 uint64 // T0
	R13 uint64 // T1
	R14 uint64 // T2
	R15 uint64 // T3
	R16 uint64 // T4
	R17 uint64 // T5
	R18 uint64 // T6
	R19 uint64 // T7
	R20 uint64 // T8
	R21 uint64 // FP (frame pointer)
	R22 uint64 // S0
	R23 uint64 // S1
	R24 uint64 // S2
	R25 uint64 // S3
	R26 uint64 // S4
	R27 uint64 // S5
	R28 uint64 // S6
	R29 uint64 // S7
	R30 uint64 // S8
	R31 uint64 // PC
}

// GetPC returns the program counter.
func (r *Regs) GetPC() uint64 { return r.R31 }

// SetPC sets the program counter.
func (r *Regs) SetPC(pc uint64) { r.R31 = pc }

// GetSP returns the stack pointer.
func (r *Regs) GetSP() uint64 { return r.R3 }

// RegValue returns the value of the named register, or false if unknown.
func (r *Regs) RegValue(name string) (uint64, bool) {
	switch name {
	case "r0", "zero":
		return r.R0, true
	case "r1", "ra":
		return r.R1, true
	case "r2", "tp":
		return r.R2, true
	case "r3", "sp":
		return r.R3, true
	case "r4", "a0":
		return r.R4, true
	case "r5", "a1":
		return r.R5, true
	case "r6", "a2":
		return r.R6, true
	case "r7", "a3":
		return r.R7, true
	case "r8", "a4":
		return r.R8, true
	case "r9", "a5":
		return r.R9, true
	case "r10", "a6":
		return r.R10, true
	case "r11", "a7":
		return r.R11, true
	case "r12", "t0":
		return r.R12, true
	case "r13", "t1":
		return r.R13, true
	case "r14", "t2":
		return r.R14, true
	case "r15", "t3":
		return r.R15, true
	case "r16", "t4":
		return r.R16, true
	case "r17", "t5":
		return r.R17, true
	case "r18", "t6":
		return r.R18, true
	case "r19", "t7":
		return r.R19, true
	case "r20", "t8":
		return r.R20, true
	case "r21", "fp":
		return r.R21, true
	case "r22", "s0":
		return r.R22, true
	case "r23", "s1":
		return r.R23, true
	case "r24", "s2":
		return r.R24, true
	case "r25", "s3":
		return r.R25, true
	case "r26", "s4":
		return r.R26, true
	case "r27", "s5":
		return r.R27, true
	case "r28", "s6":
		return r.R28, true
	case "r29", "s7":
		return r.R29, true
	case "r30", "s8":
		return r.R30, true
	case "r31", "pc":
		return r.R31, true
	default:
		return 0, false
	}
}

// breakpointInsn is the software breakpoint instruction (BRK $0).
var breakpointInsn = []byte{0x05, 0x00, 0x2a, 0x00} // break 0

// breakpointPCAdjust is how far PC is past the breakpoint instruction after
// a trap: 0, because the kernel delivers the break SIGTRAP with csr_era
// still on the break instruction.  do_bp passes regs->csr_era straight to
// force_sig_fault(SIGTRAP, TRAP_BRKPT, ...) and never adjusts era on the
// signal path (arch/loongarch/kernel/traps.c).
const breakpointPCAdjust = 0