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

//go:build freebsd && amd64

package debug

// Regs holds the full general-purpose register set of a traced process
// (the FreeBSD amd64 struct reg layout, sys/x86/include/reg.h).  FreeBSD
// reports segment selectors (FS/GS/ES/DS), not the bases the Linux ptrace
// surface carries, and has no ORIG_RAX slot.
type Regs struct {
	R15    uint64
	R14    uint64
	R13    uint64
	R12    uint64
	RBP    uint64
	RBX    uint64
	R11    uint64
	R10    uint64
	R9     uint64
	R8     uint64
	RAX    uint64
	RCX    uint64
	RDX    uint64
	RSI    uint64
	RDI    uint64
	RIP    uint64
	CS     uint64
	RFLAGS uint64
	RSP    uint64
	SS     uint64
	FS     uint64
	GS     uint64
	DS     uint64
	ES     uint64
}

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

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

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

// RegValue returns the value of the named register, or false if unknown.
func (r *Regs) RegValue(name string) (uint64, bool) {
	switch name {
	case "rax", "eax", "ax", "al":
		return r.RAX, true
	case "rbx", "ebx", "bx", "bl":
		return r.RBX, true
	case "rcx", "ecx", "cx", "cl":
		return r.RCX, true
	case "rdx", "edx", "dx", "dl":
		return r.RDX, true
	case "rsi", "esi", "si":
		return r.RSI, true
	case "rdi", "edi", "di":
		return r.RDI, true
	case "rbp", "ebp", "bp":
		return r.RBP, true
	case "rsp", "esp", "sp":
		return r.RSP, true
	case "r8":
		return r.R8, true
	case "r9":
		return r.R9, true
	case "r10":
		return r.R10, true
	case "r11":
		return r.R11, true
	case "r12":
		return r.R12, true
	case "r13":
		return r.R13, true
	case "r14":
		return r.R14, true
	case "r15":
		return r.R15, true
	case "rip", "eip":
		return r.RIP, true
	default:
		return 0, false
	}
}

// breakpointInsn is the software breakpoint instruction.
var breakpointInsn = []byte{0xCC} // INT3

// breakpointPCAdjust is how far PC is past the breakpoint instruction after
// a trap.  INT3 leaves the hardware PC on the following instruction (Intel
// SDM vol 3, "Debug Exceptions") and the FreeBSD T_BPTFLT path delivers
// that frame unmodified (sys/amd64/amd64/trap.c), so the trap address is
// PC-1, the same correction the Linux side applies.
const breakpointPCAdjust = 1