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

package verify

// abiResult records register-clobber violations detected by the ABI-checking
// trampolines.  Bit 0: frame pointer clobbered.  Bit 1: goroutine pointer
// clobbered.
var abiResult uint64

// ABIReport describes the result of an ABI-checking call.  The register
// fields are architecture-dependent:
//
//   - FPClobbered: the frame pointer the Go runtime maintains
//     (amd64 BP, arm64 R29).  riscv64 and loong64 keep no hardware frame
//     pointer, so the field is always false there.
//   - GClobbered: the goroutine pointer (amd64 R14, arm64 R28,
//     riscv64 X27, loong64 R22).
type ABIReport struct {
	FPClobbered bool
	GClobbered  bool
	RedZoneHit  bool
}

// OK returns true when no violations were detected.
func (r ABIReport) OK() bool {
	return !r.FPClobbered && !r.GClobbered && !r.RedZoneHit
}

// String returns a human-readable summary.
func (r ABIReport) String() string {
	if r.OK() {
		return "ABI clean"
	}
	s := "ABI violation:"
	if r.FPClobbered {
		s += " frame pointer clobbered"
	}
	if r.GClobbered {
		s += " goroutine pointer clobbered"
	}
	if r.RedZoneHit {
		s += " stack below SP written"
	}
	return s
}

// redZoneSize is the canary window below the prepared stack pointer.  On
// amd64 it is the System V red zone; on every architecture a Go function
// must not write below its own declared frame, so the canary sits below
// the frame plus the call margin (see CallCheckedFrame) and any corruption
// there is a bug.
const redZoneSize = 128

// redZoneFill is the byte pattern used to detect writes below SP.
const redZoneFill = 0xA5