feat(verify): ABI checks on arm64, riscv64 and loong64

Assisted-by: GLM 5.3 Flash

verify/abi_report.go

@@ -0,0 +1,54 @@
+// 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 SP, so any corruption there is a bug.
+const redZoneSize = 128
+
+// redZoneFill is the byte pattern used to detect writes below SP.
+const redZoneFill = 0xA5