From 897f2bc5fd030daa0c73dc5a530a0537ae5460f2 Mon Sep 17 00:00:00 2001
From: "MakKi (makki_d)" <d.makiuchi+gh@gmail.com>
Date: Thu, 18 Dec 2025 04:05:43 +0900
Subject: [PATCH] runtime: avoid fixed math/rand sequence on RP2040/RP2350
 (#5124)

* runtime: avoid fixed math/rand sequence on RP2040/RP2350

* fix typo
---
 src/runtime/rand_norng.go |  2 +-
 src/runtime/rand_rp2.go   | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 src/runtime/rand_rp2.go

diff --git a/src/runtime/rand_norng.go b/src/runtime/rand_norng.go
index aa79c500d..ebeba91cb 100644
--- a/src/runtime/rand_norng.go
+++ b/src/runtime/rand_norng.go
@@ -1,4 +1,4 @@
-//go:build baremetal && !(nrf || (stm32 && !(stm32f103 || stm32l0x1)) || (sam && atsamd51) || (sam && atsame5x) || esp32c3 || tkey || (tinygo.riscv32 && virt))
+//go:build baremetal && !(nrf || (stm32 && !(stm32f103 || stm32l0x1)) || (sam && atsamd51) || (sam && atsame5x) || esp32c3 || tkey || (tinygo.riscv32 && virt) || rp2040 || rp2350)
 
 package runtime
 
diff --git a/src/runtime/rand_rp2.go b/src/runtime/rand_rp2.go
new file mode 100644
index 000000000..89af3f98f
--- /dev/null
+++ b/src/runtime/rand_rp2.go
@@ -0,0 +1,20 @@
+//go:build rp2040 || rp2350
+
+package runtime
+
+import "machine"
+
+var hardwareRandValue uint64
+
+func hardwareRand() (n uint64, ok bool) {
+	if hardwareRandValue == 0 {
+		n1, _ := machine.GetRNG()
+		n2, _ := machine.GetRNG()
+		hardwareRandValue = uint64(n1)<<32 | uint64(n2)
+	}
+
+	// Return ok=false to keep using fastrand64(),
+	// with hardwareRandVal used only as its initial random state.
+
+	return hardwareRandValue, false
+}