From 8f1354b98541354c86b4b3289ef641ae16f8c2b1 Mon Sep 17 00:00:00 2001
From: no92 <leo@managarm.org>
Date: Mon, 18 Mar 2024 20:25:05 +0100
Subject: [PATCH] options/internal: fix UB in PhD mem{cpy,set}

---
 options/internal/generic/essential.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/options/internal/generic/essential.cpp b/options/internal/generic/essential.cpp
index d00df1e002..3c4f64e85b 100644
--- a/options/internal/generic/essential.cpp
+++ b/options/internal/generic/essential.cpp
@@ -5,8 +5,7 @@ namespace {
 	// Needed since we cannot declare a templated enum.
 	template<typename T>
 	struct word_helper {
-		using underlying [[gnu::aligned(1)]] = T;
-		enum class [[gnu::may_alias]] word_enum : underlying { };
+		enum class [[gnu::may_alias, gnu::aligned(1)]] word_enum : T { };
 	};
 
 	template<typename T>
@@ -15,7 +14,8 @@ namespace {
 	template<typename T>
 	[[gnu::always_inline]]
 	inline word<T> alias_load(const unsigned char *&p) {
-		word<T> value = *reinterpret_cast<const word<T> *>(p);
+		word<T> value;
+		__builtin_memcpy(&value, p, sizeof(value));
 		p += sizeof(T);
 		return value;
 	}
@@ -23,15 +23,18 @@ namespace {
 	template<typename T>
 	[[gnu::always_inline]]
 	inline void alias_store(unsigned char *&p, word<T> value) {
-		*reinterpret_cast<word<T> *>(p) = value;
+		__builtin_memcpy(p, &value, sizeof(value));
 		p += sizeof(T);
 	}
 
-#ifdef __LP64__
+#if defined(__LP64__) && !defined(__riscv)
 	void *forward_copy(void *__restrict dest, const void *__restrict src, size_t n) {
 		auto curDest = reinterpret_cast<unsigned char *>(dest);
 		auto curSrc = reinterpret_cast<const unsigned char *>(src);
 
+		for(; uintptr_t(curSrc) % 4 && n; n--)
+			*curDest++ = *curSrc++;
+
 		while(n >= 8 * 8) {
 			auto w1 = alias_load<uint64_t>(curSrc);
 			auto w2 = alias_load<uint64_t>(curSrc);
@@ -118,7 +121,7 @@ void *memset(void *dest, int val, size_t n) {
 	unsigned char byte = val;
 
 	// Get rid of misalignment.
-	while(n && (reinterpret_cast<uintptr_t>(curDest) & 7)) {
+	while(n && (uintptr_t(curDest) & 7)) {
 		*curDest++ = byte;
 		--n;
 	}