oaknut: Fix edgecases in MOVP2R on +/-4GiB boundary

merryhime · Nov 17, 2023 · 316d886 · 316d886
1 parent d8634ea
commit 316d886
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Showing 3 changed files with 37 additions and 5 deletions.
diff --git a/include/oaknut/impl/offset.hpp b/include/oaknut/impl/offset.hpp
@@ -85,6 +85,12 @@ struct PageOffset {
         return static_cast<std::uint32_t>(((diff & 3) << (bitsize - 2)) | (diff >> 2));
     }
 
+    static bool valid(std::uintptr_t current_addr, std::uintptr_t target)
+    {
+        std::uint64_t diff = static_cast<std::uint64_t>((static_cast<std::int64_t>(target) >> shift_amount) - (static_cast<std::int64_t>(current_addr) >> shift_amount));
+        return detail::sign_extend<bitsize>(diff) == diff;
+    }
+
 private:
     template<typename Policy>
     friend class BasicCodeGenerator;

diff --git a/include/oaknut/oaknut.hpp b/include/oaknut/oaknut.hpp
@@ -161,10 +161,10 @@ class BasicCodeGenerator : public Policy {
     void MOVP2R(XReg xd, const void* addr)
     {
         if constexpr (Policy::has_absolute_addresses) {
-            int64_t diff = reinterpret_cast<uint64_t>(addr) - Policy::current_address();
+            const int64_t diff = reinterpret_cast<std::uint64_t>(addr) - Policy::current_address();
             if (diff >= -0xF'FFFF && diff <= 0xF'FFFF) {
                 ADR(xd, addr);
-            } else if (diff >= -int64_t{0xFFFF'FFFF} && diff <= int64_t{0xFFFF'FFFF}) {
+            } else if (PageOffset<21, 12>::valid(Policy::current_address(), reinterpret_cast<std::uintptr_t>(addr))) {
                 ADRL(xd, addr);
             } else {
                 MOV(xd, reinterpret_cast<uint64_t>(addr));

diff --git a/tests/basic.cpp b/tests/basic.cpp
@@ -220,16 +220,17 @@ TEST_CASE("ADRL (far)", "[slow]")
     }
 }
 
-TEST_CASE("MOVP2R", "[slow]")
+TEST_CASE("MOVP2R (far)", "[slow]")
 {
     CodeBlock mem{4096};
+    std::uint32_t* const mem_ptr = mem.ptr() + 42;  // create small offset for testing
 
     for (int i = 0; i < 0x200000; i++) {
         const std::int64_t diff = RandInt<std::int64_t>(std::numeric_limits<std::int64_t>::min(),
                                                         std::numeric_limits<std::int64_t>::max());
-        const std::intptr_t value = reinterpret_cast<std::intptr_t>(mem.ptr()) + diff;
+        const std::intptr_t value = reinterpret_cast<std::intptr_t>(mem_ptr) + diff;
 
-        CodeGenerator code{mem.ptr()};
+        CodeGenerator code{mem_ptr};
 
         auto f = code.ptr<std::uint64_t (*)()>();
         mem.unprotect();
@@ -241,3 +242,28 @@ TEST_CASE("MOVP2R", "[slow]")
         REQUIRE(f() == static_cast<std::uint64_t>(value));
     }
 }
+
+TEST_CASE("MOVP2R (4GiB boundary)")
+{
+    CodeBlock mem{4096};
+    std::uint32_t* const mem_ptr = mem.ptr() + 42;  // create small offset for testing
+
+    for (std::int64_t i = 0xFFFF'F000; i < 0x1'0000'1000; i++) {
+        const auto test = [&](std::int64_t diff) {
+            const std::intptr_t value = reinterpret_cast<std::intptr_t>(mem_ptr) + diff;
+
+            CodeGenerator code{mem_ptr};
+
+            auto f = code.ptr<std::uint64_t (*)()>();
+            mem.unprotect();
+            code.MOVP2R(X0, reinterpret_cast<void*>(value));
+            code.RET();
+            mem.protect();
+            mem.invalidate_all();
+
+            REQUIRE(f() == static_cast<std::uint64_t>(value));
+        };
+        test(i);
+        test(-i);
+    }
+}