From 419f4bebff5745b46bf30092dc7a7ca43449ea2e Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Wed, 1 Apr 2026 11:12:20 +0200
Subject: kernel/tests: implement basic simulated memory

---
 kernel/tests/kapi/memory.cpp | 77 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 76 insertions(+), 1 deletion(-)

(limited to 'kernel/tests/kapi')

diff --git a/kernel/tests/kapi/memory.cpp b/kernel/tests/kapi/memory.cpp
index 4482c74..6de2f60 100644
--- a/kernel/tests/kapi/memory.cpp
+++ b/kernel/tests/kapi/memory.cpp
@@ -1,11 +1,86 @@
+#include "kapi/memory.hpp"
+
 #include <kapi/memory.hpp>
 
+#include "kernel/tests/simulated_memory.hpp"
+
+#include <kstd/print>
+#include <kstd/units>
+
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <utility>
+
 namespace kapi::memory
 {
 
+  namespace
+  {
+    //! The size of the simulated RAM.
+    constexpr auto simulate_memory_size = kstd::units::MiB(32);
+
+    struct test_boostrap_frame_allocator : frame_allocator
+    {
+      auto mark_used(frame) -> void override {}
+
+      auto allocate_many(std::size_t count) noexcept -> std::optional<std::pair<frame, std::size_t>> override
+      {
+        auto start = next_free_frame;
+        next_free_frame += count;
+        return std::pair{frame{start}, count};
+      }
+
+      auto release_many(std::pair<frame, std::size_t>) -> void override {}
+
+      std::size_t next_free_frame{};
+    } boostrap_allocator;
+
+    struct test_page_mapper : page_mapper
+    {
+      auto map(page page, frame frame, flags flags) -> std::byte * override
+      {
+        kstd::println("mapping page {} onto frame {} with flags {}", page.number(), frame.number(),
+                      static_cast<std::uint64_t>(flags));
+
+        if ((page.start_address() & pmm_metadata_base.raw()) == pmm_metadata_base.raw())
+        {
+          auto offset = page.start_address() & ~pmm_metadata_base.raw();
+          return kernel::tests::simulated_memory::pmm_metadata_base() + offset;
+        }
+
+        return nullptr;
+      }
+
+      auto unmap(page page) -> void override
+      {
+        kstd::println("unmapping page {}", page.number());
+      }
+
+      auto try_unmap(page page) noexcept -> bool override
+      {
+        kstd::println("trying to unmap page {}", page.number());
+        return false;
+      }
+    } test_mapper;
+
+    auto handoff_to_kernel_pmm(frame_allocator & new_allocator) -> void
+    {
+      for (auto i = 0uz; i < boostrap_allocator.next_free_frame; ++i)
+      {
+        new_allocator.mark_used(frame{i});
+      }
+    }
+
+  }  // namespace
+
   auto init() -> void
   {
-    // TODO: initialize simulated memory.
+    kernel::tests::simulated_memory::init(simulate_memory_size);
+    set_frame_allocator(boostrap_allocator);
+    set_page_mapper(test_mapper);
+
+    init_pmm(simulate_memory_size / frame::size, handoff_to_kernel_pmm);
   }
 
 }  // namespace kapi::memory
\ No newline at end of file
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