From f7ff847498d629c05bb206b41a172f6735e2afe6 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 2 Apr 2026 09:51:44 +0200
Subject: kernel/tests: clean up implementation structure

---
 kernel/src/test_support/simulated_memory.cpp | 77 +++++++++++++++++-----------
 1 file changed, 47 insertions(+), 30 deletions(-)

(limited to 'kernel/src/test_support/simulated_memory.cpp')

diff --git a/kernel/src/test_support/simulated_memory.cpp b/kernel/src/test_support/simulated_memory.cpp
index fa3d36c..0648df2 100644
--- a/kernel/src/test_support/simulated_memory.cpp
+++ b/kernel/src/test_support/simulated_memory.cpp
@@ -4,50 +4,50 @@
 
 #include <kstd/units>
 
+#include <cerrno>
 #include <cstddef>
 #include <cstring>
+#include <format>
 #include <stdexcept>
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <unistd.h>
 
-using namespace kstd::units_literals;
-
 namespace kernel::tests
 {
-  namespace
-  {
-    constexpr auto virtual_size = 1_GiB;
-  }
 
-  simulated_memory::simulated_memory(kstd::units::bytes size)
-      : m_memory_descriptor{memfd_create("teachos_simulated_memory", 0)}
-      , m_size{size}
+  simulated_memory::simulated_memory(kstd::units::bytes physical_size, kstd::units::bytes virtual_size)
+      : m_descriptor{memfd_create("teachos_simulated_memory", 0)}
+      , m_physical_size{physical_size}
+      , m_virtual_size{virtual_size}
   {
-    if (m_memory_descriptor < 0)
+    if (m_descriptor < 0)
     {
-      throw std::runtime_error("Failed to create simulated memory");
+      auto error = std::format("Failed to allocate backing memory: {}", strerror(errno));
+      throw std::runtime_error(error);
     }
 
-    if (ftruncate(m_memory_descriptor, static_cast<off_t>(m_size.value)) < 0)
+    if (ftruncate(m_descriptor, static_cast<off_t>(m_physical_size.value)) < 0)
     {
-      throw std::runtime_error("Failed to resize simulated memory");
+      auto error = std::format("Failed to reserve backing memory: {}", strerror(errno));
+      throw std::runtime_error(error);
     }
 
-    auto mapped_pointer = mmap(nullptr, m_size.value, PROT_READ | PROT_WRITE, MAP_SHARED, m_memory_descriptor, 0);
-    if (mapped_pointer == MAP_FAILED)
+    auto physical_storage = mmap(nullptr, m_physical_size.value, PROT_READ | PROT_WRITE, MAP_SHARED, m_descriptor, 0);
+    if (physical_storage == MAP_FAILED)
     {
-      throw std::runtime_error("Failed to map simulated memory");
+      auto error = std::format("Failed to map backing memory: {}", strerror(errno));
+      throw std::runtime_error(error);
     }
 
-    m_physical_base = static_cast<std::byte *>(mapped_pointer);
-
     auto virtual_pointer = mmap(nullptr, virtual_size.value, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (virtual_pointer == MAP_FAILED)
     {
-      throw std::runtime_error("Failed to map simulated memory");
+      auto error = std::format("Failed to reserve virtual memory: {}", strerror(errno));
+      throw std::runtime_error(error);
     }
 
+    m_physical_base = static_cast<std::byte *>(physical_storage);
     m_virtual_base = static_cast<std::byte *>(virtual_pointer);
 
     clear();
@@ -55,39 +55,56 @@ namespace kernel::tests
 
   simulated_memory::~simulated_memory()
   {
-    munmap(m_physical_base, m_size.value);
-    munmap(m_virtual_base, virtual_size.value);
-    close(m_memory_descriptor);
+    munmap(m_virtual_base, m_virtual_size.value);
+    munmap(m_physical_base, m_physical_size.value);
+    close(m_descriptor);
   }
 
   auto simulated_memory::clear() -> void
   {
-    std::memset(m_physical_base, 0, m_size.value);
+    std::memset(m_physical_base, 0, m_physical_size.value);
   }
 
-  auto simulated_memory::ram_base() noexcept -> std::byte *
+  auto simulated_memory::physical_base() noexcept -> std::byte *
   {
     return m_physical_base;
   }
 
-  auto simulated_memory::ram_base() const noexcept -> std::byte const *
+  auto simulated_memory::physical_base() const noexcept -> std::byte const *
   {
     return m_physical_base;
   }
 
-  auto simulated_memory::heap_base() const noexcept -> kapi::memory::linear_address
+  auto simulated_memory::physical_size() const noexcept -> kstd::units::bytes
+  {
+    return m_physical_size;
+  }
+
+  auto simulated_memory::virtual_base() const noexcept -> kapi::memory::linear_address
   {
     return kapi::memory::linear_address{m_virtual_base};
   }
 
-  auto simulated_memory::heap_size() const noexcept -> kstd::units::bytes
+  auto simulated_memory::virtual_size() const noexcept -> kstd::units::bytes
   {
-    return virtual_size;
+    return m_virtual_size;
   }
 
-  auto simulated_memory::memory_descriptor() const noexcept -> int
+  auto simulated_memory::descriptor() const noexcept -> int
   {
-    return m_memory_descriptor;
+    return m_descriptor;
+  }
+
+  auto simulated_memory::map(kstd::units::bytes size, std::byte * to, off_t offset) -> std::byte *
+  {
+    auto mapped_ptr = mmap(to, size.value, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, m_descriptor, offset);
+    if (mapped_ptr == MAP_FAILED)
+    {
+      auto error = std::format("Failed to map page: {}", strerror(errno));
+      throw std::runtime_error(error);
+    }
+
+    return static_cast<std::byte *>(mapped_ptr);
   }
 
 }  // namespace kernel::tests
\ No newline at end of file
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