handle read / write behind module boundaries

1 files changed, 23 insertions, 10 deletions

diff --git a/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp b/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp
index 1bc475d..627641c 100644
--- a/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp
+++ b/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp
@@ -27,13 +27,22 @@ namespace devices::storage::ram_disk
       kapi::system::panic("[RAM DISK DEVICE] read_block called with null buffer.");
     }
 
-    // TODO BA-FS26 add bounds checking based on module size?
-    // TODO BA-FS26 fill with 0 after the end of the module, if the block extends beyond it?
+    size_t const offset = block_index * block_size;
+    size_t const limit = m_boot_module.size;
 
-    auto const offset = block_index * block_size;
-    auto const source = static_cast<std::byte *>(m_boot_module.start_address) + offset;
+    size_t const available = (offset < limit) ? (limit - offset) : 0;
+    size_t const to_copy = (available < block_size) ? available : block_size;
 
-    kstd::libc::memcpy(buffer, source, block_size);
+    if (to_copy > 0)
+    {
+      auto const source = static_cast<std::byte const *>(m_boot_module.start_address) + offset;
+      kstd::libc::memcpy(buffer, source, to_copy);
+    }
+
+    if (to_copy < block_size)
+    {
+      kstd::libc::memset(static_cast<std::byte *>(buffer) + to_copy, std::byte{0}, block_size - to_copy);
+    }
   }
 
   auto ram_disk_device::write_block(size_t block_index, void const * buffer) -> void
@@ -43,12 +52,16 @@ namespace devices::storage::ram_disk
       kapi::system::panic("[RAM DISK DEVICE] write_block called with null buffer.");
     }
 
-    // TODO BA-FS26 add bounds checking based on module size?
-    // TODO BA-FS26 ignore writes beyond the end of the module?
+    size_t const offset = block_index * block_size;
+    size_t const limit = m_boot_module.size;
 
-    auto const offset = block_index * block_size;
-    auto const destination = static_cast<std::byte *>(m_boot_module.start_address) + offset;
+    if (offset >= limit)
+      return;
 
-    kstd::libc::memcpy(destination, buffer, block_size);
+    size_t const available = limit - offset;
+    size_t const to_write = (available < block_size) ? available : block_size;
+
+    auto const destination = static_cast<std::byte *>(m_boot_module.start_address) + offset;
+    kstd::libc::memcpy(destination, buffer, to_write);
   }
 }  // namespace devices::storage::ram_disk
\ No newline at end of file