Luna/kernel/src/memory/MemoryMap.cpp

#include "memory/MemoryMap.h"
#include <luna/Result.h>
#include <luna/SystemError.h>

extern const BOOTBOOT bootboot;

MemoryMapEntry::MemoryMapEntry(u64 address, usize size, bool is_free)
    : m_address(address), m_size(size), m_is_free(is_free)
{
}

MemoryMapEntry& MemoryMapEntry::operator=(const MemoryMapEntry& other)
{
    if (&other == this) return *this;

    m_address = other.address();
    m_size = other.size();
    m_is_free = other.is_free();

    return *this;
}

static MemoryMapEntry memory_map_entry_from_mmapent(const MMapEnt* ent)
{
    return { MMapEnt_Ptr(ent), MMapEnt_Size(ent), MMapEnt_IsFree(ent) };
}

MemoryMapIterator::MemoryMapIterator() : m_mmap_entries((bootboot.size - 128) / 16), m_base_ent(&bootboot.mmap)
{
    rewind();
}

void MemoryMapIterator::rewind()
{
    m_cur_ent = 0;
}

Option<MemoryMapEntry> MemoryMapIterator::at(usize index) const
{
    if (index >= m_mmap_entries) return {};
    return memory_map_entry_from_mmapent(m_base_ent + index);
}

Option<MemoryMapEntry> MemoryMapIterator::next()
{
    auto entry = TRY(at(m_cur_ent++));

#ifdef ARCH_X86_64
    // Workaround for https://gitlab.com/qemu-project/qemu/-/commit/8504f129450b909c88e199ca44facd35d38ba4de
    // This invalid 12GiB reserved entry is made up by QEMU (doesn't appear on any real hardware), so we can simply
    // ignore it and move on to the next entry.
    if (entry.address() == 0x000000fd00000000 && entry.size() == (0x000000ffffffffff - 0x000000fd00000000) + 1)
        return at(m_cur_ent++);
#endif

    return entry;
}

MemoryMapEntry MemoryMapIterator::largest_free()
{
    usize largest_size = 0;
    usize largest_index = 0;

    rewind();

    MemoryMapEntry entry;
    while (next().try_set_value(entry))
    {
        if (entry.is_free() && entry.size() > largest_size)
        {
            largest_size = entry.size();
            largest_index = m_cur_ent - 1;
        }
    }

    return at(largest_index).value();
}

MemoryMapEntry MemoryMapIterator::highest()
{
    usize highest_address = 0;
    usize highest_index = 0;

    rewind();

    MemoryMapEntry entry;
    while (next().try_set_value(entry))
    {
        if (entry.address() > highest_address)
        {
            highest_address = entry.address();
            highest_index = m_cur_ent - 1;
        }
    }

    return at(highest_index).value();
}