k-memrange.hh

#ifndef CHICKADEE_K_MEMRANGE_HH
#define CHICKADEE_K_MEMRANGE_HH
#include "types.h"
template <unsigned maxsize> class memrangeset;

// `memrangeset` stores type information for a range of memory addresses.
// Chickadee uses it to remember which physical addresses are reserved or
// occupied by the kernel.

class memrange {
  public:
    inline uint8_t type() const;            // type of range
    inline uintptr_t first() const;         // first address in range
    inline uintptr_t last() const;          // one past last address in range
    inline size_t size() const;             // size of range in bytes

  private:
    uintptr_t addr_;
    uint8_t type_;

    template <unsigned maxsize> friend class memrangeset;
};


template <unsigned maxsize>
class memrangeset {
  public:
    // initialize range mapping [0, `limit`) to type 0
    inline memrangeset(uintptr_t limit);

    // return `limit`
    inline uintptr_t limit() const;
    // return number of ranges
    inline unsigned size() const;
    // return pointer to first range
    inline const memrange* begin() const;
    // return pointer to range bound
    inline const memrange* end() const;

    // return range containing `addr`, or `end()`
    const memrange* find(uintptr_t addr) const;
    // return type for `addr`. Requires `0 <= addr < limit()`
    uint8_t type(uintptr_t addr) const;

    // set type of address range [`first`, `last`) to `type`.
    // Requires `0 <= first <= last <= limit()`. Returns true iff
    // assignment succeeded.
    bool set(uintptr_t first, uintptr_t last, uint8_t type);

    // print contents to log
    void log_print(const char* prefix = "") const;
    // validate correctness of data structure
    void validate() const;

  private:
    unsigned n_;
    memrange r_[maxsize + 1];

    void split(unsigned i, uintptr_t addr);
};


inline uint8_t memrange::type() const {
    return type_;
}
inline uintptr_t memrange::first() const {
    return addr_;
}
inline uintptr_t memrange::last() const {
    return this[1].addr_;
}
inline size_t memrange::size() const {
    return this[1].addr_ - addr_;
}

template <unsigned maxsize>
inline memrangeset<maxsize>::memrangeset(uintptr_t limit)
    : n_(1) {
    r_[0].addr_ = 0;
    r_[0].type_ = 0;
    r_[1].addr_ = limit;
}
template <unsigned maxsize>
inline uintptr_t memrangeset<maxsize>::limit() const {
    return r_[n_].addr_;
}
template <unsigned maxsize>
inline unsigned memrangeset<maxsize>::size() const {
    return n_;
}
template <unsigned maxsize>
inline const memrange* memrangeset<maxsize>::begin() const {
    return &r_[0];
}
template <unsigned maxsize>
inline const memrange* memrangeset<maxsize>::end() const {
    return &r_[n_];
}
template <unsigned maxsize>
inline const memrange* memrangeset<maxsize>::find(uintptr_t addr) const {
    unsigned i = 0;
    while (i < n_ && addr >= r_[i + 1].addr_) {
        ++i;
    }
    return &r_[i];
}
template <unsigned maxsize>
inline uint8_t memrangeset<maxsize>::type(uintptr_t addr) const {
    auto r = find(addr);
    assert(r != end());
    return r->type();
}
template <unsigned maxsize>
void memrangeset<maxsize>::split(unsigned i, uintptr_t addr) {
    assert(i < n_ && n_ + 1 <= maxsize);
    assert(r_[i].addr_ < addr && r_[i + 1].addr_ > addr);
    memmove(&r_[i + 2], &r_[i + 1], (n_ - i) * sizeof(memrange));
    r_[i + 1].addr_ = addr;
    r_[i + 1].type_ = r_[i].type_;
    ++n_;
}
template <unsigned maxsize>
bool memrangeset<maxsize>::set(uintptr_t first, uintptr_t last, uint8_t type) {
    assert(first <= last && last <= r_[n_].addr_);
    if (first == last) {
        return true;
    }

    // find lower bound of insertion position for range
    unsigned i = 0;
    while (first >= r_[i + 1].addr_) {
        ++i;
    }
    assert(i < n_ && first >= r_[i].addr_ && first < r_[i + 1].addr_);
    // try consolidating range
    if (first == r_[i].addr_ && i > 0 && r_[i - 1].type_ == type) {
        --i;
    }
    if (r_[i].type_ == type) {
        first = r_[i].addr_;
    }

    // find upper bound of insertion position for range
    unsigned j = i;
    while (j < n_ && last >= r_[j + 1].addr_) {
        ++j;
    }
    assert(j <= n_ && last >= r_[j].addr_
           && (j == n_ || last < r_[j + 1].addr_));
    if (j < n_ && r_[j].type_ == type) {
        ++j;
        last = r_[j].addr_;
    } else if (j > i && first == r_[i].addr_) {
        r_[j].addr_ = last;
    }

    // split range at left and right
    if (n_ + (first != r_[i].addr_) + (last != r_[j].addr_) > maxsize) {
        return false;
    }
    if (first != r_[i].addr_) {
        split(i, first);
        ++i;
        ++j;
    }
    if (last != r_[j].addr_) {
        split(j, last);
        ++j;
    }

    // assign new range
    assert(r_[i].addr_ == first && r_[j].addr_ == last);
    r_[i].type_ = type;
    if (i + 1 < j) {
        memmove(&r_[i + 1], &r_[j], (n_ + 1 - j) * sizeof(memrange));
        n_ -= j - (i + 1);
    }
    return true;
}
template <unsigned maxsize>
void memrangeset<maxsize>::validate() const {
    assert(n_ > 0 && n_ <= maxsize);
    assert(r_[0].addr_ == 0);
    for (unsigned i = 0; i < n_; ++i) {
        assert(r_[i].addr_ < r_[i + 1].addr_);
        assert(i == 0 || r_[i].type_ != r_[i - 1].type_);
    }
}
template <unsigned maxsize>
void memrangeset<maxsize>::log_print(const char* prefix) const {
    void log_printf(const char* format, ...) __attribute__((noinline));
    for (unsigned i = 0; i < n_; ++i) {
        log_printf("%s[%u]: [%p,%p)=%d\n",
                   prefix, i, r_[i].first(), r_[i].last(), r_[i].type());
    }
}

#endif