zircon/kernel/vm/include/vm/vm_aspace.h

// Copyright 2016 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#ifndef ZIRCON_KERNEL_VM_INCLUDE_VM_VM_ASPACE_H_
#define ZIRCON_KERNEL_VM_INCLUDE_VM_VM_ASPACE_H_

#include <assert.h>
#include <lib/crypto/prng.h>
#include <zircon/types.h>

#include <arch/aspace.h>
#include <fbl/canary.h>
#include <fbl/intrusive_double_list.h>
#include <fbl/intrusive_wavl_tree.h>
#include <fbl/macros.h>
#include <fbl/ref_counted.h>
#include <fbl/ref_ptr.h>
#include <kernel/lockdep.h>
#include <kernel/mutex.h>
#include <vm/arch_vm_aspace.h>
#include <vm/vm.h>

class VmAddressRegion;
class VmEnumerator;
class VmMapping;
class VmAddressRegionOrMapping;

namespace hypervisor {
class GuestPhysicalAddressSpace;
}  // namespace hypervisor

class VmObject;

class VmAspace : public fbl::DoublyLinkedListable<VmAspace*>, public fbl::RefCounted<VmAspace> {
 public:
  // Create an address space of the type specified in |flags| with name |name|.
  //
  // Although reference counted, the returned VmAspace must be explicitly destroyed via Destroy.
  //
  // Returns null on failure (e.g. due to resource starvation).
  static fbl::RefPtr<VmAspace> Create(uint flags, const char* name);

  // Destroy this address space.
  //
  // Destroy does not free this object, but rather allows it to be freed when the last retaining
  // RefPtr is destroyed.
  zx_status_t Destroy();

  void Rename(const char* name);

  // flags
  static const uint32_t TYPE_USER = (0 << 0);
  static const uint32_t TYPE_KERNEL = (1 << 0);
  // You probably do not want to use LOW_KERNEL.  It is primarily
  // used for SMP bootstrap to allow mappings of very low memory using
  // the standard VMM subsystem.
  static const uint32_t TYPE_LOW_KERNEL = (2 << 0);
  static const uint32_t TYPE_GUEST_PHYS = (3 << 0);
  static const uint32_t TYPE_MASK = (3 << 0);

  // simple accessors
  vaddr_t base() const { return base_; }
  size_t size() const { return size_; }
  const char* name() const { return name_; }
  ArchVmAspace& arch_aspace() { return arch_aspace_; }
  bool is_user() const { return (flags_ & TYPE_MASK) == TYPE_USER; }
  bool is_aslr_enabled() const { return aslr_enabled_; }

  // Get the root VMAR (briefly acquires the aspace lock)
  // May return nullptr if the aspace has been destroyed or is not yet initialized.
  fbl::RefPtr<VmAddressRegion> RootVmar();

  // Returns true if the address space has been destroyed.
  bool is_destroyed() const;

  // accessor for singleton kernel address space
  static VmAspace* kernel_aspace() { return kernel_aspace_; }

  // given an address, return either the kernel aspace or the current user one
  static VmAspace* vaddr_to_aspace(uintptr_t address);

  // set the per thread aspace pointer to this
  void AttachToThread(Thread* t);

  void Dump(bool verbose) const;

  static void DropAllUserPageTables();
  void DropUserPageTables();

  // Harvests all used page tables based on the passed in action by calling the
  // |HarvestUserPageTables| in every VmAspace. This requires holding the aspaces_list_lock_ over
  // the entire duration and whilst not a commonly used lock this function should still only be
  // called infrequently to avoid monopolizing the lock.
  using NonTerminalAction = ArchVmAspace::NonTerminalAction;
  static void HarvestAllUserPageTables(NonTerminalAction action);

  // If this is a user aspace instructs the backing arch aspace to free any unaccessed page tables
  // using ArchVmAspace::HarvestNonTerminalAccessed() and the supplied |NonTerminalAction|.
  void HarvestUserPageTables(NonTerminalAction action);

  // Traverses the VM tree rooted at this node, in depth-first pre-order. If
  // any methods of |ve| return false, the traversal stops and this method
  // returns false. Returns true otherwise.
  bool EnumerateChildren(VmEnumerator* ve);

  // A collection of memory usage counts.
  struct vm_usage_t {
    // A count of pages covered by VmMapping ranges.
    size_t mapped_pages;

    // For the fields below, a page is considered committed if a VmMapping
    // covers a range of a VmObject that contains that page, and that page
    // has physical memory allocated to it.

    // A count of committed pages that are only mapped into this address
    // space.
    size_t private_pages;

    // A count of committed pages that are mapped into this and at least
    // one other address spaces.
    size_t shared_pages;

    // A number that estimates the fraction of shared_pages that this
    // address space is responsible for keeping alive.
    //
    // An estimate of:
    //   For each shared, committed page:
    //   scaled_shared_bytes +=
    //       PAGE_SIZE / (number of address spaces mapping this page)
    //
    // This number is strictly smaller than shared_pages * PAGE_SIZE.
    size_t scaled_shared_bytes;
  };

  // Counts memory usage under the VmAspace.
  zx_status_t GetMemoryUsage(vm_usage_t* usage);

  size_t AllocatedPages() const;

  // Generates a soft fault against this aspace. This is similar to a PageFault except:
  //  * This aspace may not currently be active and this does not have to be called from the
  //    hardware exception handler.
  //  * May be invoked spuriously in situations where the hardware mappings would have prevented a
  //    real PageFault from occurring.
  zx_status_t SoftFault(vaddr_t va, uint flags);

  // Generates an accessed flag fault against this aspace. This is a specialized version of
  // SoftFault that will only resolve a potential missing access flag and nothing else.
  zx_status_t AccessedFault(vaddr_t va);

  // Convenience method for traversing the tree of VMARs to find the deepest
  // VMAR in the tree that includes *va*.
  // Returns nullptr if the aspace has been destroyed or is not yet initialized.
  fbl::RefPtr<VmAddressRegionOrMapping> FindRegion(vaddr_t va);

  // For region creation routines
  static const uint VMM_FLAG_VALLOC_SPECIFIC = (1u << 0);  // allocate at specific address
  static const uint VMM_FLAG_COMMIT = (1u << 1);  // commit memory up front (no demand paging)

  // legacy functions to assist in the transition to VMARs
  // These all assume a flat VMAR structure in which all VMOs are mapped
  // as children of the root.  They will all assert if used on user aspaces
  // TODO(teisenbe): remove uses of these in favor of new VMAR interfaces
  zx_status_t ReserveSpace(const char* name, size_t size, vaddr_t vaddr);
  zx_status_t AllocPhysical(const char* name, size_t size, void** ptr, uint8_t align_pow2,
                            paddr_t paddr, uint vmm_flags, uint arch_mmu_flags);
  zx_status_t AllocContiguous(const char* name, size_t size, void** ptr, uint8_t align_pow2,
                              uint vmm_flags, uint arch_mmu_flags);
  zx_status_t Alloc(const char* name, size_t size, void** ptr, uint8_t align_pow2, uint vmm_flags,
                    uint arch_mmu_flags);
  zx_status_t FreeRegion(vaddr_t va);

  // Internal use function for mapping VMOs.  Do not use.  This is exposed in
  // the public API purely for tests.
  zx_status_t MapObjectInternal(fbl::RefPtr<VmObject> vmo, const char* name, uint64_t offset,
                                size_t size, void** ptr, uint8_t align_pow2, uint vmm_flags,
                                uint arch_mmu_flags);

  uintptr_t vdso_base_address() const;
  uintptr_t vdso_code_address() const;

  // Helper function to test for collision with vdso_code_mapping_.
  bool IntersectsVdsoCode(vaddr_t base, size_t size) const;

 protected:
  // Share the aspace lock with VmAddressRegion/VmMapping so they can serialize
  // changes to the aspace.
  friend class VmAddressRegionOrMapping;
  friend class VmAddressRegion;
  friend class VmMapping;
  Lock<Mutex>* lock() const TA_RET_CAP(lock_) { return &lock_; }
  Lock<Mutex>& lock_ref() const TA_RET_CAP(lock_) { return lock_; }

  // Expose the PRNG for ASLR to VmAddressRegion
  crypto::PRNG& AslrPrng() {
    DEBUG_ASSERT(aslr_enabled_);
    return aslr_prng_;
  }

  uint8_t AslrEntropyBits(bool compact) const {
    return compact ? aslr_compact_entropy_bits_ : aslr_entropy_bits_;
  }

 private:
  // can only be constructed via factory
  VmAspace(vaddr_t base, size_t size, uint32_t flags, const char* name);

  DISALLOW_COPY_ASSIGN_AND_MOVE(VmAspace);

  // private destructor that can only be used from the ref ptr
  ~VmAspace();
  friend fbl::RefPtr<VmAspace>;

  // complete initialization, may fail in OOM cases
  zx_status_t Init();

  void InitializeAslr();

  static constexpr uint arch_aspace_flags_from_flags(uint32_t flags) {
    bool is_high_kernel = (flags & TYPE_MASK) == TYPE_KERNEL;
    bool is_guest = (flags & TYPE_MASK) == TYPE_GUEST_PHYS;
    return (is_high_kernel ? ARCH_ASPACE_FLAG_KERNEL : 0u) |
           (is_guest ? ARCH_ASPACE_FLAG_GUEST : 0u);
  }

  // internal page fault routine, friended to be only called by vmm_page_fault_handler
  zx_status_t PageFault(vaddr_t va, uint flags);
  friend zx_status_t vmm_page_fault_handler(vaddr_t va, uint flags);
  friend class hypervisor::GuestPhysicalAddressSpace;

  // magic
  fbl::Canary<fbl::magic("VMAS")> canary_;

  // members
  const vaddr_t base_;
  const size_t size_;
  const uint32_t flags_;
  char name_[32];
  bool aspace_destroyed_ = false;
  bool aslr_enabled_ = false;
  uint8_t aslr_entropy_bits_ = 0;
  uint8_t aslr_compact_entropy_bits_ = 0;

  mutable DECLARE_MUTEX(VmAspace) lock_;

  // root of virtual address space
  // Access to this reference is guarded by lock_.
  fbl::RefPtr<VmAddressRegion> root_vmar_;

  // PRNG used by VMARs for address choices.  We record the seed to enable
  // reproducible debugging.
  crypto::PRNG aslr_prng_;
  uint8_t aslr_seed_[crypto::PRNG::kMinEntropy];

  // architecturally specific part of the aspace
  ArchVmAspace arch_aspace_;

  fbl::RefPtr<VmMapping> vdso_code_mapping_;

  // initialization routines need to construct the singleton kernel address space
  // at a particular points in the bootup process
  static void KernelAspaceInitPreHeap();
  static VmAspace* kernel_aspace_;
  friend void vm_init_preheap();
};

void DumpAllAspaces(bool verbose);

#endif  // ZIRCON_KERNEL_VM_INCLUDE_VM_VM_ASPACE_H_