zircon/kernel/object/vm_address_region_dispatcher.cc

// 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

#include "object/vm_address_region_dispatcher.h"

#include <align.h>
#include <assert.h>
#include <inttypes.h>
#include <lib/counters.h>
#include <trace.h>
#include <zircon/errors.h>
#include <zircon/rights.h>
#include <zircon/types.h>

#include <fbl/alloc_checker.h>
#include <vm/vm_address_region.h>
#include <vm/vm_aspace.h>
#include <vm/vm_object.h>

#define LOCAL_TRACE 0

KCOUNTER(dispatcher_vmar_create_count, "dispatcher.vmar.create")
KCOUNTER(dispatcher_vmar_destroy_count, "dispatcher.vmar.destroy")

namespace {

template <uint32_t FromFlag, uint32_t ToFlag>
uint32_t ExtractFlag(uint32_t* flags) {
  if (*flags & FromFlag) {
    *flags &= ~FromFlag;
    return ToFlag;
  }
  return 0;
}

// Split out the syscall flags into vmar flags and mmu flags.  Note that this
// does not validate that the requested protections in *flags* are valid.  For
// that use is_valid_mapping_protection()
zx_status_t split_syscall_flags(uint32_t flags, uint32_t* vmar_flags, uint* arch_mmu_flags,
                                uint8_t* align_pow2) {
  // Figure out arch_mmu_flags
  uint mmu_flags = 0;
  switch (flags & (ZX_VM_PERM_READ | ZX_VM_PERM_WRITE)) {
    case ZX_VM_PERM_READ:
      mmu_flags |= ARCH_MMU_FLAG_PERM_READ;
      break;
    case ZX_VM_PERM_READ | ZX_VM_PERM_WRITE:
      mmu_flags |= ARCH_MMU_FLAG_PERM_READ | ARCH_MMU_FLAG_PERM_WRITE;
      break;
  }

  if (flags & ZX_VM_PERM_EXECUTE) {
    mmu_flags |= ARCH_MMU_FLAG_PERM_EXECUTE;
  }

  // Mask out arch_mmu_flags options
  flags &= ~(ZX_VM_PERM_READ | ZX_VM_PERM_WRITE | ZX_VM_PERM_EXECUTE);

  // Figure out vmar flags
  uint32_t vmar = 0;
  vmar |= ExtractFlag<ZX_VM_COMPACT, VMAR_FLAG_COMPACT>(&flags);
  vmar |= ExtractFlag<ZX_VM_SPECIFIC, VMAR_FLAG_SPECIFIC>(&flags);
  vmar |= ExtractFlag<ZX_VM_SPECIFIC_OVERWRITE, VMAR_FLAG_SPECIFIC_OVERWRITE>(&flags);
  vmar |= ExtractFlag<ZX_VM_CAN_MAP_SPECIFIC, VMAR_FLAG_CAN_MAP_SPECIFIC>(&flags);
  vmar |= ExtractFlag<ZX_VM_CAN_MAP_READ, VMAR_FLAG_CAN_MAP_READ>(&flags);
  vmar |= ExtractFlag<ZX_VM_CAN_MAP_WRITE, VMAR_FLAG_CAN_MAP_WRITE>(&flags);
  vmar |= ExtractFlag<ZX_VM_CAN_MAP_EXECUTE, VMAR_FLAG_CAN_MAP_EXECUTE>(&flags);
  vmar |= ExtractFlag<ZX_VM_REQUIRE_NON_RESIZABLE, VMAR_FLAG_REQUIRE_NON_RESIZABLE>(&flags);
  vmar |= ExtractFlag<ZX_VM_ALLOW_FAULTS, VMAR_FLAG_ALLOW_FAULTS>(&flags);
  vmar |= ExtractFlag<ZX_VM_OFFSET_IS_UPPER_LIMIT, VMAR_FLAG_OFFSET_IS_UPPER_LIMIT>(&flags);

  if (flags & ((1u << ZX_VM_ALIGN_BASE) - 1u)) {
    return ZX_ERR_INVALID_ARGS;
  }

  // Figure out alignment.
  uint8_t alignment = static_cast<uint8_t>(flags >> ZX_VM_ALIGN_BASE);

  if (((alignment < 10) && (alignment != 0)) || (alignment > 32)) {
    return ZX_ERR_INVALID_ARGS;
  }

  *vmar_flags = vmar;
  *arch_mmu_flags |= mmu_flags;
  *align_pow2 = alignment;
  return ZX_OK;
}

}  // namespace

zx_status_t VmAddressRegionDispatcher::Create(fbl::RefPtr<VmAddressRegion> vmar,
                                              uint base_arch_mmu_flags,
                                              KernelHandle<VmAddressRegionDispatcher>* handle,
                                              zx_rights_t* rights) {
  // The initial rights should match the VMAR's creation permissions
  zx_rights_t vmar_rights = default_rights();
  uint32_t vmar_flags = vmar->flags();
  if (vmar_flags & VMAR_FLAG_CAN_MAP_READ) {
    vmar_rights |= ZX_RIGHT_READ;
  }
  if (vmar_flags & VMAR_FLAG_CAN_MAP_WRITE) {
    vmar_rights |= ZX_RIGHT_WRITE;
  }
  if (vmar_flags & VMAR_FLAG_CAN_MAP_EXECUTE) {
    vmar_rights |= ZX_RIGHT_EXECUTE;
  }

  fbl::AllocChecker ac;
  KernelHandle new_handle(
      fbl::AdoptRef(new (&ac) VmAddressRegionDispatcher(ktl::move(vmar), base_arch_mmu_flags)));
  if (!ac.check())
    return ZX_ERR_NO_MEMORY;

  *rights = vmar_rights;
  *handle = ktl::move(new_handle);
  return ZX_OK;
}

VmAddressRegionDispatcher::VmAddressRegionDispatcher(fbl::RefPtr<VmAddressRegion> vmar,
                                                     uint base_arch_mmu_flags)
    : vmar_(ktl::move(vmar)), base_arch_mmu_flags_(base_arch_mmu_flags) {
  kcounter_add(dispatcher_vmar_create_count, 1);
}

VmAddressRegionDispatcher::~VmAddressRegionDispatcher() {
  kcounter_add(dispatcher_vmar_destroy_count, 1);
}

zx_status_t VmAddressRegionDispatcher::Allocate(size_t offset, size_t size, uint32_t flags,
                                                KernelHandle<VmAddressRegionDispatcher>* handle,
                                                zx_rights_t* new_rights) {
  canary_.Assert();

  uint32_t vmar_flags;
  uint arch_mmu_flags = 0;
  uint8_t alignment = 0;
  zx_status_t status = split_syscall_flags(flags, &vmar_flags, &arch_mmu_flags, &alignment);
  if (status != ZX_OK)
    return status;

  // Check if any MMU-related flags were requested.
  if (arch_mmu_flags != 0) {
    return ZX_ERR_INVALID_ARGS;
  }

  fbl::RefPtr<VmAddressRegion> new_vmar;
  status = vmar_->CreateSubVmar(offset, size, alignment, vmar_flags, "useralloc", &new_vmar);
  if (status != ZX_OK)
    return status;

  return VmAddressRegionDispatcher::Create(ktl::move(new_vmar), base_arch_mmu_flags_, handle,
                                           new_rights);
}

zx_status_t VmAddressRegionDispatcher::Destroy() {
  canary_.Assert();

  // Disallow destroying the root vmar of an aspace as this violates the aspace invariants.
  if (vmar()->aspace()->RootVmar().get() == vmar().get()) {
    return ZX_ERR_NOT_SUPPORTED;
  }

  return vmar_->Destroy();
}

zx_status_t VmAddressRegionDispatcher::Map(size_t vmar_offset, fbl::RefPtr<VmObject> vmo,
                                           uint64_t vmo_offset, size_t len, uint32_t flags,
                                           fbl::RefPtr<VmMapping>* out) {
  canary_.Assert();

  if (!is_valid_mapping_protection(flags))
    return ZX_ERR_INVALID_ARGS;

  // Split flags into vmar_flags and arch_mmu_flags
  uint32_t vmar_flags;
  uint arch_mmu_flags = base_arch_mmu_flags_;
  uint8_t alignment = 0;
  zx_status_t status = split_syscall_flags(flags, &vmar_flags, &arch_mmu_flags, &alignment);
  if (status != ZX_OK)
    return status;

  if (vmar_flags & VMAR_FLAG_REQUIRE_NON_RESIZABLE) {
    vmar_flags &= ~VMAR_FLAG_REQUIRE_NON_RESIZABLE;
    if (vmo->is_resizable())
      return ZX_ERR_NOT_SUPPORTED;
  }
  if (vmar_flags & VMAR_FLAG_ALLOW_FAULTS) {
    vmar_flags &= ~VMAR_FLAG_ALLOW_FAULTS;
  } else {
    // TODO(stevensd): Add checks once all clients (resizable and pager-backed VMOs) start using the
    // VMAR_FLAG_ALLOW_FAULTS flag.
  }

  fbl::RefPtr<VmMapping> result(nullptr);
  status = vmar_->CreateVmMapping(vmar_offset, len, alignment, vmar_flags, ktl::move(vmo),
                                  vmo_offset, arch_mmu_flags, "useralloc", &result);
  if (status != ZX_OK) {
    return status;
  }

  *out = ktl::move(result);
  return ZX_OK;
}

zx_status_t VmAddressRegionDispatcher::Protect(vaddr_t base, size_t len, uint32_t flags) {
  canary_.Assert();

  if (!IS_PAGE_ALIGNED(base)) {
    return ZX_ERR_INVALID_ARGS;
  }

  if (!is_valid_mapping_protection(flags))
    return ZX_ERR_INVALID_ARGS;

  uint32_t vmar_flags;
  uint arch_mmu_flags = base_arch_mmu_flags_;
  uint8_t alignment = 0;
  zx_status_t status = split_syscall_flags(flags, &vmar_flags, &arch_mmu_flags, &alignment);
  if (status != ZX_OK)
    return status;

  // This request does not allow any VMAR flags or alignment flags to be set.
  if (vmar_flags || (alignment != 0))
    return ZX_ERR_INVALID_ARGS;

  return vmar_->Protect(base, len, arch_mmu_flags);
}

zx_status_t VmAddressRegionDispatcher::RangeOp(uint32_t op, vaddr_t base, size_t len,
                                               user_inout_ptr<void> buffer, size_t buffer_size) {
  canary_.Assert();

  if (op == ZX_VMAR_OP_DECOMMIT) {
    return vmar_->RangeOp(VmAddressRegion::RangeOpType::Decommit, base, len, buffer, buffer_size);
  } else if (op == ZX_VMAR_OP_MAP_RANGE) {
    return vmar_->RangeOp(VmAddressRegion::RangeOpType::MapRange, base, len, buffer, buffer_size);
  }
  return ZX_ERR_INVALID_ARGS;
}

zx_status_t VmAddressRegionDispatcher::Unmap(vaddr_t base, size_t len) {
  canary_.Assert();

  if (!IS_PAGE_ALIGNED(base)) {
    return ZX_ERR_INVALID_ARGS;
  }

  return vmar_->Unmap(base, len);
}

bool VmAddressRegionDispatcher::is_valid_mapping_protection(uint32_t flags) {
  if (!(flags & ZX_VM_PERM_READ)) {
    // No way to express non-readable mappings that are also writeable or
    // executable.
    if (flags & (ZX_VM_PERM_WRITE | ZX_VM_PERM_EXECUTE)) {
      return false;
    }
  }
  return true;
}