kernel/vm/vm_object.cpp - zircon/ - Git at Google

 // 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 "vm/vm_object.h"

 #include "vm_priv.h"

 #include <assert.h>
 #include <err.h>
 #include <fbl/auto_lock.h>
 #include <fbl/mutex.h>
 #include <fbl/ref_ptr.h>
 #include <inttypes.h>
 #include <ktl/move.h>
 #include <lib/console.h>
 #include <stdlib.h>
 #include <string.h>
 #include <trace.h>

 #include <vm/vm.h>
 #include <vm/vm_address_region.h>

 #include <zircon/types.h>

 #define LOCAL_TRACE MAX(VM_GLOBAL_TRACE, 0)

 VmObject::GlobalList VmObject::all_vmos_ = {};

 VmObject::VmObject(fbl::RefPtr<VmObject> parent)
     : lock_(parent ? parent->lock_ref() : local_lock_),
       parent_(ktl::move(parent)) {
     LTRACEF("%p\n", this);

     // Add ourself to the global VMO list, newer VMOs at the end.
     {
         Guard<fbl::Mutex> guard{AllVmosLock::Get()};
         all_vmos_.push_back(this);
     }
 }

 VmObject::~VmObject() {
     canary_.Assert();
     LTRACEF("%p\n", this);

     // remove ourself from our parent (if present)
     if (parent_) {
         LTRACEF("removing ourself from our parent %p\n", parent_.get());

         // conditionally grab our shared lock with the parent, but only if it's
         // not held. There are some destruction paths that may try to tear
         // down the object with the parent locks held.
         const bool need_lock = !lock_.lock().IsHeld();
         if (need_lock) {
             Guard<fbl::Mutex> guard{&lock_};
             parent_->RemoveChildLocked(this);
         } else {
             parent_->RemoveChildLocked(this);
         }
     }

     DEBUG_ASSERT(mapping_list_.is_empty());
     DEBUG_ASSERT(children_list_.is_empty());

     // Remove ourself from the global VMO list.
     {
         Guard<fbl::Mutex> guard{AllVmosLock::Get()};
         DEBUG_ASSERT(global_list_state_.InContainer() == true);
         all_vmos_.erase(*this);
     }
 }

 void VmObject::get_name(char* out_name, size_t len) const {
     canary_.Assert();
     name_.get(len, out_name);
 }

 zx_status_t VmObject::set_name(const char* name, size_t len) {
     canary_.Assert();
     return name_.set(name, len);
 }

 void VmObject::set_user_id(uint64_t user_id) {
     canary_.Assert();
     Guard<fbl::Mutex> guard{&lock_};
     DEBUG_ASSERT(user_id_ == 0);
     user_id_ = user_id;
 }

 uint64_t VmObject::user_id() const {
     canary_.Assert();
     Guard<fbl::Mutex> guard{&lock_};
     return user_id_;
 }

 uint64_t VmObject::parent_user_id() const {
     canary_.Assert();
     // Don't hold both our lock and our parent's lock at the same time, because
     // it's probably the same lock.
     fbl::RefPtr<VmObject> parent;
     {
         Guard<fbl::Mutex> guard{&lock_};
         if (parent_ == nullptr) {
             return 0u;
         }
         parent = parent_;
     }
     return parent->user_id();
 }

 bool VmObject::is_cow_clone() const {
     canary_.Assert();
     Guard<fbl::Mutex> guard{&lock_};
     return parent_ != nullptr;
 }

 void VmObject::AddMappingLocked(VmMapping* r) {
     canary_.Assert();
     DEBUG_ASSERT(lock_.lock().IsHeld());
     mapping_list_.push_front(r);
     mapping_list_len_++;
 }

 void VmObject::RemoveMappingLocked(VmMapping* r) {
     canary_.Assert();
     DEBUG_ASSERT(lock_.lock().IsHeld());
     mapping_list_.erase(*r);
     DEBUG_ASSERT(mapping_list_len_ > 0);
     mapping_list_len_--;
 }

 uint32_t VmObject::num_mappings() const {
     canary_.Assert();
     Guard<fbl::Mutex> guard{&lock_};
     return mapping_list_len_;
 }

 bool VmObject::IsMappedByUser() const {
     canary_.Assert();
     Guard<fbl::Mutex> guard{&lock_};
     for (const auto& m : mapping_list_) {
         if (m.aspace()->is_user()) {
             return true;
         }
     }
     return false;
 }

 uint32_t VmObject::share_count() const {
     canary_.Assert();

     Guard<fbl::Mutex> guard{&lock_};
     if (mapping_list_len_ < 2) {
         return 1;
     }

     // Find the number of unique VmAspaces that we're mapped into.
     // Use this buffer to hold VmAspace pointers.
     static constexpr int kAspaceBuckets = 64;
     uintptr_t aspaces[kAspaceBuckets];
     unsigned int num_mappings = 0; // Number of mappings we've visited
     unsigned int num_aspaces = 0;  // Unique aspaces we've seen
     for (const auto& m : mapping_list_) {
         uintptr_t as = reinterpret_cast<uintptr_t>(m.aspace().get());
         // Simple O(n^2) should be fine.
         for (unsigned int i = 0; i < num_aspaces; i++) {
             if (aspaces[i] == as) {
                 goto found;
             }
         }
         if (num_aspaces < kAspaceBuckets) {
             aspaces[num_aspaces++] = as;
         } else {
             // Maxed out the buffer. Estimate the remaining number of aspaces.
             num_aspaces +=
                 // The number of mappings we haven't visited yet
                 (mapping_list_len_ - num_mappings)
                 // Scaled down by the ratio of unique aspaces we've seen so far.
                 * num_aspaces / num_mappings;
             break;
         }
     found:
         num_mappings++;
     }
     DEBUG_ASSERT_MSG(num_aspaces <= mapping_list_len_,
                      "num_aspaces %u should be <= mapping_list_len_ %" PRIu32,
                      num_aspaces, mapping_list_len_);

     // TODO: Cache this value as long as the set of mappings doesn't change.
     // Or calculate it when adding/removing a new mapping under an aspace
     // not in the list.
     return num_aspaces;
 }

 void VmObject::SetChildObserver(VmObjectChildObserver* child_observer) {
     Guard<fbl::Mutex> guard{&lock_};
     child_observer_ = child_observer;
 }

 void VmObject::AddChildLocked(VmObject* o) {
     canary_.Assert();
     DEBUG_ASSERT(lock_.lock().IsHeld());
     children_list_.push_front(o);
     children_list_len_++;

     // Signal the dispatcher that there are child VMOS
     if ((child_observer_ != nullptr) && (children_list_len_ == 1)) {
         child_observer_->OnOneChild();
     }
 }

 void VmObject::RemoveChildLocked(VmObject* o) {
     canary_.Assert();
     DEBUG_ASSERT(lock_.lock().IsHeld());
     children_list_.erase(*o);
     DEBUG_ASSERT(children_list_len_ > 0);
     children_list_len_--;

     // Signal the dispatcher that there are no more child VMOS
     if ((child_observer_ != nullptr) && (children_list_len_ == 0)) {
         child_observer_->OnZeroChild();
     }
 }

 uint32_t VmObject::num_children() const {
     canary_.Assert();
     Guard<fbl::Mutex> guard{&lock_};
     return children_list_len_;
 }

 void VmObject::RangeChangeUpdateLocked(uint64_t offset, uint64_t len) {
     canary_.Assert();
     DEBUG_ASSERT(lock_.lock().IsHeld());

     // offsets for vmos needn't be aligned, but vmars use aligned offsets
     const uint64_t aligned_offset = ROUNDDOWN(offset, PAGE_SIZE);
     const uint64_t aligned_len = ROUNDUP(offset + len, PAGE_SIZE) - aligned_offset;

     // other mappings may have covered this offset into the vmo, so unmap those ranges
     for (auto& m : mapping_list_) {
         m.UnmapVmoRangeLocked(aligned_offset, aligned_len);
     }

     // inform all our children this as well, so they can inform their mappings
     for (auto& child : children_list_) {
         child.RangeChangeUpdateFromParentLocked(offset, len);
     }
 }

 static int cmd_vm_object(int argc, const cmd_args* argv, uint32_t flags) {
     if (argc < 2) {
     notenoughargs:
         printf("not enough arguments\n");
     usage:
         printf("usage:\n");
         printf("%s dump <address>\n", argv[0].str);
         printf("%s dump_pages <address>\n", argv[0].str);
         return ZX_ERR_INTERNAL;
     }

     if (!strcmp(argv[1].str, "dump")) {
         if (argc < 2) {
             goto notenoughargs;
         }

         VmObject* o = reinterpret_cast<VmObject*>(argv[2].u);

         o->Dump(0, false);
     } else if (!strcmp(argv[1].str, "dump_pages")) {
         if (argc < 2) {
             goto notenoughargs;
         }

         VmObject* o = reinterpret_cast<VmObject*>(argv[2].u);

         o->Dump(0, true);
     } else {
         printf("unknown command\n");
         goto usage;
     }

     return ZX_OK;
 }

 STATIC_COMMAND_START
 #if LK_DEBUGLEVEL > 0
 STATIC_COMMAND("vm_object", "vm object debug commands", &cmd_vm_object)
 #endif
 STATIC_COMMAND_END(vm_object);
	// 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 "vm/vm_object.h"

	#include "vm_priv.h"

	#include <assert.h>
	#include <err.h>
	#include <fbl/auto_lock.h>
	#include <fbl/mutex.h>
	#include <fbl/ref_ptr.h>
	#include <inttypes.h>
	#include <ktl/move.h>
	#include <lib/console.h>
	#include <stdlib.h>
	#include <string.h>
	#include <trace.h>

	#include <vm/vm.h>
	#include <vm/vm_address_region.h>

	#include <zircon/types.h>

	#define LOCAL_TRACE MAX(VM_GLOBAL_TRACE, 0)

	VmObject::GlobalList VmObject::all_vmos_ = {};

	VmObject::VmObject(fbl::RefPtr<VmObject> parent)
	: lock_(parent ? parent->lock_ref() : local_lock_),
	parent_(ktl::move(parent)) {
	LTRACEF("%p\n", this);

	// Add ourself to the global VMO list, newer VMOs at the end.
	{
	Guard<fbl::Mutex> guard{AllVmosLock::Get()};
	all_vmos_.push_back(this);
	}
	}

	VmObject::~VmObject() {
	canary_.Assert();
	LTRACEF("%p\n", this);

	// remove ourself from our parent (if present)
	if (parent_) {
	LTRACEF("removing ourself from our parent %p\n", parent_.get());

	// conditionally grab our shared lock with the parent, but only if it's
	// not held. There are some destruction paths that may try to tear
	// down the object with the parent locks held.
	const bool need_lock = !lock_.lock().IsHeld();
	if (need_lock) {
	Guard<fbl::Mutex> guard{&lock_};
	parent_->RemoveChildLocked(this);
	} else {
	parent_->RemoveChildLocked(this);
	}
	}

	DEBUG_ASSERT(mapping_list_.is_empty());
	DEBUG_ASSERT(children_list_.is_empty());

	// Remove ourself from the global VMO list.
	{
	Guard<fbl::Mutex> guard{AllVmosLock::Get()};
	DEBUG_ASSERT(global_list_state_.InContainer() == true);
	all_vmos_.erase(*this);
	}
	}

	void VmObject::get_name(char* out_name, size_t len) const {
	canary_.Assert();
	name_.get(len, out_name);
	}

	zx_status_t VmObject::set_name(const char* name, size_t len) {
	canary_.Assert();
	return name_.set(name, len);
	}

	void VmObject::set_user_id(uint64_t user_id) {
	canary_.Assert();
	Guard<fbl::Mutex> guard{&lock_};
	DEBUG_ASSERT(user_id_ == 0);
	user_id_ = user_id;
	}

	uint64_t VmObject::user_id() const {
	canary_.Assert();
	Guard<fbl::Mutex> guard{&lock_};
	return user_id_;
	}

	uint64_t VmObject::parent_user_id() const {
	canary_.Assert();
	// Don't hold both our lock and our parent's lock at the same time, because
	// it's probably the same lock.
	fbl::RefPtr<VmObject> parent;
	{
	Guard<fbl::Mutex> guard{&lock_};
	if (parent_ == nullptr) {
	return 0u;
	}
	parent = parent_;
	}
	return parent->user_id();
	}

	bool VmObject::is_cow_clone() const {
	canary_.Assert();
	Guard<fbl::Mutex> guard{&lock_};
	return parent_ != nullptr;
	}

	void VmObject::AddMappingLocked(VmMapping* r) {
	canary_.Assert();
	DEBUG_ASSERT(lock_.lock().IsHeld());
	mapping_list_.push_front(r);
	mapping_list_len_++;
	}

	void VmObject::RemoveMappingLocked(VmMapping* r) {
	canary_.Assert();
	DEBUG_ASSERT(lock_.lock().IsHeld());
	mapping_list_.erase(*r);
	DEBUG_ASSERT(mapping_list_len_ > 0);
	mapping_list_len_--;
	}

	uint32_t VmObject::num_mappings() const {
	canary_.Assert();
	Guard<fbl::Mutex> guard{&lock_};
	return mapping_list_len_;
	}

	bool VmObject::IsMappedByUser() const {
	canary_.Assert();
	Guard<fbl::Mutex> guard{&lock_};
	for (const auto& m : mapping_list_) {
	if (m.aspace()->is_user()) {
	return true;
	}
	}
	return false;
	}

	uint32_t VmObject::share_count() const {
	canary_.Assert();

	Guard<fbl::Mutex> guard{&lock_};
	if (mapping_list_len_ < 2) {
	return 1;
	}

	// Find the number of unique VmAspaces that we're mapped into.
	// Use this buffer to hold VmAspace pointers.
	static constexpr int kAspaceBuckets = 64;
	uintptr_t aspaces[kAspaceBuckets];
	unsigned int num_mappings = 0; // Number of mappings we've visited
	unsigned int num_aspaces = 0; // Unique aspaces we've seen
	for (const auto& m : mapping_list_) {
	uintptr_t as = reinterpret_cast<uintptr_t>(m.aspace().get());
	// Simple O(n^2) should be fine.
	for (unsigned int i = 0; i < num_aspaces; i++) {
	if (aspaces[i] == as) {
	goto found;
	}
	}
	if (num_aspaces < kAspaceBuckets) {
	aspaces[num_aspaces++] = as;
	} else {
	// Maxed out the buffer. Estimate the remaining number of aspaces.
	num_aspaces +=
	// The number of mappings we haven't visited yet
	(mapping_list_len_ - num_mappings)
	// Scaled down by the ratio of unique aspaces we've seen so far.
	* num_aspaces / num_mappings;
	break;
	}
	found:
	num_mappings++;
	}
	DEBUG_ASSERT_MSG(num_aspaces <= mapping_list_len_,
	"num_aspaces %u should be <= mapping_list_len_ %" PRIu32,
	num_aspaces, mapping_list_len_);

	// TODO: Cache this value as long as the set of mappings doesn't change.
	// Or calculate it when adding/removing a new mapping under an aspace
	// not in the list.
	return num_aspaces;
	}

	void VmObject::SetChildObserver(VmObjectChildObserver* child_observer) {
	Guard<fbl::Mutex> guard{&lock_};
	child_observer_ = child_observer;
	}

	void VmObject::AddChildLocked(VmObject* o) {
	canary_.Assert();
	DEBUG_ASSERT(lock_.lock().IsHeld());
	children_list_.push_front(o);
	children_list_len_++;

	// Signal the dispatcher that there are child VMOS
	if ((child_observer_ != nullptr) && (children_list_len_ == 1)) {
	child_observer_->OnOneChild();
	}
	}

	void VmObject::RemoveChildLocked(VmObject* o) {
	canary_.Assert();
	DEBUG_ASSERT(lock_.lock().IsHeld());
	children_list_.erase(*o);
	DEBUG_ASSERT(children_list_len_ > 0);
	children_list_len_--;

	// Signal the dispatcher that there are no more child VMOS
	if ((child_observer_ != nullptr) && (children_list_len_ == 0)) {
	child_observer_->OnZeroChild();
	}
	}

	uint32_t VmObject::num_children() const {
	canary_.Assert();
	Guard<fbl::Mutex> guard{&lock_};
	return children_list_len_;
	}

	void VmObject::RangeChangeUpdateLocked(uint64_t offset, uint64_t len) {
	canary_.Assert();
	DEBUG_ASSERT(lock_.lock().IsHeld());

	// offsets for vmos needn't be aligned, but vmars use aligned offsets
	const uint64_t aligned_offset = ROUNDDOWN(offset, PAGE_SIZE);
	const uint64_t aligned_len = ROUNDUP(offset + len, PAGE_SIZE) - aligned_offset;

	// other mappings may have covered this offset into the vmo, so unmap those ranges
	for (auto& m : mapping_list_) {
	m.UnmapVmoRangeLocked(aligned_offset, aligned_len);
	}

	// inform all our children this as well, so they can inform their mappings
	for (auto& child : children_list_) {
	child.RangeChangeUpdateFromParentLocked(offset, len);
	}
	}

	static int cmd_vm_object(int argc, const cmd_args* argv, uint32_t flags) {
	if (argc < 2) {
	notenoughargs:
	printf("not enough arguments\n");
	usage:
	printf("usage:\n");
	printf("%s dump <address>\n", argv[0].str);
	printf("%s dump_pages <address>\n", argv[0].str);
	return ZX_ERR_INTERNAL;
	}

	if (!strcmp(argv[1].str, "dump")) {
	if (argc < 2) {
	goto notenoughargs;
	}

	VmObject* o = reinterpret_cast<VmObject*>(argv[2].u);

	o->Dump(0, false);
	} else if (!strcmp(argv[1].str, "dump_pages")) {
	if (argc < 2) {
	goto notenoughargs;
	}

	VmObject* o = reinterpret_cast<VmObject*>(argv[2].u);

	o->Dump(0, true);
	} else {
	printf("unknown command\n");
	goto usage;
	}

	return ZX_OK;
	}

	STATIC_COMMAND_START
	#if LK_DEBUGLEVEL > 0
	STATIC_COMMAND("vm_object", "vm object debug commands", &cmd_vm_object)
	#endif
	STATIC_COMMAND_END(vm_object);