Kernel: Simplify the File memory-mapping API

Before this change, we had File::mmap() which did all the work of
setting up a VMObject, and then creating a Region in the current
process's address space.

This patch simplifies the interface by removing the region part.
Files now only have to return a suitable VMObject from
vmobject_for_mmap(), and then sys$mmap() itself will take care of
actually mapping it into the address space.

This fixes an issue where we'd try to block on I/O (for inode metadata
lookup) while holding the address space spinlock. It also reduces time
spent holding the address space lock.
This commit is contained in:
Andreas Kling 2022-08-23 18:51:18 +02:00
parent cf16b2c8e6
commit 30861daa93
Notes: sideshowbarker 2024-07-17 18:08:55 +09:00
15 changed files with 49 additions and 58 deletions

View file

@ -116,7 +116,7 @@ ErrorOr<void> KCOVDevice::ioctl(OpenFileDescription&, unsigned request, Userspac
}
}
ErrorOr<Memory::Region*> KCOVDevice::mmap(Process& process, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> KCOVDevice::vmobject_for_mmap(Process& process, Memory::VirtualRange const&, u64&, bool)
{
auto pid = process.pid();
auto maybe_kcov_instance = proc_instance->get(pid);
@ -126,7 +126,7 @@ ErrorOr<Memory::Region*> KCOVDevice::mmap(Process& process, Memory::AddressSpace
if (!kcov_instance->vmobject())
return ENOBUFS; // mmaped, before KCOV_SETBUFSIZE
return address_space.allocate_region_with_vmobject(range, *kcov_instance->vmobject(), offset, {}, prot, shared);
return *kcov_instance->vmobject();
}
}

View file

@ -22,7 +22,7 @@ public:
static void free_process();
// ^File
ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> open(int options) override;
protected:

View file

@ -42,7 +42,7 @@ ErrorOr<size_t> MemoryDevice::read(OpenFileDescription&, u64 offset, UserOrKerne
return length;
}
ErrorOr<Memory::Region*> MemoryDevice::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> MemoryDevice::vmobject_for_mmap(Process&, Memory::VirtualRange const& range, u64& offset, bool)
{
auto viewed_address = PhysicalAddress(offset);
@ -61,15 +61,8 @@ ErrorOr<Memory::Region*> MemoryDevice::mmap(Process&, Memory::AddressSpace& addr
return EINVAL;
}
auto vmobject = TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
return address_space.allocate_region_with_vmobject(
range,
move(vmobject),
0,
"Mapped Physical Memory"sv,
prot,
shared);
offset = 0;
return TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
}
}

View file

@ -19,7 +19,7 @@ public:
static NonnullLockRefPtr<MemoryDevice> must_create();
~MemoryDevice();
virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
private:
MemoryDevice();

View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -17,12 +17,12 @@ AnonymousFile::AnonymousFile(NonnullLockRefPtr<Memory::AnonymousVMObject> vmobje
AnonymousFile::~AnonymousFile() = default;
ErrorOr<Memory::Region*> AnonymousFile::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> AnonymousFile::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool)
{
if (offset != 0)
return EINVAL;
return address_space.allocate_region_with_vmobject(range, m_vmobject, offset, {}, prot, shared);
return m_vmobject;
}
ErrorOr<NonnullOwnPtr<KString>> AnonymousFile::pseudo_path(OpenFileDescription const&) const

View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -20,7 +20,7 @@ public:
virtual ~AnonymousFile() override;
virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
private:
virtual StringView class_name() const override { return "AnonymousFile"sv; }

View file

@ -35,7 +35,7 @@ ErrorOr<void> File::ioctl(OpenFileDescription&, unsigned, Userspace<void*>)
return ENOTTY;
}
ErrorOr<Memory::Region*> File::mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64, int, bool)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> File::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64&, bool)
{
return ENODEV;
}

View file

@ -64,11 +64,11 @@ public:
// - Can be overridden in subclasses to implement arbitrary functionality.
// - Subclasses should take care to validate incoming addresses before dereferencing.
//
// mmap()
// vmobject_for_mmap()
//
// - Optional. If unimplemented, mmap() on this File will fail with -ENODEV.
// - Called by mmap() when userspace wants to memory-map this File somewhere.
// - Should create a Region in the Process and return it if successful.
// - Should return a VMObject suitable for mapping into the calling process.
class File
: public AtomicRefCounted<File>
@ -90,7 +90,7 @@ public:
virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) = 0;
virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) = 0;
virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg);
virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared);
virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared);
virtual ErrorOr<struct stat> stat() const { return EBADF; }
// Although this might be better described "name" or "description", these terms already have other meanings.

View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -85,16 +85,11 @@ ErrorOr<void> InodeFile::ioctl(OpenFileDescription& description, unsigned reques
}
}
ErrorOr<Memory::Region*> InodeFile::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription& description, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> InodeFile::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64&, bool shared)
{
// FIXME: If PROT_EXEC, check that the underlying file system isn't mounted noexec.
LockRefPtr<Memory::InodeVMObject> vmobject;
if (shared)
vmobject = TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode()));
else
vmobject = TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode()));
auto path = TRY(description.pseudo_path());
return address_space.allocate_region_with_vmobject(range, vmobject.release_nonnull(), offset, path->view(), prot, shared);
return TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode()));
return TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode()));
}
ErrorOr<NonnullOwnPtr<KString>> InodeFile::pseudo_path(OpenFileDescription const&) const

View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -33,7 +33,7 @@ public:
virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override;
virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) override;
virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
virtual ErrorOr<struct stat> stat() const override { return inode().metadata().stat(); }
virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(OpenFileDescription const&) const override;

View file

@ -374,9 +374,9 @@ InodeMetadata OpenFileDescription::metadata() const
return {};
}
ErrorOr<Memory::Region*> OpenFileDescription::mmap(Process& process, Memory::AddressSpace& address_space, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> OpenFileDescription::vmobject_for_mmap(Process& process, Memory::VirtualRange const& range, u64& offset, bool shared)
{
return m_file->mmap(process, address_space, *this, range, offset, prot, shared);
return m_file->vmobject_for_mmap(process, range, offset, shared);
}
ErrorOr<void> OpenFileDescription::truncate(u64 length)

View file

@ -92,7 +92,7 @@ public:
RefPtr<Custody> custody();
RefPtr<Custody const> custody() const;
ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, Memory::VirtualRange const&, u64 offset, int prot, bool shared);
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared);
bool is_blocking() const;
void set_blocking(bool b);

View file

@ -32,19 +32,13 @@ DisplayConnector::DisplayConnector(size_t framebuffer_resource_size, bool enable
{
}
ErrorOr<Memory::Region*> DisplayConnector::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> DisplayConnector::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool)
{
VERIFY(m_shared_framebuffer_vmobject);
if (offset != 0)
return Error::from_errno(ENOTSUP);
return address_space.allocate_region_with_vmobject(
range,
*m_shared_framebuffer_vmobject,
0,
"Mapped Framebuffer"sv,
prot,
shared);
return *m_shared_framebuffer_vmobject;
}
ErrorOr<size_t> DisplayConnector::read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t)

View file

@ -137,7 +137,7 @@ private:
virtual bool can_write(OpenFileDescription const&, u64) const final override { return true; }
virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override final;
virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override final;
virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64, int, bool) override final;
virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64&, bool) override final;
virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) override final;
virtual StringView class_name() const override final { return "DisplayConnector"sv; }

View file

@ -190,10 +190,17 @@ ErrorOr<FlatPtr> Process::sys$mmap(Userspace<Syscall::SC_mmap_params const*> use
if (map_stack && (!map_private || !map_anonymous))
return EINVAL;
Memory::VirtualRange requested_range { VirtualAddress { addr }, rounded_size };
if (addr && !(map_fixed || map_fixed_noreplace)) {
// If there's an address but MAP_FIXED wasn't specified, the address is just a hint.
requested_range = { {}, rounded_size };
}
Memory::Region* region = nullptr;
LockRefPtr<OpenFileDescription> description;
LockRefPtr<Memory::AnonymousVMObject> vmobject;
LockRefPtr<Memory::VMObject> vmobject;
u64 used_offset = 0;
if (map_anonymous) {
auto strategy = map_noreserve ? AllocationStrategy::None : AllocationStrategy::Reserve;
@ -206,6 +213,7 @@ ErrorOr<FlatPtr> Process::sys$mmap(Userspace<Syscall::SC_mmap_params const*> use
} else {
if (offset < 0)
return EINVAL;
used_offset = static_cast<u64>(offset);
if (static_cast<size_t>(offset) & ~PAGE_MASK)
return EINVAL;
description = TRY(open_file_description(fd));
@ -220,6 +228,8 @@ ErrorOr<FlatPtr> Process::sys$mmap(Userspace<Syscall::SC_mmap_params const*> use
}
if (description->inode())
TRY(validate_inode_mmap_prot(prot, *description->inode(), map_shared));
vmobject = TRY(description->vmobject_for_mmap(*this, requested_range, used_offset, map_shared));
}
return address_space().with([&](auto& space) -> ErrorOr<FlatPtr> {
@ -227,17 +237,16 @@ ErrorOr<FlatPtr> Process::sys$mmap(Userspace<Syscall::SC_mmap_params const*> use
if (map_fixed)
TRY(space->unmap_mmap_range(VirtualAddress(addr), size));
Memory::VirtualRange requested_range { VirtualAddress { addr }, rounded_size };
if (addr && !(map_fixed || map_fixed_noreplace)) {
// If there's an address but MAP_FIXED wasn't specified, the address is just a hint.
requested_range = { {}, rounded_size };
}
if (map_anonymous) {
region = TRY(space->allocate_region_with_vmobject(map_randomized ? Memory::RandomizeVirtualAddress::Yes : Memory::RandomizeVirtualAddress::No, requested_range.base(), requested_range.size(), alignment, vmobject.release_nonnull(), 0, {}, prot, map_shared));
} else {
region = TRY(description->mmap(*this, *space, requested_range, static_cast<u64>(offset), prot, map_shared));
}
region = TRY(space->allocate_region_with_vmobject(
map_randomized ? Memory::RandomizeVirtualAddress::Yes : Memory::RandomizeVirtualAddress::No,
requested_range.base(),
requested_range.size(),
alignment,
vmobject.release_nonnull(),
used_offset,
{},
prot,
map_shared));
if (!region)
return ENOMEM;