Serenity Operating System
Kernel: Implement basic support for sys$mmap() with MAP_PRIVATE
You can now mmap a file as private and writable, and the changes you
make will only be visible to you.
This works because internally a MAP_PRIVATE region is backed by a
unique PrivateInodeVMObject instead of using the globally shared
SharedInodeVMObject like we always did before. :^)
Fixes #1045.
+44
-30
+3
-1
Kernel/Devices/BXVGADevice.cpp
+3
-1
Kernel/Devices/BXVGADevice.cpp
···
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return framebuffer_address;
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}
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-
KResultOr<Region*> BXVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot)
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+
KResultOr<Region*> BXVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared)
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{
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REQUIRE_PROMISE(video);
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+
if (!shared)
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return KResult(-ENODEV);
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ASSERT(offset == 0);
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ASSERT(size == framebuffer_size_in_bytes());
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auto vmobject = AnonymousVMObject::create_for_physical_range(m_framebuffer_address, framebuffer_size_in_bytes());
+1
-1
Kernel/Devices/BXVGADevice.h
+1
-1
Kernel/Devices/BXVGADevice.h
···
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BXVGADevice();
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virtual int ioctl(FileDescription&, unsigned request, unsigned arg) override;
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-
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot) override;
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virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot, bool shared) override;
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private:
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virtual const char* class_name() const override { return "BXVGA"; }
+3
-1
Kernel/Devices/MBVGADevice.cpp
+3
-1
Kernel/Devices/MBVGADevice.cpp
···
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s_the = this;
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}
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-
KResultOr<Region*> MBVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot)
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+
KResultOr<Region*> MBVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared)
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{
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REQUIRE_PROMISE(video);
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+
if (!shared)
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return KResult(-ENODEV);
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ASSERT(offset == 0);
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ASSERT(size == framebuffer_size_in_bytes());
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auto vmobject = AnonymousVMObject::create_for_physical_range(m_framebuffer_address, framebuffer_size_in_bytes());
+1
-1
Kernel/Devices/MBVGADevice.h
+1
-1
Kernel/Devices/MBVGADevice.h
···
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MBVGADevice(PhysicalAddress addr, int pitch, int width, int height);
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virtual int ioctl(FileDescription&, unsigned request, unsigned arg) override;
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virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot) override;
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virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot, bool shared) override;
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private:
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virtual const char* class_name() const override { return "MBVGA"; }
+1
-1
Kernel/FileSystem/File.cpp
+1
-1
Kernel/FileSystem/File.cpp
+1
-1
Kernel/FileSystem/File.h
+1
-1
Kernel/FileSystem/File.h
···
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virtual ssize_t read(FileDescription&, u8*, ssize_t) = 0;
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virtual ssize_t write(FileDescription&, const u8*, ssize_t) = 0;
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virtual int ioctl(FileDescription&, unsigned request, unsigned arg);
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-
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot);
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virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared);
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virtual String absolute_path(const FileDescription&) const = 0;
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+2
-2
Kernel/FileSystem/FileDescription.cpp
+2
-2
Kernel/FileSystem/FileDescription.cpp
···
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return {};
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}
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-
KResultOr<Region*> FileDescription::mmap(Process& process, VirtualAddress vaddr, size_t offset, size_t size, int prot)
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+
KResultOr<Region*> FileDescription::mmap(Process& process, VirtualAddress vaddr, size_t offset, size_t size, int prot, bool shared)
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{
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LOCKER(m_lock);
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return m_file->mmap(process, *this, vaddr, offset, size, prot);
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return m_file->mmap(process, *this, vaddr, offset, size, prot, shared);
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}
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KResult FileDescription::truncate(u64 length)
+1
-1
Kernel/FileSystem/FileDescription.h
+1
-1
Kernel/FileSystem/FileDescription.h
···
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Custody* custody() { return m_custody.ptr(); }
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const Custody* custody() const { return m_custody.ptr(); }
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-
KResultOr<Region*> mmap(Process&, VirtualAddress, size_t offset, size_t, int prot);
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+
KResultOr<Region*> mmap(Process&, VirtualAddress, size_t offset, size_t, int prot, bool shared);
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bool is_blocking() const { return m_is_blocking; }
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void set_blocking(bool b) { m_is_blocking = b; }
+10
-2
Kernel/FileSystem/InodeFile.cpp
+10
-2
Kernel/FileSystem/InodeFile.cpp
···
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#include <Kernel/FileSystem/InodeFile.h>
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#include <Kernel/FileSystem/VirtualFileSystem.h>
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#include <Kernel/Process.h>
32
+
#include <Kernel/VM/PrivateInodeVMObject.h>
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#include <Kernel/VM/SharedInodeVMObject.h>
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namespace Kernel {
···
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return nwritten;
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}
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-
KResultOr<Region*> InodeFile::mmap(Process& process, FileDescription& description, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot)
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+
KResultOr<Region*> InodeFile::mmap(Process& process, FileDescription& description, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared)
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{
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ASSERT(offset == 0);
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// FIXME: If PROT_EXEC, check that the underlying file system isn't mounted noexec.
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-
auto* region = process.allocate_region_with_vmobject(preferred_vaddr, size, SharedInodeVMObject::create_with_inode(inode()), offset, description.absolute_path(), prot);
68
+
RefPtr<InodeVMObject> vmobject;
69
+
if (shared)
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vmobject = SharedInodeVMObject::create_with_inode(inode());
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+
else
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vmobject = PrivateInodeVMObject::create_with_inode(inode());
73
+
if (!vmobject)
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return KResult(-ENOMEM);
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auto* region = process.allocate_region_with_vmobject(preferred_vaddr, size, *vmobject, offset, description.absolute_path(), prot);
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if (!region)
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return KResult(-ENOMEM);
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return region;
+1
-1
Kernel/FileSystem/InodeFile.h
+1
-1
Kernel/FileSystem/InodeFile.h
···
49
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virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
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virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
52
-
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot) override;
52
+
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared) override;
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virtual String absolute_path(const FileDescription&) const override;
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+20
-18
Kernel/Process.cpp
+20
-18
Kernel/Process.cpp
···
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return true;
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}
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-
static bool validate_inode_mmap_prot(const Process& process, int prot, const Inode& inode)
324
+
static bool validate_inode_mmap_prot(const Process& process, int prot, const Inode& inode, bool map_shared)
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{
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auto metadata = inode.metadata();
327
-
if ((prot & PROT_WRITE) && !metadata.may_write(process))
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-
return false;
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if ((prot & PROT_READ) && !metadata.may_read(process))
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return false;
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-
InterruptDisabler disabler;
332
-
if (inode.shared_vmobject()) {
333
-
if ((prot & PROT_EXEC) && inode.shared_vmobject()->writable_mappings())
329
+
330
+
if (map_shared) {
331
+
if ((prot & PROT_WRITE) && !metadata.may_write(process))
334
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return false;
335
-
if ((prot & PROT_WRITE) && inode.shared_vmobject()->executable_mappings())
336
-
return false;
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+
InterruptDisabler disabler;
334
+
if (inode.shared_vmobject()) {
335
+
if ((prot & PROT_EXEC) && inode.shared_vmobject()->writable_mappings())
336
+
return false;
337
+
if ((prot & PROT_WRITE) && inode.shared_vmobject()->executable_mappings())
338
+
return false;
339
+
}
337
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}
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return true;
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}
···
433
436
return (void*)-EINVAL;
434
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if (static_cast<size_t>(offset) & ~PAGE_MASK)
435
438
return (void*)-EINVAL;
436
-
// FIXME: Implement MAP_PRIVATE for FileDescription-backed mmap
437
-
if (map_private)
438
-
return (void*)-ENOTSUP;
439
439
auto description = file_description(fd);
440
440
if (!description)
441
441
return (void*)-EBADF;
···
443
443
return (void*)-ENODEV;
444
444
if ((prot & PROT_READ) && !description->is_readable())
445
445
return (void*)-EACCES;
446
-
if ((prot & PROT_WRITE) && !description->is_writable())
447
-
return (void*)-EACCES;
446
+
if (map_shared) {
447
+
if ((prot & PROT_WRITE) && !description->is_writable())
448
+
return (void*)-EACCES;
449
+
}
448
450
if (description->inode()) {
449
-
if (!validate_inode_mmap_prot(*this, prot, *description->inode()))
451
+
if (!validate_inode_mmap_prot(*this, prot, *description->inode(), map_shared))
450
452
return (void*)-EACCES;
451
453
}
452
-
auto region_or_error = description->mmap(*this, VirtualAddress(addr), static_cast<size_t>(offset), size, prot);
454
+
auto region_or_error = description->mmap(*this, VirtualAddress(addr), static_cast<size_t>(offset), size, prot, map_shared);
453
455
if (region_or_error.is_error()) {
454
456
// Fail if MAP_FIXED or address is 0, retry otherwise
455
457
if (map_fixed || addr == 0)
456
458
return (void*)(int)region_or_error.error();
457
-
region_or_error = description->mmap(*this, {}, static_cast<size_t>(offset), size, prot);
459
+
region_or_error = description->mmap(*this, {}, static_cast<size_t>(offset), size, prot, map_shared);
458
460
}
459
461
if (region_or_error.is_error())
460
462
return (void*)(int)region_or_error.error();
···
537
539
if (whole_region->access() == prot_to_region_access_flags(prot))
538
540
return 0;
539
541
if (whole_region->vmobject().is_inode()
540
-
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(whole_region->vmobject()).inode())) {
542
+
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(whole_region->vmobject()).inode(), whole_region->is_shared())) {
541
543
return -EACCES;
542
544
}
543
545
whole_region->set_readable(prot & PROT_READ);
···
556
558
if (old_region->access() == prot_to_region_access_flags(prot))
557
559
return 0;
558
560
if (old_region->vmobject().is_inode()
559
-
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(old_region->vmobject()).inode())) {
561
+
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(old_region->vmobject()).inode(), old_region->is_shared())) {
560
562
return -EACCES;
561
563
}
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564