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Kernel: Implement basic support for sys$mmap() with MAP_PRIVATE

Browse source 
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.
This commit is contained in:
Andreas Kling 2020-02-28 20:47:27 +01:00
parent aa1e209845
commit 8fbdda5a2d
11 changed files with 45 additions and 31 deletions
Download patch file Download diff file Expand all files Collapse all files

4
Kernel/Devices/BXVGADevice.cpp
View file

@ -166,9 +166,11 @@ u32 BXVGADevice::find_framebuffer_address()
return framebuffer_address;
}
KResultOr<Region*> BXVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot)
KResultOr<Region*> BXVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared)
{
REQUIRE_PROMISE(video);
if (!shared)
return KResult(-ENODEV);
ASSERT(offset == 0);
ASSERT(size == framebuffer_size_in_bytes());
auto vmobject = AnonymousVMObject::create_for_physical_range(m_framebuffer_address, framebuffer_size_in_bytes());

2
Kernel/Devices/BXVGADevice.h
View file

@ -41,7 +41,7 @@ public:
BXVGADevice();
virtual int ioctl(FileDescription&, unsigned request, unsigned arg) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot, bool shared) override;
private:
virtual const char* class_name() const override { return "BXVGA"; }

4
Kernel/Devices/MBVGADevice.cpp
View file

@ -51,9 +51,11 @@ MBVGADevice::MBVGADevice(PhysicalAddress addr, int pitch, int width, int height)
s_the = this;
}
KResultOr<Region*> MBVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot)
KResultOr<Region*> MBVGADevice::mmap(Process& process, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared)
{
REQUIRE_PROMISE(video);
if (!shared)
return KResult(-ENODEV);
ASSERT(offset == 0);
ASSERT(size == framebuffer_size_in_bytes());
auto vmobject = AnonymousVMObject::create_for_physical_range(m_framebuffer_address, framebuffer_size_in_bytes());

2
Kernel/Devices/MBVGADevice.h
View file

@ -41,7 +41,7 @@ public:
MBVGADevice(PhysicalAddress addr, int pitch, int width, int height);
virtual int ioctl(FileDescription&, unsigned request, unsigned arg) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t, int prot, bool shared) override;
private:
virtual const char* class_name() const override { return "MBVGA"; }

2
Kernel/FileSystem/File.cpp
View file

@ -54,7 +54,7 @@ int File::ioctl(FileDescription&, unsigned, unsigned)
return -ENOTTY;
}
KResultOr<Region*> File::mmap(Process&, FileDescription&, VirtualAddress, size_t, size_t, int)
KResultOr<Region*> File::mmap(Process&, FileDescription&, VirtualAddress, size_t, size_t, int, bool)
{
return KResult(-ENODEV);
}

2
Kernel/FileSystem/File.h
View file

@ -77,7 +77,7 @@ public:
virtual ssize_t read(FileDescription&, u8*, ssize_t) = 0;
virtual ssize_t write(FileDescription&, const u8*, ssize_t) = 0;
virtual int ioctl(FileDescription&, unsigned request, unsigned arg);
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot);
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared);
virtual String absolute_path(const FileDescription&) const = 0;

4
Kernel/FileSystem/FileDescription.cpp
View file

@ -281,10 +281,10 @@ InodeMetadata FileDescription::metadata() const
return {};
}
KResultOr<Region*> FileDescription::mmap(Process& process, VirtualAddress vaddr, size_t offset, size_t size, int prot)
KResultOr<Region*> FileDescription::mmap(Process& process, VirtualAddress vaddr, size_t offset, size_t size, int prot, bool shared)
{
LOCKER(m_lock);
return m_file->mmap(process, *this, vaddr, offset, size, prot);
return m_file->mmap(process, *this, vaddr, offset, size, prot, shared);
}
KResult FileDescription::truncate(u64 length)

2
Kernel/FileSystem/FileDescription.h
View file

@ -109,7 +109,7 @@ public:
Custody* custody() { return m_custody.ptr(); }
const Custody* custody() const { return m_custody.ptr(); }
KResultOr<Region*> mmap(Process&, VirtualAddress, size_t offset, size_t, int prot);
KResultOr<Region*> mmap(Process&, VirtualAddress, size_t offset, size_t, int prot, bool shared);
bool is_blocking() const { return m_is_blocking; }
void set_blocking(bool b) { m_is_blocking = b; }

12
Kernel/FileSystem/InodeFile.cpp
View file

@ -29,6 +29,7 @@
#include <Kernel/FileSystem/InodeFile.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
#include <Kernel/Process.h>
#include <Kernel/VM/PrivateInodeVMObject.h>
#include <Kernel/VM/SharedInodeVMObject.h>
namespace Kernel {
@ -60,11 +61,18 @@ ssize_t InodeFile::write(FileDescription& description, const u8* data, ssize_t c
return nwritten;
}
KResultOr<Region*> InodeFile::mmap(Process& process, FileDescription& description, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot)
KResultOr<Region*> InodeFile::mmap(Process& process, FileDescription& description, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared)
{
ASSERT(offset == 0);
// FIXME: If PROT_EXEC, check that the underlying file system isn't mounted noexec.
auto* region = process.allocate_region_with_vmobject(preferred_vaddr, size, SharedInodeVMObject::create_with_inode(inode()), offset, description.absolute_path(), prot);
RefPtr<InodeVMObject> vmobject;
if (shared)
vmobject = SharedInodeVMObject::create_with_inode(inode());
else
vmobject = PrivateInodeVMObject::create_with_inode(inode());
if (!vmobject)
return KResult(-ENOMEM);
auto* region = process.allocate_region_with_vmobject(preferred_vaddr, size, *vmobject, offset, description.absolute_path(), prot);
if (!region)
return KResult(-ENOMEM);
return region;

2
Kernel/FileSystem/InodeFile.h
View file

@ -49,7 +49,7 @@ public:
virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot, bool shared) override;
virtual String absolute_path(const FileDescription&) const override;

24
Kernel/Process.cpp
View file

@ -321,13 +321,15 @@ static bool validate_mmap_prot(int prot, bool map_stack)
return true;
}
static bool validate_inode_mmap_prot(const Process& process, int prot, const Inode& inode)
static bool validate_inode_mmap_prot(const Process& process, int prot, const Inode& inode, bool map_shared)
{
auto metadata = inode.metadata();
if ((prot & PROT_WRITE) && !metadata.may_write(process))
return false;
if ((prot & PROT_READ) && !metadata.may_read(process))
return false;
if (map_shared) {
if ((prot & PROT_WRITE) && !metadata.may_write(process))
return false;
InterruptDisabler disabler;
if (inode.shared_vmobject()) {
if ((prot & PROT_EXEC) && inode.shared_vmobject()->writable_mappings())
@ -335,6 +337,7 @@ static bool validate_inode_mmap_prot(const Process& process, int prot, const Ino
if ((prot & PROT_WRITE) && inode.shared_vmobject()->executable_mappings())
return false;
}
}
return true;
}
@ -433,9 +436,6 @@ void* Process::sys$mmap(const Syscall::SC_mmap_params* user_params)
return (void*)-EINVAL;
if (static_cast<size_t>(offset) & ~PAGE_MASK)
return (void*)-EINVAL;
// FIXME: Implement MAP_PRIVATE for FileDescription-backed mmap
if (map_private)
return (void*)-ENOTSUP;
auto description = file_description(fd);
if (!description)
return (void*)-EBADF;
@ -443,18 +443,20 @@ void* Process::sys$mmap(const Syscall::SC_mmap_params* user_params)
return (void*)-ENODEV;
if ((prot & PROT_READ) && !description->is_readable())
return (void*)-EACCES;
if (map_shared) {
if ((prot & PROT_WRITE) && !description->is_writable())
return (void*)-EACCES;
}
if (description->inode()) {
if (!validate_inode_mmap_prot(*this, prot, *description->inode()))
if (!validate_inode_mmap_prot(*this, prot, *description->inode(), map_shared))
return (void*)-EACCES;
}
auto region_or_error = description->mmap(*this, VirtualAddress(addr), static_cast<size_t>(offset), size, prot);
auto region_or_error = description->mmap(*this, VirtualAddress(addr), static_cast<size_t>(offset), size, prot, map_shared);
if (region_or_error.is_error()) {
// Fail if MAP_FIXED or address is 0, retry otherwise
if (map_fixed || addr == 0)
return (void*)(int)region_or_error.error();
region_or_error = description->mmap(*this, {}, static_cast<size_t>(offset), size, prot);
region_or_error = description->mmap(*this, {}, static_cast<size_t>(offset), size, prot, map_shared);
}
if (region_or_error.is_error())
return (void*)(int)region_or_error.error();
@ -537,7 +539,7 @@ int Process::sys$mprotect(void* addr, size_t size, int prot)
if (whole_region->access() == prot_to_region_access_flags(prot))
return 0;
if (whole_region->vmobject().is_inode()
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(whole_region->vmobject()).inode())) {
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(whole_region->vmobject()).inode(), whole_region->is_shared())) {
return -EACCES;
}
whole_region->set_readable(prot & PROT_READ);
@ -556,7 +558,7 @@ int Process::sys$mprotect(void* addr, size_t size, int prot)
if (old_region->access() == prot_to_region_access_flags(prot))
return 0;
if (old_region->vmobject().is_inode()
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(old_region->vmobject()).inode())) {
&& !validate_inode_mmap_prot(*this, prot, static_cast<const SharedInodeVMObject&>(old_region->vmobject()).inode(), old_region->is_shared())) {
return -EACCES;
}