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c8d9f1b9c9
Since the CPU already does almost all necessary validation steps for us, we don't really need to attempt to do this. Doing it ourselves doesn't really work very reliably, because we'd have to account for other processors modifying virtual memory, and we'd have to account for e.g. pages not being able to be allocated due to insufficient resources. So change the copy_to/from_user (and associated helper functions) to use the new safe_memcpy, which will return whether it succeeded or not. The only manual validation step needed (which the CPU can't perform for us) is making sure the pointers provided by user mode aren't pointing to kernel mappings. To make it easier to read/write from/to either kernel or user mode data add the UserOrKernelBuffer helper class, which will internally either use copy_from/to_user or directly memcpy, or pass the data through directly using a temporary buffer on the stack. Last but not least we need to keep syscall params trivial as we need to copy them from/to user mode using copy_from/to_user.
111 lines
4.4 KiB
C++
111 lines
4.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/NonnullRefPtr.h>
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#include <AK/RefCounted.h>
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#include <AK/String.h>
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#include <AK/Types.h>
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#include <AK/Weakable.h>
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#include <Kernel/Forward.h>
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#include <Kernel/KResult.h>
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#include <Kernel/UnixTypes.h>
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#include <Kernel/UserOrKernelBuffer.h>
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#include <Kernel/VirtualAddress.h>
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namespace Kernel {
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// File is the base class for anything that can be referenced by a FileDescription.
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//
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// The most important functions in File are:
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//
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// read() and write()
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// - Implement reading and writing.
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// - Return the number of bytes read/written, OR a negative error code.
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//
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// can_read() and can_write()
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//
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// - Used to implement blocking I/O, and the select() and poll() syscalls.
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// - Return true if read() or write() would succeed, respectively.
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// - Note that can_read() should return true in EOF conditions,
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// and a subsequent call to read() should return 0.
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//
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// ioctl()
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//
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// - Optional. If unimplemented, ioctl() on this File will fail with -ENOTTY.
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// - Can be overridden in subclasses to implement arbitrary functionality.
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// - Subclasses should take care to validate incoming addresses before dereferencing.
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//
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// mmap()
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//
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// - Optional. If unimplemented, mmap() on this File will fail with -ENODEV.
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// - Called by mmap() when userspace wants to memory-map this File somewhere.
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// - Should create a Region in the Process and return it if successful.
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class File
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: public RefCounted<File>
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, public Weakable<File> {
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public:
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virtual ~File();
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virtual KResultOr<NonnullRefPtr<FileDescription>> open(int options);
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virtual KResult close();
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virtual bool can_read(const FileDescription&, size_t) const = 0;
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virtual bool can_write(const FileDescription&, size_t) const = 0;
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virtual KResultOr<size_t> read(FileDescription&, size_t, UserOrKernelBuffer&, size_t) = 0;
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virtual KResultOr<size_t> write(FileDescription&, size_t, const UserOrKernelBuffer&, size_t) = 0;
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virtual int ioctl(FileDescription&, unsigned request, FlatPtr arg);
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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 KResult stat(::stat&) const { return KResult(-EBADF); }
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virtual String absolute_path(const FileDescription&) const = 0;
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virtual KResult truncate(u64) { return KResult(-EINVAL); }
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virtual KResult chown(FileDescription&, uid_t, gid_t) { return KResult(-EBADF); }
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virtual KResult chmod(FileDescription&, mode_t) { return KResult(-EBADF); }
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virtual const char* class_name() const = 0;
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virtual bool is_seekable() const { return false; }
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virtual bool is_inode() const { return false; }
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virtual bool is_fifo() const { return false; }
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virtual bool is_device() const { return false; }
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virtual bool is_tty() const { return false; }
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virtual bool is_master_pty() const { return false; }
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virtual bool is_block_device() const { return false; }
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virtual bool is_character_device() const { return false; }
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virtual bool is_socket() const { return false; }
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protected:
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File();
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};
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}
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