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38 lines
1.4 KiB
C++
38 lines
1.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/StringView.h>
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#include <Kernel/FileSystem/VirtualFileSystem.h>
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#include <Kernel/Tasks/Process.h>
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namespace Kernel {
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ErrorOr<FlatPtr> Process::sys$readlink(Userspace<Syscall::SC_readlink_params const*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::rpath));
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auto params = TRY(copy_typed_from_user(user_params));
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auto path = TRY(get_syscall_path_argument(params.path));
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auto description = TRY(VirtualFileSystem::the().open(credentials(), path->view(), O_RDONLY | O_NOFOLLOW_NOERROR, 0, TRY(custody_for_dirfd(params.dirfd))));
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if (!description->metadata().is_symlink())
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return EINVAL;
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// Make sure that our assumptions about the path length hold up.
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// Note that this doesn't mean that the reported size can be trusted, some inodes just report zero.
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VERIFY(description->inode()->size() <= MAXPATHLEN);
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Array<u8, MAXPATHLEN> link_target;
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auto read_bytes = TRY(description->inode()->read_until_filled_or_end(0, link_target.size(), UserOrKernelBuffer::for_kernel_buffer(link_target.data()), description));
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auto size_to_copy = min(read_bytes, params.buffer.size);
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TRY(copy_to_user(params.buffer.data, link_target.data(), size_to_copy));
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// Note: we return the whole size here, not the copied size.
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return read_bytes;
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}
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}
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