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diff --git a/static/md/srvre/kernel/wiki/vfs.md b/static/md/srvre/kernel/wiki/vfs.md deleted file mode 100644 index 377095e..0000000 --- a/static/md/srvre/kernel/wiki/vfs.md +++ /dev/null @@ -1,128 +0,0 @@ ---- -title: "VFS - SRVRE Kernel Wiki" -date: "Wed Jun 19 2024" ---- - -The VFS (Virtual File System) is the universal interface between processes -and resources. It is protected by the permission system. - -Authorized processes have the ability to access or provide resources. - -Resources -========= - -A resource is a control or data interface in the file system. -Examples include process metadata and termination, files on storage media -and network protocols. They are uniquely identified by unique POSIX paths, -though it is possible to reuse the same implementation with multiple paths. -There are several different kinds of resources. - -Stream ------- - -A stream is a shared byte stream that can be readable, writable, -both or none. The data will be distributed across all readers -in an unpredictable (but cryptographically insecure) fashion. -Writes can be interleaved. The combination of process authorization -and provider-side implementation decides which directions are available. - -Example use cases: Random byte stream, infinite zeroes, null/void - -File ----- - -A file is similar to a stream in that it provides a byte stream -that can be readable, writable, both or none. The main difference -is that the provider can tell the handles to it apart. - -Example use cases: Stored files, network sockets, runtime configuration -and control options - -Hook ----- - -A hook performs an action when opened. Resources of this kind -don't allocate a resource descriptor when opened, meaning that they can't -and never need to be closed. The provider can return any `usize` value instead. - -Example use cases: Process termination, system shutdown, UNIX time retrieval - -Directory ---------- - -A directory is a collection of resources and managed by the kernel. -Nesting is supported. - -Example use cases: Grouping of runtime configuration and control options, -hardware devices, network protocols etc. - -Directory hook --------------- - -A directory hook functions like a regular directory, but is managed by -a U-mode provider instead of the kernel keeping track of the items -contained within. - -Example use cases: Filesystem drivers, network protocols - -Builtin resources -================= - -The kernel provides the following builtin resources for providers -and other programs to build upon: - -`/io` ------ - -The `/io` directory provides interfaces for byte-grained, often text-based -communication with the environment the program is running in. - -* `/io/debug`: Write-only access to the debug console, usually provided by the SBI (firmware) - -`/userinit` ------------ - -The `/userinit` directory provides read-only access to the -[userinit](/md/srvre/kernel/wiki/userinit.md) tree. -Its purpose is to make essential drivers and the data required to run them -to the init process. - -* `/userinit/init`: The executable started as the init process. There is nothing special about it internally but it's noteworthy enough to be listed here explicitly. - -`/process` ----------- - -The `/process` directory provides information about as well as control -interfaces to processes and threads, including the caller. - -* `/process/create`: A [hook](#hook) that adds a new process to the scheduler, returning its ID. The extra data is the null-terminated path of the program to start. - -### `/process/self` - -The `/process/self` subdirectory provides information about as well as control -interfaces to the calling process and thread. - -* `/process/self/terminate`: A [hook](#hook) that terminates the current thread. The extra data is ignored. This is likely to be made more powerful in the future. -* `/process/self/id`: A [hook](#hook) that returns the ID of the current process. The extra data is ignored. -* `/process/self/thread_id`: A [hook](#hook) that returns the ID of the current thread within the current process. The extra data is ignored. - -Interaction from U-mode -======================= - -VFS resources are provided or accessed using -[system calls](/md/srvre/kernel/wiki/syscalls.md): - -* [open](/md/srvre/kernel/wiki/syscalls.md#open-100001): Opens a resource, obtaining a resource descriptor handle. -* [close](/md/srvre/kernel/wiki/syscalls.md#close-100002): Closes a resource descriptor handle. -* [provideStream](/md/srvre/kernel/wiki/syscalls.md#providestream-100003): Provides a stream resource. -* [provideFile](/md/srvre/kernel/wiki/syscalls.md#providefile-100004): Provides a file resource. -* [provideHook](/md/srvre/kernel/wiki/syscalls.md#providehook-100005): Provides a hook resource. -* [mkdir](/md/srvre/kernel/wiki/syscalls.md#mkdir-100006): Creates a kernel-managed directory. -* [provideDirHook](/md/srvre/kernel/wiki/syscalls.md#providedirhook-100007): Provides a directory hook. -* [remove](/md/srvre/kernel/wiki/syscalls.md#remove-100008): Removes a resource from the VFS. -* [read](/md/srvre/kernel/wiki/syscalls.md#read-100009): Reads from a resource descriptor handle into a buffer. -* [write](/md/srvre/kernel/wiki/syscalls.md#write-100010): Writes to a resource descriptor handle from a buffer. - -[Return to Wiki Main Page](/md/srvre/kernel/wiki.md) - -[Return to Index Page](/md/index.md) |