maccess: clarify kerneldoc comments
Add proper kerneldoc comments for probe_kernel_read_strict and probe_kernel_read strncpy_from_unsafe_strict and explain the different versus the non-strict version. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20200521152301.2587579-5-hch@lst.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mm/maccess.c
60
mm/maccess.c
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@ -31,29 +31,36 @@ probe_write_common(void __user *dst, const void *src, size_t size)
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}
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/**
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* probe_kernel_read(): safely attempt to read from a kernel-space location
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* probe_kernel_read(): safely attempt to read from any location
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* @dst: pointer to the buffer that shall take the data
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* @src: address to read from
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* @size: size of the data chunk
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*
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* Safely read from address @src to the buffer at @dst. If a kernel fault
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* happens, handle that and return -EFAULT.
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* Same as probe_kernel_read_strict() except that for architectures with
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* not fully separated user and kernel address spaces this function also works
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* for user address tanges.
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*
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* DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
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* separate kernel and user address spaces, and also a bad idea otherwise.
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*/
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long __weak probe_kernel_read(void *dst, const void *src, size_t size)
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__attribute__((alias("__probe_kernel_read")));
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/**
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* probe_kernel_read_strict(): safely attempt to read from kernel-space
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* @dst: pointer to the buffer that shall take the data
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* @src: address to read from
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* @size: size of the data chunk
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*
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* Safely read from kernel address @src to the buffer at @dst. If a kernel
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* fault happens, handle that and return -EFAULT.
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*
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* We ensure that the copy_from_user is executed in atomic context so that
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* do_page_fault() doesn't attempt to take mmap_lock. This makes
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* probe_kernel_read() suitable for use within regions where the caller
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* already holds mmap_lock, or other locks which nest inside mmap_lock.
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*
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* probe_kernel_read_strict() is the same as probe_kernel_read() except for
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* the case where architectures have non-overlapping user and kernel address
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* ranges: probe_kernel_read_strict() will additionally return -EFAULT for
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* probing memory on a user address range where probe_user_read() is supposed
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* to be used instead.
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*/
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long __weak probe_kernel_read(void *dst, const void *src, size_t size)
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__attribute__((alias("__probe_kernel_read")));
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long __weak probe_kernel_read_strict(void *dst, const void *src, size_t size)
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__attribute__((alias("__probe_kernel_read")));
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@ -154,15 +161,34 @@ EXPORT_SYMBOL_GPL(probe_user_write);
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* If @count is smaller than the length of the string, copies @count-1 bytes,
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* sets the last byte of @dst buffer to NUL and returns @count.
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*
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* strncpy_from_unsafe_strict() is the same as strncpy_from_unsafe() except
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* for the case where architectures have non-overlapping user and kernel address
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* ranges: strncpy_from_unsafe_strict() will additionally return -EFAULT for
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* probing memory on a user address range where strncpy_from_unsafe_user() is
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* supposed to be used instead.
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* Same as strncpy_from_unsafe_strict() except that for architectures with
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* not fully separated user and kernel address spaces this function also works
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* for user address tanges.
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*
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* DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
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* separate kernel and user address spaces, and also a bad idea otherwise.
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*/
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long __weak strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
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__attribute__((alias("__strncpy_from_unsafe")));
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/**
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* strncpy_from_unsafe_strict: - Copy a NUL terminated string from unsafe
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* address.
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* @dst: Destination address, in kernel space. This buffer must be at
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* least @count bytes long.
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* @unsafe_addr: Unsafe address.
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* @count: Maximum number of bytes to copy, including the trailing NUL.
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*
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* Copies a NUL-terminated string from unsafe address to kernel buffer.
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*
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* On success, returns the length of the string INCLUDING the trailing NUL.
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*
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* If access fails, returns -EFAULT (some data may have been copied
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* and the trailing NUL added).
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*
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* If @count is smaller than the length of the string, copies @count-1 bytes,
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* sets the last byte of @dst buffer to NUL and returns @count.
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*/
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long __weak strncpy_from_unsafe_strict(char *dst, const void *unsafe_addr,
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long count)
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__attribute__((alias("__strncpy_from_unsafe")));
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