Re: [2/6] uaccess: add probe_kernel_write()

Randy Dunlap
2008-02-11T19:58:46Z

On Sun, 10 Feb 2008 21:05:40 +0100 Ingo Molnar wrote:

> Subject: uaccess: add probe_kernel_write()
> From: Ingo Molnar <mingo@elte.hu>
>
> add probe_kernel_read() and probe_kernel_write().
>
> Uninlined and restricted to kernel range memory only, as suggested
> by Linus.
>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
> include/linux/uaccess.h | 22 ++++++++++++++++++++++
> mm/Makefile | 2 +-
> mm/maccess.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 69 insertions(+), 1 deletion(-)
>
> Index: linux-kgdb.q/include/linux/uaccess.h
> ===================================================================
> --- linux-kgdb.q.orig/include/linux/uaccess.h
> +++ linux-kgdb.q/include/linux/uaccess.h
> @@ -84,4 +84,26 @@ static inline unsigned long __copy_from_
> ret; \
> })
>
> +/*
> + * probe_kernel_read(): safely attempt to read from a location

Please insert a hyphen/dash/'-' between function name and its
short description on the line above and on other similar lines.

Documentation/kernel-doc-nano-HOWTO.txt .

> + * @dst: pointer to the buffer that shall take the data
> + * @src: address to read from
> + * @size: size of the data chunk
> + *
> + * Safely read from address @src to the buffer at @dst. If a kernel fault
> + * happens, handle that and return -EFAULT.
> + */
> +extern long probe_kernel_read(void *dst, void *src, size_t size);
> +
> +/*
> + * probe_kernel_write(): safely attempt to write to a location
> + * @dst: address to write to
> + * @src: pointer to the data that shall be written
> + * @size: size of the data chunk
> + *
> + * Safely write to address @dst from the buffer at @src. If a kernel fault
> + * happens, handle that and return -EFAULT.
> + */
> +extern long probe_kernel_write(void *dst, void *src, size_t size);
> +
> #endif /* __LINUX_UACCESS_H__ */

> Index: linux-kgdb.q/mm/maccess.c
> ===================================================================
> --- /dev/null
> +++ linux-kgdb.q/mm/maccess.c
> @@ -0,0 +1,46 @@
> +/*
> + * Access kernel memory without faulting.
> + */
> +#include <linux/uaccess.h>
> +#include <linux/mm.h>
> +
> +/**
> + * probe_kernel_read(): safely attempt to read from a location
> + * @dst: pointer to the buffer that shall take the data
> + * @src: address to read from
> + * @size: size of the data chunk
> + *
> + * Safely read from address @src to the buffer at @dst. If a kernel fault
> + * happens, handle that and return -EFAULT.
> + */
> +long probe_kernel_read(void *dst, void *src, size_t size)
> +{
> + long ret;
> +
> + pagefault_disable();
> + ret = __copy_from_user_inatomic(dst,
> + (__force const void __user *)src, size);
> + pagefault_enable();
> +
> + return ret ? -EFAULT : 0;
> +}
> +
> +/**
> + * probe_kernel_write(): safely attempt to write to a location
> + * @dst: address to write to
> + * @src: pointer to the data that shall be written
> + * @size: size of the data chunk
> + *
> + * Safely write to address @dst from the buffer at @src. If a kernel fault
> + * happens, handle that and return -EFAULT.
> + */
> +long probe_kernel_write(void *dst, void *src, size_t size)
> +{
> + long ret;
> +
> + pagefault_disable();
> + ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
> + pagefault_enable();
> +
> + return ret ? -EFAULT : 0;
> +}

---
~Randy