diff options
Diffstat (limited to 'mm/maccess.c')
-rw-r--r-- | mm/maccess.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/mm/maccess.c b/mm/maccess.c new file mode 100644 index 00000000..4cee182a --- /dev/null +++ b/mm/maccess.c @@ -0,0 +1,62 @@ +/* + * Access kernel memory without faulting. + */ +#include <linux/module.h> +#include <linux/mm.h> +#include <linux/uaccess.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 __weak probe_kernel_read(void *dst, const void *src, size_t size) + __attribute__((alias("__probe_kernel_read"))); + +long __probe_kernel_read(void *dst, const void *src, size_t size) +{ + long ret; + mm_segment_t old_fs = get_fs(); + + set_fs(KERNEL_DS); + pagefault_disable(); + ret = __copy_from_user_inatomic(dst, + (__force const void __user *)src, size); + pagefault_enable(); + set_fs(old_fs); + + return ret ? -EFAULT : 0; +} +EXPORT_SYMBOL_GPL(probe_kernel_read); + +/** + * 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 __weak probe_kernel_write(void *dst, const void *src, size_t size) + __attribute__((alias("__probe_kernel_write"))); + +long __probe_kernel_write(void *dst, const void *src, size_t size) +{ + long ret; + mm_segment_t old_fs = get_fs(); + + set_fs(KERNEL_DS); + pagefault_disable(); + ret = __copy_to_user_inatomic((__force void __user *)dst, src, size); + pagefault_enable(); + set_fs(old_fs); + + return ret ? -EFAULT : 0; +} +EXPORT_SYMBOL_GPL(probe_kernel_write); |