uaccess.h
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#ifndef __LINUX_UACCESS_H__
#define __LINUX_UACCESS_H__
#include <linux/preempt.h>
#include <asm/uaccess.h>
/*
* These routines enable/disable the pagefault handler in that
* it will not take any locks and go straight to the fixup table.
*
* They have great resemblance to the preempt_disable/enable calls
* and in fact they are identical; this is because currently there is
* no other way to make the pagefault handlers do this. So we do
* disable preemption but we don't necessarily care about that.
*/
static inline void pagefault_disable(void)
{
preempt_count_inc();
/*
* make sure to have issued the store before a pagefault
* can hit.
*/
barrier();
}
static inline void pagefault_enable(void)
{
#ifndef CONFIG_PREEMPT
/*
* make sure to issue those last loads/stores before enabling
* the pagefault handler again.
*/
barrier();
preempt_count_dec();
#else
preempt_enable();
#endif
}
#ifndef ARCH_HAS_NOCACHE_UACCESS
static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
const void __user *from, unsigned long n)
{
return __copy_from_user_inatomic(to, from, n);
}
static inline unsigned long __copy_from_user_nocache(void *to,
const void __user *from, unsigned long n)
{
return __copy_from_user(to, from, n);
}
#endif /* ARCH_HAS_NOCACHE_UACCESS */
/**
* probe_kernel_address(): safely attempt to read from a location
* @addr: address to read from - its type is type typeof(retval)*
* @retval: read into this variable
*
* Safely read from address @addr into variable @revtal. If a kernel fault
* happens, handle that and return -EFAULT.
* We ensure that the __get_user() is executed in atomic context so that
* do_page_fault() doesn't attempt to take mmap_sem. This makes
* probe_kernel_address() suitable for use within regions where the caller
* already holds mmap_sem, or other locks which nest inside mmap_sem.
* This must be a macro because __get_user() needs to know the types of the
* args.
*
* We don't include enough header files to be able to do the set_fs(). We
* require that the probe_kernel_address() caller will do that.
*/
#define probe_kernel_address(addr, retval) \
({ \
long ret; \
mm_segment_t old_fs = get_fs(); \
\
set_fs(KERNEL_DS); \
pagefault_disable(); \
ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval)); \
pagefault_enable(); \
set_fs(old_fs); \
ret; \
})
/*
* 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.
*/
extern long probe_kernel_read(void *dst, const void *src, size_t size);
extern long __probe_kernel_read(void *dst, const 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 notrace probe_kernel_write(void *dst, const void *src, size_t size);
extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
#endif /* __LINUX_UACCESS_H__ */