1 #ifndef __LINUX_UACCESS_H__ 2 #define __LINUX_UACCESS_H__ 3 4 #include <linux/preempt.h> 5 #include <asm/uaccess.h> 6 7 /* 8 * These routines enable/disable the pagefault handler in that 9 * it will not take any locks and go straight to the fixup table. 10 * 11 * They have great resemblance to the preempt_disable/enable calls 12 * and in fact they are identical; this is because currently there is 13 * no other way to make the pagefault handlers do this. So we do 14 * disable preemption but we don't necessarily care about that. 15 */ 16 static inline void pagefault_disable(void) 17 { 18 preempt_count_inc(); 19 /* 20 * make sure to have issued the store before a pagefault 21 * can hit. 22 */ 23 barrier(); 24 } 25 26 static inline void pagefault_enable(void) 27 { 28 #ifndef CONFIG_PREEMPT 29 /* 30 * make sure to issue those last loads/stores before enabling 31 * the pagefault handler again. 32 */ 33 barrier(); 34 preempt_count_dec(); 35 #else 36 preempt_enable(); 37 #endif 38 } 39 40 #ifndef ARCH_HAS_NOCACHE_UACCESS 41 42 static inline unsigned long __copy_from_user_inatomic_nocache(void *to, 43 const void __user *from, unsigned long n) 44 { 45 return __copy_from_user_inatomic(to, from, n); 46 } 47 48 static inline unsigned long __copy_from_user_nocache(void *to, 49 const void __user *from, unsigned long n) 50 { 51 return __copy_from_user(to, from, n); 52 } 53 54 #endif /* ARCH_HAS_NOCACHE_UACCESS */ 55 56 /** 57 * probe_kernel_address(): safely attempt to read from a location 58 * @addr: address to read from - its type is type typeof(retval)* 59 * @retval: read into this variable 60 * 61 * Safely read from address @addr into variable @revtal. If a kernel fault 62 * happens, handle that and return -EFAULT. 63 * We ensure that the __get_user() is executed in atomic context so that 64 * do_page_fault() doesn't attempt to take mmap_sem. This makes 65 * probe_kernel_address() suitable for use within regions where the caller 66 * already holds mmap_sem, or other locks which nest inside mmap_sem. 67 * This must be a macro because __get_user() needs to know the types of the 68 * args. 69 * 70 * We don't include enough header files to be able to do the set_fs(). We 71 * require that the probe_kernel_address() caller will do that. 72 */ 73 #define probe_kernel_address(addr, retval) \ 74 ({ \ 75 long ret; \ 76 mm_segment_t old_fs = get_fs(); \ 77 \ 78 set_fs(KERNEL_DS); \ 79 pagefault_disable(); \ 80 ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval)); \ 81 pagefault_enable(); \ 82 set_fs(old_fs); \ 83 ret; \ 84 }) 85 86 /* 87 * probe_kernel_read(): safely attempt to read from a location 88 * @dst: pointer to the buffer that shall take the data 89 * @src: address to read from 90 * @size: size of the data chunk 91 * 92 * Safely read from address @src to the buffer at @dst. If a kernel fault 93 * happens, handle that and return -EFAULT. 94 */ 95 extern long probe_kernel_read(void *dst, const void *src, size_t size); 96 extern long __probe_kernel_read(void *dst, const void *src, size_t size); 97 98 /* 99 * probe_kernel_write(): safely attempt to write to a location 100 * @dst: address to write to 101 * @src: pointer to the data that shall be written 102 * @size: size of the data chunk 103 * 104 * Safely write to address @dst from the buffer at @src. If a kernel fault 105 * happens, handle that and return -EFAULT. 106 */ 107 extern long notrace probe_kernel_write(void *dst, const void *src, size_t size); 108 extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size); 109 110 #endif /* __LINUX_UACCESS_H__ */ 111