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410 lines
13 KiB
410 lines
13 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef __LINUX_UACCESS_H__ |
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#define __LINUX_UACCESS_H__ |
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#include <linux/fault-inject-usercopy.h> |
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#include <linux/instrumented.h> |
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#include <linux/minmax.h> |
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#include <linux/sched.h> |
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#include <linux/thread_info.h> |
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#include <asm/uaccess.h> |
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/* |
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* Architectures should provide two primitives (raw_copy_{to,from}_user()) |
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* and get rid of their private instances of copy_{to,from}_user() and |
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* __copy_{to,from}_user{,_inatomic}(). |
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* |
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* raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and |
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* return the amount left to copy. They should assume that access_ok() has |
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* already been checked (and succeeded); they should *not* zero-pad anything. |
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* No KASAN or object size checks either - those belong here. |
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* |
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* Both of these functions should attempt to copy size bytes starting at from |
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* into the area starting at to. They must not fetch or store anything |
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* outside of those areas. Return value must be between 0 (everything |
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* copied successfully) and size (nothing copied). |
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* |
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* If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting |
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* at to must become equal to the bytes fetched from the corresponding area |
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* starting at from. All data past to + size - N must be left unmodified. |
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* |
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* If copying succeeds, the return value must be 0. If some data cannot be |
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* fetched, it is permitted to copy less than had been fetched; the only |
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* hard requirement is that not storing anything at all (i.e. returning size) |
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* should happen only when nothing could be copied. In other words, you don't |
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* have to squeeze as much as possible - it is allowed, but not necessary. |
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* |
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* For raw_copy_from_user() to always points to kernel memory and no faults |
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* on store should happen. Interpretation of from is affected by set_fs(). |
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* For raw_copy_to_user() it's the other way round. |
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* |
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* Both can be inlined - it's up to architectures whether it wants to bother |
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* with that. They should not be used directly; they are used to implement |
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* the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic()) |
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* that are used instead. Out of those, __... ones are inlined. Plain |
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* copy_{to,from}_user() might or might not be inlined. If you want them |
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* inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER. |
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* |
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* NOTE: only copy_from_user() zero-pads the destination in case of short copy. |
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* Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything |
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* at all; their callers absolutely must check the return value. |
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* |
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* Biarch ones should also provide raw_copy_in_user() - similar to the above, |
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* but both source and destination are __user pointers (affected by set_fs() |
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* as usual) and both source and destination can trigger faults. |
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*/ |
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static __always_inline __must_check unsigned long |
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__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) |
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{ |
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instrument_copy_from_user(to, from, n); |
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check_object_size(to, n, false); |
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return raw_copy_from_user(to, from, n); |
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} |
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static __always_inline __must_check unsigned long |
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__copy_from_user(void *to, const void __user *from, unsigned long n) |
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{ |
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might_fault(); |
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if (should_fail_usercopy()) |
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return n; |
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instrument_copy_from_user(to, from, n); |
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check_object_size(to, n, false); |
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return raw_copy_from_user(to, from, n); |
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} |
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/** |
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* __copy_to_user_inatomic: - Copy a block of data into user space, with less checking. |
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* @to: Destination address, in user space. |
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* @from: Source address, in kernel space. |
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* @n: Number of bytes to copy. |
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* |
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* Context: User context only. |
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* |
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* Copy data from kernel space to user space. Caller must check |
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* the specified block with access_ok() before calling this function. |
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* The caller should also make sure he pins the user space address |
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* so that we don't result in page fault and sleep. |
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*/ |
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static __always_inline __must_check unsigned long |
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__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) |
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{ |
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if (should_fail_usercopy()) |
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return n; |
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instrument_copy_to_user(to, from, n); |
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check_object_size(from, n, true); |
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return raw_copy_to_user(to, from, n); |
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} |
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static __always_inline __must_check unsigned long |
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__copy_to_user(void __user *to, const void *from, unsigned long n) |
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{ |
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might_fault(); |
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if (should_fail_usercopy()) |
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return n; |
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instrument_copy_to_user(to, from, n); |
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check_object_size(from, n, true); |
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return raw_copy_to_user(to, from, n); |
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} |
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#ifdef INLINE_COPY_FROM_USER |
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static inline __must_check unsigned long |
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_copy_from_user(void *to, const void __user *from, unsigned long n) |
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{ |
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unsigned long res = n; |
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might_fault(); |
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if (!should_fail_usercopy() && likely(access_ok(from, n))) { |
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instrument_copy_from_user(to, from, n); |
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res = raw_copy_from_user(to, from, n); |
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} |
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if (unlikely(res)) |
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memset(to + (n - res), 0, res); |
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return res; |
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} |
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#else |
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extern __must_check unsigned long |
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_copy_from_user(void *, const void __user *, unsigned long); |
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#endif |
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#ifdef INLINE_COPY_TO_USER |
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static inline __must_check unsigned long |
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_copy_to_user(void __user *to, const void *from, unsigned long n) |
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{ |
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might_fault(); |
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if (should_fail_usercopy()) |
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return n; |
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if (access_ok(to, n)) { |
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instrument_copy_to_user(to, from, n); |
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n = raw_copy_to_user(to, from, n); |
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} |
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return n; |
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} |
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#else |
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extern __must_check unsigned long |
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_copy_to_user(void __user *, const void *, unsigned long); |
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#endif |
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static __always_inline unsigned long __must_check |
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copy_from_user(void *to, const void __user *from, unsigned long n) |
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{ |
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if (check_copy_size(to, n, false)) |
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n = _copy_from_user(to, from, n); |
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return n; |
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} |
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static __always_inline unsigned long __must_check |
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copy_to_user(void __user *to, const void *from, unsigned long n) |
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{ |
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if (check_copy_size(from, n, true)) |
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n = _copy_to_user(to, from, n); |
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return n; |
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} |
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#ifndef copy_mc_to_kernel |
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/* |
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* Without arch opt-in this generic copy_mc_to_kernel() will not handle |
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* #MC (or arch equivalent) during source read. |
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*/ |
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static inline unsigned long __must_check |
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copy_mc_to_kernel(void *dst, const void *src, size_t cnt) |
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{ |
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memcpy(dst, src, cnt); |
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return 0; |
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} |
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#endif |
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static __always_inline void pagefault_disabled_inc(void) |
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{ |
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current->pagefault_disabled++; |
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} |
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static __always_inline void pagefault_disabled_dec(void) |
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{ |
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current->pagefault_disabled--; |
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} |
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/* |
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* These routines enable/disable the pagefault handler. If disabled, it will |
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* not take any locks and go straight to the fixup table. |
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* |
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* User access methods will not sleep when called from a pagefault_disabled() |
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* environment. |
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*/ |
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static inline void pagefault_disable(void) |
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{ |
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pagefault_disabled_inc(); |
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/* |
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* make sure to have issued the store before a pagefault |
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* can hit. |
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*/ |
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barrier(); |
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} |
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static inline void pagefault_enable(void) |
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{ |
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/* |
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* make sure to issue those last loads/stores before enabling |
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* the pagefault handler again. |
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*/ |
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barrier(); |
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pagefault_disabled_dec(); |
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} |
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/* |
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* Is the pagefault handler disabled? If so, user access methods will not sleep. |
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*/ |
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static inline bool pagefault_disabled(void) |
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{ |
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return current->pagefault_disabled != 0; |
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} |
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/* |
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* The pagefault handler is in general disabled by pagefault_disable() or |
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* when in irq context (via in_atomic()). |
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* |
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* This function should only be used by the fault handlers. Other users should |
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* stick to pagefault_disabled(). |
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* Please NEVER use preempt_disable() to disable the fault handler. With |
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* !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled. |
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* in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT. |
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*/ |
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#define faulthandler_disabled() (pagefault_disabled() || in_atomic()) |
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#ifndef CONFIG_ARCH_HAS_SUBPAGE_FAULTS |
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/** |
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* probe_subpage_writeable: probe the user range for write faults at sub-page |
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* granularity (e.g. arm64 MTE) |
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* @uaddr: start of address range |
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* @size: size of address range |
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* |
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* Returns 0 on success, the number of bytes not probed on fault. |
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* |
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* It is expected that the caller checked for the write permission of each |
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* page in the range either by put_user() or GUP. The architecture port can |
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* implement a more efficient get_user() probing if the same sub-page faults |
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* are triggered by either a read or a write. |
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*/ |
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static inline size_t probe_subpage_writeable(char __user *uaddr, size_t size) |
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{ |
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return 0; |
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} |
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#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */ |
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#ifndef ARCH_HAS_NOCACHE_UACCESS |
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static inline __must_check unsigned long |
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__copy_from_user_inatomic_nocache(void *to, const void __user *from, |
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unsigned long n) |
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{ |
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return __copy_from_user_inatomic(to, from, n); |
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} |
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#endif /* ARCH_HAS_NOCACHE_UACCESS */ |
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extern __must_check int check_zeroed_user(const void __user *from, size_t size); |
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/** |
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* copy_struct_from_user: copy a struct from userspace |
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* @dst: Destination address, in kernel space. This buffer must be @ksize |
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* bytes long. |
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* @ksize: Size of @dst struct. |
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* @src: Source address, in userspace. |
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* @usize: (Alleged) size of @src struct. |
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* |
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* Copies a struct from userspace to kernel space, in a way that guarantees |
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* backwards-compatibility for struct syscall arguments (as long as future |
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* struct extensions are made such that all new fields are *appended* to the |
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* old struct, and zeroed-out new fields have the same meaning as the old |
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* struct). |
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* |
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* @ksize is just sizeof(*dst), and @usize should've been passed by userspace. |
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* The recommended usage is something like the following: |
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* |
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* SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize) |
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* { |
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* int err; |
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* struct foo karg = {}; |
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* |
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* if (usize > PAGE_SIZE) |
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* return -E2BIG; |
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* if (usize < FOO_SIZE_VER0) |
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* return -EINVAL; |
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* |
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* err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize); |
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* if (err) |
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* return err; |
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* |
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* // ... |
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* } |
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* |
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* There are three cases to consider: |
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* * If @usize == @ksize, then it's copied verbatim. |
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* * If @usize < @ksize, then the userspace has passed an old struct to a |
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* newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize) |
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* are to be zero-filled. |
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* * If @usize > @ksize, then the userspace has passed a new struct to an |
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* older kernel. The trailing bytes unknown to the kernel (@usize - @ksize) |
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* are checked to ensure they are zeroed, otherwise -E2BIG is returned. |
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* |
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* Returns (in all cases, some data may have been copied): |
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* * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src. |
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* * -EFAULT: access to userspace failed. |
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*/ |
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static __always_inline __must_check int |
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copy_struct_from_user(void *dst, size_t ksize, const void __user *src, |
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size_t usize) |
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{ |
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size_t size = min(ksize, usize); |
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size_t rest = max(ksize, usize) - size; |
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/* Deal with trailing bytes. */ |
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if (usize < ksize) { |
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memset(dst + size, 0, rest); |
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} else if (usize > ksize) { |
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int ret = check_zeroed_user(src + size, rest); |
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if (ret <= 0) |
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return ret ?: -E2BIG; |
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} |
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/* Copy the interoperable parts of the struct. */ |
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if (copy_from_user(dst, src, size)) |
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return -EFAULT; |
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return 0; |
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} |
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bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size); |
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long copy_from_kernel_nofault(void *dst, const void *src, size_t size); |
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long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size); |
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long copy_from_user_nofault(void *dst, const void __user *src, size_t size); |
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long notrace copy_to_user_nofault(void __user *dst, const void *src, |
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size_t size); |
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long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, |
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long count); |
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long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr, |
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long count); |
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long strnlen_user_nofault(const void __user *unsafe_addr, long count); |
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#ifndef __get_kernel_nofault |
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#define __get_kernel_nofault(dst, src, type, label) \ |
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do { \ |
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type __user *p = (type __force __user *)(src); \ |
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type data; \ |
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if (__get_user(data, p)) \ |
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goto label; \ |
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*(type *)dst = data; \ |
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} while (0) |
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#define __put_kernel_nofault(dst, src, type, label) \ |
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do { \ |
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type __user *p = (type __force __user *)(dst); \ |
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type data = *(type *)src; \ |
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if (__put_user(data, p)) \ |
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goto label; \ |
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} while (0) |
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#endif |
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/** |
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* get_kernel_nofault(): safely attempt to read from a location |
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* @val: read into this variable |
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* @ptr: address to read from |
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* |
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* Returns 0 on success, or -EFAULT. |
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*/ |
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#define get_kernel_nofault(val, ptr) ({ \ |
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const typeof(val) *__gk_ptr = (ptr); \ |
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copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\ |
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}) |
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#ifndef user_access_begin |
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#define user_access_begin(ptr,len) access_ok(ptr, len) |
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#define user_access_end() do { } while (0) |
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#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0) |
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#define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e) |
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#define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e) |
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#define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e) |
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#define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e) |
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static inline unsigned long user_access_save(void) { return 0UL; } |
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static inline void user_access_restore(unsigned long flags) { } |
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#endif |
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#ifndef user_write_access_begin |
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#define user_write_access_begin user_access_begin |
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#define user_write_access_end user_access_end |
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#endif |
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#ifndef user_read_access_begin |
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#define user_read_access_begin user_access_begin |
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#define user_read_access_end user_access_end |
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#endif |
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#ifdef CONFIG_HARDENED_USERCOPY |
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void __noreturn usercopy_abort(const char *name, const char *detail, |
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bool to_user, unsigned long offset, |
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unsigned long len); |
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#endif |
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#endif /* __LINUX_UACCESS_H__ */
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