mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-03 23:58:05 +00:00
cae2a173fe
The rule for 'copy_from_user()' is that it zeroes the remaining kernel buffer even when the copy fails halfway, just to make sure that we don't leave uninitialized kernel memory around. Because even if we check for errors, some kernel buffers stay around after thge copy (think page cache). However, the x86-64 logic for user copies uses a copy_user_generic() function for all the cases, that set the "zerorest" flag for any fault on the source buffer. Which meant that it didn't just try to clear the kernel buffer after a failure in copy_from_user(), it also tried to clear the destination user buffer for the "copy_in_user()" case. Not only is that pointless, it also means that the clearing code has to worry about the tail clearing taking page faults for the user buffer case. Which is just stupid, since that case shouldn't happen in the first place. Get rid of the whole "zerorest" thing entirely, and instead just check if the destination is in kernel space or not. And then just use memset() to clear the tail of the kernel buffer if necessary. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
236 lines
6.2 KiB
C
236 lines
6.2 KiB
C
#ifndef _ASM_X86_UACCESS_64_H
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#define _ASM_X86_UACCESS_64_H
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/*
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* User space memory access functions
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*/
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#include <linux/compiler.h>
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#include <linux/errno.h>
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#include <linux/lockdep.h>
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#include <asm/alternative.h>
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#include <asm/cpufeature.h>
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#include <asm/page.h>
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/*
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* Copy To/From Userspace
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*/
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/* Handles exceptions in both to and from, but doesn't do access_ok */
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__must_check unsigned long
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copy_user_enhanced_fast_string(void *to, const void *from, unsigned len);
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__must_check unsigned long
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copy_user_generic_string(void *to, const void *from, unsigned len);
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__must_check unsigned long
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copy_user_generic_unrolled(void *to, const void *from, unsigned len);
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static __always_inline __must_check unsigned long
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copy_user_generic(void *to, const void *from, unsigned len)
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{
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unsigned ret;
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/*
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* If CPU has ERMS feature, use copy_user_enhanced_fast_string.
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* Otherwise, if CPU has rep_good feature, use copy_user_generic_string.
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* Otherwise, use copy_user_generic_unrolled.
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*/
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alternative_call_2(copy_user_generic_unrolled,
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copy_user_generic_string,
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X86_FEATURE_REP_GOOD,
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copy_user_enhanced_fast_string,
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X86_FEATURE_ERMS,
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ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from),
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"=d" (len)),
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"1" (to), "2" (from), "3" (len)
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: "memory", "rcx", "r8", "r9", "r10", "r11");
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return ret;
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}
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__must_check unsigned long
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copy_in_user(void __user *to, const void __user *from, unsigned len);
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static __always_inline __must_check
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int __copy_from_user_nocheck(void *dst, const void __user *src, unsigned size)
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{
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int ret = 0;
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if (!__builtin_constant_p(size))
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return copy_user_generic(dst, (__force void *)src, size);
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switch (size) {
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case 1:__get_user_asm(*(u8 *)dst, (u8 __user *)src,
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ret, "b", "b", "=q", 1);
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return ret;
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case 2:__get_user_asm(*(u16 *)dst, (u16 __user *)src,
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ret, "w", "w", "=r", 2);
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return ret;
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case 4:__get_user_asm(*(u32 *)dst, (u32 __user *)src,
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ret, "l", "k", "=r", 4);
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return ret;
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case 8:__get_user_asm(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 8);
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return ret;
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case 10:
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__get_user_asm(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 10);
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if (unlikely(ret))
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return ret;
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__get_user_asm(*(u16 *)(8 + (char *)dst),
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(u16 __user *)(8 + (char __user *)src),
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ret, "w", "w", "=r", 2);
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return ret;
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case 16:
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__get_user_asm(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 16);
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if (unlikely(ret))
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return ret;
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__get_user_asm(*(u64 *)(8 + (char *)dst),
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(u64 __user *)(8 + (char __user *)src),
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ret, "q", "", "=r", 8);
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return ret;
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default:
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return copy_user_generic(dst, (__force void *)src, size);
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}
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}
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static __always_inline __must_check
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int __copy_from_user(void *dst, const void __user *src, unsigned size)
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{
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might_fault();
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return __copy_from_user_nocheck(dst, src, size);
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}
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static __always_inline __must_check
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int __copy_to_user_nocheck(void __user *dst, const void *src, unsigned size)
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{
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int ret = 0;
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if (!__builtin_constant_p(size))
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return copy_user_generic((__force void *)dst, src, size);
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switch (size) {
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case 1:__put_user_asm(*(u8 *)src, (u8 __user *)dst,
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ret, "b", "b", "iq", 1);
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return ret;
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case 2:__put_user_asm(*(u16 *)src, (u16 __user *)dst,
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ret, "w", "w", "ir", 2);
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return ret;
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case 4:__put_user_asm(*(u32 *)src, (u32 __user *)dst,
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ret, "l", "k", "ir", 4);
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return ret;
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case 8:__put_user_asm(*(u64 *)src, (u64 __user *)dst,
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ret, "q", "", "er", 8);
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return ret;
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case 10:
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__put_user_asm(*(u64 *)src, (u64 __user *)dst,
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ret, "q", "", "er", 10);
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if (unlikely(ret))
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return ret;
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asm("":::"memory");
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__put_user_asm(4[(u16 *)src], 4 + (u16 __user *)dst,
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ret, "w", "w", "ir", 2);
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return ret;
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case 16:
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__put_user_asm(*(u64 *)src, (u64 __user *)dst,
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ret, "q", "", "er", 16);
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if (unlikely(ret))
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return ret;
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asm("":::"memory");
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__put_user_asm(1[(u64 *)src], 1 + (u64 __user *)dst,
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ret, "q", "", "er", 8);
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return ret;
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default:
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return copy_user_generic((__force void *)dst, src, size);
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}
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}
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static __always_inline __must_check
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int __copy_to_user(void __user *dst, const void *src, unsigned size)
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{
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might_fault();
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return __copy_to_user_nocheck(dst, src, size);
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}
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static __always_inline __must_check
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int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
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{
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int ret = 0;
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might_fault();
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if (!__builtin_constant_p(size))
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return copy_user_generic((__force void *)dst,
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(__force void *)src, size);
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switch (size) {
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case 1: {
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u8 tmp;
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__get_user_asm(tmp, (u8 __user *)src,
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ret, "b", "b", "=q", 1);
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if (likely(!ret))
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__put_user_asm(tmp, (u8 __user *)dst,
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ret, "b", "b", "iq", 1);
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return ret;
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}
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case 2: {
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u16 tmp;
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__get_user_asm(tmp, (u16 __user *)src,
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ret, "w", "w", "=r", 2);
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if (likely(!ret))
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__put_user_asm(tmp, (u16 __user *)dst,
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ret, "w", "w", "ir", 2);
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return ret;
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}
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case 4: {
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u32 tmp;
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__get_user_asm(tmp, (u32 __user *)src,
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ret, "l", "k", "=r", 4);
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if (likely(!ret))
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__put_user_asm(tmp, (u32 __user *)dst,
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ret, "l", "k", "ir", 4);
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return ret;
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}
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case 8: {
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u64 tmp;
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__get_user_asm(tmp, (u64 __user *)src,
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ret, "q", "", "=r", 8);
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if (likely(!ret))
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__put_user_asm(tmp, (u64 __user *)dst,
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ret, "q", "", "er", 8);
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return ret;
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}
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default:
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return copy_user_generic((__force void *)dst,
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(__force void *)src, size);
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}
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}
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static __must_check __always_inline int
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__copy_from_user_inatomic(void *dst, const void __user *src, unsigned size)
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{
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return __copy_from_user_nocheck(dst, src, size);
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}
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static __must_check __always_inline int
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__copy_to_user_inatomic(void __user *dst, const void *src, unsigned size)
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{
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return __copy_to_user_nocheck(dst, src, size);
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}
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extern long __copy_user_nocache(void *dst, const void __user *src,
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unsigned size, int zerorest);
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static inline int
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__copy_from_user_nocache(void *dst, const void __user *src, unsigned size)
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{
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might_fault();
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return __copy_user_nocache(dst, src, size, 1);
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}
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static inline int
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__copy_from_user_inatomic_nocache(void *dst, const void __user *src,
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unsigned size)
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{
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return __copy_user_nocache(dst, src, size, 0);
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}
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unsigned long
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copy_user_handle_tail(char *to, char *from, unsigned len);
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#endif /* _ASM_X86_UACCESS_64_H */
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