cregit-Linux how code gets into the kernel

Release 4.12 include/linux/uaccess.h

Directory: include/linux
#ifndef __LINUX_UACCESS_H__

#define __LINUX_UACCESS_H__

#include <linux/sched.h>
#include <linux/thread_info.h>
#include <linux/kasan-checks.h>


#define VERIFY_READ 0

#define VERIFY_WRITE 1


#define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)

#include <asm/uaccess.h>

/*
 * Architectures should provide two primitives (raw_copy_{to,from}_user())
 * and get rid of their private instances of copy_{to,from}_user() and
 * __copy_{to,from}_user{,_inatomic}().
 *
 * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
 * return the amount left to copy.  They should assume that access_ok() has
 * already been checked (and succeeded); they should *not* zero-pad anything.
 * No KASAN or object size checks either - those belong here.
 *
 * Both of these functions should attempt to copy size bytes starting at from
 * into the area starting at to.  They must not fetch or store anything
 * outside of those areas.  Return value must be between 0 (everything
 * copied successfully) and size (nothing copied).
 *
 * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
 * at to must become equal to the bytes fetched from the corresponding area
 * starting at from.  All data past to + size - N must be left unmodified.
 *
 * If copying succeeds, the return value must be 0.  If some data cannot be
 * fetched, it is permitted to copy less than had been fetched; the only
 * hard requirement is that not storing anything at all (i.e. returning size)
 * should happen only when nothing could be copied.  In other words, you don't
 * have to squeeze as much as possible - it is allowed, but not necessary.
 *
 * For raw_copy_from_user() to always points to kernel memory and no faults
 * on store should happen.  Interpretation of from is affected by set_fs().
 * For raw_copy_to_user() it's the other way round.
 *
 * Both can be inlined - it's up to architectures whether it wants to bother
 * with that.  They should not be used directly; they are used to implement
 * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
 * that are used instead.  Out of those, __... ones are inlined.  Plain
 * copy_{to,from}_user() might or might not be inlined.  If you want them
 * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
 *
 * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
 * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
 * at all; their callers absolutely must check the return value.
 *
 * Biarch ones should also provide raw_copy_in_user() - similar to the above,
 * but both source and destination are __user pointers (affected by set_fs()
 * as usual) and both source and destination can trigger faults.
 */


static __always_inline unsigned long __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) { kasan_check_write(to, n); check_object_size(to, n, false); return raw_copy_from_user(to, from, n); }

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static __always_inline unsigned long __copy_from_user(void *to, const void __user *from, unsigned long n) { might_fault(); kasan_check_write(to, n); check_object_size(to, n, false); return raw_copy_from_user(to, from, n); }

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/** * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking. * @to: Destination address, in user space. * @from: Source address, in kernel space. * @n: Number of bytes to copy. * * Context: User context only. * * Copy data from kernel space to user space. Caller must check * the specified block with access_ok() before calling this function. * The caller should also make sure he pins the user space address * so that we don't result in page fault and sleep. */
static __always_inline unsigned long __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) { kasan_check_read(from, n); check_object_size(from, n, true); return raw_copy_to_user(to, from, n); }

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static __always_inline unsigned long __copy_to_user(void __user *to, const void *from, unsigned long n) { might_fault(); kasan_check_read(from, n); check_object_size(from, n, true); return raw_copy_to_user(to, from, n); }

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#ifdef INLINE_COPY_FROM_USER
static inline unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n) { unsigned long res = n; if (likely(access_ok(VERIFY_READ, from, n))) res = raw_copy_from_user(to, from, n); if (unlikely(res)) memset(to + (n - res), 0, res); return res; }

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#else extern unsigned long _copy_from_user(void *, const void __user *, unsigned long); #endif #ifdef INLINE_COPY_TO_USER
static inline unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n) { if (access_ok(VERIFY_WRITE, to, n)) n = raw_copy_to_user(to, from, n); return n; }

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#else extern unsigned long _copy_to_user(void __user *, const void *, unsigned long); #endif extern void __compiletime_error("usercopy buffer size is too small") __bad_copy_user(void);
static inline void copy_user_overflow(int size, unsigned long count) { WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); }

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static __always_inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n) { int sz = __compiletime_object_size(to); might_fault(); kasan_check_write(to, n); if (likely(sz < 0 || sz >= n)) { check_object_size(to, n, false); n = _copy_from_user(to, from, n); } else if (!__builtin_constant_p(n)) copy_user_overflow(sz, n); else __bad_copy_user(); return n; }

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static __always_inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n) { int sz = __compiletime_object_size(from); kasan_check_read(from, n); might_fault(); if (likely(sz < 0 || sz >= n)) { check_object_size(from, n, true); n = _copy_to_user(to, from, n); } else if (!__builtin_constant_p(n)) copy_user_overflow(sz, n); else __bad_copy_user(); return n; }

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#ifdef CONFIG_COMPAT
static __always_inline unsigned long __must_check __copy_in_user(void __user *to, const void *from, unsigned long n) { might_fault(); return raw_copy_in_user(to, from, n); }

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static __always_inline unsigned long __must_check copy_in_user(void __user *to, const void *from, unsigned long n) { might_fault(); if (access_ok(VERIFY_WRITE, to, n) && access_ok(VERIFY_READ, from, n)) n = raw_copy_in_user(to, from, n); return n; }

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#endif
static __always_inline void pagefault_disabled_inc(void) { current->pagefault_disabled++; }

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static __always_inline void pagefault_disabled_dec(void) { current->pagefault_disabled--; }

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/* * These routines enable/disable the pagefault handler. If disabled, it will * not take any locks and go straight to the fixup table. * * User access methods will not sleep when called from a pagefault_disabled() * environment. */
static inline void pagefault_disable(void) { pagefault_disabled_inc(); /* * make sure to have issued the store before a pagefault * can hit. */ barrier(); }

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static inline void pagefault_enable(void) { /* * make sure to issue those last loads/stores before enabling * the pagefault handler again. */ barrier(); pagefault_disabled_dec(); }

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/* * Is the pagefault handler disabled? If so, user access methods will not sleep. */ #define pagefault_disabled() (current->pagefault_disabled != 0) /* * The pagefault handler is in general disabled by pagefault_disable() or * when in irq context (via in_atomic()). * * This function should only be used by the fault handlers. Other users should * stick to pagefault_disabled(). * Please NEVER use preempt_disable() to disable the fault handler. With * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled. * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT. */ #define faulthandler_disabled() (pagefault_disabled() || in_atomic()) #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); }

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#endif /* ARCH_HAS_NOCACHE_UACCESS */ /* * 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); extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); /** * probe_kernel_address(): safely attempt to read from a location * @addr: address to read from * @retval: read into this variable * * Returns 0 on success, or -EFAULT. */ #define probe_kernel_address(addr, retval) \ probe_kernel_read(&retval, addr, sizeof(retval)) #ifndef user_access_begin #define user_access_begin() do { } while (0) #define user_access_end() do { } while (0) #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0) #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0) #endif #endif /* __LINUX_UACCESS_H__ */

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Jason Wessel343.43%15.88%
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Total990100.00%17100.00%
Directory: include/linux
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