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![David Hildenbrand](/assets/img/avatar_default.png)
As the fault handlers now all rely on the pagefault_disabled() checks and implicit preempt_disable() calls by pagefault_disable() have been made explicit, we can completely rely on the pagefault_disableD counter. So let's no longer touch the preempt count when disabling/enabling pagefaults. After a call to pagefault_disable(), pagefault_disabled() will return true, but in_atomic() won't. Reviewed-and-tested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: airlied@linux.ie Cc: akpm@linux-foundation.org Cc: benh@kernel.crashing.org Cc: bigeasy@linutronix.de Cc: borntraeger@de.ibm.com Cc: daniel.vetter@intel.com Cc: heiko.carstens@de.ibm.com Cc: herbert@gondor.apana.org.au Cc: hocko@suse.cz Cc: hughd@google.com Cc: mst@redhat.com Cc: paulus@samba.org Cc: ralf@linux-mips.org Cc: schwidefsky@de.ibm.com Cc: yang.shi@windriver.com Link: http://lkml.kernel.org/r/1431359540-32227-16-git-send-email-dahi@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
132 lines
4 KiB
C
132 lines
4 KiB
C
#ifndef __LINUX_UACCESS_H__
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#define __LINUX_UACCESS_H__
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#include <linux/sched.h>
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#include <asm/uaccess.h>
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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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WARN_ON(current->pagefault_disabled < 0);
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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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#define pagefault_disabled() (current->pagefault_disabled != 0)
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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 ARCH_HAS_NOCACHE_UACCESS
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static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
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const void __user *from, 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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static inline unsigned long __copy_from_user_nocache(void *to,
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const void __user *from, unsigned long n)
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{
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return __copy_from_user(to, from, n);
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}
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#endif /* ARCH_HAS_NOCACHE_UACCESS */
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/**
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* probe_kernel_address(): safely attempt to read from a location
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* @addr: address to read from - its type is type typeof(retval)*
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* @retval: read into this variable
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*
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* Safely read from address @addr into variable @revtal. If a kernel fault
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* happens, handle that and return -EFAULT.
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* We ensure that the __get_user() is executed in atomic context so that
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* do_page_fault() doesn't attempt to take mmap_sem. This makes
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* probe_kernel_address() suitable for use within regions where the caller
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* already holds mmap_sem, or other locks which nest inside mmap_sem.
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* This must be a macro because __get_user() needs to know the types of the
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* args.
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*
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* We don't include enough header files to be able to do the set_fs(). We
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* require that the probe_kernel_address() caller will do that.
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*/
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#define probe_kernel_address(addr, retval) \
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({ \
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long ret; \
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mm_segment_t old_fs = get_fs(); \
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\
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set_fs(KERNEL_DS); \
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pagefault_disable(); \
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ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval)); \
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pagefault_enable(); \
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set_fs(old_fs); \
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ret; \
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})
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/*
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* probe_kernel_read(): safely attempt to read from a location
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* @dst: pointer to the buffer that shall take the data
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* @src: address to read from
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* @size: size of the data chunk
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*
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* Safely read from address @src to the buffer at @dst. If a kernel fault
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* happens, handle that and return -EFAULT.
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*/
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extern long probe_kernel_read(void *dst, const void *src, size_t size);
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extern long __probe_kernel_read(void *dst, const void *src, size_t size);
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/*
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* probe_kernel_write(): safely attempt to write to a location
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* @dst: address to write to
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* @src: pointer to the data that shall be written
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* @size: size of the data chunk
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*
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* Safely write to address @dst from the buffer at @src. If a kernel fault
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* happens, handle that and return -EFAULT.
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*/
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extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
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extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
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#endif /* __LINUX_UACCESS_H__ */
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