83        often the more restrictive constraint on large-memory configurations.
  84 
  85 
  86        Excessive use of kernel memory is likely to affect overall system
  87        performance.  Overcommitment of kernel memory will cause the system to
  88        hang or panic.
  89 
  90 
  91        Misuse of the kernel memory allocator, such as writing past the end of
  92        a buffer, using a buffer after freeing it, freeing a buffer twice, or
  93        freeing a null or invalid pointer, will corrupt the kernel heap and may
  94        cause the system to corrupt data or panic.
  95 
  96 
  97        The initial contents of memory allocated using kmem_alloc() are random
  98        garbage. This random garbage may include secure kernel data. Therefore,
  99        uninitialized kernel memory should be handled carefully. For example,
 100        never copyout(9F) a potentially uninitialized buffer.
 101 
 102 NOTES
 103        kmem_alloc(0, flag) always returns NULL.  kmem_free(NULL, 0) is legal.



 104 
 105 
 106 
 107                                October 22, 2014                 KMEM_ALLOC(9F)

  83        often the more restrictive constraint on large-memory configurations.
  84 
  85 
  86        Excessive use of kernel memory is likely to affect overall system
  87        performance.  Overcommitment of kernel memory will cause the system to
  88        hang or panic.
  89 
  90 
  91        Misuse of the kernel memory allocator, such as writing past the end of
  92        a buffer, using a buffer after freeing it, freeing a buffer twice, or
  93        freeing a null or invalid pointer, will corrupt the kernel heap and may
  94        cause the system to corrupt data or panic.
  95 
  96 
  97        The initial contents of memory allocated using kmem_alloc() are random
  98        garbage. This random garbage may include secure kernel data. Therefore,
  99        uninitialized kernel memory should be handled carefully. For example,
 100        never copyout(9F) a potentially uninitialized buffer.
 101 
 102 NOTES
 103        kmem_alloc(0, flag) always returns NULL, but if KM_SLEEP is set, this
 104        behavior is considered to be deprecated; the system may be configured
 105        to explicitly panic in this case in lieu of returning NULL.
 106        kmem_free(NULL, 0) is legal, however.
 107 
 108 
 109 
 110                                November 20, 2019                KMEM_ALLOC(9F)