kmem_alloc man page on SmartOS

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       kmem_alloc, kmem_zalloc, kmem_free - allocate kernel memory

       #include <sys/types.h>
       #include <sys/kmem.h>

       void *kmem_alloc(size_t size, int flag);

       void *kmem_zalloc(size_t size, int flag);

       void kmem_free(void*buf, size_t size);

       Architecture independent level 1 (DDI/DKI).

	       Number of bytes to allocate.

	       Determines  whether caller can sleep for memory. Possible flags
	       are KM_SLEEP to allow sleeping until memory  is	available,  or
	       KM_NOSLEEP  to  return NULL immediately if memory is not avail‐

	       Pointer to allocated memory.

       The kmem_alloc() function allocates size bytes  of  kernel  memory  and
       returns	a  pointer to the allocated memory. The allocated memory is at
       least double-word aligned, so it can hold  any  C  data	structure.  No
       greater	alignment  can	be assumed. flag determines whether the caller
       can sleep for memory.  KM_SLEEP allocations may sleep but  are  guaran‐
       teed  to	 succeed.   KM_NOSLEEP allocations are guaranteed not to sleep
       but may fail (return NULL) if no memory	is  currently  available.  The
       initial	contents  of  memory  allocated	 using kmem_alloc() are random

       The kmem_zalloc() function is like kmem_alloc() but returns zero-filled

       The  kmem_free() function frees previously allocated kernel memory. The
       buffer address and size must exactly  match  the	 original  allocation.
       Memory cannot be returned piecemeal.

       If  successful,	kmem_alloc() and kmem_zalloc() return a pointer to the
       allocated memory. If KM_NOSLEEP is set and memory cannot	 be  allocated
       without sleeping, kmem_alloc() and kmem_zalloc() return NULL.

       The  kmem_alloc() and kmem_zalloc() functions can be called from inter‐
       rupt context only if the KM_NOSLEEP flag is set.	 They  can  be	called
       from  user context with any valid flag. The kmem_free() function can be
       called from from user, interrupt, or kernel context.

       copyout(9F), freerbuf(9F), getrbuf(9F)

       Writing Device Drivers

       Memory allocated using kmem_alloc() is not paged. Available  memory  is
       therefore  limited  by  the  total physical memory on the system. It is
       also limited by the available kernel virtual address  space,  which  is
       often the more restrictive constraint on large-memory configurations.

       Excessive  use of kernel memory is likely to affect overall system per‐
       formance.  Overcommitment of kernel memory will	cause  the  system  to
       hang or panic.

       Misuse  of the kernel memory allocator, such as writing past the end of
       a buffer, using a buffer after freeing it, freeing a buffer  twice,  or
       freeing a null or invalid pointer, will corrupt the kernel heap and may
       cause the system to corrupt data or panic.

       The initial contents of memory allocated using kmem_alloc() are	random
       garbage. This random garbage may include secure kernel data. Therefore,
       uninitialized kernel memory should be handled carefully.	 For  example,
       never copyout(9F) a potentially uninitialized buffer.

       kmem_alloc(0, flag) always returns NULL.	 kmem_free(NULL, 0) is legal.

				 Jan 16, 2006			KMEM_ALLOC(9F)

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