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kmalloc_array(9) [centos man page]

KMALLOC_ARRAY(9)					    Memory Management in Linux						  KMALLOC_ARRAY(9)

NAME
kmalloc_array - allocate memory for an array. SYNOPSIS
void * kmalloc_array(size_t n, size_t size, gfp_t flags); ARGUMENTS
n number of elements. size element size. flags the type of memory to allocate. DESCRIPTION
The flags argument may be one of: GFP_USER - Allocate memory on behalf of user. May sleep. GFP_KERNEL - Allocate normal kernel ram. May sleep. GFP_ATOMIC - Allocation will not sleep. May use emergency pools. For example, use this inside interrupt handlers. GFP_HIGHUSER - Allocate pages from high memory. GFP_NOIO - Do not do any I/O at all while trying to get memory. GFP_NOFS - Do not make any fs calls while trying to get memory. GFP_NOWAIT - Allocation will not sleep. __GFP_THISNODE - Allocate node-local memory only. GFP_DMA - Allocation suitable for DMA. Should only be used for kmalloc caches. Otherwise, use a slab created with SLAB_DMA. Also it is possible to set different flags by OR'ing in one or more of the following additional flags: __GFP_COLD - Request cache-cold pages instead of trying to return cache-warm pages. __GFP_HIGH - This allocation has high priority and may use emergency pools. __GFP_NOFAIL - Indicate that this allocation is in no way allowed to fail (think twice before using). __GFP_NORETRY - If memory is not immediately available, then give up at once. __GFP_NOWARN - If allocation fails, don't issue any warnings. __GFP_REPEAT - If allocation fails initially, try once more before failing. There are other flags available as well, but these are not intended for general use, and so are not documented here. For a full list of potential flags, always refer to linux/gfp.h. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 KMALLOC_ARRAY(9)

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kmem_alloc(9F)						   Kernel Functions for Drivers 					    kmem_alloc(9F)

NAME
kmem_alloc, kmem_zalloc, kmem_free - allocate kernel memory SYNOPSIS
#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); INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI). PARAMETERS
size Number of bytes to allocate. flag 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 available. buf Pointer to allocated memory. DESCRIPTION
kmem_alloc() 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 guaranteed 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 garbage. kmem_zalloc() is like kmem_alloc() but returns zero-filled memory. kmem_free() frees previously allocated kernel memory. The buffer address and size must exactly match the original allocation. Memory can- not be returned piecemeal. RETURN VALUES
If successful, kmem_alloc() and kmem_zalloc() return a pointer to the allocated memory. If KM_NOSLEEP is set and memory cannot be allo- cated without sleeping, kmem_alloc() and kmem_zalloc() return NULL. CONTEXT
kmem_alloc() and kmem_zalloc() can be called from interrupt context only if the KM_NOSLEEP flag is set. They can be called from user con- text with any valid flag. kmem_free() can be called from user or interrupt context. SEE ALSO
copyout(9F), freerbuf(9F), getrbuf(9F) Writing Device Drivers WARNINGS
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 performance. 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. There- fore, uninitialized kernel memory should be handled carefully. For example, never copyout(9F) a potentially uninitialized buffer. NOTES
kmem_alloc(0, flag) always returns NULL. kmem_free(NULL, 0) is legal. SunOS 5.10 24 Mar 2003 kmem_alloc(9F)
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