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FREE(9r)
NAME
  FREE - General: Deallocates (frees) the allocated kernel virtual memory

SYNOPSIS
  #include <sys/malloc.h>

  FREE(
	  void *addr,
	  int type );

ARGUMENTS
  addr
      Specifies the memory pointer that points to the allocated memory to be
      freed. You must have previously set this pointer in the call to MALLOC.
      You also define the data type for this argument in the call to MALLOC.

  type
      Specifies the purpose for which the memory is being allocated.  The
      memory types are defined in the file <malloc.h>. Typically, kernel
      modules use the constant M_DEVBUF to indicate that kernel module memory
      is being allocated (or freed).

DESCRIPTION
  The FREE routine deallocates (frees) the allocated kernel virtual memory,
  which you allocated in a previous call to MALLOC.

NOTES
  A memory corruption can occur if a kernel module continues to use the
  memory after freeing it. The operating system provides a built-in mechanism
  to debug such erroneous use of memory. You can enable this debugging
  feature at boot time by providing the following boot parameter:
  kmem_debug=1. When you enable this debugging feature, the FREE routine
  stores the following in the last word of freed memory:

    ·  The program counter (pc) of the module that last freed the memory

    ·  The checksum of the memory content

  The MALLOC routine checks the checksum of the memory content before
  reallocating this corrupted memory. If the checksum of the memory content
  does not match the corrupted memory, MALLOC stores the debug information
  and then causes the kernel to panic. The MALLOC routine stores the address
  and size of the corrupted memory and the pc of the routine that last freed
  it in a kmem_corrupt_data structure.

  You should consider the following when using this debugging feature:

    ·  This debugging feature does not detect cases where the corruption
       occurs after malloc reallocates the freed memory to some other module.

    ·  There is a small chance that the pc of the routine that freed the
       memory (stored in the last word of freed memory) may itself become
       corrupted.

RETURN VALUES
  None

SEE ALSO
  Routines: MALLOC(9r)

Index for Section 9r

Alphabetical listing for F

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