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== WARNING - COMMUNIST PROPAGANDA DETECTED. MATERIAL THAT GENERATED THE OFFENSE: ==
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[[File:freedom-bird.jpg|thumb|Never forget.]]
 +
This is what we all strive for. We want to be big strong independent basement dwellers who still live in their parents' home. Achieving total freedom in his use of technology is the greatest accomplishment a [[gentoomen]] can attain. There are rumors that when this happens, golden light starts to emanate from your computer screen and [[Richard Stallman]] materializes in your room.  He has written the [[GPL]] to help you reach this state of nirvana.
  
  This is what we all strive for. We want to be big strong independent basement dwellers who still live in their parents' home. Achieving total freedom in his use of technology is the greatest accomplishment a [[gentoomen]] can attain.
 
  There are rumors that when this happens, golden light starts to emanate from your computer screen and [[Richard Stallman]] materializes in your room.  He has written the [[GPL]] to help you reach this state of nirvana.
 
  [https://www.youtube.com/watch?v=EJ_wXOFQV3M  In order to have true freedom, you must have:]
 
  * The freedom to run the program, for any purpose (freedom 0).
 
  * The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this.
 
  * The freedom to redistribute copies so you can help your neighbor (freedom 2).
 
  * The freedom to distribute copies of your modified versions to others (freedom 3). By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.
 
  
=== ADMINISTERING SANE AND RATIONAL COUNTERMEASURES FOR THOSE SEEKING THE /g/ WIKI PAGE "Free": ===
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[https://www.youtube.com/watch?v=EJ_wXOFQV3M In order to have true freedom, you must have:]
 
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* The freedom to run the program, for any purpose (freedom 0).
 
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* The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this.
MALLOC(3)                OpenBSD Programmer's Manual                MALLOC(3)
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* The freedom to redistribute copies so you can help your neighbor (freedom 2).
 
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* The freedom to distribute copies of your modified versions to others (freedom 3). By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.
NAME
 
    malloc, calloc, realloc, free, cfree - memory allocation and deallocation
 
 
 
SYNOPSIS
 
    #include <stdlib.h>
 
 
 
    void *
 
    malloc(size_t size);
 
 
 
    void *
 
    calloc(size_t nmemb, size_t size);
 
 
 
    void *
 
    realloc(void *ptr, size_t size);
 
 
 
    void
 
    free(void *ptr);
 
 
 
    void
 
    cfree(void *ptr);
 
 
 
    char * malloc_options;
 
 
 
DESCRIPTION
 
    The malloc() function allocates uninitialized space for an object whose
 
    size is specified by size. The malloc() function maintains multiple
 
    lists of free blocks according to size, allocating space from the
 
    appropriate list.
 
 
 
    The allocated space is suitably aligned (after possible pointer coercion)
 
    for storage of any type of objectIf the space is of pagesize or
 
    larger, the memory returned will be page-aligned.
 
 
 
    Allocation of a zero size object returns a pointer to a zero size object.
 
    This zero size object is access protected, so any access to it will
 
    generate an exception (SIGSEGV).  Many zero-sized objects can be placed
 
    consecutively in shared protected pages.  The minimum size of the
 
    protection on each object is suitably aligned and sized as previously
 
    stated, but the protection may extend further depending on where in a
 
    protected zone the object lands.
 
 
 
    When using malloc() be careful to avoid the following idiom:
 
 
 
          if ((p = malloc(num * size)) == NULL)
 
                  err(1, "malloc");
 
 
 
    The multiplication may lead to an integer overflow.  To avoid this,
 
    calloc() is recommended.
 
 
 
    If malloc() must be used, be sure to test for overflow:
 
 
 
          if (size && num > SIZE_MAX / size) {
 
                  errno = ENOMEM;
 
                  err(1, "overflow");
 
          }
 
 
 
    The calloc() function allocates space for an array of nmemb objects, each
 
    of whose size is size.  The space is initialized to zero.  The use of
 
    calloc() is strongly encouraged when allocating multiple sized objects in
 
    order to avoid possible integer overflows.
 
 
 
    The free() function causes the space pointed to by ptr to be either
 
    placed on a list of free pages to make it available for future allocation
 
    or, if required, to be returned to the kernel using munmap(2).  If ptr is
 
    a null pointer, no action occurs.
 
 
 
    A cfree() function is also provided for compatibility with old systems
 
    and other malloc libraries; it is simply an alias for free().
 
 
 
    The realloc() function changes the size of the object pointed to by ptr
 
    to size bytes and returns a pointer to the (possibly moved) object.  The
 
    contents of the object are unchanged up to the lesser of the new and old
 
    sizes.  If the new size is larger, the value of the newly allocated
 
    portion of the object is indeterminate and uninitialized.  If ptr is a
 
    null pointer, the realloc() function behaves like the malloc() function
 
    for the specified size.  If the space cannot be allocated, the object
 
    pointed to by ptr is unchanged.  If size is zero and ptr is not a null
 
    pointer, the object it points to is freed and a new zero size object is
 
    returned.
 
 
 
    When using realloc() be careful to avoid the following idiom:
 
 
 
          size += 50;
 
          if ((p = realloc(p, size)) == NULL)
 
                  return (NULL);
 
 
 
    Do not adjust the variable describing how much memory has been allocated
 
    until the allocation has been successful.  This can cause aberrant
 
    program behavior if the incorrect size value is used.  In most cases, the
 
    above sample will also result in a leak of memory.  As stated earlier, a
 
    return value of NULL indicates that the old object still remains
 
    allocated.  Better code looks like this:
 
 
 
          newsize = size + 50;
 
          if ((newp = realloc(p, newsize)) == NULL) {
 
                  free(p);
 
                  p = NULL;
 
                  size = 0;
 
                  return (NULL);
 
          }
 
          p = newp;
 
          size = newsize;
 
 
 
    As with malloc() it is important to ensure the new size value will not
 
    overflow; i.e. avoid allocations like the following:
 
 
 
          if ((newp = realloc(p, num * size)) == NULL) {
 
                  ...
 
 
 
MALLOC_OPTIONS
 
    Malloc will first look for a symbolic link called /etc/malloc.conf and
 
    next check the environment for a variable called MALLOC_OPTIONS and
 
    finally for the global variable malloc_options and scan them for flags in
 
    that order.  Flags are single letters, uppercase means on, lowercase
 
    means off.
 
 
 
    A      ``Abort''.  malloc() will coredump the process, rather than
 
            tolerate internal inconsistencies or incorrect usage.  This is
 
            the default and a very handy debugging aid, since the core file
 
            represents the time of failure, rather than when the bogus
 
            pointer was used.
 
 
 
    D      ``Dump''.  malloc() will dump statistics to the file
 
            ./malloc.out, if it already exists, at exit.  This option
 
            requires the library to have been compiled with -DMALLOC_STATS in
 
            order to have any effect.
 
 
 
    F      ``Freeguard''.  Enable use after free detection.  Unused pages on
 
            the freelist are read and write protected to cause a segmentation
 
            fault upon access.  This will also switch off the delayed freeing
 
            of chunks, reducing random behaviour but detecting double free()
 
            calls as early as possible.  This option is intended for
 
            debugging rather than improved security (use the U option for
 
            security).
 
 
 
    G      ``Guard''.  Enable guard pages.  Each page size or larger
 
            allocation is followed by a guard page that will cause a
 
            segmentation fault upon any access.
 
 
 
    H      ``Hint''.  Pass a hint to the kernel about pages we don't use.
 
            If the machine is paging a lot this may help a bit.
 
 
 
    J      ``Junk''.  Fill some junk into the area allocated.  Currently
 
            junk is bytes of 0xd0 when allocating; this is pronounced
 
            ``Duh''.  :-) Freed chunks are filled with 0xdf.
 
 
 
    P      ``Move allocations within a page.''  Allocations larger than half
 
            a page but smaller than a page are aligned to the end of a page
 
            to catch buffer overruns in more cases.  This is the default.
 
 
 
    R      ``realloc''.  Always reallocate when realloc() is called, even if
 
            the initial allocation was big enough.  This can substantially
 
            aid in compacting memory.
 
 
 
    S      Enable all options suitable for security auditing.
 
 
 
    U      ``Free unmap''.  Enable use after free protection for larger
 
            allocations.  Unused pages on the freelist are read and write
 
            protected to cause a segmentation fault upon access.
 
 
 
    X      ``xmalloc''.  Rather than return failure, abort(3) the program
 
            with a diagnostic message on stderr. It is the intention that
 
            this option be set at compile time by including in the source:
 
 
 
                  extern char *malloc_options;
 
                  malloc_options = "X";
 
 
 
            Note that this will cause code that is supposed to handle out-of-
 
            memory conditions gracefully to abort instead.
 
 
 
    Z      ``Zero''.  Fill some junk into the area allocated (see J), except
 
            for the exact length the user asked for, which is zeroed.
 
 
 
    <      ``Half the cache size''.  Decrease the size of the free page
 
            cache by a factor of two.
 
 
 
    >      ``Double the cache size''.  Increase the size of the free page
 
            cache by a factor of two.
 
 
 
    So to set a systemwide reduction of the cache to a quarter of the default
 
    size and use guard pages:
 
          # ln -s 'G<<' /etc/malloc.conf
 
 
 
    The flags are mostly for testing and debugging.  If a program changes
 
    behavior if any of these options (except X) are used, it is buggy.
 
 
 
    The default number of free pages cached is 64.
 
 
 
RETURN VALUES
 
    The malloc() and calloc() functions return a pointer to the allocated
 
    space if successful; otherwise, a null pointer is returned and errno is
 
    set to ENOMEM.
 
 
 
    The free() and cfree() functions return no value.
 
 
 
    The realloc() function returns a pointer to the (possibly moved)
 
    allocated space if successful; otherwise, a null pointer is returned and
 
    errno is set to ENOMEM.
 
 
 
ENVIRONMENT
 
    MALLOC_OPTIONS  See above.
 
 
 
FILES
 
    /etc/malloc.conf  symbolic link to filename containing option flags
 
 
 
DIAGNOSTICS
 
    If malloc(), calloc(), realloc(), or free() detect an error condition, a
 
    message will be printed to file descriptor 2 (not using stdio).  Errors
 
    will result in the process being aborted, unless the a option has been
 
    specified.
 
 
 
    Here is a brief description of the error messages and what they mean:
 
 
 
    ``out of memory''
 
            If the X option is specified it is an error for malloc(),
 
            calloc(), or realloc() to return NULL.
 
 
 
    ``malloc init mmap failed''
 
            This is a rather weird condition that is most likely to indicate
 
            a seriously overloaded system or a ulimit restriction.
 
 
 
    ``bogus pointer (double free?)''
 
            An attempt to free() or realloc() an unallocated pointer was
 
            made.
 
 
 
    ``chunk is already free''
 
            There was an attempt to free a chunk that had already been freed.
 
 
 
    ``modified chunk-pointer''
 
            The pointer passed to free() or realloc() has been modified.
 
 
 
    ``recursive call''
 
            An attempt was made to call recursively into these functions,
 
            i.e., from a signal handler.  This behavior is not supported.  In
 
            particular, signal handlers should not use any of the malloc()
 
            functions nor utilize any other functions which may call malloc()
 
            (e.g., stdio(3) routines).
 
 
 
    ``unknown char in MALLOC_OPTIONS''
 
            We found something we didn't understand.
 
 
 
    ``malloc cache overflow/underflow''
 
            The internal malloc page cache has been corrupted.
 
 
 
    ``malloc free slot lost''
 
            The internal malloc page cache has been corrupted.
 
 
 
    ``guard size''
 
            An inconsistent guard size was detected.
 
 
 
    any other error
 
            malloc() detected an internal error; consult sources and/or
 
            wizards.
 
 
 
SEE ALSO
 
    brk(2), mmap(2), munmap(2), alloca(3), getpagesize(3), posix_memalign(3)
 
 
 
STANDARDS
 
    The malloc() function conforms to ANSI X3.159-1989 (``ANSI C89'').
 
 
 
HISTORY
 
    A free() internal kernel function and a predecessor to malloc(), alloc(),
 
    first appeared in Version 1 AT&T UNIX.  C library functions alloc() and
 
    free() appeared in Version 6 AT&T UNIX.  The functions malloc(),
 
    calloc(), and realloc() first appeared in Version 7 AT&T UNIX.
 
 
 
    A new implementation by Chris Kingsley was introduced in 4.2BSD, followed
 
    by a complete rewrite by Poul-Henning Kamp which appeared in FreeBSD 2.2
 
    and was included in OpenBSD 2.0.  These implementations were all sbrk(2)
 
    based.  In OpenBSD 3.8, Thierry Deval rewrote malloc to use the mmap(2)
 
    system call, making the page addresses returned by malloc random.  A
 
    rewrite by Otto Moerbeek introducing a new central data structure and
 
    more randomization appeared in OpenBSD 4.4.
 
 
 
OpenBSD 5.4                      July 18, 2013                    OpenBSD 5.4
 

Revision as of 19:41, 14 November 2014

Never forget.

This is what we all strive for. We want to be big strong independent basement dwellers who still live in their parents' home. Achieving total freedom in his use of technology is the greatest accomplishment a gentoomen can attain. There are rumors that when this happens, golden light starts to emanate from your computer screen and Richard Stallman materializes in your room. He has written the GPL to help you reach this state of nirvana.


In order to have true freedom, you must have:

  • The freedom to run the program, for any purpose (freedom 0).
  • The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this.
  • The freedom to redistribute copies so you can help your neighbor (freedom 2).
  • The freedom to distribute copies of your modified versions to others (freedom 3). By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.