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explain_ptrace(3)	   Library Functions Manual	     explain_ptrace(3)

NAME
       explain_ptrace -	explain	ptrace(2) errors

SYNOPSIS
       #include	<libexplain/ptrace.h>
       const char *explain_ptrace(int request, pid_t pid, void *addr, void
       *data);
       const char *explain_errno_ptrace(int errnum, int	request, pid_t pid,
       void *addr, void	*data);
       void explain_message_ptrace(char	*message, int message_size, int	re-
       quest, pid_t pid, void *addr, void *data);
       void explain_message_errno_ptrace(char *message,	int message_size, int
       errnum, int request, pid_t pid, void *addr, void	*data);

DESCRIPTION
       These  functions	may be used to obtain explanations for errors returned
       by the ptrace(2)	system call.

   explain_ptrace
       const char *explain_ptrace(int request, pid_t pid, void *addr, void
       *data);

       The  explain_ptrace function is used to obtain an explanation of	an er-
       ror returned by the ptrace(2) system call. The least the	 message  will
       contain	is  the	 value of strerror(errno), but usually it will do much
       better, and indicate the	underlying cause in more detail.

       The errno global	variable will be used to obtain	the error value	to  be
       decoded.

       request The original request, exactly as	passed to the ptrace(2)	system
	       call.

       pid     The original pid, exactly as passed  to	the  ptrace(2)	system
	       call.

       addr    The  original  addr,  exactly as	passed to the ptrace(2)	system
	       call.

       data    The original data, exactly as passed to	the  ptrace(2)	system
	       call.

       Returns:
	       The message explaining the error. This message buffer is	shared
	       by all libexplain functions which do not	 supply	 a  buffer  in
	       their argument list.  This will be overwritten by the next call
	       to any libexplain function which	shares this buffer,  including
	       other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer across all threads, and many	other functions	in this	library.

       Example:	This function is intended to be	used in	a fashion  similar  to
       the following example:
	      long result = ptrace(request, pid, addr, data);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_ptrace(request, pid, addr,
		  data));
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is  available	 pre-packaged	as   the   ex-
       plain_ptrace_or_die(3) function.

   explain_errno_ptrace
       const char *explain_errno_ptrace(int errnum, int	request, pid_t pid,
       void *addr, void	*data);

       The explain_errno_ptrace	function is used to obtain an  explanation  of
       an  error  returned by the ptrace(2) system call. The least the message
       will contain is the value of strerror(errno), but usually  it  will  do
       much better, and	indicate the underlying	cause in more detail.

       errnum  The  error value	to be decoded, usually obtained	from the errno
	       global variable just before this	function is  called.  This  is
	       necessary  if you need to call any code between the system call
	       to be explained and this	function, because many libc  functions
	       will alter the value of errno.

       request The original request, exactly as	passed to the ptrace(2)	system
	       call.

       pid     The original pid, exactly as passed  to	the  ptrace(2)	system
	       call.

       addr    The  original  addr,  exactly as	passed to the ptrace(2)	system
	       call.

       data    The original data, exactly as passed to	the  ptrace(2)	system
	       call.

       Returns:
	       The message explaining the error. This message buffer is	shared
	       by all libexplain functions which do not	 supply	 a  buffer  in
	       their argument list.  This will be overwritten by the next call
	       to any libexplain function which	shares this buffer,  including
	       other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer across all threads, and many	other functions	in this	library.

       Example:	This function is intended to be	used in	a fashion  similar  to
       the following example:
	      long result = ptrace(request, pid, addr, data);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_ptrace(err, request,
		  pid, addr, data));
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is  available	 pre-packaged	as   the   ex-
       plain_ptrace_or_die(3) function.

   explain_message_ptrace
       void explain_message_ptrace(char	*message, int message_size, int	re-
       quest, pid_t pid, void *addr, void *data);

       The explain_message_ptrace function is used to obtain an	explanation of
       an  error  returned by the ptrace(2) system call. The least the message
       will contain is the value of strerror(errno), but usually  it  will  do
       much better, and	indicate the underlying	cause in more detail.

       The  errno global variable will be used to obtain the error value to be
       decoded.

       message The location in which to	store the returned message. If a suit-
	       able message return buffer is supplied, this function is	thread
	       safe.

       message_size
	       The size	in bytes of the	location in which  to  store  the  re-
	       turned message.

       request The original request, exactly as	passed to the ptrace(2)	system
	       call.

       pid     The original pid, exactly as passed  to	the  ptrace(2)	system
	       call.

       addr    The  original  addr,  exactly as	passed to the ptrace(2)	system
	       call.

       data    The original data, exactly as passed to	the  ptrace(2)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      long result = ptrace(request, pid, addr, data);
	      if (result < 0)
	      {
		  char message[3000];
		  explain_message_ptrace(message, sizeof(message), request,
		  pid, addr, data);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The   above   code   example  is	 available  pre-packaged  as  the  ex-
       plain_ptrace_or_die(3) function.

   explain_message_errno_ptrace
       void explain_message_errno_ptrace(char *message,	int message_size, int
       errnum, int request, pid_t pid, void *addr, void	*data);

       The explain_message_errno_ptrace	function is used to obtain an explana-
       tion of an error	returned by the	ptrace(2) system call. The  least  the
       message	will  contain  is the value of strerror(errno),	but usually it
       will do much better, and	indicate the underlying	cause in more detail.

       message The location in which to	store the returned message. If a suit-
	       able message return buffer is supplied, this function is	thread
	       safe.

       message_size
	       The size	in bytes of the	location in which  to  store  the  re-
	       turned message.

       errnum  The  error value	to be decoded, usually obtained	from the errno
	       global variable just before this	function is  called.  This  is
	       necessary  if you need to call any code between the system call
	       to be explained and this	function, because many libc  functions
	       will alter the value of errno.

       request The original request, exactly as	passed to the ptrace(2)	system
	       call.

       pid     The original pid, exactly as passed  to	the  ptrace(2)	system
	       call.

       addr    The  original  addr,  exactly as	passed to the ptrace(2)	system
	       call.

       data    The original data, exactly as passed to	the  ptrace(2)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      long result = ptrace(request, pid, addr, data);
	      if (result < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_ptrace(message,	sizeof(message), err,
		  request, pid,	addr, data);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The   above   code   example  is	 available  pre-packaged  as  the  ex-
       plain_ptrace_or_die(3) function.

SEE ALSO
       ptrace(2)
	       process trace

       explain_ptrace_or_die(3)
	       process trace and report	errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2010 Peter	Miller

							     explain_ptrace(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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