Provided by: libexplain-dev_1.4.D001-12_amd64 bug

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 request, 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 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.

       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  buffer  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 explain_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  buffer  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 explain_ptrace_or_die(3) function.

   explain_message_ptrace
       void explain_message_ptrace(char *message, int message_size, int request, 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 suitable message  return
               buffer is supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned 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 explain_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 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.

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

       message_size
               The size in bytes of the location in which to store the returned 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 explain_ptrace_or_die(3) function.

SEE ALSO

       ptrace(2)
               process trace

       explain_ptrace_or_die(3)
               process trace and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2010 Peter Miller

                                                                                explain_ptrace(3)