libexplain/ptrace.h File Reference

explain ptrace(2) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>

Go to the source code of this file.

Functions
long	explain_ptrace_or_die (int request, pid_t pid, void *addr, void *data)
long	explain_ptrace_on_error (int request, pid_t pid, void *addr, void *data)
const char *	explain_ptrace (int request, pid_t pid, void *addr, void *data) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_ptrace (int errnum, int request, pid_t pid, void *addr, void *data) LIBEXPLAIN_WARN_UNUSED_RESULT
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)

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Detailed Description

explain ptrace(2) errors

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

Definition in file ptrace.h.

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Function Documentation

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(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

Parameters:

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 function.

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(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

Parameters:

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 function.

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(errnum), 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.

Parameters:

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 function.

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.

Parameters:

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 function.

long explain_ptrace_on_error	(	int	request,
		pid_t	pid,
		void *	addr,
		void *	data
	)

The explain_ptrace_on_error function is used to call the ptrace(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_ptrace(3) function.

Parameters:

request	The request, exactly as to be passed to the ptrace(2) system call.
pid	The pid, exactly as to be passed to the ptrace(2) system call.
addr	The addr, exactly as to be passed to the ptrace(2) system call.
data	The data, exactly as to be passed to the ptrace(2) system call.

Returns:

The value returned by the wrapped ptrace(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 long result = explain_ptrace_on_error(request, pid, addr, data);
 if (result < 0)
 {
     ...cope with error
     ...no need to print error message
 }

long explain_ptrace_or_die	(	int	request,
		pid_t	pid,
		void *	addr,
		void *	data
	)

The explain_ptrace_or_die function is used to call the ptrace(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_ptrace(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

Parameters:

request	The request, exactly as to be passed to the ptrace(2) system call.
pid	The pid, exactly as to be passed to the ptrace(2) system call.
addr	The addr, exactly as to be passed to the ptrace(2) system call.
data	The data, exactly as to be passed to the ptrace(2) system call.

Returns:

This function only returns on success, see ptrace(2) for more information. On failure, prints an explanation and exits, it does not return.

Example:

This function is intended to be used in a fashion similar to the following example:

 long result = explain_ptrace_or_die(request, pid, addr, data);