man explain_ptrace (3): 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.

SYNOPSIS

DESCRIPTION

explain_ptrace

explain_errno_ptrace

explain_message_ptrace

explain_message_errno_ptrace

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