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 request, pid_t pid, void *addr, void *data); void explain_message_errno_ptrace(char *message, int message_size, int er- rnum, 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 de- coded. 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 ar- gument list. This will be overwritten by the next call to any lib- explain 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 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 bet- ter, 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 neces- sary if you need to call any code between the system call to be ex- plained 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 ar- gument list. This will be overwritten by the next call to any lib- explain 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 ex- plain_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 bet- ter, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be de- coded. 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 ex- plain_ptrace_or_die(3) function. explain_message_errno_ptrace void explain_message_errno_ptrace(char *message, int message_size, int er- rnum, 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 neces- sary if you need to call any code between the system call to be ex- plained 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, re- quest, 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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