Syscall handlers tweaks

[kristopher-pellizzi]

Some system call use structs as arguments.
For simplicity and speed, the corresponding syscall handlers will consider the whole struct as read.
However, those struct may have holes due to fields padding.
These paddings are not actually used by the struct, and is therefore highly probable that they are uninitialized when the system call is executed, thus causing MemTrace reporting uninitialized reads which must be considered false positives.
It is possible to slightly change syscall handlers to make them read only the used parts of the structs used as arguments.

This Issue will be used as a thread to report syscall handlers that caused some false positives during testing and possibly also the structure of the struct they use as a parameter.

[kristopher-pellizzi]

ssize_t recvmsg(int sockfd, struct msghdr *msg, int flags)

/* offset    |  size */  type = struct msghdr {
/*    0      |     8 */    void *msg_name;
/*    8      |     4 */    socklen_t msg_namelen;
/* XXX  4-byte hole  */
/*   16      |     8 */    struct iovec *msg_iov;
/*   24      |     8 */    size_t msg_iovlen;
/*   32      |     8 */    void *msg_control;
/*   40      |     8 */    size_t msg_controllen;
/*   48      |     4 */    int msg_flags;
/* XXX  4-byte padding  */

                           /* total size (bytes):   56 */
                         }