Go to main content

Oracle® Solaris 64-bit Developer's Guide

Exit Print View

Updated: March 2019
 
 

6.13 System Call Issues

The following sections discuss system call issues.

6.13.1 EOVERFLOW Indicates System Call Issue

The EOVERFLOW return value is returned from a system call whenever one or more fields of the data structure used to pass information out of the kernel is too small to hold the value.

A number of 32-bit system calls now return EOVERFLOW when faced with large objects on the 64-bit kernel. While this was already true when dealing with large files, the fact that daddr_t, dev_t, time_t, and its derivative types struct timeval and timespec_t now contain 64-bit quantities might mean more EOVERFLOW return values are observed by 32-bit applications.

6.13.2 ioctl() Does Not Type Check at Compile Time

Some ioctl(2) calls have been rather poorly specified in the past. Unfortunately, ioctl() is completely devoid of compile-time type checking. Therefore, ioctl() can be a source of bugs that are difficult to track down.

Consider two ioctl() calls – one that manipulates a pointer to a 32-bit quantity (IOP32), the other that manipulates a pointer to a long quantity (IOPLONG).

The following code sample works correctly in a 32-bit application when it is compiled:

	int a, d;
	long b;
	...
	if (ioctl(d, IOP32, &b) == -1)
			return (errno);
	if (ioctl(d, IOPLONG, &a) == -1)
			return (errno);

    In a 64-bit application, the preceding ioctl() calls succeed but do not work correctly:

  • The first ioctl() call passes a container that is too big, and on a big-endian implementation, the kernel will copy in or copy out from the wrong part of the 64-bit word. Even on a little-endian implementation, the container probably contains stack garbage in the upper 32 bits.

  • The second ioctl() call will copy in or copy out too much, either reading an incorrect value, or corrupting adjacent variables on the user stack.