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In modern use on most architectures these are much rarer than segmentation faults, which occur primarily due to memory access violations: problems in the logical address or permissions. On POSIX-compliant platforms, bus errors usually
Segmentation faults can also occur independently of page faults: illegal access to a valid page is a segmentation fault, but not an invalid page fault, and segmentation faults can occur in the middle of a page (hence no page fault), for example in a buffer overflow that stays within a page but illegally overwrites memory.
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Illegal accesses and invalid page faults can result in a segmentation fault or bus error, resulting in an app or OS crash. Software bugs are often the causes of these problems, but hardware memory errors, such as those caused by overclocking, may corrupt pointers and cause valid code to fail.
This will typically occur because of a programming error, and the operating system must take some action to deal with the problem. On modern operating systems, it will cause a segmentation fault signal being sent to the offending program. The lookup may also fail if the page is currently not resident in physical memory.
Protection may encompass all accesses to a specified area of memory, write accesses, or attempts to execute the contents of the area. An attempt to access unauthorized [a] memory results in a hardware fault, e.g., a segmentation fault, storage violation exception, generally causing abnormal termination of the offending process.
When segmentation is enabled by turning on protected mode, the segment number acts as an index into a table of segment descriptors; a segment descriptor contains a base physical address, a segment length, a presence bit to indicate whether the segment is currently in memory, permission bits, and control bits, If the offset in the segment is ...
In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.