What is a "segmentation violation"?
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Background and common causes are discussed in more detail below.
Modern general purpose hardware includes a "memory management unit" (or MMU). This hardware feature is used by operating systems like Linux to implement memory protection, i.e. to prevent different processes from accessing or modifying each other's memory (except in a strictly controlled fashion through specific APIs). This simplifies troubleshooting and increases resilience as processes are carefully contained and separated from one another.
A "segmentation violation" signal is sent to a process of which the memory management unit detected an attempt to use a memory address that does not belong to it.
Common cause: programming error
If a process tries to access memory through a pointer which has not been properly initialised, or which is pointing to memory that has previously been deallocated, this will likely result in a segfault. In this case, the segfault is occurring with a specific process or binary, possibly under a specific set of circumstances.
To deal with this type of segfault, begin by applying all relevant service packs and maintenance updates. Next, if the problem is still reproducible with current code, try to capture an application core dump for analysis. Details for this are found in TID 3054866 - How to obtain application core dumps.
If the problematic binary is shipped by Novell as part of the product, open a service request with Novell Technical services, supplying
- a description of the circumstances under which the core dump was generated,
- a supportconfig -v report for the affected system (supportconfig home page), and
- the core dump file itself, if smaller than 50 MB. If it is larger, wait for the service request to be assigned to an engineer and then work with the engineer to transfer it.
Common cause: mismatched binary and libraries
Segfaults can occur with processes that combine binaries and shared libraries which aren't (fully) compatible. This can occur, for instance, when a library is updated in a way that changes the library's ABI (application binary interface), but the library's internal version number is not updated to reflect this. A binary that was built against an older version of the library may start to segfault when loaded against the newer version.
This case may be difficult to recognise, and there is no step list for dealing with it. When this case is suspected, some things to consider are:
- Checking the system for file corruption (e.g. using the rpm-verify.txt file in a supportconfig -v report)
- Checking the system's settings that relate to shared libraries, like the /etc/ld.so.conf and /etc/ld.so.conf.d/* configuration files and the LD_LIBRARY_PATH and LD_PRELOAD environment variables.
- Using the objdump tool to check the binary for a built-in library search path override (RPATH).
When segfaults are occurring frequently, or with different processes or without a clear pattern to them, this can indicate that a system's hardware (memory subsystem) is problematic, or that low-level system configuration settings are inappropriate. Please refer to TID 3301593 - Linux system hangs or is unstable for more information on how to handle this situation.
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- Document ID:7001662
- Creation Date:15-OCT-08
- Modified Date:08-NOV-12
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