02-14-2011
Let the process produce a core file
There are two ways you can deal with this problem.
The first, and most obvious one, is to run the program under the debugger (e.g.: dbx). When it crashes, you'll get the debugger's prompt and you can explore the location and causes of the crash.
Since running under the debugger may change the behavior of the program, you may want to let it run normally. If the program crashes due to certain signals (e.g.: SIGSEGV - indicating accessing a bad address, such as address 0), it can produce a core file, at least under Unix variants, including Linux. You can then use the debugger to look at the state of the program at the time of the crash and analyze the reason for the crash.
For example, if the name of the program is prog, then
use: dbx prog core
to explore the state of the program at the time of the crash.
The core file is not always produced even when the program crashes due to a signal such as SIGSEGV. The reason is that there is a limit on the size of the core file. Often, this limit is 0. You can change this limit to "unlimited" and then the core file will be produced when the need arises.
The command to change the core file size limit is shell dependent.
For example, under bash I am using: ulimit -c unlimited
under tcsh, I use: limit coredumpsize unlimited
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crash(8v) crash(8v)
Name
crash - what happens when the system crashes
Description
This section explains what happens when the system crashes and shows how to analyze crash dumps.
When the system crashes voluntarily it prints a message on the console in the form:
panic: explanation
The system takes a dump on a mass storage peripheral device or the network, and then invokes an automatic reboot procedure as described in
Unless there is some unexpected inconsistency in the state of the file systems due to hardware or software failure, the system then resumes
multi-user operations. If auto-reboot is disabled, the system halts at this point.
The system has a large number of internal consistency checks; if one of these fails, it prints a short message indicating which one failed.
The most common cause of system failures is hardware failure. In all cases there is the possibility that hardware or software error pro-
duced the message in some unexpected way. These messages are the ones you are likely to encounter:
IO err in push
hard IO err in swap
The system encountered an error when trying to write to the paging device or an error in reading critical information from a disk
drive. Fix your disk if it is broken or unreliable.
timeout table overflow
Due to the current data structure, running out of entries causes a crash. If this happens, make the timeout table bigger.
Exception Condition
An unexpected system error has occurred. The exception types are as follows:
---------------------------------------------------------------
Mnemonic Description
---------------------------------------------------------------
INT External interrupt
MOD TLB modification exception
TLBL TLB miss exception (load or instruction fetch)
TLBS TLB miss exception (store)
AdEL Address error exception (load or instruction fetch)
AdES Address error exception (store)
IBE Bus error exception (for an instruction fetch)
DBE Bus error exception (for a data load or store)
Sys Sys call exception
Bp Breakpoint exception
CpU Coprocessor unusable exception
Ovf Arithmetic overflow exception
---------------------------------------------------------------
KSP not valid
This indicates either a problem in the system or failing hardware.
init died
The system initialization process has exited. The only solution is the automatic reboot procedure described in Until this is done,
new users cannot log in.
When the system crashes, it attempts to write an image of memory into the back end of the primary swap area. After the system is rebooted,
the program runs and preserves a copy of this core image and the current system in a specified directory for later access. See for
details.
To analyze a dump, you should begin by running with the flag on the core dump.
See Also
dbx(1), reboot(8), savecore(8)
RISC crash(8v)