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<concept id="GUID-4993AF8E-28C3-54BA-8D27-D86E05D39CFD" xml:lang="en"><title>Crash
Logger Technology</title><shortdesc>The Crash Logger contains a logger program that stores system state
information when a crash occurs, and a reader application that can be used
later to get this information</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-060E1937-9BB9-5A81-A1FA-7EAEA04B9DEF"><title>The
crash logger</title> <p>When the kernel crashes, control is handed to the
crash logger. It tries to read as much state information as it can reasonably
find, and dumps it to a pre-reserved location in permanent storage flash storage). </p> <p>Support
exists for dumping information to <i>nor</i> flash and <i>nand</i> flash.
The crash logger must have its own drivers to do this, as it cannot be assumed
that any specific part of the kernel is operating correctly in these circumstances.
These drivers are essentially simplified versions of the standard drivers. </p> <p>All
monitoring functionality, crash logging and crash debugging is placed in kernel
extensions. Functionality can be enabled or disabled by placing the appropriate
kernel extensions into ROM at ROM build time. </p> <p>To support both crash
logging and debugging without duplicating code, a common module, <filepath>exmoncommon.dll</filepath>,
has been created. This extension contains all of the generic monitoring code,
and supports features such as dumping registers, thread stacks and object
containers and is responsible for registering with the kernel’s crash monitor
entry point: </p> <codeblock id="GUID-F1EF54CF-614D-5459-ABA1-07F5E9D3969E" xml:space="preserve">Epoc::SetMonitorEntryPoint()</codeblock> <p>This
extension must be placed in ROM before either of the two monitoring extensions,
as they both rely on its functionality. As <filepath>exmoncommon.dll</filepath> depends
on the underlying memory model, it is built from the Variant. </p> <p>After
the common monitoring code registers itself with the kernel, further debugging
extensions may register with the common code. These extensions are called
when the kernel fails, in the order that they register. The maximum number
of extensions currently supported is nine though only two- the interactive
debugger, and the non-interactive crash logger are provided. However, this
is an arbitrary limit set by the macro definition <codeblock xml:space="preserve">MONITOR_MAXCOUNT</codeblock> in
the file <filepath>E32\include\kernel\monitor.h</filepath>, and can be increased
given sensible use cases. </p> <ul>
<li id="GUID-75C55DE2-982C-59E2-8A93-43457B687165"><p> <filepath>exmondebug.dll</filepath> is
the traditional interactive debugger. </p> </li>
<li id="GUID-12933627-FEBC-5D1A-9573-81F15FEDA328"><p> <filepath>exmonlog.dll</filepath> is
the crash logger. </p> </li>
</ul> <p>These DLLs are also built from the Variant. In the case of the crash
logger, two separate <filepath>.mmp</filepath> files exist: </p> <ul>
<li id="GUID-88D7A132-143A-519A-8645-FAA11D484FC7"><p>one for NAND flash,
building <filepath>exmonlognand.dll</filepath>  </p> </li>
<li id="GUID-EE02A14E-9E19-516D-93F9-B6590736D71C"><p>one for NOR flash, building <filepath>exmonlognor.dll</filepath>  </p> </li>
</ul> <p>The rombuild scripts ensure that the crash logger for only one type
of flash is placed into the ROM, and named as <filepath>exmonlog.dll</filepath>. </p> </section>
<section id="GUID-7CAFA8C9-597C-5F20-AB15-22FFC7EFA203"><title>The crash reader</title> <p>At
the next system boot, the crash reader application uses the normal system
flash drivers to read the crash log from the reserved non-filesystem (non-uservisible)
flash area, and to write it into the user-visible file system. </p> <p>The
output file from the crash reader is a text file, or a compressed <filepath>GZIP-compatible</filepath> file. </p> <p>The
crash reader application is called <filepath>crashread.exe</filepath>, which
is built from <filepath>e32utils\crashread\crashread.mmp</filepath>. </p> </section>
</conbody></concept>