https://homeostasis.scs.carleton.ca/wiki/index.php?action=history&feed=atom&title=Operating_Systems_2019F_Lecture_18 2026-05-18T20:02:23Z Revision history for this page on the wiki MediaWiki 1.42.1 https://homeostasis.scs.carleton.ca/wiki/index.php?title=Operating_Systems_2019F_Lecture_18&diff=22540&oldid=prev 2020-03-20T02:09:06Z

<p>Created page with &quot;==Video== Video from the lecture given on November 13, 2019 [https://homeostasis.scs.carleton.ca/~soma/os-2019f/lectures/comp3000-2019f-lec18-20191113.m4v is now available]....&quot;</p> <p><b>New page</b></p><div>==Video==<br /> <br /> Video from the lecture given on November 13, 2019 [https://homeostasis.scs.carleton.ca/~soma/os-2019f/lectures/comp3000-2019f-lec18-20191113.m4v is now available].<br /> <br /> ==Notes==<br /> <br /> &lt;pre&gt;<br /> Lecture 18<br /> ----------<br /> <br /> When you&#039;re in a kernel module, you&#039;re in the Linux kernel<br /> * context is *all* of the code in the linux kernel<br /> * you have access to all code and data structures, if you can figure<br /> out how to access them<br /> * You include linux kernel headers to be able to access this functionality<br /> * You *cannot* access standard libraries, they don&#039;t exist<br /> - and even if you did ad the code, key abstractions such as file descriptors,<br /> ttys, and such don&#039;t exist! So you&#039;re probably in trouble<br /> <br /> One big problem is that the Linux kernel changes fast<br /> * so online documentation gets out of date<br /> * authority is really the code itself<br /> * but articles on lwn.net are helpful<br /> <br /> <br /> Processes vs. threads<br /> * process: one or more CPU contexts + address space<br /> * thread: a CPU context in an address space<br /> <br /> So a process can have one or more threads<br /> <br /> In the kernel, &quot;current&quot; refers to the process/thread (task) that made the current system call.<br /> <br /> initrd = initial ram disk<br /> - how do you load modules needed to access the root filesystem when<br /> you don&#039;t have access to the root filesystem?<br /> - drivers, fs, network<br /> - initrds will have<br /> - kernel modules<br /> - scripts &amp; executables necessary for loading modules, other setup<br /> <br /> Boot loader loads kernel image &amp; initrd into memory, then starts kernel<br /> - telling it where in memory the initrd is<br /> &lt;/pre&gt;</div>

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