Operating Systems 2021F: Tutorial 7 - Revision history

Soma: /* D: Getting process information from a module */

2021-11-16T01:39:16Z

D: Getting process information from a module

← Older revision		Revision as of 01:39, 16 November 2021
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	# '''(Advanced)''' Modify /dev/describe so that if you write a process ID to it, it will output the information on the provided process. To make this work, you'll need to:		# '''(Advanced)''' Modify /dev/describe so that if you write a process ID to it, it will output the information on the provided process. To make this work, you'll need to:
	#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).		#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).
	#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.~~4.83~~/ident/kstrtoint_from_user kstrtoint_from_user()].		#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v5.11/ident/kstrtoint_from_user kstrtoint_from_user()].
	#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L1465 looks up the pid struct] and then [https://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].		#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L1465 looks up the pid struct] and then [https://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].
	#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.		#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.

Soma: /* D: Getting process information from a module */

2021-11-16T01:38:25Z

D: Getting process information from a module

← Older revision		Revision as of 01:38, 16 November 2021
Line 100:		Line 100:
	#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).		#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).
	#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.4.83/ident/kstrtoint_from_user kstrtoint_from_user()].		#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.4.83/ident/kstrtoint_from_user kstrtoint_from_user()].
	#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L1465 looks up the pid struct] and then [~~http~~://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].		#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L1465 looks up the pid struct] and then [https://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].
	#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.		#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.

Soma: /* D: Getting process information from a module */

2021-11-16T01:37:26Z

D: Getting process information from a module

← Older revision		Revision as of 01:37, 16 November 2021
Line 100:		Line 100:
	#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).		#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).
	#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.4.83/ident/kstrtoint_from_user kstrtoint_from_user()].		#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.4.83/ident/kstrtoint_from_user kstrtoint_from_user()].
	#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [~~http~~://elixir.free-electrons.com/linux/v4.~~4.83~~/source/kernel/signal.c#~~L1388~~ looks up the pid struct] and then [http://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].		#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L1465 looks up the pid struct] and then [http://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].
	#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.		#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.

Soma: /* D: Getting process information from a module */

2021-11-16T01:31:30Z

D: Getting process information from a module

← Older revision		Revision as of 01:31, 16 November 2021
Line 100:		Line 100:
	#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).		#* Add a write method by adding a write operation to the file operations struct. Write operations have the same prototype as read operations, except the buffer is marked constant (because it shouldn't be modified).
	#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.4.83/ident/kstrtoint_from_user kstrtoint_from_user()].		#* Convert the written text to an integer and store in a global variable (to the module). Check out [https://elixir.bootlin.com/linux/v4.4.83/ident/kstrtoint_from_user kstrtoint_from_user()].
	#* Find the right task struct. See the implementation of the [~~http~~://elixir.free-electrons.com/linux/v4.~~4.83~~/source/kernel/signal.c#~~L2855~~ kill system call], and how it [http://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1388 looks up the pid struct] and then [http://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].		#* Find the right task struct. See the implementation of the [https://elixir.free-electrons.com/linux/v5.11/source/kernel/signal.c#L3677 kill system call], and how it [http://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1388 looks up the pid struct] and then [http://elixir.free-electrons.com/linux/v4.4.83/source/kernel/signal.c#L1303 gets the right task struct using that pid struct].
	#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.		#* After returning info on the selected process, further calls should return info on the current process. You can do this by setting the global process ID to 0 and checking this value, using the current task if it is zero.

Soma: /* C: A character device kernel module */

2021-11-16T01:11:40Z

C: A character device kernel module

← Older revision		Revision as of 01:11, 16 November 2021
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	# How can you modify your module to generate a kernel "Oops" as reported in the kernel logs or outright crash the kernel?		# How can you modify your module to generate a kernel "Oops" as reported in the kernel logs or outright crash the kernel?
	# Before inserting your module, run <tt>trace -K 'p::__register_chrdev'</tt> in another terminal to print the kernel stack trace for <tt>__register_chrdev</tt>. Insert your module and examine the output from your <tt>trace</tt> command. Did you expect all those function calls? What do you think they do?		# Before inserting your module, run <tt>trace -K 'p::__register_chrdev'</tt> in another terminal to print the kernel stack trace for <tt>__register_chrdev</tt>. Insert your module and examine the output from your <tt>trace</tt> command. Did you expect all those function calls? What do you think they do?
			<!--
	# While running <tt>cat /dev/ones</tt> in one terminal, run <tt>trace -p `pidof cat` -K -M 10 '__put_user_1 printf "writing %c to 0x%lx" arg1, arg2'</tt> to trace the first 10 calls to <tt>put_user</tt> and print the kernel stack trace, along with the userspace address that <tt>/dev/ones</tt> is writing to. Consider the following:		# While running <tt>cat /dev/ones</tt> in one terminal, run <tt>trace -p `pidof cat` -K -M 10 '__put_user_1 printf "writing %c to 0x%lx" arg1, arg2'</tt> to trace the first 10 calls to <tt>put_user</tt> and print the kernel stack trace, along with the userspace address that <tt>/dev/ones</tt> is writing to. Consider the following:
	#* What kernel functions are being called that result in <tt>put_user</tt> being invoked?		#* What kernel functions are being called that result in <tt>put_user</tt> being invoked?
	#* How much is the userspace address incrementing on each <tt>put_user</tt> call? Does this increase make sense? Why?		#* How much is the userspace address incrementing on each <tt>put_user</tt> call? Does this increase make sense? Why?
			-->

	==D: Getting process information from a module==		==D: Getting process information from a module==

Soma: /* Code */

2021-11-15T03:54:56Z

Code

← Older revision		Revision as of 03:54, 15 November 2021
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	failed_devreg:		failed_devreg:
	class_unregister(ones_class);		class_unregister(ones_class);
	~~class_destroy(ones_class);~~
	failed_classreg:		failed_classreg:
	unregister_chrdev(ones_major, DEVICE_NAME);		unregister_chrdev(ones_major, DEVICE_NAME);
Line 379:		Line 378:
	failed_devreg:		failed_devreg:
	class_unregister(newgetpid_class);		class_unregister(newgetpid_class);
	~~class_destroy(newgetpid_class);~~
	failed_classreg:		failed_classreg:
	unregister_chrdev(newgetpid_major, DEVICE_NAME);		unregister_chrdev(newgetpid_major, DEVICE_NAME);

Soma: /* Makefile */

2021-11-15T03:53:22Z

Makefile

← Older revision		Revision as of 03:53, 15 November 2021
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	</syntaxhighlight>		</syntaxhighlight>

	You also need a Kbuild file with following:		You also need a Kbuild file with the following:

	<syntaxhighlight lang=make line>		<syntaxhighlight lang=make line>

Soma: /* Code */

2021-11-15T03:53:00Z

Code

← Older revision		Revision as of 03:53, 15 November 2021
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	module_exit(simple_exit);		module_exit(simple_exit);
	</syntaxhighlight>		</syntaxhighlight>


	==[https://homeostasis.scs.carleton.ca/~soma/os-2021f/code/ones.zip ones module]==		==[https://homeostasis.scs.carleton.ca/~soma/os-2021f/code/ones.zip ones module]==

Soma at 03:52, 15 November 2021

2021-11-15T03:52:25Z

Show changes

Soma: /* newgetpid module */

2021-11-15T03:27:37Z

newgetpid module

← Older revision		Revision as of 03:27, 15 November 2021
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	</syntaxhighlight>		</syntaxhighlight>

	==[https://homeostasis.scs.carleton.ca/~soma/os-~~2017f~~/code~~/lec16~~/newgetpid.zip newgetpid module]==		==[https://homeostasis.scs.carleton.ca/~soma/os-2021f/code/newgetpid.zip newgetpid module]==

	===newgetpid.c===		===newgetpid.c===