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\section{Kernel Start}
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\section{Kernel Start}
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When the HelenOS kernel starts up, it configures its output device
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When the HelenOS kernel starts up, it configures its output device
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and starts booting. During the boot process it writes out some some
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and starts booting. During the boot process it writes out some some
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lines regarding memory size and available CPUs. The userspace
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lines regarding memory size and available CPUs. The userspace
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drivers and tasks take over the console as soon as the start-up activity
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drivers and tasks take over the console as soon as the start-up activities are finished.
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and developer kernel tests are finished.
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When kernel tests are compiled in, the userspace layer is not started.
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The console driver provides 12 virtual consoles, 11 reserved
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The console driver provides 12 virtual consoles, 11 are used
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for applications, console 12 is reserved for kernel console. Pressing
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for applications, console 12 is reserved for kernel console. Pressing
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function keys F1-F12 switches between the consoles.
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function keys F1-F12 switches between the consoles.
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If the architecture supports framebuffer device larger with
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If the architecture supports framebuffer device with
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resolution at least 800x600, nice graphical console is shown. At the top
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at least 800x600 resolution, a nice graphical console is shown. At the top
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of the screen a row of buttons for the virtual console is drawn. If
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of the screen, a row of buttons for the virtual console is drawn. If
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the button contains console number, an application is connected to it.
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the button contains console number, an application is connected to it.
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The red button signifies that there was an activity on the terminal
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The red button means that there was an activity on the terminal
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since it was last shown to the user.
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since it was last shown to the user.
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\section{KConsole}
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\section{Kernel Console}
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KConsole is a kernel thread operating completely in priviledged mode.
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{\em kconsole} is a kernel thread operating completely in priviledged mode.
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It allows user to interact directly with the kernel and even start directly
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It allows the user to interact directly with the kernel and even start directly
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functions inside the kernel.
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functions inside the kernel.
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The KConsole is shown by switching to console number 12. On some platforms
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The kernel console is shown by switching to console number 12. On some platforms
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the kconsole screen is not restored to its previous contents. Press
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the kconsole screen is not restored to its previous contents. Press
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enter to see a KConsole prompt. The function keys for switching terminals
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enter to see {\em kconsole}'s prompt. The function keys for switching terminals
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do not work in KConsole, to switch back to other console, use
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do not work in the console. In order to switch back to other consoles, use
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the {\em continue} command. After executing the command, press a function key
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the {\em continue} command. After executing the command, press a function key
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to switch to other consoles.
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to switch to the console of your choice.
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The basic editing facilities are very similar to {\em readline} conventions.
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The basic editing facilities are very similar to {\em readline} conventions.
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The left and right arrows, backspace and delete keys allow for convenient
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The left and right arrows, backspace and delete keys allow convenient
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editing of the text. The history of last ten commands can be retrieved
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editing of text. The history of last ten commands can be retrieved
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using up and down arrows. KConsole supports tab completion, double tab
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using up and down arrows. The kernel console supports tab completion, double tab
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shows a list of available commands.
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shows a list of available commands.
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The first class of commands prints useful statistics from the running
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The first class of commands prints useful statistics from the running
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operating systems. The commands are:
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operating systems. The commands are:
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\begin{description}
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\begin{description}
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\item[zones] --- Prints a list of memory zones.
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\item[zones] --- Prints a list of memory zones.
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\item[zone $<$zone number$>$] --- Prints a detailed statistics about frame allocator.
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\item[zone $<$zone number$>$] --- Prints a detailed statistics about the frame allocator.
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\item[slabs] --- Prints a details statistics about slab allocator.
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\item[slabs] --- Prints detailed statistics about the slab allocator.
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\item[scheduler] --- Prints scheduler queues on all cpus.
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\item[scheduler] --- Prints out the contents of scheduler run queues for all cpus.
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\item[threads] --- Prints list of existing threads, including information about
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\item[threads] --- Prints list of existing threads, including information about
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the thread state
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their state.
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\item[tasks] --- Prints list of tasks along with some basic IPC informations.
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\item[tasks] --- Prints list of tasks along with some basic IPC information.
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\item[ipc\_task $<$taskid$>$] --- Prints detailed information about IPC queues of a particular task.
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\item[ipc\_task $<$taskid$>$] --- Prints detailed information about IPC queues of a particular task.
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\item[tlb] --- Prints contents of the Translation Lookaside Buffer on a processor (supported only on some platforms)
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\item[tlb] --- Prints contents of the Translation Lookaside Buffer on a processor (supported only on some platforms).
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\item[exc] --- Prints table of registered exception handlers
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\item[exc] --- Prints table of registered exception handlers.
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\end{description}
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\end{description}
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Kernel contains a searchable version of its symbol table. This is used
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The kernel contains a searchable version of its symbol table. This is used
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in error processing as well as for extending functionality of KConsole.
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in error processing as well as for extending functionality of the kernel console.
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The following commands are supported:
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The following commands are supported:
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\begin{description}
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\begin{description}
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\item[symaddr $<$address$>$] --- Finds an address in symbol table and prints appropriate
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\item[symaddr $<$address$>$] --- Finds an address in symbol table and prints the appropriate
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symbol name.
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symbol name.
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\item[call0, call1... $<$function$>$ $<$args...$>$] --- Calls a C function function(args...).
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\item[call0, call1... $<$function$>$ $<$args...$>$] --- Calls a C function {\em function(args...)}.
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Note that the tab-completion works for the function names. Because
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Note that the tab-completion also works for function names. Because
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of architecture calling convention, this command does not work correctly
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of architecture calling convention, this command does not work correctly
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on the ia64 platform. The arguments can be specified
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on the ia64 platform. The arguments can be specified
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 \begin{itemize}
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 \begin{itemize}
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  \item as a number or hexadecimal number: call1 task\_kill 8
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  \item as a number or hexadecimal number: call1 task\_kill 8
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  \item as a string: call1 printf "Hello world"
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  \item as a string: call1 printf "Hello world"
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  \item as a hexadecimal number preceded by '*'. The argument is then read from
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  \item as a hexadecimal number preceeded by '*'. The argument is then read from
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the given address: call2 printf "%X" *0x8000000
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the given address: call2 printf "%X" *0x8000000
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  \item as a symbol name. In such case the value located in the memory
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  \item as a symbol name. In such case, the value located in the memory
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    in the symbols address is used: call2 printf "%d" task_counter
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    location corresponding to the symbol name is used: call2 printf "%d" task_counter
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  \item as a symbol name preceded by '\&'. The address is used.
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  \item as a symbol name preceeded by '\&'. The address is used.
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  \item as a symbol name preceded by '*'. In such a case the symbol is dereferenced.
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  \item as a symbol name preceeded by '*'. In such case, the symbol is dereferenced.
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 \end{itemize}
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 \end{itemize}
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\item[set4 <address|symbol name>] --- Saves 4-byte value on a given address.
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\item[set4 <address|symbol name>] --- Stores a 4-byte value into a given address.
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\end{description}
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\end{description}
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The mips, ia32 and amd64 platforms provide additional commands regarding
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The mips32, ia32 and amd64 platforms provide additional commands regarding
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debugging facility - set and clear hardware breakpoints and watchpoints.
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debugging facility - set and clear hardware breakpoints and watchpoints.
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\section{KConsole Task Control}
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\section{Kernel Console Task Control}
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KConsole {\em call} commands can be used to start and kill the tasks.
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The kconsole {\em call} commands can be used to start and kill tasks.
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To repeatably start the task, the following procedure should be used:
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To repeatably start a task, the following procedure should be used:
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\begin{verbatim}
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\begin{verbatim}
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.... kernel boot data ....
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.... kernel boot data ....
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init[8].addr=0x8027b000, init[8].size=86016
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init[8].addr=0x8027b000, init[8].size=86016
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.... rest of boot data ...
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.... rest of boot data ...
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kconsole> call2 task_run_program 0x8027b000 0
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kconsole> call2 task_run_program 0x8027b000 0
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Calling f(0x8027b000,0): 0x80119283: generic/src/proc/task.o:task_run_program
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Calling f(0x8027b000,0): 0x80119283: generic/src/proc/task.o:task_run_program
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Result: 0x80086500
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Result: 0x80086500
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\end{verbatim}
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\end{verbatim}
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To kill a task, the function {\em task\_kill} is appropriate. The {\em taskid}
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To kill a task, use of the function {\em task\_kill} is appropriate. The {\em taskid}
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parameter is a 64-bit number on all platforms, thus on the 32-bit platforms
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parameter is a 64-bit number on all platforms, thus on the 32-bit platforms
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call2 should be used with 2 32-bit parameters instead.
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call2 should be used with 2 32-bit parameters instead.
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\begin{verbatim}
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\begin{verbatim}
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kconsole> call2 task_kill 8 0
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kconsole> call2 task_kill 8 0
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Calling f(0x8,0x0): 0x801197e8: generic/src/proc/task.o:task_kill
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Calling f(0x8,0x0): 0x801197e8: generic/src/proc/task.o:task_kill
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Result: 0x0
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Result: 0x0
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\end{verbatim}
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\end{verbatim}
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\section{Emergency Functions}
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\section{Emergency Functions}
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It may happen that the IPC communication dies or that there appear some
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It may happen that the IPC communication dies or that some
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problems in the communication chain
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problems arise in the communication chain
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{\em keboard driver} - {\em console} - {\em output driver}.
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{\em keboard driver} - {\em console} - {\em output driver}.
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As long that at least the keyboard driver works, pressing Escape key three
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As long as at least the keyboard driver works, pressing Escape key three
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times transfers control to the KConsole immediately. Because the screen is not
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times transfers control to the kernel console immediately. Because the screen is not
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updated, the user should press Enter to see the kconsole prompt.
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updated, the user should press Enter to see the kconsole prompt.
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If a kernel panic occurs, the error handling automatially switches control
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If a kernel panic occurs, the error handling automatially switches control
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to the KConsole and allows users to inspect the failed kernel online.
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to the KConsole and allows users to inspect the failed kernel online.
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On the SMP system the other processors are halted immediately. The kernel
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On the SMP system the other processors are halted immediately. The kernel
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contains its symbol table, so you can probably read some useful information
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contains its symbol table, so you can probably read some useful information
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about the exact place where the panic occured.
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about the exact place where the panic occured.
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\section{How to Do a Kernel Panic}
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\section{How to Do a Kernel Panic}
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Kernel panic is extremely rare in HelenOS. However, if the user wishes to
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Kernel panic is extremely rare in HelenOS. However, if the user wishes to
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simulate it, KConsole contains proper commands. For example the following
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simulate it, the kernel console contains proper commands. For example, the following
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command simulates a write to the unmapped address 0x4:
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command simulates a write to the unmapped address 0x4:
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\begin{verbatim}
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\begin{verbatim}
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kconsole> set4 4 0
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kconsole> set4 4 0
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\end{verbatim}
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\end{verbatim}
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To test the autodebugging possibilities of the IA32 platform, the following
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To test the autodebugging possibilities of the ia32 platform, the following
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sequence can be executed:
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sequence can be executed:
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\begin{verbatim}
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\begin{verbatim}
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kconsole> bkpts
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kconsole> bkpts
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0. 0x80032010 in (NULL)
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0. 0x80032010 in (NULL)
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    Count(0)
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    Count(0)
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debug>
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debug>
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\end{verbatim}
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\end{verbatim}
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\section{KLog}
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\section{KLog}
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To avoid disturbing the framebuffer driver with kernel messages, a circular
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In order to avoid disturbing the framebuffer driver with kernel messages, a circular
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buffer communication between kernel and userspace area is established.
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buffer communication between the kernel and the userspace area is established.
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Non-critical messages are sent to the
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KLog application. User can see messages about task faults
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Non-critical messages are sent to the KLog application. The user can see messages about
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and task cleanup completion.
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task faults and task cleanup completion.
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\section{IPCC - testing application}
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\section{IPCC - testing application}
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To test thouroughly some aspects of the task activities, IPCC application
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For the sake of thourough testing of some aspects of task activities, IPCC application
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allows the user to generate faulting behaviour such as page faults and unaligned references\footnote{Some architectures
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allows user to generate page faults
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do not fault on an unaligned memory reference.}.
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\section{Tetris}
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