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Rev	Author	Line No.	Line
124	decky	1	\chapter{Boot Loading Process}
		2
		3	The startup of HelenOS happens in several steps.
153	jermar	4	Depending on the platform, these steps can be either
124	decky	5	described as \textit{piggybacker loading}:
		6
		7	\begin{enumerate}
		8	\item Platform boot loader loads the piggybacker image
		9	and jumps to its entry point.
		10	\item The piggybacker unwraps the kernel image and
		11	the images of the initial user space tasks, creates
		12	a boot information structure and jumps to the
		13	entry point of the kernel.
		14	\item The kernel initializes and runs the initial tasks
		15	according the boot information structure from the
		16	piggybacker.
		17	\end{enumerate}
		18
		19	If the platform supports a more sophisticated native boot loader,
153	jermar	20	the \textit{multiboot loading} consists of the following steps:
124	decky	21
		22	\begin{enumerate}
		23	\item Platform boot loader loads the kernel image and initial
		24	user space tasks, creates a boot information structure
		25	and jumps to the entry point of the kernel.
		26	\item The kernel initializes and runs the initial tasks
153	jermar	27	according the the boot information structure from the
124	decky	28	boot loader.
		29	\end{enumerate}
		30
		31	A third kind of boot loading occurs on platforms with no support
153	jermar	32	from boot loader. It is called \textit{image loading} and is
124	decky	33	used mostly on simulated architectures.
		34
		35	\begin{enumerate}
		36	\item The kernel and initial user space images are placed
		37	on well-known physical memory locations (usually
		38	by a simulator configuration file). The execution
		39	starts directly on the kernel entry point.
153	jermar	40	\item The kernel initializes and spawns compiled-in
124	decky	41	number of initial user space tasks.
		42	\end{enumerate}
		43
153	jermar	44	The following sections describe the particular features of the
149	palkovsky	45	boot loading process on the supported platforms. Sample
		46	configuration files for all simulators are in the directory
		47	{\em kernel/contrib/conf}.
124	decky	48
		49	\section{IA-32 and AMD64}
		50
153	jermar	51	On both platforms, HelenOS depends on a boot loader which
		52	supports the Multiboot Specification (e.g. GRUB). The kernel
		53	image (usually called \texttt{image.iso}) is loaded by the
124	decky	54	boot loader just above the 1st megabyte of the physical
149	palkovsky	55	memory (the exact location is 1081344 bytes). Modules loaded by
		56	GRUB are automatically detected by the kernel and after initialization
		57	they are started as userspace tasks. The GRUB loading is the
		58	easiest in terms of using userspace tasks.
		59
		60	An example GRUB configuration file {\em menu.lst}:
		61	\begin{verbatim}
		62	title=HelenOS
		63	root (cd)
		64	kernel /boot/kernel.bin
		65	module /boot/ns
		66	module /boot/init
		67	module /boot/pci
		68	module /boot/fb
		69	module /boot/kbd
		70	module /boot/console
		71	module /boot/tetris
		72	module /boot/ipcc
		73	module /boot/klog
		74	\end{verbatim}
		75
		76	\section{32-bit MIPS}
		77	The MIPS port is fully supported in the {\em msim} and {\em gxemul} simulators.
153	jermar	78	These simulators allow to specify a memory contents of the simulated
149	palkovsky	79	computer. Unfortunately, the autodetection of loaded modules does
		80	not work. In order to change number of loaded modules, the file
		81	kernel/arch/mips32/src/mips32.c must be modified.
		82
		83	Sample msim configuration file:
		84	\begin{verbatim}
		85	add dcpu mips1
		86
150	palkovsky	87	add rwm mainmem 0x0 8M load "/dev/zero"
149	palkovsky	88	add rom startmem 0x1fc00000 1024k load "image.boot"
150	palkovsky	89	add rwm ns 0x01000000 1M load "ns"
		90	add rwm kbd 0x01100000 1M load "fb"
		91	add rwm fb 0x01200000 1M load "kbd"
		92	add rwm console 0x01300000 1M load "console"
		93	add rwm init 0x01400000 1M load "init"
		94	add rwm tetris 0x01500000 1M load "tetris"
149	palkovsky	95	\end{verbatim}
		96
150	palkovsky	97	Sample gxemul command line arguments:
149	palkovsky	98	\begin{verbatim}
150	palkovsky	99	gxemul -E testmips -X 0x81800000:../uspace/ns/ns 0x81900000:../uspace/kbd/kbd \
		100	0x81a00000:../uspace/fb/fb 0x81b00000:../uspace/init/init \
		101	0x81c00000:../uspace/console/console 0x81d00000:../uspace/tetris/tetris kernel.bin
149	palkovsky	102	\end{verbatim}
		103
		104	The kernel can boot on the SGI Indy (and probably other SGI computers
		105	with 32-bit ARC firmware). It uses ARC for output and input. When
		106	the kernel is compiled to be loaded on the SGI Indy, an ECOFF image
		107	is created which can be later loaded directly with ARC boot loader
		108	e.g. using BOOTP protocol.
		109
153	jermar	110	\section{IA-64}
		111	The IA-64 port is supported on the Ski simulator. The situation is very similar
149	palkovsky	112	to the MIPS loader - the loaded modules must be loaded on correct addresses in
153	jermar	113	the Ski configuration file and specified in the file
149	palkovsky	114	kernel/arch/ia64/src/ia64.c.
		115
153	jermar	116	Sample IA-64 configuration file:
149	palkovsky	117	\begin{verbatim}
		118	load kernel.bin
		119	romload ../uspace/ns/ns 0x400000
		120	romload ../uspace/init/init 0x800000
		121	romload ../uspace/console/console 0xc00000
		122	romload ../uspace/fb/fb 0x1000000
		123	romload ../uspace/kbd/kbd 0x1400000
		124	romload ../uspace/tetris/tetris 0x1800000
		125	romload ../uspace/klog/klog 0x1c00000
		126	romload ../uspace/ipcc/ipcc 0x2000000
		127	\end{verbatim}
		128
		129	\section{Power PC}
		130	The PowerPC boot image contains complete kernel with user tasks.
		131	The loader build system automatically creates such image using information
		132	residing in boot/arch/ppc32/loader/Makefile.inc. The variable COMPONENTS
		133	specifies, which tasks will be loaded into the image.

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