the bootloader itself can be thought of as a first-stage loader.
39
The term machine as used here refers to a specific hardware reference platform.
40
Often called Instruction Pointer, the register which holds the address of the next machine instruction in memory.
41
Modifying head.S for your custom platform is highly discouraged. There is almost always a better way. See Chapter 16, 'Porting Linux,' for additional information.
42
Modifying head.S for your custom platform is highly discouraged. There is almost always a better way. See Chapter 16, 'Porting Linux,' for additional information.
43
Normally, the compiler will complain if a variable is defined static and never referenced in the compilation unit. Because these variables are not explicitly referenced, the warning would be emitted without this directive.
44
You might have to lower the default loglevel on your system to see these debug messages. This is described in many references about Linux system administration. In any case, you should see them in the kernel log file.
45
Userland is an often-used term for any program, library, script, or anything else in user space.
46
Especially the sections on function attributes, type attributes, and variable attributes.
47
Often embedded systems do not have user accounts other than a single root user.
48
BusyBox commands are covered in Chapter 11.
49
Device nodes are explained in detail in Chapter 8.
50
In actuality, modern Linux kernels create a userspace-like environment earlier in the boot sequence for specialized activities, which are beyond the scope of this book.
51
When busybox is invoked via the sh symbolic link, it spawns a shell. We cover this in detail in Chapter 11.
52
This inittab is a nice example of a small, purpose-built embedded system.
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