arch/alpha/boot/bootp.c

Source file repositories/reference/linux-study-clean/arch/alpha/boot/bootp.c

File Facts

System
Linux kernel
Corpus path
arch/alpha/boot/bootp.c
Extension
.c
Size
5708 bytes
Lines
215
Domain
Architecture Layer
Bucket
arch/alpha
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

start_kernel(void)
{
	/*
	 * Note that this crufty stuff with static and envval
	 * and envbuf is because:
	 *
	 * 1. Frequently, the stack is short, and we don't want to overrun;
	 * 2. Frequently the stack is where we are going to copy the kernel to;
	 * 3. A certain SRM console required the GET_ENV output to stack.
	 *    ??? A comment in the aboot sources indicates that the GET_ENV
	 *    destination must be quadword aligned.  Might this explain the
	 *    behaviour, rather than requiring output to the stack, which
	 *    seems rather far-fetched.
	 */
	static long nbytes;
	static char envval[256] __attribute__((aligned(8)));
	static unsigned long initrd_start;

	srm_printk("Linux/AXP bootp loader for Linux " UTS_RELEASE "\n");
	if (INIT_HWRPB->pagesize != 8192) {
		srm_printk("Expected 8kB pages, got %ldkB\n",
		           INIT_HWRPB->pagesize >> 10);
		return;
	}
	if (INIT_HWRPB->vptb != (unsigned long) VPTB) {
		srm_printk("Expected vptb at %p, got %p\n",
			   VPTB, (void *)INIT_HWRPB->vptb);
		return;
	}
	pal_init();

	/* The initrd must be page-aligned.  See below for the 
	   cause of the magic number 5.  */
	initrd_start = ((START_ADDR + 5*KERNEL_SIZE + PAGE_SIZE) |
			(PAGE_SIZE-1)) + 1;
#ifdef INITRD_IMAGE_SIZE
	srm_printk("Initrd positioned at %#lx\n", initrd_start);
#endif

	/*
	 * Move the stack to a safe place to ensure it won't be
	 * overwritten by kernel image.
	 */
	move_stack(initrd_start - PAGE_SIZE);

	nbytes = callback_getenv(ENV_BOOTED_OSFLAGS, envval, sizeof(envval));
	if (nbytes < 0 || nbytes >= sizeof(envval)) {
		nbytes = 0;
	}
	envval[nbytes] = '\0';
	srm_printk("Loading the kernel...'%s'\n", envval);

	/* NOTE: *no* callbacks or printouts from here on out!!! */

	/* This is a hack, as some consoles seem to get virtual 20000000 (ie
	 * where the SRM console puts the kernel bootp image) memory
	 * overlapping physical memory where the kernel wants to be put,
	 * which causes real problems when attempting to copy the former to
	 * the latter... :-(
	 *
	 * So, we first move the kernel virtual-to-physical way above where
	 * we physically want the kernel to end up, then copy it from there
	 * to its final resting place... ;-}
	 *
	 * Sigh...  */

#ifdef INITRD_IMAGE_SIZE
	load(initrd_start, KERNEL_ORIGIN+KERNEL_SIZE, INITRD_IMAGE_SIZE);
#endif
        load(START_ADDR+(4*KERNEL_SIZE), KERNEL_ORIGIN, KERNEL_SIZE);
        load(START_ADDR, START_ADDR+(4*KERNEL_SIZE), KERNEL_SIZE);

	memset((char*)ZERO_PGE, 0, PAGE_SIZE);
	strcpy((char*)ZERO_PGE, envval);
#ifdef INITRD_IMAGE_SIZE
	((long *)(ZERO_PGE+256))[0] = initrd_start;
	((long *)(ZERO_PGE+256))[1] = INITRD_IMAGE_SIZE;
#endif

	runkernel();
}

Annotation

Implementation Notes