int __init linux_main()

in kernel/um_arch.c [305:400]

• 60 lines of code
• 11 McCabe index (conditional complexity)

int __init linux_main(int argc, char **argv)
{
	unsigned long avail, diff;
	unsigned long virtmem_size, max_physmem;
	unsigned long stack;
	unsigned int i;
	int add;

	for (i = 1; i < argc; i++) {
		if ((i == 1) && (argv[i][0] == ' '))
			continue;
		add = 1;
		uml_checksetup(argv[i], &add);
		if (add)
			add_arg(argv[i]);
	}
	if (have_root == 0)
		add_arg(DEFAULT_COMMAND_LINE_ROOT);

	if (have_console == 0)
		add_arg(DEFAULT_COMMAND_LINE_CONSOLE);

	host_task_size = os_get_top_address();
	/* reserve two pages for the stubs */
	host_task_size -= 2 * PAGE_SIZE;
	stub_start = host_task_size;

	/*
	 * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
	 * out
	 */
	task_size = host_task_size & PGDIR_MASK;

	/* OS sanity checks that need to happen before the kernel runs */
	os_early_checks();

	get_host_cpu_features(parse_host_cpu_flags, parse_cache_line);

	brk_start = (unsigned long) sbrk(0);

	/*
	 * Increase physical memory size for exec-shield users
	 * so they actually get what they asked for. This should
	 * add zero for non-exec shield users
	 */

	diff = UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
	if (diff > 1024 * 1024) {
		os_info("Adding %ld bytes to physical memory to account for "
			"exec-shield gap\n", diff);
		physmem_size += UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
	}

	uml_physmem = (unsigned long) __binary_start & PAGE_MASK;

	/* Reserve up to 4M after the current brk */
	uml_reserved = ROUND_4M(brk_start) + (1 << 22);

	setup_machinename(init_utsname()->machine);

	highmem = 0;
	iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK;
	max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC;

	/*
	 * Zones have to begin on a 1 << MAX_ORDER page boundary,
	 * so this makes sure that's true for highmem
	 */
	max_physmem &= ~((1 << (PAGE_SHIFT + MAX_ORDER)) - 1);
	if (physmem_size + iomem_size > max_physmem) {
		highmem = physmem_size + iomem_size - max_physmem;
		physmem_size -= highmem;
	}

	high_physmem = uml_physmem + physmem_size;
	end_iomem = high_physmem + iomem_size;
	high_memory = (void *) end_iomem;

	start_vm = VMALLOC_START;

	virtmem_size = physmem_size;
	stack = (unsigned long) argv;
	stack &= ~(1024 * 1024 - 1);
	avail = stack - start_vm;
	if (physmem_size > avail)
		virtmem_size = avail;
	end_vm = start_vm + virtmem_size;

	if (virtmem_size < physmem_size)
		os_info("Kernel virtual memory size shrunk to %lu bytes\n",
			virtmem_size);

	os_flush_stdout();

	return start_uml();
}