Stuff

/* This is a code sample from arch/i386/setup.c in the Linux kernel, Copyright of Linus Torvalds, licensed under the GPL. */

static void __init parse_cmdline_early (char ** cmdline_p)
{
	char c = ' ', *to = command_line, *from = saved_command_line;
	int len = 0;
	int userdef = 0;

	/* Save unparsed command line copy for /proc/cmdline */
	saved_command_line[COMMAND_LINE_SIZE-1] = '\0';

	for (;;) {
		/*
		 * "mem=nopentium" disables the 4MB page tables.
		 * "mem=XXX[kKmM]" defines a memory region from HIGH_MEM
		 * to <mem>, overriding the bios size.
		 * "memmap=XXX[KkmM]@XXX[KkmM]" defines a memory region from
		 * <start> to <start>+<mem>, overriding the bios size.
		 *
		 * HPA tells me bootloaders need to parse mem=, so no new
		 * option should be mem=  [also see Documentation/i386/boot.txt]
		 */
		if (c == ' ' && !memcmp(from, "mem=", 4)) {
			if (to != command_line)
				to--;
			if (!memcmp(from+4, "nopentium", 9)) {
				from += 9+4;
				clear_bit(X86_FEATURE_PSE, boot_cpu_data.x86_capability);
				disable_pse = 1;
			} else {
				/* If the user specifies memory size, we
				 * limit the BIOS-provided memory map to
				 * that size. exactmap can be used to specify
				 * the exact map. mem=number can be used to
				 * trim the existing memory map.
				 */
				unsigned long long mem_size;
 
				mem_size = memparse(from+4, &from);
				limit_regions(mem_size);
				userdef=1;
			}
		}

		if (c == ' ' && !memcmp(from, "memmap=", 7)) {
			if (to != command_line)
				to--;
			if (!memcmp(from+7, "exactmap", 8)) {
				from += 8+7;
				e820.nr_map = 0;
				userdef = 1;
			} else {
				/* If the user specifies memory size, we
				 * limit the BIOS-provided memory map to
				 * that size. exactmap can be used to specify
				 * the exact map. mem=number can be used to
				 * trim the existing memory map.
				 */
				unsigned long long start_at, mem_size;
 
				mem_size = memparse(from+7, &from);
				if (*from == '@') {
					start_at = memparse(from+1, &from);
					add_memory_region(start_at, mem_size, E820_RAM);
				} else if (*from == '#') {
					start_at = memparse(from+1, &from);
					add_memory_region(start_at, mem_size, E820_ACPI);
				} else if (*from == '$') {
					start_at = memparse(from+1, &from);
					add_memory_region(start_at, mem_size, E820_RESERVED);
				} else {
					limit_regions(mem_size);
					userdef=1;
				}
			}
		}

#ifdef  CONFIG_X86_SMP
		/*
		 * If the BIOS enumerates physical processors before logical,
		 * maxcpus=N at enumeration-time can be used to disable HT.
		 */
		else if (!memcmp(from, "maxcpus=", 8)) {
			extern unsigned int maxcpus;

			maxcpus = simple_strtoul(from + 8, NULL, 0);
		}
#endif

#ifdef CONFIG_ACPI_BOOT
		/* "acpi=off" disables both ACPI table parsing and interpreter */
		else if (!memcmp(from, "acpi=off", 8)) {
			disable_acpi();
		}

		/* acpi=force to over-ride black-list */
		else if (!memcmp(from, "acpi=force", 10)) {
			acpi_force = 1;
			acpi_ht = 1;
			acpi_disabled = 0;
		}

		/* acpi=strict disables out-of-spec workarounds */
		else if (!memcmp(from, "acpi=strict", 11)) {
			acpi_strict = 1;
		}

		/* Limit ACPI just to boot-time to enable HT */
		else if (!memcmp(from, "acpi=ht", 7)) {
			if (!acpi_force)
				disable_acpi();
			acpi_ht = 1;
		}
		
		/* "pci=noacpi" disable ACPI IRQ routing and PCI scan */
		else if (!memcmp(from, "pci=noacpi", 10)) {
			acpi_disable_pci();
		}
		/* "acpi=noirq" disables ACPI interrupt routing */
		else if (!memcmp(from, "acpi=noirq", 10)) {
			acpi_noirq_set();
		}

		else if (!memcmp(from, "acpi_sci=edge", 13))
			acpi_sci_flags.trigger =  1;

		else if (!memcmp(from, "acpi_sci=level", 14))
			acpi_sci_flags.trigger = 3;

		else if (!memcmp(from, "acpi_sci=high", 13))
			acpi_sci_flags.polarity = 1;

		else if (!memcmp(from, "acpi_sci=low", 12))
			acpi_sci_flags.polarity = 3;

#ifdef CONFIG_X86_IO_APIC
		else if (!memcmp(from, "acpi_skip_timer_override", 24))
			acpi_skip_timer_override = 1;
#endif

#ifdef CONFIG_X86_LOCAL_APIC
		/* disable IO-APIC */
		else if (!memcmp(from, "noapic", 6))
			disable_ioapic_setup();
#endif /* CONFIG_X86_LOCAL_APIC */
#endif /* CONFIG_ACPI_BOOT */

		/*
		 * highmem=size forces highmem to be exactly 'size' bytes.
		 * This works even on boxes that have no highmem otherwise.
		 * This also works to reduce highmem size on bigger boxes.
		 */
		if (c == ' ' && !memcmp(from, "highmem=", 8))
			highmem_pages = memparse(from+8, &from) >> PAGE_SHIFT;
	
		c = *(from++);
		if (!c)
			break;
		if (COMMAND_LINE_SIZE <= ++len)
			break;
		*(to++) = c;
	}
	*to = '\0';
	*cmdline_p = command_line;
	if (userdef) {
		printk(KERN_INFO "user-defined physical RAM map:\n");
		print_memory_map("user");
	}
}