void __init setup_arch_memory()

in mm/init.c [140:238]

• 45 lines of code
• 3 McCabe index (conditional complexity)

void __init setup_arch_memory(void)
{
	/*  XXX Todo: this probably should be cleaned up  */
	u32 *segtable = (u32 *) &swapper_pg_dir[0];
	u32 *segtable_end;

	/*
	 * Set up boot memory allocator
	 *
	 * The Gorman book also talks about these functions.
	 * This needs to change for highmem setups.
	 */

	/*  Prior to this, bootmem_lastpg is actually mem size  */
	bootmem_lastpg += ARCH_PFN_OFFSET;

	/* Memory size needs to be a multiple of 16M */
	bootmem_lastpg = PFN_DOWN((bootmem_lastpg << PAGE_SHIFT) &
		~((BIG_KERNEL_PAGE_SIZE) - 1));

	memblock_add(PHYS_OFFSET,
		     (bootmem_lastpg - ARCH_PFN_OFFSET) << PAGE_SHIFT);

	/* Reserve kernel text/data/bss */
	memblock_reserve(PHYS_OFFSET,
			 (bootmem_startpg - ARCH_PFN_OFFSET) << PAGE_SHIFT);
	/*
	 * Reserve the top DMA_RESERVE bytes of RAM for DMA (uncached)
	 * memory allocation
	 */
	max_low_pfn = bootmem_lastpg - PFN_DOWN(DMA_RESERVED_BYTES);
	min_low_pfn = ARCH_PFN_OFFSET;
	memblock_reserve(PFN_PHYS(max_low_pfn), DMA_RESERVED_BYTES);

	printk(KERN_INFO "bootmem_startpg:  0x%08lx\n", bootmem_startpg);
	printk(KERN_INFO "bootmem_lastpg:  0x%08lx\n", bootmem_lastpg);
	printk(KERN_INFO "min_low_pfn:  0x%08lx\n", min_low_pfn);
	printk(KERN_INFO "max_low_pfn:  0x%08lx\n", max_low_pfn);

	/*
	 * The default VM page tables (will be) populated with
	 * VA=PA+PAGE_OFFSET mapping.  We go in and invalidate entries
	 * higher than what we have memory for.
	 */

	/*  this is pointer arithmetic; each entry covers 4MB  */
	segtable = segtable + (PAGE_OFFSET >> 22);

	/*  this actually only goes to the end of the first gig  */
	segtable_end = segtable + (1<<(30-22));

	/*
	 * Move forward to the start of empty pages; take into account
	 * phys_offset shift.
	 */

	segtable += (bootmem_lastpg-ARCH_PFN_OFFSET)>>(22-PAGE_SHIFT);
	{
		int i;

		for (i = 1 ; i <= DMA_RESERVE ; i++)
			segtable[-i] = ((segtable[-i] & __HVM_PTE_PGMASK_4MB)
				| __HVM_PTE_R | __HVM_PTE_W | __HVM_PTE_X
				| __HEXAGON_C_UNC << 6
				| __HVM_PDE_S_4MB);
	}

	printk(KERN_INFO "clearing segtable from %p to %p\n", segtable,
		segtable_end);
	while (segtable < (segtable_end-8))
		*(segtable++) = __HVM_PDE_S_INVALID;
	/* stop the pointer at the device I/O 4MB page  */

	printk(KERN_INFO "segtable = %p (should be equal to _K_io_map)\n",
		segtable);

#if 0
	/*  Other half of the early device table from vm_init_segtable. */
	printk(KERN_INFO "&_K_init_devicetable = 0x%08x\n",
		(unsigned long) _K_init_devicetable-PAGE_OFFSET);
	*segtable = ((u32) (unsigned long) _K_init_devicetable-PAGE_OFFSET) |
		__HVM_PDE_S_4KB;
	printk(KERN_INFO "*segtable = 0x%08x\n", *segtable);
#endif

	/*
	 *  The bootmem allocator seemingly just lives to feed memory
	 *  to the paging system
	 */
	printk(KERN_INFO "PAGE_SIZE=%lu\n", PAGE_SIZE);
	paging_init();  /*  See Gorman Book, 2.3  */

	/*
	 *  At this point, the page allocator is kind of initialized, but
	 *  apparently no pages are available (just like with the bootmem
	 *  allocator), and need to be freed themselves via mem_init(),
	 *  which is called by start_kernel() later on in the process
	 */
}