static void __init map_ram()

in mm/init.c [50:96]

• 33 lines of code
• 7 McCabe index (conditional complexity)

static void __init map_ram(void)
{
	unsigned long v, p, e;
	pgd_t *pge;
	p4d_t *p4e;
	pud_t *pue;
	pmd_t *pme;
	pte_t *pte;
	/* These mark extents of read-only kernel pages...
	 * ...from vmlinux.lds.S
	 */

	p = (u32) memblock_start_of_DRAM() & PAGE_MASK;
	e = min((u32) memblock_end_of_DRAM(), (u32) __pa(high_memory));

	v = (u32) __va(p);
	pge = pgd_offset_k(v);

	while (p < e) {
		int j;
		p4e = p4d_offset(pge, v);
		pue = pud_offset(p4e, v);
		pme = pmd_offset(pue, v);

		if ((u32) pue != (u32) pge || (u32) pme != (u32) pge) {
			panic("%s: Kernel hardcoded for "
			      "two-level page tables", __func__);
		}

		/* Alloc one page for holding PTE's... */
		pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
		if (!pte)
			panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
			      __func__, PAGE_SIZE, PAGE_SIZE);
		set_pmd(pme, __pmd(__pa(pte) + _PAGE_KERNEL_TABLE));

		/* Fill the newly allocated page with PTE'S */
		for (j = 0; p < e && j < PTRS_PER_PTE;
		     v += PAGE_SIZE, p += PAGE_SIZE, j++, pte++) {
			/* Create mapping between p and v. */
			/* TODO: more fine grant for page access permission */
			set_pte(pte, __pte(p + pgprot_val(PAGE_KERNEL)));
		}

		pge++;
	}
}