RFC: add code to dump the kernel page tables for visual inspection by kernel developers

[Dragos Tatulea <dragos.tatulea@xxxxxxxxx>]

On the linux-mips.org TODO list, there's the $SUBJ item. Ralf B.
hinted that a good starting point would be the dump_list_process
function which was removed in 2.6.23 (during lib-32 & lib-64 merge?).
This patch is just a copy paste from the lib-64 version of this
function (with small modifications for 32 bit compatibility).

Any other interesting "features" that should get in?

diff --git a/arch/mips/lib/dump_tlb.c b/arch/mips/lib/dump_tlb.c
index 3f69725..7d705c8 100644
--- a/arch/mips/lib/dump_tlb.c
+++ b/arch/mips/lib/dump_tlb.c
@@ -6,6 +6,7 @@
  */
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/sched.h>

 #include <asm/mipsregs.h>
 #include <asm/page.h>
@@ -109,3 +110,71 @@ void dump_tlb_all(void)
 {
 	dump_tlb(0, current_cpu_data.tlbsize - 1);
 }
+
+void dump_list_process(struct task_struct *t, void *address)
+{
+	pgd_t	*page_dir, *pgd;
+	pud_t	*pud;
+	pmd_t	*pmd;
+	pte_t	*pte, page;
+	unsigned long addr, val;
+	int width;
+
+#if defined(CONFIG_64BIT)
+	width = 16;
+#else
+	width = 8;
+#endif
+
+	addr = (unsigned long) address;
+
+	printk("Addr                 == %0*lx\n", width, addr);
+	printk("tasks->mm.pgd        == %0*lx\n", width,
+	       (unsigned long) t->mm->pgd);
+
+	page_dir = pgd_offset(t->mm, 0UL);
+	printk("page_dir == %0*lx\n", width, (unsigned long) page_dir);
+
+	pgd = pgd_offset(t->mm, addr);
+	printk("pgd == %0*lx\n", width, (unsigned long) pgd);
+
+	pud = pud_offset(pgd, addr);
+	printk("pud == %0*lx\n", width, (unsigned long) pud);
+
+	pmd = pmd_offset(pud, addr);
+	printk("pmd == %0*lx\n", width, (unsigned long) pmd);
+
+	pte = pte_offset(pmd, addr);
+	printk("pte == %0*lx\n", width, (long) pte);
+
+	page = *pte;
+	printk("page == %08lx\n", pte_val(page));
+
+	val = pte_val(page);
+	if (val & _PAGE_PRESENT)
+		printk("present ");
+	if (val & _PAGE_READ)
+		printk("read ");
+	if (val & _PAGE_WRITE)
+		printk("write ");
+	if (val & _PAGE_ACCESSED)
+		printk("accessed ");
+	if (val & _PAGE_MODIFIED)
+		printk("modified ");
+#if defined(CONFIG_64BIT_PHYS_ADDR) && defined(CONFIG_CPU_MIPS32)
+	if (val & _PAGE_R4KBUG)
+		printk("r4kbug ");
+#endif
+	if (val & _PAGE_GLOBAL)
+		printk("global ");
+	if (val & _PAGE_VALID)
+		printk("valid ");
+	if (val & _PAGE_DIRTY)
+		printk("dirty ");
+	printk("\n");
+}
+
+void dump_list_current(void *address)
+{
+	dump_list_process(current, address);
+}