sh: Improve oops error reporting

In some cases the opps error reporting doesn't give enough information
to diagnose the problem, only printing information if it is thought
to be valid. Replace the current code with more detailed output.

This code is based on the ARM reporting, with minor changes for the SH.

[lethal@linux-sh.org: fixed up for 64-bit PTEs and pte_offset_kernel()]
Signed-off-by: NStuart Menefy <stuart.menefy@st.com>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/mm/fault_32.c

@@ -35,6 +35,74 @@ static inline int notify_page_fault(struct pt_regs *regs, int trap)
 	return ret;
 }
 
+/*
+ * This is useful to dump out the page tables associated with
+ * 'addr' in mm 'mm'.
+ */
+static void show_pte(struct mm_struct *mm, unsigned long addr)
+{
+	pgd_t *pgd;
+
+	if (mm)
+		pgd = mm->pgd;
+	else
+		pgd = get_TTB();
+
+	printk(KERN_ALERT "pgd = %p\n", pgd);
+	pgd += pgd_index(addr);
+	printk(KERN_ALERT "[%08lx] *pgd=%0*Lx", addr,
+	       sizeof(*pgd) * 2, (u64)pgd_val(*pgd));
+
+	do {
+		pud_t *pud;
+		pmd_t *pmd;
+		pte_t *pte;
+
+		if (pgd_none(*pgd))
+			break;
+
+		if (pgd_bad(*pgd)) {
+			printk("(bad)");
+			break;
+		}
+
+		pud = pud_offset(pgd, addr);
+		if (PTRS_PER_PUD != 1)
+			printk(", *pud=%0*Lx", sizeof(*pud) * 2,
+			       (u64)pud_val(*pud));
+
+		if (pud_none(*pud))
+			break;
+
+		if (pud_bad(*pud)) {
+			printk("(bad)");
+			break;
+		}
+
+		pmd = pmd_offset(pud, addr);
+		if (PTRS_PER_PMD != 1)
+			printk(", *pmd=%0*Lx", sizeof(*pmd) * 2,
+			       (u64)pmd_val(*pmd));
+
+		if (pmd_none(*pmd))
+			break;
+
+		if (pmd_bad(*pmd)) {
+			printk("(bad)");
+			break;
+		}
+
+		/* We must not map this if we have highmem enabled */
+		if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
+			break;
+
+		pte = pte_offset_kernel(pmd, addr);
+		printk(", *pte=%0*Lx", sizeof(*pte) * 2, (u64)pte_val(*pte));
+	} while (0);
+
+	printk("\n");
+}
+
 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
 {
 	unsigned index = pgd_index(address);
@@ -254,29 +322,12 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 	bust_spinlocks(1);
 
 	if (oops_may_print()) {
-		unsigned long page;
-
-		if (address < PAGE_SIZE)
-			printk(KERN_ALERT "Unable to handle kernel NULL "
-					  "pointer dereference");
-		else
-			printk(KERN_ALERT "Unable to handle kernel paging "
-					  "request");
-		printk(" at virtual address %08lx\n", address);
-		printk(KERN_ALERT "pc = %08lx\n", regs->pc);
-		page = (unsigned long)get_TTB();
-		if (page) {
-			page = ((__typeof__(page) *)page)[address >> PGDIR_SHIFT];
-			printk(KERN_ALERT "*pde = %08lx\n", page);
-			if (page & _PAGE_PRESENT) {
-				page &= PAGE_MASK;
-				address &= 0x003ff000;
-				page = ((__typeof__(page) *)
-						__va(page))[address >>
-							    PAGE_SHIFT];
-				printk(KERN_ALERT "*pte = %08lx\n", page);
-			}
-		}
+		printk(KERN_ALERT
+		       "Unable to handle kernel %s at virtual address %08lx\n",
+		       (address < PAGE_SIZE) ? "NULL pointer dereference" :
+		       "paging request", address);
+
+		show_pte(mm, address);
 	}
 
 	die("Oops", regs, writeaccess);