[S390] DEBUG_PAGEALLOC support for s390.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig.debug

@@ -6,4 +6,12 @@ config TRACE_IRQFLAGS_SUPPORT
 
 source "lib/Kconfig.debug"
 
+config DEBUG_PAGEALLOC
+	bool "Debug page memory allocations"
+	depends on DEBUG_KERNEL
+	help
+	  Unmap pages from the kernel linear mapping after free_pages().
+	  This results in a slowdown, but helps to find certain types of
+	  memory corruptions.
+
 endmenu

arch/s390/kernel/traps.c

@@ -271,7 +271,10 @@ void die(const char * str, struct pt_regs * regs, long err)
 	printk("PREEMPT ");
 #endif
 #ifdef CONFIG_SMP
-	printk("SMP");
+	printk("SMP ");
+#endif
+#ifdef CONFIG_DEBUG_PAGEALLOC
+	printk("DEBUG_PAGEALLOC");
 #endif
 	printk("\n");
 	notify_die(DIE_OOPS, str, regs, err, current->thread.trap_no, SIGSEGV);

arch/s390/mm/init.c

@@ -167,6 +167,33 @@ void __init mem_init(void)
 	       PFN_ALIGN((unsigned long)&_eshared) - 1);
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void kernel_map_pages(struct page *page, int numpages, int enable)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	unsigned long address;
+	int i;
+
+	for (i = 0; i < numpages; i++) {
+		address = page_to_phys(page + i);
+		pgd = pgd_offset_k(address);
+		pud = pud_offset(pgd, address);
+		pmd = pmd_offset(pud, address);
+		pte = pte_offset_kernel(pmd, address);
+		if (!enable) {
+			ptep_invalidate(address, pte);
+			continue;
+		}
+		*pte = mk_pte_phys(address, __pgprot(_PAGE_TYPE_RW));
+		/* Flush cpu write queue. */
+		mb();
+	}
+}
+#endif
+
 void free_initmem(void)
 {
         unsigned long addr;

include/asm-s390/cacheflush.h

@@ -24,4 +24,8 @@
 #define copy_from_user_page(vma, page, vaddr, dst, src, len) \
 	memcpy(dst, src, len)
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void kernel_map_pages(struct page *page, int numpages, int enable);
+#endif
+
 #endif /* _S390_CACHEFLUSH_H */