4 files changed, 43 insertions, 1 deletions

diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
index 2283933a9a93..4599fa06bd82 100644
--- a/arch/s390/Kconfig.debug
+++ b/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
diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
index 52b8342c6bf2..1a2fdb6991df 100644
--- a/arch/s390/kernel/traps.c
+++ b/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);
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index b234bb4a6da7..983ec6ec0e7c 100644
--- a/arch/s390/mm/init.c
+++ b/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;
diff --git a/include/asm-s390/cacheflush.h b/include/asm-s390/cacheflush.h
index f7cade8083f3..49d5af916d01 100644
--- a/include/asm-s390/cacheflush.h
+++ b/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 */