UPSTREAM: mm: init: report memory auto-initialization features at boot time

Upstream commit 23a5c8cb7a91939cb08bc2dc880a7aa882bc6241.

Print the currently enabled stack and heap initialization modes.

Stack initialization is enabled by a config flag, while heap
initialization is configured at boot time with defaults being set in the
config.  It's more convenient for the user to have all information about
these hardening measures in one place at boot, so the user can reason
about the expected behavior of the running system.

The possible options for stack are:
 - "all" for CONFIG_INIT_STACK_ALL;
 - "byref_all" for CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL;
 - "byref" for CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF;
 - "__user" for CONFIG_GCC_PLUGIN_STRUCTLEAK_USER;
 - "off" otherwise.

Depending on the values of init_on_alloc and init_on_free boottime options
we also report "heap alloc" and "heap free" as "on"/"off".

In the init_on_free mode initializing pages at boot time may take a while,
so print a notice about that as well.  This depends on how much memory is
installed, the memory bandwidth, etc.  On a relatively modern x86 system,
it takes about 0.75s/GB to wipe all memory:

  [    0.418722] mem auto-init: stack:byref_all, heap alloc:off, heap free:on
  [    0.419765] mem auto-init: clearing system memory may take some time...
  [   12.376605] Memory: 16408564K/16776672K available (14339K kernel code, 1397K rwdata, 3756K rodata, 1636K init, 11460K bss, 368108K reserved, 0K cma-reserved)

Link: http://lkml.kernel.org/r/20190617151050.92663-3-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Sandeep Patil <sspatil@android.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Kaiwan N Billimoria <kaiwan@kaiwantech.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Change-Id: Idd3044824c3cfdf6c9ff4807fe9e6fae651792c7
Bug: 138435492
Test: Boot cuttlefish with and without
Test:   CONFIG_INIT_ON_ALLOC_DEFAULT_ON/CONFIG_INIT_ON_FREE_DEFAULT_ON
Test: Boot an ARM64 mobile device with and without
Test:   CONFIG_INIT_ON_ALLOC_DEFAULT_ON/CONFIG_INIT_ON_FREE_DEFAULT_ON
Signed-off-by: Alexander Potapenko <glider@google.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/init/main.c b/init/main.c
index 51067e2db509..f2845215b1e3 100644
--- a/init/main.c
+++ b/init/main.c
@@ -489,6 +489,29 @@ void __init __weak thread_stack_cache_init(void)
 
 void __init __weak mem_encrypt_init(void) { }
 
+/* Report memory auto-initialization states for this boot. */
+static void __init report_meminit(void)
+{
+	const char *stack;
+
+	if (IS_ENABLED(CONFIG_INIT_STACK_ALL))
+		stack = "all";
+	else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL))
+		stack = "byref_all";
+	else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF))
+		stack = "byref";
+	else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER))
+		stack = "__user";
+	else
+		stack = "off";
+
+	pr_info("mem auto-init: stack:%s, heap alloc:%s, heap free:%s\n",
+		stack, want_init_on_alloc(GFP_KERNEL) ? "on" : "off",
+		want_init_on_free() ? "on" : "off");
+	if (want_init_on_free())
+		pr_info("mem auto-init: clearing system memory may take some time...\n");
+}
+
 /*
  * Set up kernel memory allocators
  */
@@ -499,6 +522,7 @@ static void __init mm_init(void)
 	 * bigger than MAX_ORDER unless SPARSEMEM.
 	 */
 	page_ext_init_flatmem();
+	report_meminit();
 	mem_init();
 	kmem_cache_init();
 	pgtable_init();