[PATCH v4 2/3] mm: init: report memory auto-initialization features at boot time

[Alexander Potapenko]

Print the currently enabled stack and heap initialization modes.

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 some
time, so print a notice about that as well.

Signed-off-by: Alexander Potapenko <glider at google.com>
Suggested-by: Kees Cook <keescook at chromium.org>
To: Andrew Morton <akpm at linux-foundation.org>
To: Christoph Lameter <cl at linux.com>
Cc: Dmitry Vyukov <dvyukov at google.com>
Cc: James Morris <jmorris at namei.org>
Cc: Jann Horn <jannh at google.com>
Cc: Kostya Serebryany <kcc at google.com>
Cc: Laura Abbott <labbott at redhat.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
Cc: Matthew Wilcox <willy at infradead.org>
Cc: Nick Desaulniers <ndesaulniers at google.com>
Cc: Randy Dunlap <rdunlap at infradead.org>
Cc: Sandeep Patil <sspatil at android.com>
Cc: "Serge E. Hallyn" <serge at hallyn.com>
Cc: Souptick Joarder <jrdr.linux at gmail.com>
Cc: kernel-hardening at lists.openwall.com
Cc: linux-mm at kvack.org
Cc: linux-security-module at vger.kernel.org
---
 init/main.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/init/main.c b/init/main.c
index 5a2c69b4d7b3..90f721c58e61 100644
--- a/init/main.c
+++ b/init/main.c
@@ -519,6 +519,29 @@ static inline void initcall_debug_enable(void)
 }
 #endif
 
+/* Report memory auto-initialization states for this boot. */
+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("Clearing system memory may take some time...\n");
+}
+
 /*
  * Set up kernel memory allocators
  */
@@ -529,6 +552,7 @@ 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();
-- 
2.21.0.1020.gf2820cf01a-goog