Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables

The changes to automatically test for working stack protector compiler
support in the Kconfig files removed the special STACKPROTECTOR_AUTO
option that picked the strongest stack protector that the compiler
supported.

That was all a nice cleanup - it makes no sense to have the AUTO case
now that the Kconfig phase can just determine the compiler support
directly.

HOWEVER.

It also meant that doing "make oldconfig" would now _disable_ the strong
stackprotector if you had AUTO enabled, because in a legacy config file,
the sane stack protector configuration would look like

  CONFIG_HAVE_CC_STACKPROTECTOR=y
  # CONFIG_CC_STACKPROTECTOR_NONE is not set
  # CONFIG_CC_STACKPROTECTOR_REGULAR is not set
  # CONFIG_CC_STACKPROTECTOR_STRONG is not set
  CONFIG_CC_STACKPROTECTOR_AUTO=y

and when you ran this through "make oldconfig" with the Kbuild changes,
it would ask you about the regular CONFIG_CC_STACKPROTECTOR (that had
been renamed from CONFIG_CC_STACKPROTECTOR_REGULAR to just
CONFIG_CC_STACKPROTECTOR), but it would think that the STRONG version
used to be disabled (because it was really enabled by AUTO), and would
disable it in the new config, resulting in:

  CONFIG_HAVE_CC_STACKPROTECTOR=y
  CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
  CONFIG_CC_STACKPROTECTOR=y
  # CONFIG_CC_STACKPROTECTOR_STRONG is not set
  CONFIG_CC_HAS_SANE_STACKPROTECTOR=y

That's dangerously subtle - people could suddenly find themselves with
the weaker stack protector setup without even realizing.

The solution here is to just rename not just the old RECULAR stack
protector option, but also the strong one.  This does that by just
removing the CC_ prefix entirely for the user choices, because it really
is not about the compiler support (the compiler support now instead
automatially impacts _visibility_ of the options to users).

This results in "make oldconfig" actually asking the user for their
choice, so that we don't have any silent subtle security model changes.
The end result would generally look like this:

  CONFIG_HAVE_CC_STACKPROTECTOR=y
  CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
  CONFIG_STACKPROTECTOR=y
  CONFIG_STACKPROTECTOR_STRONG=y
  CONFIG_CC_HAS_SANE_STACKPROTECTOR=y

where the "CC_" versions really are about internal compiler
infrastructure, not the user selections.

Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 4 insertions, 4 deletions

diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 27c5381518d8..974d8d7d1bcd 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -61,7 +61,7 @@
 int main(void)
 {
   DEFINE(TSK_ACTIVE_MM,		offsetof(struct task_struct, active_mm));
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
   DEFINE(TSK_STACK_CANARY,	offsetof(struct task_struct, stack_canary));
 #endif
   BLANK();
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 1752033b0070..179a9f6bd1e3 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -791,7 +791,7 @@ ENTRY(__switch_to)
 	ldr	r6, [r2, #TI_CPU_DOMAIN]
 #endif
 	switch_tls r1, r4, r5, r3, r7
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	ldr	r7, [r2, #TI_TASK]
 	ldr	r8, =__stack_chk_guard
 	.if (TSK_STACK_CANARY > IMM12_MASK)
@@ -807,7 +807,7 @@ ENTRY(__switch_to)
 	ldr	r0, =thread_notify_head
 	mov	r1, #THREAD_NOTIFY_SWITCH
 	bl	atomic_notifier_call_chain
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	str	r7, [r8]
 #endif
  THUMB(	mov	ip, r4			   )
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 1523cb18b109..225d1c58d2de 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -39,7 +39,7 @@
 #include <asm/tls.h>
 #include <asm/vdso.h>
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 #include <linux/stackprotector.h>
 unsigned long __stack_chk_guard __read_mostly;
 EXPORT_SYMBOL(__stack_chk_guard);