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>

Documentation/kbuild/kconfig-language.txt

@@ -480,7 +480,7 @@ There are several features that need compiler support. The recommended way
 to describe the dependency on the compiler feature is to use "depends on"
 followed by a test macro.
 
-config CC_STACKPROTECTOR
+config STACKPROTECTOR
 	bool "Stack Protector buffer overflow detection"
 	depends on $(cc-option,-fstack-protector)
 	...

Documentation/security/self-protection.rst

@@ -156,7 +156,7 @@ The classic stack buffer overflow involves writing past the expected end
 of a variable stored on the stack, ultimately writing a controlled value
 to the stack frame's stored return address. The most widely used defense
 is the presence of a stack canary between the stack variables and the
-return address (``CONFIG_CC_STACKPROTECTOR``), which is verified just before
+return address (``CONFIG_STACKPROTECTOR``), which is verified just before
 the function returns. Other defenses include things like shadow stacks.
 
 Stack depth overflow

Makefile

@@ -687,8 +687,8 @@ KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
 endif
 
 stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
-stackp-flags-$(CONFIG_CC_STACKPROTECTOR)          := -fstack-protector
-stackp-flags-$(CONFIG_CC_STACKPROTECTOR_STRONG)   := -fstack-protector-strong
+stackp-flags-$(CONFIG_STACKPROTECTOR)             := -fstack-protector
+stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
 
 KBUILD_CFLAGS += $(stackp-flags-y)
 

arch/Kconfig

@@ -558,7 +558,7 @@ config HAVE_CC_STACKPROTECTOR
 config CC_HAS_STACKPROTECTOR_NONE
 	def_bool $(cc-option,-fno-stack-protector)
 
-config CC_STACKPROTECTOR
+config STACKPROTECTOR
 	bool "Stack Protector buffer overflow detection"
 	depends on HAVE_CC_STACKPROTECTOR
 	depends on $(cc-option,-fstack-protector)
@@ -582,9 +582,9 @@ config CC_STACKPROTECTOR
 	  about 3% of all kernel functions, which increases kernel code size
 	  by about 0.3%.
 
-config CC_STACKPROTECTOR_STRONG
+config STACKPROTECTOR_STRONG
 	bool "Strong Stack Protector"
-	depends on CC_STACKPROTECTOR
+	depends on STACKPROTECTOR
 	depends on $(cc-option,-fstack-protector-strong)
 	default y
 	help

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();

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			   )

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);

arch/arm64/kernel/process.c

@@ -59,7 +59,7 @@
 #include <asm/processor.h>
 #include <asm/stacktrace.h>
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 #include <linux/stackprotector.h>
 unsigned long __stack_chk_guard __read_mostly;
 EXPORT_SYMBOL(__stack_chk_guard);

arch/mips/kernel/asm-offsets.c

@@ -83,7 +83,7 @@ void output_task_defines(void)
 	OFFSET(TASK_FLAGS, task_struct, flags);
 	OFFSET(TASK_MM, task_struct, mm);
 	OFFSET(TASK_PID, task_struct, pid);
-#if defined(CONFIG_CC_STACKPROTECTOR)
+#if defined(CONFIG_STACKPROTECTOR)
 	OFFSET(TASK_STACK_CANARY, task_struct, stack_canary);
 #endif
 	DEFINE(TASK_STRUCT_SIZE, sizeof(struct task_struct));

arch/mips/kernel/octeon_switch.S

@@ -61,7 +61,7 @@
 #endif
 3:
 
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	PTR_LA	t8, __stack_chk_guard
 	LONG_L	t9, TASK_STACK_CANARY(a1)
 	LONG_S	t9, 0(t8)

arch/mips/kernel/process.c

@@ -180,7 +180,7 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp,
 	return 0;
 }
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 #include <linux/stackprotector.h>
 unsigned long __stack_chk_guard __read_mostly;
 EXPORT_SYMBOL(__stack_chk_guard);

arch/mips/kernel/r2300_switch.S

@@ -36,7 +36,7 @@ LEAF(resume)
 	cpu_save_nonscratch a0
 	sw	ra, THREAD_REG31(a0)
 
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	PTR_LA	t8, __stack_chk_guard
 	LONG_L	t9, TASK_STACK_CANARY(a1)
 	LONG_S	t9, 0(t8)

arch/mips/kernel/r4k_switch.S

@@ -31,7 +31,7 @@
 	cpu_save_nonscratch a0
 	LONG_S	ra, THREAD_REG31(a0)
 
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	PTR_LA	t8, __stack_chk_guard
 	LONG_L	t9, TASK_STACK_CANARY(a1)
 	LONG_S	t9, 0(t8)

arch/sh/kernel/process.c

@@ -12,7 +12,7 @@
 struct kmem_cache *task_xstate_cachep = NULL;
 unsigned int xstate_size;
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 unsigned long __stack_chk_guard __read_mostly;
 EXPORT_SYMBOL(__stack_chk_guard);
 #endif

arch/sh/kernel/process_32.c

@@ -177,7 +177,7 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
 {
 	struct thread_struct *next_t = &next->thread;
 
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	__stack_chk_guard = next->stack_canary;
 #endif
 

arch/x86/entry/entry_32.S

@@ -239,7 +239,7 @@ ENTRY(__switch_to_asm)
 	movl	%esp, TASK_threadsp(%eax)
 	movl	TASK_threadsp(%edx), %esp
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	movl	TASK_stack_canary(%edx), %ebx
 	movl	%ebx, PER_CPU_VAR(stack_canary)+stack_canary_offset
 #endif

arch/x86/entry/entry_64.S

@@ -357,7 +357,7 @@ ENTRY(__switch_to_asm)
 	movq	%rsp, TASK_threadsp(%rdi)
 	movq	TASK_threadsp(%rsi), %rsp
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	movq	TASK_stack_canary(%rsi), %rbx
 	movq	%rbx, PER_CPU_VAR(irq_stack_union)+stack_canary_offset
 #endif

arch/x86/include/asm/processor.h

@@ -412,7 +412,7 @@ extern asmlinkage void ignore_sysret(void);
 void save_fsgs_for_kvm(void);
 #endif
 #else	/* X86_64 */
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 /*
  * Make sure stack canary segment base is cached-aligned:
  *   "For Intel Atom processors, avoid non zero segment base address

arch/x86/include/asm/segment.h

@@ -146,7 +146,7 @@
 # define __KERNEL_PERCPU		0
 #endif
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 # define __KERNEL_STACK_CANARY		(GDT_ENTRY_STACK_CANARY*8)
 #else
 # define __KERNEL_STACK_CANARY		0

arch/x86/include/asm/stackprotector.h

@@ -34,7 +34,7 @@
 #ifndef _ASM_STACKPROTECTOR_H
 #define _ASM_STACKPROTECTOR_H 1
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 
 #include <asm/tsc.h>
 #include <asm/processor.h>
@@ -105,7 +105,7 @@ static inline void load_stack_canary_segment(void)
 #endif
 }
 
-#else	/* CC_STACKPROTECTOR */
+#else	/* STACKPROTECTOR */
 
 #define GDT_STACK_CANARY_INIT
 
@@ -121,5 +121,5 @@ static inline void load_stack_canary_segment(void)
 #endif
 }
 
-#endif	/* CC_STACKPROTECTOR */
+#endif	/* STACKPROTECTOR */
 #endif	/* _ASM_STACKPROTECTOR_H */

arch/x86/kernel/asm-offsets.c

@@ -32,7 +32,7 @@
 void common(void) {
 	BLANK();
 	OFFSET(TASK_threadsp, task_struct, thread.sp);
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	OFFSET(TASK_stack_canary, task_struct, stack_canary);
 #endif
 

arch/x86/kernel/asm-offsets_32.c

@@ -50,7 +50,7 @@ void foo(void)
 	DEFINE(TSS_sysenter_sp0, offsetof(struct cpu_entry_area, tss.x86_tss.sp0) -
 	       offsetofend(struct cpu_entry_area, entry_stack_page.stack));
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	BLANK();
 	OFFSET(stack_canary_offset, stack_canary, canary);
 #endif

arch/x86/kernel/asm-offsets_64.c

@@ -69,7 +69,7 @@ int main(void)
 	OFFSET(TSS_sp1, tss_struct, x86_tss.sp1);
 	BLANK();
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	DEFINE(stack_canary_offset, offsetof(union irq_stack_union, stack_canary));
 	BLANK();
 #endif

arch/x86/kernel/cpu/common.c

@@ -1599,7 +1599,7 @@ DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) =
 	(unsigned long)&init_thread_union + THREAD_SIZE;
 EXPORT_PER_CPU_SYMBOL(cpu_current_top_of_stack);
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 DEFINE_PER_CPU_ALIGNED(struct stack_canary, stack_canary);
 #endif
 

arch/x86/kernel/head_32.S

@@ -375,7 +375,7 @@ ENDPROC(startup_32_smp)
  */
 __INIT
 setup_once:
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	/*
 	 * Configure the stack canary. The linker can't handle this by
 	 * relocation.  Manually set base address in stack canary

arch/xtensa/kernel/asm-offsets.c

@@ -76,7 +76,7 @@ int main(void)
 	DEFINE(TASK_PID, offsetof (struct task_struct, pid));
 	DEFINE(TASK_THREAD, offsetof (struct task_struct, thread));
 	DEFINE(TASK_THREAD_INFO, offsetof (struct task_struct, stack));
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	DEFINE(TASK_STACK_CANARY, offsetof(struct task_struct, stack_canary));
 #endif
 	DEFINE(TASK_STRUCT_SIZE, sizeof (struct task_struct));

arch/xtensa/kernel/entry.S

@@ -1971,7 +1971,7 @@ ENTRY(_switch_to)
 	s32i	a1, a2, THREAD_SP	# save stack pointer
 #endif
 
-#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
+#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
 	movi	a6, __stack_chk_guard
 	l32i	a8, a3, TASK_STACK_CANARY
 	s32i	a8, a6, 0

arch/xtensa/kernel/process.c

@@ -58,7 +58,7 @@ void (*pm_power_off)(void) = NULL;
 EXPORT_SYMBOL(pm_power_off);
 
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 #include <linux/stackprotector.h>
 unsigned long __stack_chk_guard __read_mostly;
 EXPORT_SYMBOL(__stack_chk_guard);

include/linux/sched.h

@@ -742,7 +742,7 @@ struct task_struct {
 	pid_t				pid;
 	pid_t				tgid;
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	/* Canary value for the -fstack-protector GCC feature: */
 	unsigned long			stack_canary;
 #endif

include/linux/stackprotector.h

@@ -6,7 +6,7 @@
 #include <linux/sched.h>
 #include <linux/random.h>
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 # include <asm/stackprotector.h>
 #else
 static inline void boot_init_stack_canary(void)

kernel/configs/android-recommended.config

@@ -12,7 +12,7 @@ CONFIG_BLK_DEV_DM=y
 CONFIG_BLK_DEV_LOOP=y
 CONFIG_BLK_DEV_RAM=y
 CONFIG_BLK_DEV_RAM_SIZE=8192
-CONFIG_CC_STACKPROTECTOR_STRONG=y
+CONFIG_STACKPROTECTOR_STRONG=y
 CONFIG_COMPACTION=y
 CONFIG_CPU_SW_DOMAIN_PAN=y
 CONFIG_DM_CRYPT=y

kernel/fork.c

@@ -811,7 +811,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	clear_tsk_need_resched(tsk);
 	set_task_stack_end_magic(tsk);
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 	tsk->stack_canary = get_random_canary();
 #endif
 

kernel/panic.c

@@ -623,7 +623,7 @@ static __init int register_warn_debugfs(void)
 device_initcall(register_warn_debugfs);
 #endif
 
-#ifdef CONFIG_CC_STACKPROTECTOR
+#ifdef CONFIG_STACKPROTECTOR
 
 /*
  * Called when gcc's -fstack-protector feature is used, and