x86/mm: Remove CONFIG_DEBUG_NX_TEST

kees · Ingo Molnar · commit 3ad38ceb2769 · 2017-01-31T08:31:58.000+01:00
CONFIG_DEBUG_NX_TEST has been broken since CONFIG_DEBUG_SET_MODULE_RONX=y was added in v2.6.37 via: 84e1c6b ("x86: Add RO/NX protection for loadable kernel modules") since the exception table was then made read-only. Additionally, the manually constructed extables were never fixed when relative extables were introduced in v3.5 via: 7062765 ("x86, extable: Switch to relative exception table entries") However, relative extables won't work for test_nx.c, since test instruction memory areas may be more than INT_MAX away from an executable fixup (e.g. stack and heap too far away from executable memory with the fixup). Since clearly no one has been using this code for a while now, and similar tests exist in LKDTM, this should just be removed entirely. Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jinbum Park <jinb.park7@gmail.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170131003711.GA74048@beast Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
@@ -120,14 +120,6 @@ config DEBUG_SET_MODULE_RONX
 	  against certain classes of kernel exploits.
 	  If in doubt, say "N".
 
-config DEBUG_NX_TEST
-	tristate "Testcase for the NX non-executable stack feature"
-	depends on DEBUG_KERNEL && m
-	---help---
-	  This option enables a testcase for the CPU NX capability
-	  and the software setup of this feature.
-	  If in doubt, say "N"
-
 config DOUBLEFAULT
 	default y
 	bool "Enable doublefault exception handler" if EXPERT
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
@@ -101,7 +101,6 @@ obj-$(CONFIG_APB_TIMER)		+= apb_timer.o
 
 obj-$(CONFIG_AMD_NB)		+= amd_nb.o
 obj-$(CONFIG_DEBUG_RODATA_TEST)	+= test_rodata.o
-obj-$(CONFIG_DEBUG_NX_TEST)	+= test_nx.o
 obj-$(CONFIG_DEBUG_NMI_SELFTEST) += nmi_selftest.o
 
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvmclock.o
diff --git a/arch/x86/kernel/test_nx.c b/arch/x86/kernel/test_nx.c
