x86: Remove CONFIG_DEBUG_NX_TEST

CONFIG_DEBUG_NX_TEST has been broken since CONFIG_DEBUG_SET_MODULE_RONX was added in v2.6.37 via commit 84e1c6bb38eb ("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 commit 706276543b69 ("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.

---
 arch/x86/Kconfig.debug    |   8 ---
 arch/x86/kernel/Makefile  |   1 -
 arch/x86/kernel/test_nx.c | 173 ----------------------------------------------
 3 files changed, 182 deletions(-)
 delete mode 100644 arch/x86/kernel/test_nx.c

index 67eec55093a5..783099f2ac72 100644
@@ -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

index 581386c7e429..bdcdb3b3a219 100644
@@ -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

2.7.4


-- 
Kees Cook
Pixel Security