[PATCH v15 7/9] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX

[Jordan Niethe <jniethe5@gmail.com>]

From: Russell Currey <ruscur@russell.cc>

To enable strict module RWX on powerpc, set:

    CONFIG_STRICT_MODULE_RWX=y

You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
security benefit.

ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
makes STRICT_MODULE_RWX *on by default* in configurations where
STRICT_KERNEL_RWX is *unavailable*.

Since this doesn't make much sense, and module RWX without kernel RWX
doesn't make much sense, having the same dependencies as kernel RWX
works around this problem.

Book3s/32 603 and 604 core processors are not able to write protect
kernel pages so do not set ARCH_HAS_STRICT_MODULE_RWX for Book3s/32.

Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Russell Currey <ruscur@russell.cc>
[jpn: - predicate on !PPC_BOOK3S_604
      - make module_alloc() use PAGE_KERNEL protection]
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
v10: - Predicate on !PPC_BOOK3S_604
     - Make module_alloc() use PAGE_KERNEL protection
v11: - Neaten up
v13: Use strict_kernel_rwx_enabled()
v14: Make changes to module_alloc() its own commit
v15: - Force STRICT_KERNEL_RWX if STRICT_MODULE_RWX is selected
     - Predicate on !PPC_BOOK3S_32 instead
---
 arch/powerpc/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index abfe2e9225fa..72f307f1796b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -142,6 +142,7 @@ config PPC
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
+	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX && !PPC_BOOK3S_32
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
@@ -267,6 +268,7 @@ config PPC
 	select PPC_DAWR				if PPC64
 	select RTC_LIB
 	select SPARSE_IRQ
+	select STRICT_KERNEL_RWX if STRICT_MODULE_RWX
 	select SYSCTL_EXCEPTION_TRACE
 	select THREAD_INFO_IN_TASK
 	select VIRT_TO_BUS			if !PPC64
-- 
2.25.1