This patch adds Kernel Userspace Execution Prevention on the 8xx.
When a page is Executable, it is set Executable for Key 0 and NX
for Key 1.
Up to now, the User group is defined with Key 0 for both User and
Supervisor.
By changing the group to Key 0 for User and Key 1 for Supervisor,
this patch prevents the Kernel from being able to execute user code.
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
arch/powerpc/include/asm/mmu-8xx.h | 6 ++++++
arch/powerpc/mm/8xx_mmu.c | 10 ++++++++++
arch/powerpc/platforms/Kconfig.cputype | 1 +
3 files changed, 17 insertions(+)
diff --git a/arch/powerpc/include/asm/mmu-8xx.h
b/arch/powerpc/include/asm/mmu-8xx.h
index fa05aa566ece..53dbf0788fce 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -41,6 +41,12 @@
*/
#define MI_APG_INIT 0x44444444
+/*
+ * 0 => No user => 01 (all accesses performed according to page definition)
+ * 1 => User => 10 (all accesses performed according to swaped page definition)
+ */
+#define MI_APG_KUEP 0x66666666
+
/* The effective page number register. When read, contains the information
* about the last instruction TLB miss. When MI_RPN is written, bits in
* this register are used to create the TLB entry.
diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
index 01b7f5107c3a..597d3bd2d9b5 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -194,3 +194,13 @@ void flush_instruction_cache(void)
mtspr(SPRN_IC_CST, IDC_INVALL);
isync();
}
+
+void setup_kuep(bool disabled)
+{
+ if (disabled)
+ return;
+
+ pr_warn("Activating Kernel Userspace Execution Prevention\n");
+
+ mtspr(SPRN_MI_AP, MI_APG_KUEP);
+}
diff --git a/arch/powerpc/platforms/Kconfig.cputype
b/arch/powerpc/platforms/Kconfig.cputype
index 70830cb3c18a..bbcae320324c 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -33,6 +33,7 @@ config PPC_8xx
bool "Freescale 8xx"
select FSL_SOC
select SYS_SUPPORTS_HUGETLBFS
+ select PPC_HAVE_KUEP
config 40x
bool "AMCC 40x"
--
2.13.3
