From 06fbe81b5909847aa13f9c86c2b6f9bbc5c2795b Mon Sep 17 00:00:00 2001
From: Christophe Leroy <christophe.leroy@c-s.fr>
Date: Mon, 11 Mar 2019 08:30:33 +0000
Subject: [PATCH] powerpc/8xx: Add Kernel Userspace Execution Prevention
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.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/include/asm/nohash/32/mmu-8xx.h | 7 +++++++
arch/powerpc/mm/8xx_mmu.c | 12 ++++++++++++
arch/powerpc/platforms/Kconfig.cputype | 1 +
3 files changed, 20 insertions(+)
diff --git a/arch/powerpc/include/asm/nohash/32/mmu-8xx.h b/arch/powerpc/include/asm/nohash/32/mmu-8xx.h
index fc5a653d5dd21..3cb743284e09a 100644
--- a/arch/powerpc/include/asm/nohash/32/mmu-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/mmu-8xx.h
@@ -41,6 +41,13 @@
*/
#define MI_APG_INIT 0x4fffffff
+/*
+ * 0 => Kernel => 01 (all accesses performed according to page definition)
+ * 1 => User => 10 (all accesses performed according to swaped page definition)
+ * 2-16 => NA => 11 (all accesses performed as user iaw page definition)
+ */
+#define MI_APG_KUEP 0x6fffffff
+
/* 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 fe1f6443d57f2..e257a0c9bd080 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -213,3 +213,15 @@ void flush_instruction_cache(void)
mtspr(SPRN_IC_CST, IDC_INVALL);
isync();
}
+
+#ifdef CONFIG_PPC_KUEP
+void __init setup_kuep(bool disabled)
+{
+ if (disabled)
+ return;
+
+ pr_info("Activating Kernel Userspace Execution Prevention\n");
+
+ mtspr(SPRN_MI_AP, MI_APG_KUEP);
+}
+#endif
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 2e45a6e2bc99f..00fa0d110dcb2 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -34,6 +34,7 @@ config PPC_8xx
bool "Freescale 8xx"
select FSL_SOC
select SYS_SUPPORTS_HUGETLBFS
+ select PPC_HAVE_KUEP
config 40x
bool "AMCC 40x"
--
GitLab