powerpc: Add skeleton for Kernel Userspace Execution Prevention

This patch adds a skeleton for Kernel Userspace Execution Prevention.

Then subarches implementing it have to define CONFIG_PPC_HAVE_KUEP
and provide setup_kuep() function.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Don't split strings, use pr_crit_ratelimited()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
index 36d28e872289..83f95a5565d6 100644
--- a/arch/powerpc/mm/init-common.c
+++ b/arch/powerpc/mm/init-common.c
@@ -26,8 +26,19 @@
 #include <asm/pgtable.h>
 #include <asm/kup.h>
 
+static bool disable_kuep = !IS_ENABLED(CONFIG_PPC_KUEP);
+
+static int __init parse_nosmep(char *p)
+{
+        disable_kuep = true;
+        pr_warn("Disabling Kernel Userspace Execution Prevention\n");
+        return 0;
+}
+early_param("nosmep", parse_nosmep);
+
 void __init setup_kup(void)
 {
+        setup_kuep(disable_kuep);
 }
 
 #define CTOR(shift) static void ctor_##shift(void *addr) \