powerpc: Add a framework for Kernel Userspace Access Protection

This patch implements a framework for Kernel Userspace Access
Protection.

Then subarches will have the possibility to provide their own
implementation by providing setup_kuap() and
allow/prevent_user_access().

Some platforms will need to know the area accessed and whether it is
accessed from read, write or both. Therefore source, destination and
size and handed over to the two functions.

mpe: Rename to allow/prevent rather than unlock/lock, and add
read/write wrappers. Drop the 32-bit code for now until we have an
implementation for it. Add kuap to pt_regs for 64-bit as well as
32-bit. Don't split strings, use pr_crit_ratelimited().

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
index 83f95a5565d6..ecaedfff9992 100644
--- a/arch/powerpc/mm/init-common.c
+++ b/arch/powerpc/mm/init-common.c
@@ -27,6 +27,7 @@
 #include <asm/kup.h>
 
 static bool disable_kuep = !IS_ENABLED(CONFIG_PPC_KUEP);
+static bool disable_kuap = !IS_ENABLED(CONFIG_PPC_KUAP);
 
 static int __init parse_nosmep(char *p)
 {
@@ -36,9 +37,18 @@ static int __init parse_nosmep(char *p)
 }
 early_param("nosmep", parse_nosmep);
 
+static int __init parse_nosmap(char *p)
+{
+	disable_kuap = true;
+	pr_warn("Disabling Kernel Userspace Access Protection\n");
+	return 0;
+}
+early_param("nosmap", parse_nosmap);
+
 void __init setup_kup(void)
 {
 	setup_kuep(disable_kuep);
+	setup_kuap(disable_kuap);
 }
 
 #define CTOR(shift) static void ctor_##shift(void *addr) \