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authorChristophe Leroy <christophe.leroy@csgroup.eu>2021-06-04 04:49:25 +0000
committerMichael Ellerman <mpe@ellerman.id.au>2021-06-17 00:09:07 +1000
commitf6025a140ba8dcabdfb8a1e27ddaf44821700dce (patch)
tree11f90bdc86e96de4b1b14b687535a76f45eb71ef /arch/powerpc
parent10248dcba1205042a3a0ea65eb441030702d97cd (diff)
powerpc/8xx: Allow disabling KUAP at boot time
PPC64 uses MMU features to enable/disable KUAP at boot time. But feature fixups are applied way too early on PPC32. But since commit c16728835eec ("powerpc/32: Manage KUAP in C"), all KUAP is in C so it is now possible to use static branches. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/3dca510ce555335261a47c4799167da698f569c0.1622782111.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/include/asm/nohash/32/kup-8xx.h43
-rw-r--r--arch/powerpc/mm/nohash/8xx.c11
2 files changed, 48 insertions, 6 deletions
diff --git a/arch/powerpc/include/asm/nohash/32/kup-8xx.h b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
index 295ef5639609..f6a3c1935e75 100644
--- a/arch/powerpc/include/asm/nohash/32/kup-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
@@ -9,10 +9,22 @@
#ifndef __ASSEMBLY__
+#include <linux/jump_label.h>
+
#include <asm/reg.h>
+extern struct static_key_false disable_kuap_key;
+
+static __always_inline bool kuap_is_disabled(void)
+{
+ return static_branch_unlikely(&disable_kuap_key);
+}
+
static inline void kuap_save_and_lock(struct pt_regs *regs)
{
+ if (kuap_is_disabled())
+ return;
+
regs->kuap = mfspr(SPRN_MD_AP);
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}
@@ -23,12 +35,20 @@ static inline void kuap_user_restore(struct pt_regs *regs)
static inline void kuap_kernel_restore(struct pt_regs *regs, unsigned long kuap)
{
+ if (kuap_is_disabled())
+ return;
+
mtspr(SPRN_MD_AP, regs->kuap);
}
static inline unsigned long kuap_get_and_assert_locked(void)
{
- unsigned long kuap = mfspr(SPRN_MD_AP);
+ unsigned long kuap;
+
+ if (kuap_is_disabled())
+ return MD_APG_INIT;
+
+ kuap = mfspr(SPRN_MD_AP);
if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
WARN_ON_ONCE(kuap >> 16 != MD_APG_KUAP >> 16);
@@ -38,25 +58,36 @@ static inline unsigned long kuap_get_and_assert_locked(void)
static inline void kuap_assert_locked(void)
{
- if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
+ if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && !kuap_is_disabled())
kuap_get_and_assert_locked();
}
static inline void allow_user_access(void __user *to, const void __user *from,
unsigned long size, unsigned long dir)
{
+ if (kuap_is_disabled())
+ return;
+
mtspr(SPRN_MD_AP, MD_APG_INIT);
}
static inline void prevent_user_access(void __user *to, const void __user *from,
unsigned long size, unsigned long dir)
{
+ if (kuap_is_disabled())
+ return;
+
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}
static inline unsigned long prevent_user_access_return(void)
{
- unsigned long flags = mfspr(SPRN_MD_AP);
+ unsigned long flags;
+
+ if (kuap_is_disabled())
+ return MD_APG_INIT;
+
+ flags = mfspr(SPRN_MD_AP);
mtspr(SPRN_MD_AP, MD_APG_KUAP);
@@ -65,12 +96,18 @@ static inline unsigned long prevent_user_access_return(void)
static inline void restore_user_access(unsigned long flags)
{
+ if (kuap_is_disabled())
+ return;
+
mtspr(SPRN_MD_AP, flags);
}
static inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
+ if (kuap_is_disabled())
+ return false;
+
return !((regs->kuap ^ MD_APG_KUAP) & 0xff000000);
}
diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index 71bfdbedacee..fc663322ba58 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c
@@ -256,12 +256,17 @@ void __init setup_kuep(bool disabled)
#endif
#ifdef CONFIG_PPC_KUAP
+struct static_key_false disable_kuap_key;
+EXPORT_SYMBOL(disable_kuap_key);
+
void __init setup_kuap(bool disabled)
{
- pr_info("Activating Kernel Userspace Access Protection\n");
+ if (disabled) {
+ static_branch_enable(&disable_kuap_key);
+ return;
+ }
- if (disabled)
- pr_warn("KUAP cannot be disabled yet on 8xx when compiled in\n");
+ pr_info("Activating Kernel Userspace Access Protection\n");
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}