x86/mm/pti: Introduce pti_finalize()

Introduce a new function to finalize the kernel mappings for the userspace
page-table after all ro/nx protections have been applied to the kernel
mappings.

Also move the call to pti_clone_kernel_text() to that function so that it
will run on 32 bit kernels too.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-30-git-send-email-joro@8bytes.org

5 files changed, 22 insertions, 9 deletions

diff --git a/arch/x86/include/asm/pti.h b/arch/x86/include/asm/pti.h
index 38a17f1d5c9d..5df09a0b80b8 100644
--- a/arch/x86/include/asm/pti.h
+++ b/arch/x86/include/asm/pti.h
@@ -6,10 +6,9 @@
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 extern void pti_init(void);
 extern void pti_check_boottime_disable(void);
-extern void pti_clone_kernel_text(void);
+extern void pti_finalize(void);
 #else
 static inline void pti_check_boottime_disable(void) { }
-static inline void pti_clone_kernel_text(void) { }
 #endif
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a688617c727e..9b19f9a8948e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1291,12 +1291,6 @@ void mark_rodata_ro(void)
                         (unsigned long) __va(__pa_symbol(_sdata)));
 
         debug_checkwx();
-
-        /*
-         * Do this after all of the manipulation of the
-         * kernel text page tables are complete.
-         */
-        pti_clone_kernel_text();
 }
 
 int kern_addr_valid(unsigned long addr)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index e41ee93c430d..fcfb815d420f 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -462,7 +462,7 @@ static inline bool pti_kernel_image_global_ok(void)
  * For some configurations, map all of kernel text into the user page
  * tables.  This reduces TLB misses, especially on non-PCID systems.
  */
-void pti_clone_kernel_text(void)
+static void pti_clone_kernel_text(void)
 {
         /*
          * rodata is part of the kernel image and is normally
@@ -526,3 +526,15 @@ void __init pti_init(void)
         pti_setup_espfix64();
         pti_setup_vsyscall();
 }
+
+/*
+ * Finalize the kernel mappings in the userspace page-table.
+ */
+void pti_finalize(void)
+{
+        /*
+         * Do this after all of the manipulation of the
+         * kernel text page tables are complete.
+         */
+        pti_clone_kernel_text();
+}
diff --git a/include/linux/pti.h b/include/linux/pti.h
index 0174883a935a..1a941efcaa62 100644
--- a/include/linux/pti.h
+++ b/include/linux/pti.h
@@ -6,6 +6,7 @@
 #include <asm/pti.h>
 #else
 static inline void pti_init(void) { }
+static inline void pti_finalize(void) { }
 #endif
 
 #endif
diff --git a/init/main.c b/init/main.c
index 3b4ada11ed52..fcfef46c935a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1065,6 +1065,13 @@ static int __ref kernel_init(void *unused)
         jump_label_invalidate_initmem();
         free_initmem();
         mark_readonly();
+
+        /*
+         * Kernel mappings are now finalized - update the userspace page-table
+         * to finalize PTI.
+         */
+        pti_finalize();
+
         system_state = SYSTEM_RUNNING;
         numa_default_policy();