From: Andy Lutomirski <l...@kernel.org>
Map the ESPFIX pages into user space when PTI is enabled. Move
init_espfix_bsp() before pti_init() so it can be correcly populated.
Signed-off-by: Andy Lutomirski <l...@kernel.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Brian Gerst <brge...@gmail.com>
Cc: David Laight <david.lai...@aculab.com>
Cc: Borislav Petkov <b...@alien8.de>
---
arch/x86/mm/pti.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -232,6 +232,24 @@ pti_clone_pmds(unsigned long start, unsi
}
}
+static void __init pti_setup_espfix64(void)
+{
+#ifdef CONFIG_X86_ESPFIX64
+ /*
+ * ESPFIX64 uses a single p4d (i.e. a top-level entry on 4-level
+ * systems and a next-level entry on 5-level systems. Share that
+ * entry between the user and kernel pagetables.
+ */
+ pgd_t *kernel_pgd;
+ p4d_t *kernel_p4d, *user_p4d;
+
+ user_p4d = pti_user_pagetable_walk_p4d(ESPFIX_BASE_ADDR);
+ kernel_pgd = pgd_offset_k(ESPFIX_BASE_ADDR);
+ kernel_p4d = p4d_offset(kernel_pgd, ESPFIX_BASE_ADDR);
+ *user_p4d = *kernel_p4d;
+#endif
+}
+
/*
* Clone the populated PMDs of the user shared fixmaps into the user space
* visible page table.
@@ -270,4 +288,5 @@ void __init pti_init(void)
pti_clone_user_shared();
pti_clone_entry_text();
+ pti_setup_espfix64();
}
