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authorJoerg Roedel <jroedel@suse.de>2018-07-18 11:41:03 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-07-20 01:11:44 +0200
commitf94560cd6b5117f8913f4c42f4d9a405c26ddc1c (patch)
tree3b23e49c0b0d61a40d12c169086e71d44915a611 /arch/x86/mm
parent2c1b9fbe83412598d2dccdd448147336b085e0c6 (diff)
x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level on x86_32
Cloning on the P4D level would clone the complete kernel address space into the user-space page-tables for PAE kernels. Cloning on PMD level is fine for PAE and legacy paging. 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/1531906876-13451-27-git-send-email-joro@8bytes.org
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/pti.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 79217868dd13..a594e3b6401a 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -348,6 +348,7 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear)
}
}
+#ifdef CONFIG_X86_64
/*
* Clone a single p4d (i.e. a top-level entry on 4-level systems and a
* next-level entry on 5-level systems.
@@ -371,6 +372,25 @@ static void __init pti_clone_user_shared(void)
pti_clone_p4d(CPU_ENTRY_AREA_BASE);
}
+#else /* CONFIG_X86_64 */
+
+/*
+ * On 32 bit PAE systems with 1GB of Kernel address space there is only
+ * one pgd/p4d for the whole kernel. Cloning that would map the whole
+ * address space into the user page-tables, making PTI useless. So clone
+ * the page-table on the PMD level to prevent that.
+ */
+static void __init pti_clone_user_shared(void)
+{
+ unsigned long start, end;
+
+ start = CPU_ENTRY_AREA_BASE;
+ end = start + (PAGE_SIZE * CPU_ENTRY_AREA_PAGES);
+
+ pti_clone_pmds(start, end, 0);
+}
+#endif /* CONFIG_X86_64 */
+
/*
* Clone the ESPFIX P4D into the user space visible page table
*/