Messages in this thread Patch in this message | | | Date | Thu, 19 Jul 2018 16:32:10 -0700 | From | tip-bot for Joerg Roedel <> | Subject | [tip:x86/pti] x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level on x86_32 |
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Commit-ID: f94560cd6b5117f8913f4c42f4d9a405c26ddc1c Gitweb: https://git.kernel.org/tip/f94560cd6b5117f8913f4c42f4d9a405c26ddc1c Author: Joerg Roedel <jroedel@suse.de> AuthorDate: Wed, 18 Jul 2018 11:41:03 +0200 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Fri, 20 Jul 2018 01:11:44 +0200
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
--- arch/x86/mm/pti.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
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 */
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