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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2018-10-26 15:28:54 +0300
committerThomas Gleixner <tglx@linutronix.de>2018-11-06 23:35:11 +0300
commitd52888aa2753e3063a9d3a0c9f72f94aa9809c15 (patch)
treefbbb33771ac6c392caeb283163a594f1a7e6d04d /arch/x86
parente8a308e5f47e545e0d41d0686c00f5f5217c5f61 (diff)
downloadlinux-d52888aa2753e3063a9d3a0c9f72f94aa9809c15.tar.xz
x86/mm: Move LDT remap out of KASLR region on 5-level paging
On 5-level paging the LDT remap area is placed in the middle of the KASLR randomization region and it can overlap with the direct mapping, the vmalloc or the vmap area. The LDT mapping is per mm, so it cannot be moved into the P4D page table next to the CPU_ENTRY_AREA without complicating PGD table allocation for 5-level paging. The 4 PGD slot gap just before the direct mapping is reserved for hypervisors, so it cannot be used. Move the direct mapping one slot deeper and use the resulting gap for the LDT remap area. The resulting layout is the same for 4 and 5 level paging. [ tglx: Massaged changelog ] Fixes: f55f0501cbf6 ("x86/pti: Put the LDT in its own PGD if PTI is on") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Andy Lutomirski <luto@kernel.org> Cc: bp@alien8.de Cc: hpa@zytor.com Cc: dave.hansen@linux.intel.com Cc: peterz@infradead.org Cc: boris.ostrovsky@oracle.com Cc: jgross@suse.com Cc: bhe@redhat.com Cc: willy@infradead.org Cc: linux-mm@kvack.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181026122856.66224-2-kirill.shutemov@linux.intel.com
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/page_64_types.h12
-rw-r--r--arch/x86/include/asm/pgtable_64_types.h4
-rw-r--r--arch/x86/xen/mmu_pv.c6
3 files changed, 11 insertions, 11 deletions
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index cd0cf1c568b4..8f657286d599 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -33,12 +33,14 @@
/*
* Set __PAGE_OFFSET to the most negative possible address +
- * PGDIR_SIZE*16 (pgd slot 272). The gap is to allow a space for a
- * hypervisor to fit. Choosing 16 slots here is arbitrary, but it's
- * what Xen requires.
+ * PGDIR_SIZE*17 (pgd slot 273).
+ *
+ * The gap is to allow a space for LDT remap for PTI (1 pgd slot) and space for
+ * a hypervisor (16 slots). Choosing 16 slots for a hypervisor is arbitrary,
+ * but it's what Xen requires.
*/
-#define __PAGE_OFFSET_BASE_L5 _AC(0xff10000000000000, UL)
-#define __PAGE_OFFSET_BASE_L4 _AC(0xffff880000000000, UL)
+#define __PAGE_OFFSET_BASE_L5 _AC(0xff11000000000000, UL)
+#define __PAGE_OFFSET_BASE_L4 _AC(0xffff888000000000, UL)
#ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
#define __PAGE_OFFSET page_offset_base
diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index 04edd2d58211..84bd9bdc1987 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -111,9 +111,7 @@ extern unsigned int ptrs_per_p4d;
*/
#define MAXMEM (1UL << MAX_PHYSMEM_BITS)
-#define LDT_PGD_ENTRY_L4 -3UL
-#define LDT_PGD_ENTRY_L5 -112UL
-#define LDT_PGD_ENTRY (pgtable_l5_enabled() ? LDT_PGD_ENTRY_L5 : LDT_PGD_ENTRY_L4)
+#define LDT_PGD_ENTRY -240UL
#define LDT_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT)
#define LDT_END_ADDR (LDT_BASE_ADDR + PGDIR_SIZE)
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 0d7b3ae4960b..a5d7ed125337 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1905,7 +1905,7 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
init_top_pgt[0] = __pgd(0);
/* Pre-constructed entries are in pfn, so convert to mfn */
- /* L4[272] -> level3_ident_pgt */
+ /* L4[273] -> level3_ident_pgt */
/* L4[511] -> level3_kernel_pgt */
convert_pfn_mfn(init_top_pgt);
@@ -1925,8 +1925,8 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
addr[0] = (unsigned long)pgd;
addr[1] = (unsigned long)l3;
addr[2] = (unsigned long)l2;
- /* Graft it onto L4[272][0]. Note that we creating an aliasing problem:
- * Both L4[272][0] and L4[511][510] have entries that point to the same
+ /* Graft it onto L4[273][0]. Note that we creating an aliasing problem:
+ * Both L4[273][0] and L4[511][510] have entries that point to the same
* L2 (PMD) tables. Meaning that if you modify it in __va space
* it will be also modified in the __ka space! (But if you just
* modify the PMD table to point to other PTE's or none, then you