x86/ldt: Reserve address-space range on 32 bit for the LDT

Reserve 2MB/4MB of address-space for mapping the LDT to user-space on 32
bit PTI kernels.

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/1531906876-13451-34-git-send-email-joro@8bytes.org

2 files changed, 14 insertions, 2 deletions

diff --git a/arch/x86/include/asm/pgtable_32_types.h b/arch/x86/include/asm/pgtable_32_types.h
index d9a001a4a872..7297810747cf 100644
--- a/arch/x86/include/asm/pgtable_32_types.h
+++ b/arch/x86/include/asm/pgtable_32_types.h
@@ -50,13 +50,16 @@ extern bool __vmalloc_start_set; /* set once high_memory is set */
         ((FIXADDR_TOT_START - PAGE_SIZE * (CPU_ENTRY_AREA_PAGES + 1))   \
          & PMD_MASK)
 
-#define PKMAP_BASE              \
+#define LDT_BASE_ADDR           \
         ((CPU_ENTRY_AREA_BASE - PAGE_SIZE) & PMD_MASK)
 
+#define PKMAP_BASE              \
+        ((LDT_BASE_ADDR - PAGE_SIZE) & PMD_MASK)
+
 #ifdef CONFIG_HIGHMEM
 # define VMALLOC_END    (PKMAP_BASE - 2 * PAGE_SIZE)
 #else
-# define VMALLOC_END    (CPU_ENTRY_AREA_BASE - 2 * PAGE_SIZE)
+# define VMALLOC_END    (LDT_BASE_ADDR - 2 * PAGE_SIZE)
 #endif
 
 #define MODULES_VADDR   VMALLOC_START
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index e6fd0cdef9ad..ccd92c4da57c 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -123,6 +123,9 @@ enum address_markers_idx {
 #ifdef CONFIG_HIGHMEM
         PKMAP_BASE_NR,
 #endif
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+        LDT_NR,
+#endif
         CPU_ENTRY_AREA_NR,
         FIXADDR_START_NR,
         END_OF_SPACE_NR,
@@ -136,6 +139,9 @@ static struct addr_marker address_markers[] = {
 #ifdef CONFIG_HIGHMEM
         [PKMAP_BASE_NR]         = { 0UL,                "Persistent kmap() Area" },
 #endif
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+        [LDT_NR]                = { 0UL,                "LDT remap" },
+#endif
         [CPU_ENTRY_AREA_NR]     = { 0UL,                "CPU entry area" },
         [FIXADDR_START_NR]      = { 0UL,                "Fixmap area" },
         [END_OF_SPACE_NR]       = { -1,                 NULL }
@@ -609,6 +615,9 @@ static int __init pt_dump_init(void)
 # endif
         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
         address_markers[CPU_ENTRY_AREA_NR].start_address = CPU_ENTRY_AREA_BASE;
+# ifdef CONFIG_MODIFY_LDT_SYSCALL
+        address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
+# endif
 #endif
         return 0;
 }