x86/mm: Expand static page table for fixmap space

BugLink: https://bugs.launchpad.net/bugs/1836287
commit 05ab1d8a4b36ee912b7087c6da127439ed0a903e upstream.

We met a kernel panic when enabling earlycon, which is due to the fixmap
address of earlycon is not statically setup.

Currently the static fixmap setup in head_64.S only covers 2M virtual
address space, while it actually could be in 4M space with different
kernel configurations, e.g. when VSYSCALL emulation is disabled.

So increase the static space to 4M for now by defining FIXMAP_PMD_NUM to 2,
and add a build time check to ensure that the fixmap is covered by the
initial static page tables.

Fixes: 1ad83c858c7d ("x86_64,vsyscall: Make vsyscall emulation configurable")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: kernel test robot <rong.a.chen@intel.com>
Reviewed-by: Juergen Gross <jgross@suse.com> (Xen parts)
Cc: H Peter Anvin <hpa@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180920025828.23699-1-feng.tang@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index e203169931c721b7958c940694458c11a270b982..6390bd8c141b44cd988dd21bc4b5b3efbbf1688b 100644 (file)
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -14,6 +14,16 @@
 #ifndef _ASM_X86_FIXMAP_H
 #define _ASM_X86_FIXMAP_H
 
+/*
+ * Exposed to assembly code for setting up initial page tables. Cannot be
+ * calculated in assembly code (fixmap entries are an enum), but is sanity
+ * checked in the actual fixmap C code to make sure that the fixmap is
+ * covered fully.
+ */
+#define FIXMAP_PMD_NUM 2
+/* fixmap starts downwards from the 507th entry in level2_fixmap_pgt */
+#define FIXMAP_PMD_TOP 507
+
 #ifndef __ASSEMBLY__
 #include <linux/kernel.h>
 #include <asm/acpi.h>

diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index a9d9de0cfdf818a7a2df2bb69c3b02239e0edf17..9da336218990e3aaac83f18e73061a31edfb58ad 100644 (file)
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -14,6 +14,7 @@
 #include <asm/processor.h>
 #include <linux/bitops.h>
 #include <linux/threads.h>
+#include <asm/fixmap.h>
 
 extern p4d_t level4_kernel_pgt[512];
 extern p4d_t level4_ident_pgt[512];
@@ -22,7 +23,7 @@ extern pud_t level3_ident_pgt[512];
 extern pmd_t level2_kernel_pgt[512];
 extern pmd_t level2_fixmap_pgt[512];
 extern pmd_t level2_ident_pgt[512];
-extern pte_t level1_fixmap_pgt[512];
+extern pte_t level1_fixmap_pgt[512 * FIXMAP_PMD_NUM];
 extern pgd_t init_top_pgt[];
 
 #define swapper_pg_dir init_top_pgt

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index db6f84936dfb089c8bbe39aa0c472d39fc985414..a75a2691d9d10beb7f77b21b57cba275f87c95ff 100644 (file)
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -31,6 +31,7 @@
 #include <asm/bootparam_utils.h>
 #include <asm/microcode.h>
 #include <asm/kasan.h>
+#include <asm/fixmap.h>
 
 /*
  * Manage page tables very early on.
@@ -100,7 +101,8 @@ unsigned long __head __startup_64(unsigned long physaddr,
        pud[511] += load_delta;
 
        pmd = fixup_pointer(level2_fixmap_pgt, physaddr);
-       pmd[506] += load_delta;
+       for (i = FIXMAP_PMD_TOP; i > FIXMAP_PMD_TOP - FIXMAP_PMD_NUM; i--)
+               pmd[i] += load_delta;
 
        /*
         * Set up the identity mapping for the switchover.  These

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 8fe2445203db3901a56f66d77ea40e236fe5fb48..cba2dee2d62e201446d1ec2455c39e4e0a5ec87e 100644 (file)
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -24,6 +24,7 @@
 #include "../entry/calling.h"
 #include <asm/export.h>
 #include <asm/nospec-branch.h>
+#include <asm/fixmap.h>
 
 #ifdef CONFIG_PARAVIRT
 #include <asm/asm-offsets.h>
@@ -447,13 +448,20 @@ NEXT_PAGE(level2_kernel_pgt)
                KERNEL_IMAGE_SIZE/PMD_SIZE)
 
 NEXT_PAGE(level2_fixmap_pgt)
-       .fill   506,8,0
-       .quad   level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
-       /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
-       .fill   5,8,0
+       .fill   (512 - 4 - FIXMAP_PMD_NUM),8,0
+       pgtno = 0
+       .rept (FIXMAP_PMD_NUM)
+       .quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \
+               + _PAGE_TABLE_NOENC;
+       pgtno = pgtno + 1
+       .endr
+       /* 6 MB reserved space + a 2MB hole */
+       .fill   4,8,0
 
 NEXT_PAGE(level1_fixmap_pgt)
+       .rept (FIXMAP_PMD_NUM)
        .fill   512,8,0
+       .endr
 
 #undef PMDS
 

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index d4da0f766e919884fe88c48fbfecc966ac407744..f9a064a72fae5d3ececedc1c0e8fbee4a9b67e23 100644 (file)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -636,6 +636,15 @@ void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
 {
        unsigned long address = __fix_to_virt(idx);
 
+#ifdef CONFIG_X86_64
+       /*
+       * Ensure that the static initial page tables are covering the
+       * fixmap completely.
+       */
+       BUILD_BUG_ON(__end_of_permanent_fixed_addresses >
+                    (FIXMAP_PMD_NUM * PTRS_PER_PTE));
+#endif
+
        if (idx >= __end_of_fixed_addresses) {
                BUG();
                return;

diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index a8975b239f6c49bc919ee6fa3faedb58f1d7d173..b9d921d2b153ba98cddd2101252622bfc1df697d 100644 (file)
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1878,7 +1878,7 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
        /* L3_k[511] -> level2_fixmap_pgt */
        convert_pfn_mfn(level3_kernel_pgt);
 
-       /* L3_k[511][506] -> level1_fixmap_pgt */
+       /* L3_k[511][508-FIXMAP_PMD_NUM ... 507] -> level1_fixmap_pgt */
        convert_pfn_mfn(level2_fixmap_pgt);
 
        /* We get [511][511] and have Xen's version of level2_kernel_pgt */
@@ -1923,7 +1923,11 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
        set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
        set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
        set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
-       set_page_prot(level1_fixmap_pgt, PAGE_KERNEL_RO);
+
+       for (i = 0; i < FIXMAP_PMD_NUM; i++) {
+               set_page_prot(level1_fixmap_pgt + i * PTRS_PER_PTE,
+                             PAGE_KERNEL_RO);
+       }
 
        /* Pin down new L4 */
        pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,