x86/mm: Expand static page table for fixmap space

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>

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 4ecb728319384759eeb9c96eb94bbec7faf79aba..ef938583147ea4d7775c23427f8b13e77ae1a21a 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 7ba5d819ebe3b351ff4124ded8c598adfcb1a5f1..45b5c6c4a55edac132a855e47502eacb62225045 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.
@@ -93,7 +94,8 @@ 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 0f545b3cf926787bd986d763c843498540ef530d..8d59dfe629a96e8a53183cfb9cb4d867e039c520 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>
@@ -438,13 +439,20 @@ 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 2bdb8e8a9d7c85509d3ed2a70630e7a7c353c0eb..aafd4edfa2ac6416b4332fa171658dcf4428d85b 100644 (file)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -573,6 +573,15 @@ 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 42cfad67b6acd13786f37ea63059868b02e52c49..8ed11a5b1a9d8b2618ec43daeb264e1245205dce 100644 (file)
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1879,7 +1879,7 @@ 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 */
@@ -1924,7 +1924,11 @@ 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,