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    Subject[tip:x86/mm] x86/mm: Initialize 'page_offset_base' at boot-time
    Commit-ID:  4fa5662b6b49611f11856db8be346710217473ef
    Gitweb: https://git.kernel.org/tip/4fa5662b6b49611f11856db8be346710217473ef
    Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    AuthorDate: Wed, 14 Feb 2018 21:25:36 +0300
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Fri, 16 Feb 2018 10:48:47 +0100

    x86/mm: Initialize 'page_offset_base' at boot-time

    For 4- and 5-level paging we have different 'page_offset_base'.
    Let's initialize it at boot-time accordingly to machine capability.

    We also have to split __PAGE_OFFSET_BASE into two constants -- for 4-
    and 5-level paging.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David Woodhouse <dwmw2@infradead.org>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-mm@kvack.org
    Link: http://lkml.kernel.org/r/20180214182542.69302-4-kirill.shutemov@linux.intel.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/include/asm/page_64_types.h | 9 +++------
    arch/x86/kernel/head64.c | 13 +++++++++----
    arch/x86/kernel/head_64.S | 2 +-
    arch/x86/mm/kaslr.c | 8 ++++----
    4 files changed, 17 insertions(+), 15 deletions(-)

    diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
    index fa7dc7c..2c5a966 100644
    --- a/arch/x86/include/asm/page_64_types.h
    +++ b/arch/x86/include/asm/page_64_types.h
    @@ -37,16 +37,13 @@
    * hypervisor to fit. Choosing 16 slots here is arbitrary, but it's
    * what Xen requires.
    */
    -#ifdef CONFIG_X86_5LEVEL
    -#define __PAGE_OFFSET_BASE _AC(0xff10000000000000, UL)
    -#else
    -#define __PAGE_OFFSET_BASE _AC(0xffff880000000000, UL)
    -#endif
    +#define __PAGE_OFFSET_BASE_L5 _AC(0xff10000000000000, UL)
    +#define __PAGE_OFFSET_BASE_L4 _AC(0xffff880000000000, UL)

    #ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
    #define __PAGE_OFFSET page_offset_base
    #else
    -#define __PAGE_OFFSET __PAGE_OFFSET_BASE
    +#define __PAGE_OFFSET __PAGE_OFFSET_BASE_L4
    #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */

    #define __START_KERNEL_map _AC(0xffffffff80000000, UL)
    diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
    index 8a0a485..876d3bf 100644
    --- a/arch/x86/kernel/head64.c
    +++ b/arch/x86/kernel/head64.c
    @@ -49,7 +49,7 @@ EXPORT_SYMBOL(ptrs_per_p4d);
    #endif

    #ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
    -unsigned long page_offset_base __ro_after_init = __PAGE_OFFSET_BASE;
    +unsigned long page_offset_base __ro_after_init = __PAGE_OFFSET_BASE_L4;
    EXPORT_SYMBOL(page_offset_base);
    unsigned long vmalloc_base __ro_after_init = __VMALLOC_BASE;
    EXPORT_SYMBOL(vmalloc_base);
    @@ -64,6 +64,11 @@ static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
    return ptr - (void *)_text + (void *)physaddr;
    }

    +static unsigned long __head *fixup_long(void *ptr, unsigned long physaddr)
    +{
    + return fixup_pointer(ptr, physaddr);
    +}
    +
    #ifdef CONFIG_X86_5LEVEL
    static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr)
    {
    @@ -81,6 +86,7 @@ static void __head check_la57_support(unsigned long physaddr)
    *fixup_int(&pgtable_l5_enabled, physaddr) = 1;
    *fixup_int(&pgdir_shift, physaddr) = 48;
    *fixup_int(&ptrs_per_p4d, physaddr) = 512;
    + *fixup_long(&page_offset_base, physaddr) = __PAGE_OFFSET_BASE_L5;
    }
    #else
    static void __head check_la57_support(unsigned long physaddr) {}
    @@ -89,7 +95,7 @@ static void __head check_la57_support(unsigned long physaddr) {}
    unsigned long __head __startup_64(unsigned long physaddr,
    struct boot_params *bp)
    {
    - unsigned long load_delta, *p;
    + unsigned long load_delta;
    unsigned long pgtable_flags;
    pgdval_t *pgd;
    p4dval_t *p4d;
    @@ -196,8 +202,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
    * Fixup phys_base - remove the memory encryption mask to obtain
    * the true physical address.
    */
    - p = fixup_pointer(&phys_base, physaddr);
    - *p += load_delta - sme_get_me_mask();
    + *fixup_long(&phys_base, physaddr) += load_delta - sme_get_me_mask();

    /* Encrypt the kernel and related (if SME is active) */
    sme_encrypt_kernel(bp);
    diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
    index 04a625f..d3f8b43 100644
    --- a/arch/x86/kernel/head_64.S
    +++ b/arch/x86/kernel/head_64.S
    @@ -41,7 +41,7 @@
    #define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))

    #if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
    -PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE)
    +PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE_L4)
    PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
    #endif
    L3_START_KERNEL = pud_index(__START_KERNEL_map)
    diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
    index d079878..7828a7c 100644
    --- a/arch/x86/mm/kaslr.c
    +++ b/arch/x86/mm/kaslr.c
    @@ -34,13 +34,10 @@
    #define TB_SHIFT 40

    /*
    - * Virtual address start and end range for randomization.
    - *
    * The end address could depend on more configuration options to make the
    * highest amount of space for randomization available, but that's too hard
    * to keep straight and caused issues already.
    */
    -static const unsigned long vaddr_start = __PAGE_OFFSET_BASE;
    static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE;

    /*
    @@ -76,11 +73,14 @@ static inline bool kaslr_memory_enabled(void)
    void __init kernel_randomize_memory(void)
    {
    size_t i;
    - unsigned long vaddr = vaddr_start;
    + unsigned long vaddr_start, vaddr;
    unsigned long rand, memory_tb;
    struct rnd_state rand_state;
    unsigned long remain_entropy;

    + vaddr_start = pgtable_l5_enabled ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4;
    + vaddr = vaddr_start;
    +
    /*
    * These BUILD_BUG_ON checks ensure the memory layout is consistent
    * with the vaddr_start/vaddr_end variables. These checks are very
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