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    Subject[PATCH 2/20] x86_64: Kill temp boot pmds


    Early in the boot process we need the ability to set
    up temporary mappings, before our normal mechanisms are
    initialized. Currently this is used to map pages that
    are part of the page tables we are building and pages
    during the dmi scan.

    The core problem is that we are using the user portion of
    the page tables to implement this. Which means that while
    this mechanism is active we cannot catch NULL pointer dereferences
    and we deviate from the normal ways of handling things.

    In this patch I modify early_ioremap to map pages into
    the kernel portion of address space, roughly where
    we will later put modules, and I make the discovery of
    which addresses we can use dynamic which removes all
    kinds of static limits and remove the dependencies
    on implementation details between different parts of the code.

    Now alloc_low_page() and unmap_low_page() use
    early_iomap() and early_iounmap() to allocate/map and
    unmap a page.

    Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
    Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
    ---

    arch/x86_64/kernel/head.S | 3 -
    arch/x86_64/mm/init.c | 100 ++++++++++++++++++++--------------------------
    2 files changed, 45 insertions(+), 58 deletions(-)

    diff -puN arch/x86_64/kernel/head.S~x86_64-Kill-temp_boot_pmds arch/x86_64/kernel/head.S
    --- linux-2.6.21-rc2-reloc/arch/x86_64/kernel/head.S~x86_64-Kill-temp_boot_pmds 2007-03-07 01:21:26.000000000 +0530
    +++ linux-2.6.21-rc2-reloc-root/arch/x86_64/kernel/head.S 2007-03-07 01:21:26.000000000 +0530
    @@ -288,9 +288,6 @@ NEXT_PAGE(level2_ident_pgt)
    .quad i << 21 | 0x083
    i = i + 1
    .endr
    - /* Temporary mappings for the super early allocator in arch/x86_64/mm/init.c */
    - .globl temp_boot_pmds
    -temp_boot_pmds:
    .fill 492,8,0

    NEXT_PAGE(level2_kernel_pgt)
    diff -puN arch/x86_64/mm/init.c~x86_64-Kill-temp_boot_pmds arch/x86_64/mm/init.c
    --- linux-2.6.21-rc2-reloc/arch/x86_64/mm/init.c~x86_64-Kill-temp_boot_pmds 2007-03-07 01:21:26.000000000 +0530
    +++ linux-2.6.21-rc2-reloc-root/arch/x86_64/mm/init.c 2007-03-07 01:21:26.000000000 +0530
    @@ -167,23 +167,9 @@ __set_fixmap (enum fixed_addresses idx,

    unsigned long __initdata table_start, table_end;

    -extern pmd_t temp_boot_pmds[];
    -
    -static struct temp_map {
    - pmd_t *pmd;
    - void *address;
    - int allocated;
    -} temp_mappings[] __initdata = {
    - { &temp_boot_pmds[0], (void *)(40UL * 1024 * 1024) },
    - { &temp_boot_pmds[1], (void *)(42UL * 1024 * 1024) },
    - {}
    -};
    -
    -static __meminit void *alloc_low_page(int *index, unsigned long *phys)
    +static __meminit void *alloc_low_page(unsigned long *phys)
    {
    - struct temp_map *ti;
    - int i;
    - unsigned long pfn = table_end++, paddr;
    + unsigned long pfn = table_end++;
    void *adr;

    if (after_bootmem) {
    @@ -194,57 +180,63 @@ static __meminit void *alloc_low_page(in

    if (pfn >= end_pfn)
    panic("alloc_low_page: ran out of memory");
    - for (i = 0; temp_mappings[i].allocated; i++) {
    - if (!temp_mappings[i].pmd)
    - panic("alloc_low_page: ran out of temp mappings");
    - }
    - ti = &temp_mappings[i];
    - paddr = (pfn << PAGE_SHIFT) & PMD_MASK;
    - set_pmd(ti->pmd, __pmd(paddr | _KERNPG_TABLE | _PAGE_PSE));
    - ti->allocated = 1;
    - __flush_tlb();
    - adr = ti->address + ((pfn << PAGE_SHIFT) & ~PMD_MASK);
    +
    + adr = early_ioremap(pfn * PAGE_SIZE, PAGE_SIZE);
    memset(adr, 0, PAGE_SIZE);
    - *index = i;
    - *phys = pfn * PAGE_SIZE;
    - return adr;
    -}
    + *phys = pfn * PAGE_SIZE;
    + return adr;
    +}

    -static __meminit void unmap_low_page(int i)
    +static __meminit void unmap_low_page(void *adr)
    {
    - struct temp_map *ti;

    if (after_bootmem)
    return;

    - ti = &temp_mappings[i];
    - set_pmd(ti->pmd, __pmd(0));
    - ti->allocated = 0;
    + early_iounmap(adr, PAGE_SIZE);
    }

    /* Must run before zap_low_mappings */
    __init void *early_ioremap(unsigned long addr, unsigned long size)
    {
    - unsigned long map = round_down(addr, LARGE_PAGE_SIZE);
    -
    - /* actually usually some more */
    - if (size >= LARGE_PAGE_SIZE) {
    - return NULL;
    + unsigned long vaddr;
    + pmd_t *pmd, *last_pmd;
    + int i, pmds;
    +
    + pmds = ((addr & ~PMD_MASK) + size + ~PMD_MASK) / PMD_SIZE;
    + vaddr = __START_KERNEL_map;
    + pmd = level2_kernel_pgt;
    + last_pmd = level2_kernel_pgt + PTRS_PER_PMD - 1;
    + for (; pmd <= last_pmd; pmd++, vaddr += PMD_SIZE) {
    + for (i = 0; i < pmds; i++) {
    + if (pmd_present(pmd[i]))
    + goto next;
    + }
    + vaddr += addr & ~PMD_MASK;
    + addr &= PMD_MASK;
    + for (i = 0; i < pmds; i++, addr += PMD_SIZE)
    + set_pmd(pmd + i,__pmd(addr | _KERNPG_TABLE | _PAGE_PSE));
    + __flush_tlb();
    + return (void *)vaddr;
    + next:
    + ;
    }
    - set_pmd(temp_mappings[0].pmd, __pmd(map | _KERNPG_TABLE | _PAGE_PSE));
    - map += LARGE_PAGE_SIZE;
    - set_pmd(temp_mappings[1].pmd, __pmd(map | _KERNPG_TABLE | _PAGE_PSE));
    - __flush_tlb();
    - return temp_mappings[0].address + (addr & (LARGE_PAGE_SIZE-1));
    + printk("early_ioremap(0x%lx, %lu) failed\n", addr, size);
    + return NULL;
    }

    /* To avoid virtual aliases later */
    __init void early_iounmap(void *addr, unsigned long size)
    {
    - if ((void *)round_down((unsigned long)addr, LARGE_PAGE_SIZE) != temp_mappings[0].address)
    - printk("early_iounmap: bad address %p\n", addr);
    - set_pmd(temp_mappings[0].pmd, __pmd(0));
    - set_pmd(temp_mappings[1].pmd, __pmd(0));
    + unsigned long vaddr;
    + pmd_t *pmd;
    + int i, pmds;
    +
    + vaddr = (unsigned long)addr;
    + pmds = ((vaddr & ~PMD_MASK) + size + ~PMD_MASK) / PMD_SIZE;
    + pmd = level2_kernel_pgt + pmd_index(vaddr);
    + for (i = 0; i < pmds; i++)
    + pmd_clear(pmd + i);
    __flush_tlb();
    }

    @@ -289,7 +281,6 @@ static void __meminit phys_pud_init(pud_


    for (; i < PTRS_PER_PUD; i++, addr = (addr & PUD_MASK) + PUD_SIZE ) {
    - int map;
    unsigned long pmd_phys;
    pud_t *pud = pud_page + pud_index(addr);
    pmd_t *pmd;
    @@ -307,12 +298,12 @@ static void __meminit phys_pud_init(pud_
    continue;
    }

    - pmd = alloc_low_page(&map, &pmd_phys);
    + pmd = alloc_low_page(&pmd_phys);
    spin_lock(&init_mm.page_table_lock);
    set_pud(pud, __pud(pmd_phys | _KERNPG_TABLE));
    phys_pmd_init(pmd, addr, end);
    spin_unlock(&init_mm.page_table_lock);
    - unmap_low_page(map);
    + unmap_low_page(pmd);
    }
    __flush_tlb();
    }
    @@ -364,7 +355,6 @@ void __meminit init_memory_mapping(unsig
    end = (unsigned long)__va(end);

    for (; start < end; start = next) {
    - int map;
    unsigned long pud_phys;
    pgd_t *pgd = pgd_offset_k(start);
    pud_t *pud;
    @@ -372,7 +362,7 @@ void __meminit init_memory_mapping(unsig
    if (after_bootmem)
    pud = pud_offset(pgd, start & PGDIR_MASK);
    else
    - pud = alloc_low_page(&map, &pud_phys);
    + pud = alloc_low_page(&pud_phys);

    next = start + PGDIR_SIZE;
    if (next > end)
    @@ -380,7 +370,7 @@ void __meminit init_memory_mapping(unsig
    phys_pud_init(pud, __pa(start), __pa(next));
    if (!after_bootmem)
    set_pgd(pgd_offset_k(start), mk_kernel_pgd(pud_phys));
    - unmap_low_page(map);
    + unmap_low_page(pud);
    }

    if (!after_bootmem)
    _
    -
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