内核地址管理

1、内核内存布局

2、内核页表建立

kernel/msm-4.19/arch/arm64/mm/mmu.c

/*
 * Create fine-grained mappings for the kernel.
 */
static void __init map_kernel(pgd_t *pgdp)
{
...
    /*
     * Only rodata will be remapped with different permissions later on,
     * all other segments are allowed to use contiguous mappings.
     */
    map_kernel_segment(pgdp, _text, _etext, text_prot, &vmlinux_text, 0,
               VM_NO_GUARD);
    map_kernel_segment(pgdp, __start_rodata, __inittext_begin, PAGE_KERNEL,
               &vmlinux_rodata, NO_CONT_MAPPINGS, VM_NO_GUARD);
    map_kernel_segment(pgdp, __inittext_begin, __inittext_end, text_prot,
               &vmlinux_inittext, 0, VM_NO_GUARD);
    map_kernel_segment(pgdp, __initdata_begin, __initdata_end, PAGE_KERNEL,
               &vmlinux_initdata, 0, VM_NO_GUARD);
    map_kernel_segment(pgdp, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0);
...
}

kernel/msm-4.19/arch/arm64/mm/mmu.c

static void __init map_kernel_segment(pgd_t *pgdp, void *va_start, void *va_end,
                      pgprot_t prot, struct vm_struct *vma,
                      int flags, unsigned long vm_flags)
{
    phys_addr_t pa_start = __pa_symbol(va_start);
    unsigned long size = va_end - va_start;

    BUG_ON(!PAGE_ALIGNED(pa_start));
    BUG_ON(!PAGE_ALIGNED(size));

    __create_pgd_mapping(pgdp, pa_start, (unsigned long)va_start, size, prot,
                 early_pgtable_alloc, flags);

    if (!(vm_flags & VM_NO_GUARD))
        size += PAGE_SIZE;

    vma->addr   = va_start;
    vma->phys_addr  = pa_start;
    vma->size   = size;
    vma->flags  = VM_MAP | vm_flags;
    vma->caller = __builtin_return_address(0);

    vm_area_add_early(vma);
}

kernel/msm-4.19/arch/arm64/mm/mmu.c

static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
                 unsigned long virt, phys_addr_t size,
                 pgprot_t prot,
                 phys_addr_t (*pgtable_alloc)(void),
                 int flags)
{
    unsigned long addr, length, end, next;
    pgd_t *pgdp = pgd_offset_raw(pgdir, virt);

    /*
     * If the virtual and physical address don't have the same offset
     * within a page, we cannot map the region as the caller expects.
     */
    if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
        return;

    phys &= PAGE_MASK;
    addr = virt & PAGE_MASK;
    length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));

    end = addr + length;
    do {
        next = pgd_addr_end(addr, end);
        alloc_init_pud(pgdp, addr, next, phys, prot, pgtable_alloc,
                   flags);
        phys += next - addr;
    } while (pgdp++, addr = next, addr != end);
}

参考博客：https://www.cnblogs.com/LoyenWang/p/11440957.html