static inline pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr)
{
pgd_t * pgd;
pmd_t * pmd;
pte_t * pte = NULL;
pgd = pgd_offset(mm, addr);
if (pgd_none(*pgd))
goto end;
if (pgd_bad(*pgd)) {
pgd_ERROR(*pgd);
pgd_clear(pgd);
goto end;
}
pmd = pmd_offset(pgd, addr);
if (pmd_none(*pmd))
goto end;
if (pmd_bad(*pmd)) {
pmd_ERROR(*pmd);
pmd_clear(pmd);
goto end;
}
pte = pte_offset_map_nested(pmd, addr);
if (pte_none(*pte)) {
pte_unmap_nested(pte);
pte = NULL;
}
end:
return pte;
}
/*
* need to get a 16k page for level 1
*/
pgd_t *get_pgd_slow(struct mm_struct *mm)
{
pgd_t *new_pgd, *init_pgd;
pmd_t *new_pmd, *init_pmd;
pte_t *new_pte, *init_pte;
unsigned long flags;
new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
if (!new_pgd)
goto no_pgd;
memset(new_pgd, 0, FIRST_KERNEL_PGD_NR * sizeof(pgd_t));
/*
* Copy over the kernel and IO PGD entries
*/
init_pgd = pgd_offset_k(0);
pgd_list_lock(flags);
memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
(PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
pgd_list_add(new_pgd);
pgd_list_unlock(flags);
clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));
if (!vectors_high()) {
#ifdef CONFIG_ARM_FCSE
/* FCSE does not work without high vectors. */
BUG();
#endif /* CONFIG_ARM_FCSE */
/*
* On ARM, first page must always be allocated since it
* contains the machine vectors.
*/
new_pmd = pmd_alloc(mm, new_pgd, 0);
if (!new_pmd)
goto no_pmd;
new_pte = pte_alloc_map(mm, new_pmd, 0);
if (!new_pte)
goto no_pte;
init_pmd = pmd_offset(init_pgd, 0);
init_pte = pte_offset_map_nested(init_pmd, 0);
set_pte_ext(new_pte, *init_pte, 0);
pte_unmap_nested(init_pte);
pte_unmap(new_pte);
}
return new_pgd;
no_pte:
pmd_free(mm, new_pmd);
no_pmd:
free_pages((unsigned long)new_pgd, 2);
no_pgd:
return NULL;
}
/*
* get_pgd_slow:申请一个pgd项
* notice:一个pgd占用4个页框,每一个pgt项大小为8字节
*/
pgd_t *get_pgd_slow(struct mm_struct *mm)
{
pgd_t *new_pgd, *init_pgd;
pmd_t *new_pmd, *init_pmd;
pte_t *new_pte, *init_pte;
/*pgd占用四个页框*/
new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
if (!new_pgd)
goto no_pgd;
memset(new_pgd, 0, FIRST_KERNEL_PGD_NR * sizeof(pgd_t));
/*
* 复制内核与I/O PGD entries
*/
init_pgd = pgd_offset_k(0);
memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
(PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));
if (!vectors_high()) {
/*
* On ARM, first page must always be allocated since it
* contains the machine vectors.
*/
new_pmd = pmd_alloc(mm, new_pgd, 0);
if (!new_pmd)
goto no_pmd;
/*返回pmd的第0项页表项,因为第0项用于映射中断向量*/
new_pte = pte_alloc_map(mm, new_pmd, 0);
if (!new_pte)
goto no_pte;
/*返回中断向量的页表项,中断向量位于低地址空间时(0地址开始处)*/
init_pmd = pmd_offset(init_pgd, 0);
init_pte = pte_offset_map_nested(init_pmd, 0);
/*给新的页表项映射中断向量的页表项*/
set_pte_ext(new_pte, *init_pte, 0);
pte_unmap_nested(init_pte);
/*取消new_pte的高端内存的页表映射*/
pte_unmap(new_pte);
}
return new_pgd;
no_pte:
pmd_free(mm, new_pmd);
no_pmd:
free_pages((unsigned long)new_pgd, 2);
no_pgd:
return NULL;
}
/*
* need to get a 16k page for level 1
*/
pgd_t *get_pgd_slow(struct mm_struct *mm)
{
pgd_t *new_pgd, *init_pgd;
pmd_t *new_pmd, *init_pmd;
pte_t *new_pte, *init_pte;
new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
if (!new_pgd)
goto no_pgd;
memzero(new_pgd, FIRST_KERNEL_PGD_NR * sizeof(pgd_t));
/*
* Copy over the kernel and IO PGD entries
*/
init_pgd = pgd_offset_k(0);
memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
(PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));
if (!vectors_high()) {
/*
* On ARM, first page must always be allocated since it
* contains the machine vectors.
*/
new_pmd = pmd_alloc(mm, new_pgd, 0);
if (!new_pmd)
goto no_pmd;
new_pte = pte_alloc_map(mm, new_pmd, 0);
if (!new_pte)
goto no_pte;
init_pmd = pmd_offset(init_pgd, 0);
init_pte = pte_offset_map_nested(init_pmd, 0);
set_pte_ext(new_pte, *init_pte, 0);
pte_unmap_nested(init_pte);
pte_unmap(new_pte);
}
return new_pgd;
no_pte:
pmd_free(mm, new_pmd);
no_pmd:
free_pages((unsigned long)new_pgd, 2);
no_pgd:
return NULL;
}
/*
* need to get a 16k page for level 1
*/
pgd_t *get_pgd_slow(struct mm_struct *mm)
{
pgd_t *new_pgd, *init_pgd;
pmd_t *new_pmd, *init_pmd;
pte_t *new_pte, *init_pte;
new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
if (!new_pgd)
goto no_pgd;
memset(new_pgd, 0, FIRST_KERNEL_PGD_NR * sizeof(pgd_t));
/*
* Copy over the kernel and IO PGD entries
*/
//#define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
//其实就是要拷贝内核空间的页表项...
init_pgd = pgd_offset_k(0);
//拷贝内核空间的pgd表项到新创建的pgd表项
memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
(PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
//把Dcache行的数据写回到主存，并清除cache行的脏标记.
//参数:主存的物理地址,(确定cache行) 需要写回的长度...
clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));
//异常向量表是在高端地址或是在低端地址...
if (!vectors_high()) {
//如果是在低端地址.那么异常向量表在第一页..
/*
* On ARM, first page must always be allocated since it
* contains the machine vectors.
*/
//该函数是在new_pgd指定的PGD页表上找到地址0对应的表项，然后分配一个页.
//接着填充PGD的页表项(PMD).
//哦，好像略过了PUD了、对于ARM来说PMD也是直接返回pgd.
new_pmd = pmd_alloc(mm, new_pgd, 0);
if (!new_pmd)
goto no_pmd;
//如果为空则分配一个页面，然后设置PGD的页表项.
new_pte = pte_alloc_map(mm, new_pmd, 0);
if (!new_pte)
goto no_pte;
//init_pgd就是init进程的页表,这里得到地址0的PGD页表的表项(PMD)
init_pmd = pmd_offset(init_pgd, 0);
//根据init_pmd，得到了PMD页表，然后根据0地址得到了PMD的表项(PTE)
init_pte = pte_offset_map_nested(init_pmd, 0);
//new_pte指定了要存放PTE的地址，init_pte就是PTE的值。
set_pte_ext(new_pte, *init_pte, 0);
pte_unmap_nested(init_pte);
pte_unmap(new_pte);
}
return new_pgd;
no_pte:
pmd_free(mm, new_pmd);
no_pmd:
free_pages((unsigned long)new_pgd, 2);
no_pgd:
return NULL;
}
