参照元†
- struct task_struct *tsk
- struct mm_struct *mm
- unsigned long start
- int nr_pages
- int write
- int force
- struct page **pages
- struct vm_area_struct **vmas
返り値†
int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, int nr_pages, unsigned int gup_flags,
struct page **pages, struct vm_area_struct **vmas)
{
int i;
unsigned long vm_flags;
if (nr_pages <= 0)
return 0;
VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
/*
* Require read or write permissions.
* If FOLL_FORCE is set, we only require the "MAY" flags.
*/
vm_flags = (gup_flags & FOLL_WRITE) ?
(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= (gup_flags & FOLL_FORCE) ?
(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
i = 0;
do {
struct vm_area_struct *vma;
vma = find_extend_vma(mm, start);
if (!vma && in_gate_area(tsk, start)) {
unsigned long pg = start & PAGE_MASK;
struct vm_area_struct *gate_vma = get_gate_vma(tsk);
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
/* user gate pages are read-only */
if (gup_flags & FOLL_WRITE)
return i ? : -EFAULT;
if (pg > TASK_SIZE)
pgd = pgd_offset_k(pg);
else
pgd = pgd_offset_gate(mm, pg);
BUG_ON(pgd_none(*pgd));
pud = pud_offset(pgd, pg);
BUG_ON(pud_none(*pud));
pmd = pmd_offset(pud, pg);
if (pmd_none(*pmd))
return i ? : -EFAULT;
pte = pte_offset_map(pmd, pg);
if (pte_none(*pte)) {
pte_unmap(pte);
return i ? : -EFAULT;
}
if (pages) {
struct page *page = vm_normal_page(gate_vma, start, *pte);
pages[i] = page;
if (page)
get_page(page);
}
pte_unmap(pte);
if (vmas)
vmas[i] = gate_vma;
i++;
start += PAGE_SIZE;
nr_pages--;
continue;
}
if (!vma ||
(vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
!(vm_flags & vma->vm_flags))
return i ? : -EFAULT;
if (is_vm_hugetlb_page(vma)) {
i = follow_hugetlb_page(mm, vma, pages, vmas,
&start, &nr_pages, i, gup_flags);
continue;
}
do {
struct page *page;
unsigned int foll_flags = gup_flags;
/*
* If we have a pending SIGKILL, don't keep faulting
* pages and potentially allocating memory.
*/
if (unlikely(fatal_signal_pending(current)))
return i ? i : -ERESTARTSYS;
cond_resched();
while (!(page = follow_page(vma, start, foll_flags))) {
int ret;
ret = handle_mm_fault(mm, vma, start,
(foll_flags & FOLL_WRITE) ?
FAULT_FLAG_WRITE : 0);
if (ret & VM_FAULT_ERROR) {
if (ret & VM_FAULT_OOM)
return i ? i : -ENOMEM;
if (ret &
(VM_FAULT_HWPOISON|VM_FAULT_SIGBUS))
return i ? i : -EFAULT;
BUG();
}
if (ret & VM_FAULT_MAJOR)
tsk->maj_flt++;
else
tsk->min_flt++;
/*
* The VM_FAULT_WRITE bit tells us that
* do_wp_page has broken COW when necessary,
* even if maybe_mkwrite decided not to set
* pte_write. We can thus safely do subsequent
* page lookups as if they were reads. But only
* do so when looping for pte_write is futile:
* in some cases userspace may also be wanting
* to write to the gotten user page, which a
* read fault here might prevent (a readonly
* page might get reCOWed by userspace write).
*/
if ((ret & VM_FAULT_WRITE) &&
!(vma->vm_flags & VM_WRITE))
foll_flags &= ~FOLL_WRITE;
cond_resched();
}
if (IS_ERR(page))
return i ? i : PTR_ERR(page);
if (pages) {
pages[i] = page;
flush_anon_page(vma, page, start);
flush_dcache_page(page);
}
if (vmas)
vmas[i] = vma;
i++;
start += PAGE_SIZE;
nr_pages--;
} while (nr_pages && start < vma->vm_end);
} while (nr_pages);
return i;
}
コメント†
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