On Tue, Jun 25, 2019 at 09:04:39PM +0200, Thomas Gleixner wrote:
> On Thu, 20 Jun 2019, Kirill A. Shutemov wrote:
> > @@ -190,18 +190,18 @@ unsigned long __head __startup_64(unsigned long
> > physaddr,
> > pgd[i + 0] = (pgdval_t)p4d + pgtable_flags;
> > pgd[i + 1] = (pgdval_t)p4d + pgtable_flags;
> >
> > - i = (physaddr >> P4D_SHIFT) % PTRS_PER_P4D;
> > - p4d[i + 0] = (pgdval_t)pud + pgtable_flags;
> > - p4d[i + 1] = (pgdval_t)pud + pgtable_flags;
> > + i = physaddr >> P4D_SHIFT;
> > + p4d[(i + 0) % PTRS_PER_P4D] = (pgdval_t)pud + pgtable_flags;
> > + p4d[(i + 1) % PTRS_PER_P4D] = (pgdval_t)pud + pgtable_flags;
> > } else {
> > i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
> > pgd[i + 0] = (pgdval_t)pud + pgtable_flags;
> > pgd[i + 1] = (pgdval_t)pud + pgtable_flags;
> > }
> >
> > - i = (physaddr >> PUD_SHIFT) % PTRS_PER_PUD;
> > - pud[i + 0] = (pudval_t)pmd + pgtable_flags;
> > - pud[i + 1] = (pudval_t)pmd + pgtable_flags;
> > + i = physaddr >> PUD_SHIFT;
> > + pud[(i + 0) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags;
> > + pud[(i + 1) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags;
> >
> > pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL;
> > /* Filter out unsupported __PAGE_KERNEL_* bits: */
> > @@ -211,8 +211,8 @@ unsigned long __head __startup_64(unsigned long
> > physaddr,
> > pmd_entry += physaddr;
> >
> > for (i = 0; i < DIV_ROUND_UP(_end - _text, PMD_SIZE); i++) {
> > - int idx = i + (physaddr >> PMD_SHIFT) % PTRS_PER_PMD;
> > - pmd[idx] = pmd_entry + i * PMD_SIZE;
> > + int idx = i + (physaddr >> PMD_SHIFT);;
>
> double semicolon
Will fix.
> > + pmd[idx % PTRS_PER_PMD] = pmd_entry + i * PMD_SIZE;
>
> This part is functionally equivivalent. So what's the value of this change?
Precedence of operators were broken
idx = i + (physaddr >> PMD_SHIFT) % PTRS_PER_PMD;
reads by compiler as
idx = i + ((physaddr >> PMD_SHIFT) % PTRS_PER_PMD);
not as
idx = (i + (physaddr >> PMD_SHIFT)) % PTRS_PER_PMD;
Therefore 'idx' can become >= PTRS_PER_PMD.
--
Kirill A. Shutemov
