On Mon, 2003-07-21 at 14:06, Ravi Krishnamurthy wrote:
> --- Jim Bauer <jfbauer@nfr.com> wrote:
>
> > > I couldn't find an example in any 2.5.x driver. But
> > > here is what is needed:
> > >
> > > {
> > > struct mm_struct *mm;
> > > pgd_t *pgd;
> > > pmd_t *pmd;
> > > pte_t *ptep, pte;
> > > struct page *old_page;
> > > struct page *new_page = ...; /* new page to be mapped
> > in */
> > > pgprot_t prot = ...; /* PTE flags. _PAGE_RW,
> > PAGE_SHARED, etc.
> > > * Set appropriately. */
> > >
> > > mm = current->mm;
> > > spin_lock(&mm->page_table_lock);
> > > pgd = pgd_offset(mm, address);
> > > pmd = pmd_offset(pgd, address);
> > > ptep = pte_offset_map(pmd, address);
> > > pte = ptep_get_and_clear(ptep);
> > > set_pte(ptep, mk_pte(new_page, prot));
> > > spin_unlock(&mm->page_table_lock);
> > > old_page = pte_page(pte);
> > > ...
> > > }
> > >
> > > Not many error checks are needed in this case since we
> > > know that the required address definitely has a mapping
> > > in the process page table.
> > >
> >
> >
> > I tried this, but the user-space program's mapping was
> > still refering to the old pages.
>
> Are you sure current->mm is what you want always? If the
> remapping is triggered from an interrupt context, then
> current->mm will refer to the mm structure of some other
> process.
Yep, I am only doing that via a syscall.
> > However, if I ran it
> > through gdb and single stepped it then it saw the new
> > buffer. It I used gdb, but did not single step, then
> > the prog being debugged saw the old pages, but gdb saw
> > the new ones?
>
> I am not sure I understand that. What do you mean by
> 'gdb saw new ones'? How exactly did you check that in
> gdb?
I added some code the to kernel module to scribble
a pattern over the old buffer when I switch to the new one.
I was filling each byte with the value 0x62.
The user-space test program had something like...
if (data->len > 2000)
printf("length (0x%x) is too big\n", data->len);
and it prints out 0x62626262 for the length (old buffer contents).
But if I use gdb to print out data->len, at that point, I
get a reasonable/expected value.
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