On 06/04, Song Liu wrote:
>
> Currently, uprobe swaps the target page with a anonymous page in both
> install_breakpoint() and remove_breakpoint(). When all uprobes on a page
> are removed, the given mm is still using an anonymous page (not the
> original page).
Agreed, it would be nice to avoid this,
> @@ -461,9 +471,10 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe,
> struct mm_struct *mm,
> unsigned long vaddr, uprobe_opcode_t opcode)
> {
> struct uprobe *uprobe;
> - struct page *old_page, *new_page;
> + struct page *old_page, *new_page, *orig_page = NULL;
> struct vm_area_struct *vma;
> int ret, is_register, ref_ctr_updated = 0;
> + pgoff_t index;
>
> is_register = is_swbp_insn(&opcode);
> uprobe = container_of(auprobe, struct uprobe, arch);
> @@ -501,6 +512,19 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe,
> struct mm_struct *mm,
> copy_highpage(new_page, old_page);
> copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
>
> + index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT;
> + orig_page = find_get_page(vma->vm_file->f_inode->i_mapping, index);
I think you should take is_register into account, if it is true we are going
to install the breakpoint so we can avoid find_get_page/pages_identical.
> + if (orig_page) {
> + if (pages_identical(new_page, orig_page)) {
> + /* if new_page matches orig_page, use orig_page */
> + put_page(new_page);
> + new_page = orig_page;
Hmm. can't we simply unmap the page in this case?
Oleg.
