| Message ID | 20230727093637.1262110-3-usama.anjum@collabora.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Implement IOCTL to get and optionally clear info about PTEs | expand |
On Thu, 27 Jul 2023 at 11:37, Muhammad Usama Anjum <usama.anjum@collabora.com> wrote: > This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear > the info about page table entries. The following operations are supported > in this ioctl: > - Get the information if the pages have Async Write-Protection enabled > (``PAGE_IS_WPALLOWED``), have been written to (``PAGE_IS_WRITTEN``), file > mapped (``PAGE_IS_FILE``), present (``PAGE_IS_PRESENT``), swapped > (``PAGE_IS_SWAPPED``) or page has pfn zero (``PAGE_IS_PFNZERO``). > - Find pages which have been written to and/or write protect > (atomic ``PM_SCAN_WP_MATCHING + PM_SCAN_CHECK_WPASYNC``) the pages > atomically. The (``PM_SCAN_WP_MATCHING``) is used to WP the matched > pages. The (``PM_SCAN_CHECK_WPASYNC``) aborts the operation if > non-Async-Write-Protected pages are found. Get is automatically performed > if output buffer is specified. > > This IOCTL can be extended to get information about more PTE bits. The > entire address range passed by user [start, end) is scanned until either > the user provided buffer is full or max_pages have been found. > > Reviewed-by: Andrei Vagin <avagin@gmail.com> > Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com> Thanks for all the work! Small request below. > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c [...] > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +static unsigned long pagemap_thp_category(pmd_t pmd) > +{ > + unsigned long categories = 0; > + > + if (pmd_present(pmd)) { > + categories |= PAGE_IS_PRESENT; > + if (!pmd_uffd_wp(pmd)) > + categories |= PAGE_IS_WRITTEN; > + if (is_zero_pfn(pmd_pfn(pmd))) > + categories |= PAGE_IS_PFNZERO; > + } else if (is_swap_pmd(pmd)) { > + categories |= PAGE_IS_SWAPPED; > + if (!pmd_swp_uffd_wp(pmd)) > + categories |= PAGE_IS_WRITTEN; > + } > + > + return categories; > +} [...] > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > + > +#ifdef CONFIG_HUGETLB_PAGE > +static unsigned long pagemap_hugetlb_category(pte_t pte) > +{ > + unsigned long categories = 0; > + > + if (pte_present(pte)) { > + categories |= PAGE_IS_PRESENT; > + if (!huge_pte_uffd_wp(pte)) > + categories |= PAGE_IS_WRITTEN; > + if (!PageAnon(pte_page(pte))) > + categories |= PAGE_IS_FILE; > + if (is_zero_pfn(pte_pfn(pte))) > + categories |= PAGE_IS_PFNZERO; > + } else if (is_swap_pte(pte)) { > + categories |= PAGE_IS_SWAPPED; > + if (!pte_swp_uffd_wp_any(pte)) > + categories |= PAGE_IS_WRITTEN; > + } > + > + return categories; > +} Could you add PAGE_IS_HUGE for THP and HugeTLB pages? This would help maintaining checkpointed process'es page sizes by CRIU when THP is used. Best Regards Michał Mirosław
On Thu, 27 Jul 2023 at 11:37, Muhammad Usama Anjum <usama.anjum@collabora.com> wrote: [...] > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h [...] > +/* > + * struct pm_scan_arg - Pagemap ioctl argument > + * @size: Size of the structure > + * @flags: Flags for the IOCTL > + * @start: Starting address of the region > + * @end: Ending address of the region > + * @walk_end: Ending address of the visited memory is returned > + * (This helps if entire range hasn't been visited) "Address where the scan stopped (written by kernel). walk_end == end informs that the scan completed." (To make the userspace life easier, we can copy `end` (only) in case of full scan completion, so that the tag is retained.) > + * @vec: Address of page_region struct array for output > + * @vec_len: Length of the page_region struct array > + * @max_pages: Optional limit for number of returned pages (0 = disabled) > + * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1 > + * @category_mask: Skip pages for which any category doesn't match > + * @category_anyof_mask: Skip pages for which no category matches > + * @return_mask: PAGE_IS_* categories that are to be reported in `page_region`s returned > + */
On 7/27/23 4:40 PM, Michał Mirosław wrote: > On Thu, 27 Jul 2023 at 11:37, Muhammad Usama Anjum > <usama.anjum@collabora.com> wrote: >> This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear >> the info about page table entries. The following operations are supported >> in this ioctl: >> - Get the information if the pages have Async Write-Protection enabled >> (``PAGE_IS_WPALLOWED``), have been written to (``PAGE_IS_WRITTEN``), file >> mapped (``PAGE_IS_FILE``), present (``PAGE_IS_PRESENT``), swapped >> (``PAGE_IS_SWAPPED``) or page has pfn zero (``PAGE_IS_PFNZERO``). >> - Find pages which have been written to and/or write protect >> (atomic ``PM_SCAN_WP_MATCHING + PM_SCAN_CHECK_WPASYNC``) the pages >> atomically. The (``PM_SCAN_WP_MATCHING``) is used to WP the matched >> pages. The (``PM_SCAN_CHECK_WPASYNC``) aborts the operation if >> non-Async-Write-Protected pages are found. Get is automatically performed >> if output buffer is specified. >> >> This IOCTL can be extended to get information about more PTE bits. The >> entire address range passed by user [start, end) is scanned until either >> the user provided buffer is full or max_pages have been found. >> >> Reviewed-by: Andrei Vagin <avagin@gmail.com> >> Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> >> Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> >> Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com> > > Thanks for all the work! > > Small request below. > >> --- a/fs/proc/task_mmu.c >> +++ b/fs/proc/task_mmu.c > [...] >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> +static unsigned long pagemap_thp_category(pmd_t pmd) >> +{ >> + unsigned long categories = 0; >> + >> + if (pmd_present(pmd)) { >> + categories |= PAGE_IS_PRESENT; >> + if (!pmd_uffd_wp(pmd)) >> + categories |= PAGE_IS_WRITTEN; >> + if (is_zero_pfn(pmd_pfn(pmd))) >> + categories |= PAGE_IS_PFNZERO; >> + } else if (is_swap_pmd(pmd)) { >> + categories |= PAGE_IS_SWAPPED; >> + if (!pmd_swp_uffd_wp(pmd)) >> + categories |= PAGE_IS_WRITTEN; >> + } >> + >> + return categories; >> +} > [...] >> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >> + >> +#ifdef CONFIG_HUGETLB_PAGE >> +static unsigned long pagemap_hugetlb_category(pte_t pte) >> +{ >> + unsigned long categories = 0; >> + >> + if (pte_present(pte)) { >> + categories |= PAGE_IS_PRESENT; >> + if (!huge_pte_uffd_wp(pte)) >> + categories |= PAGE_IS_WRITTEN; >> + if (!PageAnon(pte_page(pte))) >> + categories |= PAGE_IS_FILE; >> + if (is_zero_pfn(pte_pfn(pte))) >> + categories |= PAGE_IS_PFNZERO; >> + } else if (is_swap_pte(pte)) { >> + categories |= PAGE_IS_SWAPPED; >> + if (!pte_swp_uffd_wp_any(pte)) >> + categories |= PAGE_IS_WRITTEN; >> + } >> + >> + return categories; >> +} > > Could you add PAGE_IS_HUGE for THP and HugeTLB pages? This would help > maintaining checkpointed process'es page sizes by CRIU when THP is > used. Can be done. > > Best Regards > Michał Mirosław
On 7/27/23 4:46 PM, Michał Mirosław wrote: > On Thu, 27 Jul 2023 at 11:37, Muhammad Usama Anjum > <usama.anjum@collabora.com> wrote: > [...] >> --- a/include/uapi/linux/fs.h >> +++ b/include/uapi/linux/fs.h > [...] >> +/* >> + * struct pm_scan_arg - Pagemap ioctl argument >> + * @size: Size of the structure >> + * @flags: Flags for the IOCTL >> + * @start: Starting address of the region >> + * @end: Ending address of the region >> + * @walk_end: Ending address of the visited memory is returned >> + * (This helps if entire range hasn't been visited) > > "Address where the scan stopped (written by kernel). walk_end == end > informs that the scan completed." I'll update comment. > > (To make the userspace life easier, we can copy `end` (only) in case > of full scan completion, so that the tag is retained.) Lets be consist and not copy tag from end to walk_end as we'll now know about tag every time. It should be the responsibility of the user to deal with it. > >> + * @vec: Address of page_region struct array for output >> + * @vec_len: Length of the page_region struct array >> + * @max_pages: Optional limit for number of returned pages (0 = disabled) >> + * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1 >> + * @category_mask: Skip pages for which any category doesn't match >> + * @category_anyof_mask: Skip pages for which no category matches >> + * @return_mask: PAGE_IS_* categories that are to be reported in `page_region`s returned >> + */
On Thu, Jul 27, 2023 at 02:36:34PM +0500, Muhammad Usama Anjum wrote: <snip> > + > +static void pagemap_scan_backout_range(struct pagemap_scan_private *p, > + unsigned long addr, unsigned long end, > + unsigned long end_addr) It hard to figure out what difference between end and end_addr. I would add a comment here. > +{ > + struct page_region *cur_buf = &p->cur_buf; > + > + if (cur_buf->start != addr) > + cur_buf->end = addr; > + else > + cur_buf->start = cur_buf->end = 0; > + > + p->end_addr = end_addr; > + p->found_pages -= (end - addr) / PAGE_SIZE; > +} > + > +static int pagemap_scan_output(unsigned long categories, > + struct pagemap_scan_private *p, > + unsigned long addr, unsigned long *end) > +{ > + unsigned long n_pages, total_pages; > + int ret = 0; > + > + if (!pagemap_scan_is_interesting_page(categories, p)) { > + *end = addr; > + return 0; > + } > + > + if (!p->vec_buf) > + return 0; > + > + categories &= p->arg.return_mask; > + > + n_pages = (*end - addr) / PAGE_SIZE; > + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || > + total_pages > p->arg.max_pages) { why do we need to use check_add_overflow here? > + size_t n_too_much = total_pages - p->arg.max_pages; it is unsafe to use total_pages if check_add_overflow returns non-zero. > + *end -= n_too_much * PAGE_SIZE; > + n_pages -= n_too_much; > + ret = -ENOSPC; > + } > + > + if (!pagemap_scan_push_range(categories, p, addr, *end)) { > + *end = addr; > + n_pages = 0; > + ret = -ENOSPC; > + } > + > + p->found_pages += n_pages; > + if (ret) > + p->end_addr = *end; > + > + return ret; > +} > + > +static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start, > + unsigned long end, struct mm_walk *walk) > +{ > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > + struct pagemap_scan_private *p = walk->private; > + struct vm_area_struct *vma = walk->vma; > + unsigned long categories; > + spinlock_t *ptl; > + int ret = 0; > + > + ptl = pmd_trans_huge_lock(pmd, vma); > + if (!ptl) > + return -ENOENT; > + > + categories = p->cur_vma_category | pagemap_thp_category(*pmd); > + > + ret = pagemap_scan_output(categories, p, start, &end); > + if (start == end) > + goto out_unlock; > + > + if (~p->arg.flags & PM_SCAN_WP_MATCHING) > + goto out_unlock; > + if (~categories & PAGE_IS_WRITTEN) > + goto out_unlock; > + > + /* > + * Break huge page into small pages if the WP operation > + * need to be performed is on a portion of the huge page. > + */ > + if (end != start + HPAGE_SIZE) { > + spin_unlock(ptl); > + split_huge_pmd(vma, pmd, start); > + pagemap_scan_backout_range(p, start, end, 0); pagemap_scan_backout_range looks "weird"... imho, it makes the code harder for understanding. > + return -ENOENT; I think you need to add a comment that this ENOENT is a special case. > + } > + > + make_uffd_wp_pmd(vma, start, pmd); > + flush_tlb_range(vma, start, end); > +out_unlock: > + spin_unlock(ptl); > + return ret; > +#else /* !CONFIG_TRANSPARENT_HUGEPAGE */ > + return -ENOENT; > +#endif > +} > + > +static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, > + unsigned long end, struct mm_walk *walk) > +{ > + struct pagemap_scan_private *p = walk->private; > + struct vm_area_struct *vma = walk->vma; > + pte_t *pte, *start_pte; > + unsigned long addr; > + bool flush = false; > + spinlock_t *ptl; > + int ret; > + > + arch_enter_lazy_mmu_mode(); > + > + ret = pagemap_scan_thp_entry(pmd, start, end, walk); > + if (ret != -ENOENT) { > + arch_leave_lazy_mmu_mode(); > + return ret; > + } > + > + start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); > + if (!pte) { > + arch_leave_lazy_mmu_mode(); > + walk->action = ACTION_AGAIN; > + return 0; > + } > + > + for (addr = start; addr != end; pte++, addr += PAGE_SIZE) { > + unsigned long categories = p->cur_vma_category | > + pagemap_page_category(vma, addr, ptep_get(pte)); > + unsigned long next = addr + PAGE_SIZE; > + > + ret = pagemap_scan_output(categories, p, addr, &next); > + if (next == addr) { > + if (!ret) > + continue; > + break; > + } > + > + if (~p->arg.flags & PM_SCAN_WP_MATCHING) > + continue; > + if (~categories & PAGE_IS_WRITTEN) > + continue; > + > + make_uffd_wp_pte(vma, addr, pte); > + if (!flush) { > + start = addr; > + flush = true; > + } > + } > + > + if (flush) > + flush_tlb_range(vma, start, addr); > + > + pte_unmap_unlock(start_pte, ptl); > + arch_leave_lazy_mmu_mode(); > + > + cond_resched(); > + return ret; > +} > + > +#ifdef CONFIG_HUGETLB_PAGE > +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, > + unsigned long start, unsigned long end, > + struct mm_walk *walk) > +{ > + struct pagemap_scan_private *p = walk->private; > + struct vm_area_struct *vma = walk->vma; > + unsigned long categories; > + spinlock_t *ptl; > + int ret = 0; > + pte_t pte; > + > + if (~p->arg.flags & PM_SCAN_WP_MATCHING) { > + /* Go the short route when not write-protecting pages. */ > + > + pte = huge_ptep_get(ptep); > + categories = p->cur_vma_category | pagemap_hugetlb_category(pte); > + > + return pagemap_scan_output(categories, p, start, &end); > + } > + > + i_mmap_lock_write(vma->vm_file->f_mapping); > + ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep); > + > + pte = huge_ptep_get(ptep); > + categories = p->cur_vma_category | pagemap_hugetlb_category(pte); > + > + ret = pagemap_scan_output(categories, p, start, &end); > + if (start == end) > + goto out_unlock; > + > + if (~categories & PAGE_IS_WRITTEN) > + goto out_unlock; > + > + if (end != start + HPAGE_SIZE) { > + /* Partial HugeTLB page WP isn't possible. */ > + pagemap_scan_backout_range(p, start, end, start); > + ret = -EINVAL; Why is it EINVAL in this case? > + goto out_unlock; > + } > + > + make_uffd_wp_huge_pte(vma, start, ptep, pte); > + flush_hugetlb_tlb_range(vma, start, end); > + > +out_unlock: > + spin_unlock(ptl); > + i_mmap_unlock_write(vma->vm_file->f_mapping); > + > + return ret; > +} > +#else > +#define pagemap_scan_hugetlb_entry NULL > +#endif > + > +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, > + int depth, struct mm_walk *walk) > +{ > + struct pagemap_scan_private *p = walk->private; > + struct vm_area_struct *vma = walk->vma; > + int ret, err; > + > + if (!vma) > + return 0; > + > + ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end); > + if (addr == end) > + return ret; > + > + if (~p->arg.flags & PM_SCAN_WP_MATCHING) > + return ret; > + > + err = uffd_wp_range(vma, addr, end - addr, true); > + if (err < 0) > + ret = err; > + > + return ret; > +} > + > +static const struct mm_walk_ops pagemap_scan_ops = { > + .test_walk = pagemap_scan_test_walk, > + .pmd_entry = pagemap_scan_pmd_entry, > + .pte_hole = pagemap_scan_pte_hole, > + .hugetlb_entry = pagemap_scan_hugetlb_entry, > +}; > + > +static int pagemap_scan_get_args(struct pm_scan_arg *arg, > + unsigned long uarg) > +{ > + if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg))) > + return -EFAULT; > + > + if (arg->size != sizeof(struct pm_scan_arg)) > + return -EINVAL; > + > + /* Validate requested features */ > + if (arg->flags & ~PM_SCAN_FLAGS) > + return -EINVAL; > + if ((arg->category_inverted | arg->category_mask | > + arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES) > + return -EINVAL; > + > + arg->start = untagged_addr((unsigned long)arg->start); > + arg->end = untagged_addr((unsigned long)arg->end); > + arg->vec = untagged_addr((unsigned long)arg->vec); > + > + /* Validate memory pointers */ > + if (!IS_ALIGNED(arg->start, PAGE_SIZE)) > + return -EINVAL; > + if (!access_ok((void __user *)arg->start, arg->end - arg->start)) > + return -EFAULT; > + if (!arg->vec && arg->vec_len) > + return -EFAULT; > + if (arg->vec && !access_ok((void __user *)arg->vec, > + arg->vec_len * sizeof(struct page_region))) > + return -EFAULT; > + > + /* Fixup default values */ > + arg->end = ALIGN(arg->end, PAGE_SIZE); > + if (!arg->max_pages) > + arg->max_pages = ULONG_MAX; > + > + return 0; > +} > + > +static int pagemap_scan_writeback_args(struct pm_scan_arg *arg, > + unsigned long uargl) > +{ > + struct pm_scan_arg __user *uarg = (void __user *)uargl; > + > + if (copy_to_user(&uarg->walk_end, &arg->walk_end, sizeof(arg->walk_end))) > + return -EFAULT; > + > + return 0; > +} > + > +static int pagemap_scan_init_bounce_buffer(struct pagemap_scan_private *p) > +{ > + if (!p->arg.vec_len) { > + /* > + * An arbitrary non-page-aligned sentinel value for > + * pagemap_scan_push_range(). > + */ > + p->cur_buf.start = p->cur_buf.end = ULLONG_MAX; > + if (p->arg.vec) > + p->vec_buf = ZERO_SIZE_PTR; > + return 0; > + } > + > + /* > + * Allocate a smaller buffer to get output from inside the page > + * walk functions and walk the range in PAGEMAP_WALK_SIZE chunks. > + * The last range is always stored in p.cur_buf to allow coalescing > + * consecutive ranges that have the same categories returned across > + * walk_page_range() calls. > + */ > + p->vec_buf_len = min_t(size_t, PAGEMAP_WALK_SIZE >> PAGE_SHIFT, > + p->arg.vec_len - 1); > + p->vec_buf = kmalloc_array(p->vec_buf_len, sizeof(*p->vec_buf), > + GFP_KERNEL); > + if (!p->vec_buf) > + return -ENOMEM; > + > + p->vec_out = (struct page_region __user *)p->arg.vec; > + > + return 0; > +} > + > +static int pagemap_scan_flush_buffer(struct pagemap_scan_private *p) > +{ > + const struct page_region *buf = p->vec_buf; > + int n = (int)p->vec_buf_index; > + > + if (!n) > + return 0; > + > + if (copy_to_user(p->vec_out, buf, n * sizeof(*buf))) > + return -EFAULT; > + > + p->arg.vec_len -= n; > + p->vec_out += n; > + > + p->vec_buf_index = 0; > + p->vec_buf_len = min_t(size_t, p->vec_buf_len, p->arg.vec_len - 1); > + > + return n; > +} > + > +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) > +{ > + unsigned long walk_start, walk_end; > + struct mmu_notifier_range range; > + struct pagemap_scan_private p; > + size_t n_ranges_out = 0; > + int ret; > + > + memset(&p, 0, sizeof(p)); > + ret = pagemap_scan_get_args(&p.arg, uarg); > + if (ret) > + return ret; > + > + ret = pagemap_scan_init_bounce_buffer(&p); > + if (ret) > + return ret; > + > + /* Protection change for the range is going to happen. */ > + if (p.arg.flags & PM_SCAN_WP_MATCHING) { > + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, > + mm, p.arg.start, p.arg.end); > + mmu_notifier_invalidate_range_start(&range); > + } > + > + walk_start = walk_end = p.arg.start; > + for (; walk_end != p.arg.end; walk_start = walk_end) { > + int n_out; > + > + walk_end = min_t(unsigned long, > + (walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, > + p.arg.end); > + if (fatal_signal_pending(current)) { ret = EINTR; break; } > + ret = mmap_read_lock_killable(mm); > + if (ret) > + break; > + ret = walk_page_range(mm, walk_start, walk_end, > + &pagemap_scan_ops, &p); > + mmap_read_unlock(mm); > + > + n_out = pagemap_scan_flush_buffer(&p); > + if (n_out < 0) > + ret = n_out; > + else > + n_ranges_out += n_out; > + > + if (ret) > + break; > + } > + > + if (p.cur_buf.start != p.cur_buf.end) { > + if (copy_to_user(p.vec_out, &p.cur_buf, sizeof(p.cur_buf))) > + ret = -EFAULT; > + else > + ++n_ranges_out; > + } > + > + /* ENOSPC signifies early stop (buffer full) from the walk. */ > + if (!ret || ret == -ENOSPC) > + ret = n_ranges_out; > + > + p.arg.walk_end = p.end_addr ? p.end_addr : walk_start; > + if (pagemap_scan_writeback_args(&p.arg, uarg)) > + ret = -EFAULT; > + > + if (p.arg.flags & PM_SCAN_WP_MATCHING) > + mmu_notifier_invalidate_range_end(&range); > + > + kfree(p.vec_buf); > + return ret; > +} > + > +static long do_pagemap_cmd(struct file *file, unsigned int cmd, > + unsigned long arg) > +{ > + struct mm_struct *mm = file->private_data; > + > + switch (cmd) { > + case PAGEMAP_SCAN: > + return do_pagemap_scan(mm, arg); > + > + default: > + return -EINVAL; > + } > +} > + > const struct file_operations proc_pagemap_operations = { > .llseek = mem_lseek, /* borrow this */ > .read = pagemap_read, > .open = pagemap_open, > .release = pagemap_release, > + .unlocked_ioctl = do_pagemap_cmd, > + .compat_ioctl = do_pagemap_cmd, > }; > #endif /* CONFIG_PROC_PAGE_MONITOR */ > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 0a393bc02f25b..8f8ff07453f22 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, > unsigned long cp_flags); > > bool is_hugetlb_entry_migration(pte_t pte); > +bool is_hugetlb_entry_hwpoisoned(pte_t pte); > void hugetlb_unshare_all_pmds(struct vm_area_struct *vma); > > #else /* !CONFIG_HUGETLB_PAGE */ > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index b7b56871029c5..1bb3c625c2381 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -305,4 +305,62 @@ typedef int __bitwise __kernel_rwf_t; > #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ > RWF_APPEND) > > +/* Pagemap ioctl */ > +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) > + > +/* Bits are set in flags of the page_region and masks in pm_scan_args */ > +#define PAGE_IS_WPALLOWED (1 << 0) > +#define PAGE_IS_WRITTEN (1 << 1) > +#define PAGE_IS_FILE (1 << 2) > +#define PAGE_IS_PRESENT (1 << 3) > +#define PAGE_IS_SWAPPED (1 << 4) > +#define PAGE_IS_PFNZERO (1 << 5) > + > +/* > + * struct page_region - Page region with flags > + * @start: Start of the region > + * @end: End of the region (exclusive) > + * @categories: PAGE_IS_* category bitmask for the region > + */ > +struct page_region { > + __u64 start; > + __u64 end; > + __u64 categories; > +}; > + > +/* Flags for PAGEMAP_SCAN ioctl */ > +#define PM_SCAN_WP_MATCHING (1 << 0) /* Write protect the pages matched. */ > +#define PM_SCAN_CHECK_WPASYNC (1 << 1) /* Abort the scan when a non-WP-enabled page is found. */ > + > +/* > + * struct pm_scan_arg - Pagemap ioctl argument > + * @size: Size of the structure > + * @flags: Flags for the IOCTL > + * @start: Starting address of the region > + * @end: Ending address of the region > + * @walk_end: Ending address of the visited memory is returned > + * (This helps if entire range hasn't been visited) > + * @vec: Address of page_region struct array for output > + * @vec_len: Length of the page_region struct array > + * @max_pages: Optional limit for number of returned pages (0 = disabled) > + * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1 > + * @category_mask: Skip pages for which any category doesn't match > + * @category_anyof_mask: Skip pages for which no category matches > + * @return_mask: PAGE_IS_* categories that are to be reported in `page_region`s returned > + */ > +struct pm_scan_arg { > + __u64 size; > + __u64 flags; > + __u64 start; > + __u64 end; > + __u64 walk_end; > + __u64 vec; > + __u64 vec_len; > + __u64 max_pages; > + __u64 category_inverted; > + __u64 category_mask; > + __u64 category_anyof_mask; > + __u64 return_mask; > +}; > + > #endif /* _UAPI_LINUX_FS_H */ > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index a073e6ed8900b..3b07db0a4f2d9 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5008,7 +5008,7 @@ bool is_hugetlb_entry_migration(pte_t pte) > return false; > } > > -static bool is_hugetlb_entry_hwpoisoned(pte_t pte) > +bool is_hugetlb_entry_hwpoisoned(pte_t pte) > { > swp_entry_t swp; > > -- > 2.39.2 >
On Thu, 3 Aug 2023 at 17:09, Andrei Vagin <avagin@gmail.com> wrote: > On Thu, Jul 27, 2023 at 02:36:34PM +0500, Muhammad Usama Anjum wrote: [...] > > + n_pages = (*end - addr) / PAGE_SIZE; > > + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || > > + total_pages > p->arg.max_pages) { > > why do we need to use check_add_overflow here? > > > + size_t n_too_much = total_pages - p->arg.max_pages; > > it is unsafe to use total_pages if check_add_overflow returns non-zero. Since we're adding unsigned integers, this is well defined even after overflow. Best Regards Michał Mirosław
On 8/3/23 8:08 PM, Andrei Vagin wrote: > On Thu, Jul 27, 2023 at 02:36:34PM +0500, Muhammad Usama Anjum wrote: > > <snip> > >> + >> +static void pagemap_scan_backout_range(struct pagemap_scan_private *p, >> + unsigned long addr, unsigned long end, >> + unsigned long end_addr) > > It hard to figure out what difference between end and end_addr. I would > add a comment here. I'll fix these in next version. > >> +{ >> + struct page_region *cur_buf = &p->cur_buf; >> + >> + if (cur_buf->start != addr) >> + cur_buf->end = addr; >> + else >> + cur_buf->start = cur_buf->end = 0; >> + >> + p->end_addr = end_addr; >> + p->found_pages -= (end - addr) / PAGE_SIZE; >> +} >> + >> +static int pagemap_scan_output(unsigned long categories, >> + struct pagemap_scan_private *p, >> + unsigned long addr, unsigned long *end) >> +{ >> + unsigned long n_pages, total_pages; >> + int ret = 0; >> + >> + if (!pagemap_scan_is_interesting_page(categories, p)) { >> + *end = addr; >> + return 0; >> + } >> + >> + if (!p->vec_buf) >> + return 0; >> + >> + categories &= p->arg.return_mask; >> + >> + n_pages = (*end - addr) / PAGE_SIZE; >> + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || >> + total_pages > p->arg.max_pages) { > > why do we need to use check_add_overflow here? > >> + size_t n_too_much = total_pages - p->arg.max_pages; > > it is unsafe to use total_pages if check_add_overflow returns non-zero. > >> + *end -= n_too_much * PAGE_SIZE; >> + n_pages -= n_too_much; >> + ret = -ENOSPC; >> + } >> + >> + if (!pagemap_scan_push_range(categories, p, addr, *end)) { >> + *end = addr; >> + n_pages = 0; >> + ret = -ENOSPC; >> + } >> + >> + p->found_pages += n_pages; >> + if (ret) >> + p->end_addr = *end; >> + >> + return ret; >> +} >> + >> +static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start, >> + unsigned long end, struct mm_walk *walk) >> +{ >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + unsigned long categories; >> + spinlock_t *ptl; >> + int ret = 0; >> + >> + ptl = pmd_trans_huge_lock(pmd, vma); >> + if (!ptl) >> + return -ENOENT; >> + >> + categories = p->cur_vma_category | pagemap_thp_category(*pmd); >> + >> + ret = pagemap_scan_output(categories, p, start, &end); >> + if (start == end) >> + goto out_unlock; >> + >> + if (~p->arg.flags & PM_SCAN_WP_MATCHING) >> + goto out_unlock; >> + if (~categories & PAGE_IS_WRITTEN) >> + goto out_unlock; >> + >> + /* >> + * Break huge page into small pages if the WP operation >> + * need to be performed is on a portion of the huge page. >> + */ >> + if (end != start + HPAGE_SIZE) { >> + spin_unlock(ptl); >> + split_huge_pmd(vma, pmd, start); >> + pagemap_scan_backout_range(p, start, end, 0); > > pagemap_scan_backout_range looks "weird"... imho, it makes the code > harder for understanding. > >> + return -ENOENT; > > I think you need to add a comment that this ENOENT is a special case. > >> + } >> + >> + make_uffd_wp_pmd(vma, start, pmd); >> + flush_tlb_range(vma, start, end); >> +out_unlock: >> + spin_unlock(ptl); >> + return ret; >> +#else /* !CONFIG_TRANSPARENT_HUGEPAGE */ >> + return -ENOENT; >> +#endif >> +} >> + >> +static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, >> + unsigned long end, struct mm_walk *walk) >> +{ >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + pte_t *pte, *start_pte; >> + unsigned long addr; >> + bool flush = false; >> + spinlock_t *ptl; >> + int ret; >> + >> + arch_enter_lazy_mmu_mode(); >> + >> + ret = pagemap_scan_thp_entry(pmd, start, end, walk); >> + if (ret != -ENOENT) { >> + arch_leave_lazy_mmu_mode(); >> + return ret; >> + } >> + >> + start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); >> + if (!pte) { >> + arch_leave_lazy_mmu_mode(); >> + walk->action = ACTION_AGAIN; >> + return 0; >> + } >> + >> + for (addr = start; addr != end; pte++, addr += PAGE_SIZE) { >> + unsigned long categories = p->cur_vma_category | >> + pagemap_page_category(vma, addr, ptep_get(pte)); >> + unsigned long next = addr + PAGE_SIZE; >> + >> + ret = pagemap_scan_output(categories, p, addr, &next); >> + if (next == addr) { >> + if (!ret) >> + continue; >> + break; >> + } >> + >> + if (~p->arg.flags & PM_SCAN_WP_MATCHING) >> + continue; >> + if (~categories & PAGE_IS_WRITTEN) >> + continue; >> + >> + make_uffd_wp_pte(vma, addr, pte); >> + if (!flush) { >> + start = addr; >> + flush = true; >> + } >> + } >> + >> + if (flush) >> + flush_tlb_range(vma, start, addr); >> + >> + pte_unmap_unlock(start_pte, ptl); >> + arch_leave_lazy_mmu_mode(); >> + >> + cond_resched(); >> + return ret; >> +} >> + >> +#ifdef CONFIG_HUGETLB_PAGE >> +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, >> + unsigned long start, unsigned long end, >> + struct mm_walk *walk) >> +{ >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + unsigned long categories; >> + spinlock_t *ptl; >> + int ret = 0; >> + pte_t pte; >> + >> + if (~p->arg.flags & PM_SCAN_WP_MATCHING) { >> + /* Go the short route when not write-protecting pages. */ >> + >> + pte = huge_ptep_get(ptep); >> + categories = p->cur_vma_category | pagemap_hugetlb_category(pte); >> + >> + return pagemap_scan_output(categories, p, start, &end); >> + } >> + >> + i_mmap_lock_write(vma->vm_file->f_mapping); >> + ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep); >> + >> + pte = huge_ptep_get(ptep); >> + categories = p->cur_vma_category | pagemap_hugetlb_category(pte); >> + >> + ret = pagemap_scan_output(categories, p, start, &end); >> + if (start == end) >> + goto out_unlock; >> + >> + if (~categories & PAGE_IS_WRITTEN) >> + goto out_unlock; >> + >> + if (end != start + HPAGE_SIZE) { >> + /* Partial HugeTLB page WP isn't possible. */ >> + pagemap_scan_backout_range(p, start, end, start); >> + ret = -EINVAL; > > Why is it EINVAL in this case? > >> + goto out_unlock; >> + } >> + >> + make_uffd_wp_huge_pte(vma, start, ptep, pte); >> + flush_hugetlb_tlb_range(vma, start, end); >> + >> +out_unlock: >> + spin_unlock(ptl); >> + i_mmap_unlock_write(vma->vm_file->f_mapping); >> + >> + return ret; >> +} >> +#else >> +#define pagemap_scan_hugetlb_entry NULL >> +#endif >> + >> +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, >> + int depth, struct mm_walk *walk) >> +{ >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + int ret, err; >> + >> + if (!vma) >> + return 0; >> + >> + ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end); >> + if (addr == end) >> + return ret; >> + >> + if (~p->arg.flags & PM_SCAN_WP_MATCHING) >> + return ret; >> + >> + err = uffd_wp_range(vma, addr, end - addr, true); >> + if (err < 0) >> + ret = err; >> + >> + return ret; >> +} >> + >> +static const struct mm_walk_ops pagemap_scan_ops = { >> + .test_walk = pagemap_scan_test_walk, >> + .pmd_entry = pagemap_scan_pmd_entry, >> + .pte_hole = pagemap_scan_pte_hole, >> + .hugetlb_entry = pagemap_scan_hugetlb_entry, >> +}; >> + >> +static int pagemap_scan_get_args(struct pm_scan_arg *arg, >> + unsigned long uarg) >> +{ >> + if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg))) >> + return -EFAULT; >> + >> + if (arg->size != sizeof(struct pm_scan_arg)) >> + return -EINVAL; >> + >> + /* Validate requested features */ >> + if (arg->flags & ~PM_SCAN_FLAGS) >> + return -EINVAL; >> + if ((arg->category_inverted | arg->category_mask | >> + arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES) >> + return -EINVAL; >> + >> + arg->start = untagged_addr((unsigned long)arg->start); >> + arg->end = untagged_addr((unsigned long)arg->end); >> + arg->vec = untagged_addr((unsigned long)arg->vec); >> + >> + /* Validate memory pointers */ >> + if (!IS_ALIGNED(arg->start, PAGE_SIZE)) >> + return -EINVAL; >> + if (!access_ok((void __user *)arg->start, arg->end - arg->start)) >> + return -EFAULT; >> + if (!arg->vec && arg->vec_len) >> + return -EFAULT; >> + if (arg->vec && !access_ok((void __user *)arg->vec, >> + arg->vec_len * sizeof(struct page_region))) >> + return -EFAULT; >> + >> + /* Fixup default values */ >> + arg->end = ALIGN(arg->end, PAGE_SIZE); >> + if (!arg->max_pages) >> + arg->max_pages = ULONG_MAX; >> + >> + return 0; >> +} >> + >> +static int pagemap_scan_writeback_args(struct pm_scan_arg *arg, >> + unsigned long uargl) >> +{ >> + struct pm_scan_arg __user *uarg = (void __user *)uargl; >> + >> + if (copy_to_user(&uarg->walk_end, &arg->walk_end, sizeof(arg->walk_end))) >> + return -EFAULT; >> + >> + return 0; >> +} >> + >> +static int pagemap_scan_init_bounce_buffer(struct pagemap_scan_private *p) >> +{ >> + if (!p->arg.vec_len) { >> + /* >> + * An arbitrary non-page-aligned sentinel value for >> + * pagemap_scan_push_range(). >> + */ >> + p->cur_buf.start = p->cur_buf.end = ULLONG_MAX; >> + if (p->arg.vec) >> + p->vec_buf = ZERO_SIZE_PTR; >> + return 0; >> + } >> + >> + /* >> + * Allocate a smaller buffer to get output from inside the page >> + * walk functions and walk the range in PAGEMAP_WALK_SIZE chunks. >> + * The last range is always stored in p.cur_buf to allow coalescing >> + * consecutive ranges that have the same categories returned across >> + * walk_page_range() calls. >> + */ >> + p->vec_buf_len = min_t(size_t, PAGEMAP_WALK_SIZE >> PAGE_SHIFT, >> + p->arg.vec_len - 1); >> + p->vec_buf = kmalloc_array(p->vec_buf_len, sizeof(*p->vec_buf), >> + GFP_KERNEL); >> + if (!p->vec_buf) >> + return -ENOMEM; >> + >> + p->vec_out = (struct page_region __user *)p->arg.vec; >> + >> + return 0; >> +} >> + >> +static int pagemap_scan_flush_buffer(struct pagemap_scan_private *p) >> +{ >> + const struct page_region *buf = p->vec_buf; >> + int n = (int)p->vec_buf_index; >> + >> + if (!n) >> + return 0; >> + >> + if (copy_to_user(p->vec_out, buf, n * sizeof(*buf))) >> + return -EFAULT; >> + >> + p->arg.vec_len -= n; >> + p->vec_out += n; >> + >> + p->vec_buf_index = 0; >> + p->vec_buf_len = min_t(size_t, p->vec_buf_len, p->arg.vec_len - 1); >> + >> + return n; >> +} >> + >> +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) >> +{ >> + unsigned long walk_start, walk_end; >> + struct mmu_notifier_range range; >> + struct pagemap_scan_private p; >> + size_t n_ranges_out = 0; >> + int ret; >> + >> + memset(&p, 0, sizeof(p)); >> + ret = pagemap_scan_get_args(&p.arg, uarg); >> + if (ret) >> + return ret; >> + >> + ret = pagemap_scan_init_bounce_buffer(&p); >> + if (ret) >> + return ret; >> + >> + /* Protection change for the range is going to happen. */ >> + if (p.arg.flags & PM_SCAN_WP_MATCHING) { >> + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, >> + mm, p.arg.start, p.arg.end); >> + mmu_notifier_invalidate_range_start(&range); >> + } >> + >> + walk_start = walk_end = p.arg.start; >> + for (; walk_end != p.arg.end; walk_start = walk_end) { >> + int n_out; >> + >> + walk_end = min_t(unsigned long, >> + (walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, >> + p.arg.end); >> + > > if (fatal_signal_pending(current)) { > ret = EINTR; > break; > } > >> + ret = mmap_read_lock_killable(mm); >> + if (ret) >> + break; >> + ret = walk_page_range(mm, walk_start, walk_end, >> + &pagemap_scan_ops, &p); >> + mmap_read_unlock(mm); >> + >> + n_out = pagemap_scan_flush_buffer(&p); >> + if (n_out < 0) >> + ret = n_out; >> + else >> + n_ranges_out += n_out; >> + >> + if (ret) >> + break; >> + } >> + >> + if (p.cur_buf.start != p.cur_buf.end) { >> + if (copy_to_user(p.vec_out, &p.cur_buf, sizeof(p.cur_buf))) >> + ret = -EFAULT; >> + else >> + ++n_ranges_out; >> + } >> + >> + /* ENOSPC signifies early stop (buffer full) from the walk. */ >> + if (!ret || ret == -ENOSPC) >> + ret = n_ranges_out; >> + >> + p.arg.walk_end = p.end_addr ? p.end_addr : walk_start; >> + if (pagemap_scan_writeback_args(&p.arg, uarg)) >> + ret = -EFAULT; >> + >> + if (p.arg.flags & PM_SCAN_WP_MATCHING) >> + mmu_notifier_invalidate_range_end(&range); >> + >> + kfree(p.vec_buf); >> + return ret; >> +} >> + >> +static long do_pagemap_cmd(struct file *file, unsigned int cmd, >> + unsigned long arg) >> +{ >> + struct mm_struct *mm = file->private_data; >> + >> + switch (cmd) { >> + case PAGEMAP_SCAN: >> + return do_pagemap_scan(mm, arg); >> + >> + default: >> + return -EINVAL; >> + } >> +} >> + >> const struct file_operations proc_pagemap_operations = { >> .llseek = mem_lseek, /* borrow this */ >> .read = pagemap_read, >> .open = pagemap_open, >> .release = pagemap_release, >> + .unlocked_ioctl = do_pagemap_cmd, >> + .compat_ioctl = do_pagemap_cmd, >> }; >> #endif /* CONFIG_PROC_PAGE_MONITOR */ >> >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >> index 0a393bc02f25b..8f8ff07453f22 100644 >> --- a/include/linux/hugetlb.h >> +++ b/include/linux/hugetlb.h >> @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, >> unsigned long cp_flags); >> >> bool is_hugetlb_entry_migration(pte_t pte); >> +bool is_hugetlb_entry_hwpoisoned(pte_t pte); >> void hugetlb_unshare_all_pmds(struct vm_area_struct *vma); >> >> #else /* !CONFIG_HUGETLB_PAGE */ >> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h >> index b7b56871029c5..1bb3c625c2381 100644 >> --- a/include/uapi/linux/fs.h >> +++ b/include/uapi/linux/fs.h >> @@ -305,4 +305,62 @@ typedef int __bitwise __kernel_rwf_t; >> #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ >> RWF_APPEND) >> >> +/* Pagemap ioctl */ >> +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) >> + >> +/* Bits are set in flags of the page_region and masks in pm_scan_args */ >> +#define PAGE_IS_WPALLOWED (1 << 0) >> +#define PAGE_IS_WRITTEN (1 << 1) >> +#define PAGE_IS_FILE (1 << 2) >> +#define PAGE_IS_PRESENT (1 << 3) >> +#define PAGE_IS_SWAPPED (1 << 4) >> +#define PAGE_IS_PFNZERO (1 << 5) >> + >> +/* >> + * struct page_region - Page region with flags >> + * @start: Start of the region >> + * @end: End of the region (exclusive) >> + * @categories: PAGE_IS_* category bitmask for the region >> + */ >> +struct page_region { >> + __u64 start; >> + __u64 end; >> + __u64 categories; >> +}; >> + >> +/* Flags for PAGEMAP_SCAN ioctl */ >> +#define PM_SCAN_WP_MATCHING (1 << 0) /* Write protect the pages matched. */ >> +#define PM_SCAN_CHECK_WPASYNC (1 << 1) /* Abort the scan when a non-WP-enabled page is found. */ >> + >> +/* >> + * struct pm_scan_arg - Pagemap ioctl argument >> + * @size: Size of the structure >> + * @flags: Flags for the IOCTL >> + * @start: Starting address of the region >> + * @end: Ending address of the region >> + * @walk_end: Ending address of the visited memory is returned >> + * (This helps if entire range hasn't been visited) >> + * @vec: Address of page_region struct array for output >> + * @vec_len: Length of the page_region struct array >> + * @max_pages: Optional limit for number of returned pages (0 = disabled) >> + * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1 >> + * @category_mask: Skip pages for which any category doesn't match >> + * @category_anyof_mask: Skip pages for which no category matches >> + * @return_mask: PAGE_IS_* categories that are to be reported in `page_region`s returned >> + */ >> +struct pm_scan_arg { >> + __u64 size; >> + __u64 flags; >> + __u64 start; >> + __u64 end; >> + __u64 walk_end; >> + __u64 vec; >> + __u64 vec_len; >> + __u64 max_pages; >> + __u64 category_inverted; >> + __u64 category_mask; >> + __u64 category_anyof_mask; >> + __u64 return_mask; >> +}; >> + >> #endif /* _UAPI_LINUX_FS_H */ >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index a073e6ed8900b..3b07db0a4f2d9 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -5008,7 +5008,7 @@ bool is_hugetlb_entry_migration(pte_t pte) >> return false; >> } >> >> -static bool is_hugetlb_entry_hwpoisoned(pte_t pte) >> +bool is_hugetlb_entry_hwpoisoned(pte_t pte) >> { >> swp_entry_t swp; >> >> -- >> 2.39.2 >>
On Thu, Aug 3, 2023 at 8:25 AM Michał Mirosław <emmir@google.com> wrote: > > On Thu, 3 Aug 2023 at 17:09, Andrei Vagin <avagin@gmail.com> wrote: > > On Thu, Jul 27, 2023 at 02:36:34PM +0500, Muhammad Usama Anjum wrote: > [...] > > > + n_pages = (*end - addr) / PAGE_SIZE; > > > + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || > > > + total_pages > p->arg.max_pages) { > > > > why do we need to use check_add_overflow here? > > > > > + size_t n_too_much = total_pages - p->arg.max_pages; > > > > it is unsafe to use total_pages if check_add_overflow returns non-zero. > > Since we're adding unsigned integers, this is well defined even after overflow. The description of check_add_overflow declares that is unsafe: https://elixir.bootlin.com/linux/latest/source/include/linux/overflow.h#L62 It actually doesn't matter, because it should be impossible to overflow total_pages and we can consider not to use check_add_overflow here. > > Best Regards > Michał Mirosław
On Fri, 4 Aug 2023 at 17:59, Andrei Vagin <avagin@gmail.com> wrote: > > On Thu, Aug 3, 2023 at 8:25 AM Michał Mirosław <emmir@google.com> wrote: > > > > On Thu, 3 Aug 2023 at 17:09, Andrei Vagin <avagin@gmail.com> wrote: > > > On Thu, Jul 27, 2023 at 02:36:34PM +0500, Muhammad Usama Anjum wrote: > > [...] > > > > + n_pages = (*end - addr) / PAGE_SIZE; > > > > + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || > > > > + total_pages > p->arg.max_pages) { > > > > > > why do we need to use check_add_overflow here? > > > > > > > + size_t n_too_much = total_pages - p->arg.max_pages; > > > > > > it is unsafe to use total_pages if check_add_overflow returns non-zero. > > > > Since we're adding unsigned integers, this is well defined even after overflow. > > The description of check_add_overflow declares that is unsafe: > https://elixir.bootlin.com/linux/latest/source/include/linux/overflow.h#L62 > > It actually doesn't matter, because it should be impossible to > overflow total_pages > and we can consider not to use check_add_overflow here. It seems the doc warning is quite new (d219d2a9a92e / Mon Aug 29 13:37:17 2022 -0700). The underlying __builtin_add_overflow() is well-defined for any integer type, though. Even staying with C99, arithmetic on unsigned integers is always defined as being done modulo 2^n. Best Regards Michał Mirosław
On Thu, Jul 27, 2023 at 2:37 AM Muhammad Usama Anjum <usama.anjum@collabora.com> wrote: > <snip> > +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) > +{ > + unsigned long walk_start, walk_end; > + struct mmu_notifier_range range; > + struct pagemap_scan_private p; > + size_t n_ranges_out = 0; > + int ret; > + > + memset(&p, 0, sizeof(p)); > + ret = pagemap_scan_get_args(&p.arg, uarg); > + if (ret) > + return ret; > + > + ret = pagemap_scan_init_bounce_buffer(&p); > + if (ret) > + return ret; > + > + /* Protection change for the range is going to happen. */ > + if (p.arg.flags & PM_SCAN_WP_MATCHING) { > + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, > + mm, p.arg.start, p.arg.end); > + mmu_notifier_invalidate_range_start(&range); > + } > + > + walk_start = walk_end = p.arg.start; > + for (; walk_end != p.arg.end; walk_start = walk_end) { > + int n_out; > + > + walk_end = min_t(unsigned long, > + (walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, > + p.arg.end); This approach has performance implications. The basic program that scans its address space takes around 20-30 seconds, but it has just a few small mappings. The first optimization that comes to mind is to remove the PAGEMAP_WALK_SIZE limit and instead halt walk_page_range when the bounce buffer is full. After draining the buffer, the walk_page_range function can be restarted. The test program and perf data can be found here: https://gist.github.com/avagin/c5a22f3c78f8cb34281602dfe9c43d10 > + > + ret = mmap_read_lock_killable(mm); > + if (ret) > + break; > + ret = walk_page_range(mm, walk_start, walk_end, > + &pagemap_scan_ops, &p); > + mmap_read_unlock(mm); > + > + n_out = pagemap_scan_flush_buffer(&p); > + if (n_out < 0) > + ret = n_out; > + else > + n_ranges_out += n_out; > + > + if (ret) > + break; > + } > + Thanks, Andrei
On 8/5/23 2:53 AM, Andrei Vagin wrote: > On Thu, Jul 27, 2023 at 2:37 AM Muhammad Usama Anjum > <usama.anjum@collabora.com> wrote: >> > > <snip> > >> +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) >> +{ >> + unsigned long walk_start, walk_end; >> + struct mmu_notifier_range range; >> + struct pagemap_scan_private p; >> + size_t n_ranges_out = 0; >> + int ret; >> + >> + memset(&p, 0, sizeof(p)); >> + ret = pagemap_scan_get_args(&p.arg, uarg); >> + if (ret) >> + return ret; >> + >> + ret = pagemap_scan_init_bounce_buffer(&p); >> + if (ret) >> + return ret; >> + >> + /* Protection change for the range is going to happen. */ >> + if (p.arg.flags & PM_SCAN_WP_MATCHING) { >> + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, >> + mm, p.arg.start, p.arg.end); >> + mmu_notifier_invalidate_range_start(&range); >> + } >> + >> + walk_start = walk_end = p.arg.start; >> + for (; walk_end != p.arg.end; walk_start = walk_end) { >> + int n_out; >> + >> + walk_end = min_t(unsigned long, >> + (walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, >> + p.arg.end); > > This approach has performance implications. The basic program that scans > its address space takes around 20-30 seconds, but it has just a few > small mappings. The first optimization that comes to mind is to remove > the PAGEMAP_WALK_SIZE limit and instead halt walk_page_range when the > bounce buffer is full. After draining the buffer, the walk_page_range > function can be restarted. Yeah, I've this implemented in WIP and will be posting in next revision. > > The test program and perf data can be found here: > https://gist.github.com/avagin/c5a22f3c78f8cb34281602dfe9c43d10 > >> + >> + ret = mmap_read_lock_killable(mm); >> + if (ret) >> + break; >> + ret = walk_page_range(mm, walk_start, walk_end, >> + &pagemap_scan_ops, &p); >> + mmap_read_unlock(mm); >> + >> + n_out = pagemap_scan_flush_buffer(&p); >> + if (n_out < 0) >> + ret = n_out; >> + else >> + n_ranges_out += n_out; >> + >> + if (ret) >> + break; >> + } >> + > > Thanks, > Andrei
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index c1e6531cb02ae..8e000a0f779db 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -19,6 +19,8 @@ #include <linux/shmem_fs.h> #include <linux/uaccess.h> #include <linux/pkeys.h> +#include <linux/minmax.h> +#include <linux/overflow.h> #include <asm/elf.h> #include <asm/tlb.h> @@ -1749,11 +1751,662 @@ static int pagemap_release(struct inode *inode, struct file *file) return 0; } +#define PM_SCAN_CATEGORIES (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | \ + PAGE_IS_FILE | PAGE_IS_PRESENT | \ + PAGE_IS_SWAPPED | PAGE_IS_PFNZERO) +#define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC) + +struct pagemap_scan_private { + struct pm_scan_arg arg; + unsigned long cur_vma_category; + struct page_region *vec_buf, cur_buf; + unsigned long vec_buf_len, vec_buf_index, found_pages, end_addr; + struct page_region __user *vec_out; +}; + +static unsigned long pagemap_page_category(struct vm_area_struct *vma, + unsigned long addr, pte_t pte) +{ + unsigned long categories = 0; + + if (pte_present(pte)) { + struct page *page = vm_normal_page(vma, addr, pte); + + categories |= PAGE_IS_PRESENT; + if (!pte_uffd_wp(pte)) + categories |= PAGE_IS_WRITTEN; + if (page && !PageAnon(page)) + categories |= PAGE_IS_FILE; + if (is_zero_pfn(pte_pfn(pte))) + categories |= PAGE_IS_PFNZERO; + } else if (is_swap_pte(pte)) { + swp_entry_t swp = pte_to_swp_entry(pte); + + categories |= PAGE_IS_SWAPPED; + if (!pte_swp_uffd_wp_any(pte)) + categories |= PAGE_IS_WRITTEN; + if (is_pfn_swap_entry(swp) && !PageAnon(pfn_swap_entry_to_page(swp))) + categories |= PAGE_IS_FILE; + } + + return categories; +} + +static void make_uffd_wp_pte(struct vm_area_struct *vma, + unsigned long addr, pte_t *pte) +{ + pte_t ptent = ptep_get(pte); + + if (pte_present(ptent)) { + pte_t old_pte; + + old_pte = ptep_modify_prot_start(vma, addr, pte); + ptent = pte_mkuffd_wp(ptent); + ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); + } else if (is_swap_pte(ptent)) { + ptent = pte_swp_mkuffd_wp(ptent); + set_pte_at(vma->vm_mm, addr, pte, ptent); + } else { + set_pte_at(vma->vm_mm, addr, pte, + make_pte_marker(PTE_MARKER_UFFD_WP)); + } +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static unsigned long pagemap_thp_category(pmd_t pmd) +{ + unsigned long categories = 0; + + if (pmd_present(pmd)) { + categories |= PAGE_IS_PRESENT; + if (!pmd_uffd_wp(pmd)) + categories |= PAGE_IS_WRITTEN; + if (is_zero_pfn(pmd_pfn(pmd))) + categories |= PAGE_IS_PFNZERO; + } else if (is_swap_pmd(pmd)) { + categories |= PAGE_IS_SWAPPED; + if (!pmd_swp_uffd_wp(pmd)) + categories |= PAGE_IS_WRITTEN; + } + + return categories; +} + +static void make_uffd_wp_pmd(struct vm_area_struct *vma, + unsigned long addr, pmd_t *pmdp) +{ + pmd_t old, pmd = *pmdp; + + if (pmd_present(pmd)) { + old = pmdp_invalidate_ad(vma, addr, pmdp); + pmd = pmd_mkuffd_wp(old); + set_pmd_at(vma->vm_mm, addr, pmdp, pmd); + } else if (is_migration_entry(pmd_to_swp_entry(pmd))) { + pmd = pmd_swp_mkuffd_wp(pmd); + set_pmd_at(vma->vm_mm, addr, pmdp, pmd); + } +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + +#ifdef CONFIG_HUGETLB_PAGE +static unsigned long pagemap_hugetlb_category(pte_t pte) +{ + unsigned long categories = 0; + + if (pte_present(pte)) { + categories |= PAGE_IS_PRESENT; + if (!huge_pte_uffd_wp(pte)) + categories |= PAGE_IS_WRITTEN; + if (!PageAnon(pte_page(pte))) + categories |= PAGE_IS_FILE; + if (is_zero_pfn(pte_pfn(pte))) + categories |= PAGE_IS_PFNZERO; + } else if (is_swap_pte(pte)) { + categories |= PAGE_IS_SWAPPED; + if (!pte_swp_uffd_wp_any(pte)) + categories |= PAGE_IS_WRITTEN; + } + + return categories; +} + +static void make_uffd_wp_huge_pte(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + pte_t ptent) +{ + if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent)) + return; + + if (is_hugetlb_entry_migration(ptent)) + set_huge_pte_at(vma->vm_mm, addr, ptep, + pte_swp_mkuffd_wp(ptent)); + else if (!huge_pte_none(ptent)) + huge_ptep_modify_prot_commit(vma, addr, ptep, ptent, + huge_pte_mkuffd_wp(ptent)); + else + set_huge_pte_at(vma->vm_mm, addr, ptep, + make_pte_marker(PTE_MARKER_UFFD_WP)); +} +#endif /* CONFIG_HUGETLB_PAGE */ + +static bool pagemap_scan_is_interesting_page(unsigned long categories, + const struct pagemap_scan_private *p) +{ + categories ^= p->arg.category_inverted; + if ((categories & p->arg.category_mask) != p->arg.category_mask) + return false; + if (p->arg.category_anyof_mask && !(categories & p->arg.category_anyof_mask)) + return false; + + return true; +} + +static bool pagemap_scan_is_interesting_vma(unsigned long categories, + const struct pagemap_scan_private *p) +{ + unsigned long required = p->arg.category_mask & PAGE_IS_WPALLOWED; + + categories ^= p->arg.category_inverted; + if ((categories & required) != required) + return false; + + return true; +} + +static int pagemap_scan_test_walk(unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + unsigned long vma_category = 0; + + if (userfaultfd_wp_async(vma) && userfaultfd_wp_use_markers(vma)) + vma_category |= PAGE_IS_WPALLOWED; + else if (p->arg.flags & PM_SCAN_CHECK_WPASYNC) + return -EPERM; + + if (vma->vm_flags & VM_PFNMAP) + return 1; + + if (!pagemap_scan_is_interesting_vma(vma_category, p)) + return 1; + + p->cur_vma_category = vma_category; + + return 0; +} + +static bool pagemap_scan_push_range(unsigned long categories, + struct pagemap_scan_private *p, + unsigned long addr, unsigned long end) +{ + struct page_region *cur_buf = &p->cur_buf; + + /* + * When there is no output buffer provided at all, the sentinel values + * won't match here. There is no other way for `cur_buf->end` to be + * non-zero other than it being non-empty. + */ + if (addr == cur_buf->end && categories == cur_buf->categories) { + cur_buf->end = end; + return true; + } + + if (cur_buf->end) { + if (p->vec_buf_index >= p->vec_buf_len) + return false; + + memcpy(&p->vec_buf[p->vec_buf_index], cur_buf, + sizeof(*p->vec_buf)); + ++p->vec_buf_index; + } + + cur_buf->start = addr; + cur_buf->end = end; + cur_buf->categories = categories; + + return true; +} + +static void pagemap_scan_backout_range(struct pagemap_scan_private *p, + unsigned long addr, unsigned long end, + unsigned long end_addr) +{ + struct page_region *cur_buf = &p->cur_buf; + + if (cur_buf->start != addr) + cur_buf->end = addr; + else + cur_buf->start = cur_buf->end = 0; + + p->end_addr = end_addr; + p->found_pages -= (end - addr) / PAGE_SIZE; +} + +static int pagemap_scan_output(unsigned long categories, + struct pagemap_scan_private *p, + unsigned long addr, unsigned long *end) +{ + unsigned long n_pages, total_pages; + int ret = 0; + + if (!pagemap_scan_is_interesting_page(categories, p)) { + *end = addr; + return 0; + } + + if (!p->vec_buf) + return 0; + + categories &= p->arg.return_mask; + + n_pages = (*end - addr) / PAGE_SIZE; + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || + total_pages > p->arg.max_pages) { + size_t n_too_much = total_pages - p->arg.max_pages; + *end -= n_too_much * PAGE_SIZE; + n_pages -= n_too_much; + ret = -ENOSPC; + } + + if (!pagemap_scan_push_range(categories, p, addr, *end)) { + *end = addr; + n_pages = 0; + ret = -ENOSPC; + } + + p->found_pages += n_pages; + if (ret) + p->end_addr = *end; + + return ret; +} + +static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start, + unsigned long end, struct mm_walk *walk) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + unsigned long categories; + spinlock_t *ptl; + int ret = 0; + + ptl = pmd_trans_huge_lock(pmd, vma); + if (!ptl) + return -ENOENT; + + categories = p->cur_vma_category | pagemap_thp_category(*pmd); + + ret = pagemap_scan_output(categories, p, start, &end); + if (start == end) + goto out_unlock; + + if (~p->arg.flags & PM_SCAN_WP_MATCHING) + goto out_unlock; + if (~categories & PAGE_IS_WRITTEN) + goto out_unlock; + + /* + * Break huge page into small pages if the WP operation + * need to be performed is on a portion of the huge page. + */ + if (end != start + HPAGE_SIZE) { + spin_unlock(ptl); + split_huge_pmd(vma, pmd, start); + pagemap_scan_backout_range(p, start, end, 0); + return -ENOENT; + } + + make_uffd_wp_pmd(vma, start, pmd); + flush_tlb_range(vma, start, end); +out_unlock: + spin_unlock(ptl); + return ret; +#else /* !CONFIG_TRANSPARENT_HUGEPAGE */ + return -ENOENT; +#endif +} + +static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, + unsigned long end, struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + pte_t *pte, *start_pte; + unsigned long addr; + bool flush = false; + spinlock_t *ptl; + int ret; + + arch_enter_lazy_mmu_mode(); + + ret = pagemap_scan_thp_entry(pmd, start, end, walk); + if (ret != -ENOENT) { + arch_leave_lazy_mmu_mode(); + return ret; + } + + start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); + if (!pte) { + arch_leave_lazy_mmu_mode(); + walk->action = ACTION_AGAIN; + return 0; + } + + for (addr = start; addr != end; pte++, addr += PAGE_SIZE) { + unsigned long categories = p->cur_vma_category | + pagemap_page_category(vma, addr, ptep_get(pte)); + unsigned long next = addr + PAGE_SIZE; + + ret = pagemap_scan_output(categories, p, addr, &next); + if (next == addr) { + if (!ret) + continue; + break; + } + + if (~p->arg.flags & PM_SCAN_WP_MATCHING) + continue; + if (~categories & PAGE_IS_WRITTEN) + continue; + + make_uffd_wp_pte(vma, addr, pte); + if (!flush) { + start = addr; + flush = true; + } + } + + if (flush) + flush_tlb_range(vma, start, addr); + + pte_unmap_unlock(start_pte, ptl); + arch_leave_lazy_mmu_mode(); + + cond_resched(); + return ret; +} + +#ifdef CONFIG_HUGETLB_PAGE +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, + unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + unsigned long categories; + spinlock_t *ptl; + int ret = 0; + pte_t pte; + + if (~p->arg.flags & PM_SCAN_WP_MATCHING) { + /* Go the short route when not write-protecting pages. */ + + pte = huge_ptep_get(ptep); + categories = p->cur_vma_category | pagemap_hugetlb_category(pte); + + return pagemap_scan_output(categories, p, start, &end); + } + + i_mmap_lock_write(vma->vm_file->f_mapping); + ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep); + + pte = huge_ptep_get(ptep); + categories = p->cur_vma_category | pagemap_hugetlb_category(pte); + + ret = pagemap_scan_output(categories, p, start, &end); + if (start == end) + goto out_unlock; + + if (~categories & PAGE_IS_WRITTEN) + goto out_unlock; + + if (end != start + HPAGE_SIZE) { + /* Partial HugeTLB page WP isn't possible. */ + pagemap_scan_backout_range(p, start, end, start); + ret = -EINVAL; + goto out_unlock; + } + + make_uffd_wp_huge_pte(vma, start, ptep, pte); + flush_hugetlb_tlb_range(vma, start, end); + +out_unlock: + spin_unlock(ptl); + i_mmap_unlock_write(vma->vm_file->f_mapping); + + return ret; +} +#else +#define pagemap_scan_hugetlb_entry NULL +#endif + +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, + int depth, struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + int ret, err; + + if (!vma) + return 0; + + ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end); + if (addr == end) + return ret; + + if (~p->arg.flags & PM_SCAN_WP_MATCHING) + return ret; + + err = uffd_wp_range(vma, addr, end - addr, true); + if (err < 0) + ret = err; + + return ret; +} + +static const struct mm_walk_ops pagemap_scan_ops = { + .test_walk = pagemap_scan_test_walk, + .pmd_entry = pagemap_scan_pmd_entry, + .pte_hole = pagemap_scan_pte_hole, + .hugetlb_entry = pagemap_scan_hugetlb_entry, +}; + +static int pagemap_scan_get_args(struct pm_scan_arg *arg, + unsigned long uarg) +{ + if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg))) + return -EFAULT; + + if (arg->size != sizeof(struct pm_scan_arg)) + return -EINVAL; + + /* Validate requested features */ + if (arg->flags & ~PM_SCAN_FLAGS) + return -EINVAL; + if ((arg->category_inverted | arg->category_mask | + arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES) + return -EINVAL; + + arg->start = untagged_addr((unsigned long)arg->start); + arg->end = untagged_addr((unsigned long)arg->end); + arg->vec = untagged_addr((unsigned long)arg->vec); + + /* Validate memory pointers */ + if (!IS_ALIGNED(arg->start, PAGE_SIZE)) + return -EINVAL; + if (!access_ok((void __user *)arg->start, arg->end - arg->start)) + return -EFAULT; + if (!arg->vec && arg->vec_len) + return -EFAULT; + if (arg->vec && !access_ok((void __user *)arg->vec, + arg->vec_len * sizeof(struct page_region))) + return -EFAULT; + + /* Fixup default values */ + arg->end = ALIGN(arg->end, PAGE_SIZE); + if (!arg->max_pages) + arg->max_pages = ULONG_MAX; + + return 0; +} + +static int pagemap_scan_writeback_args(struct pm_scan_arg *arg, + unsigned long uargl) +{ + struct pm_scan_arg __user *uarg = (void __user *)uargl; + + if (copy_to_user(&uarg->walk_end, &arg->walk_end, sizeof(arg->walk_end))) + return -EFAULT; + + return 0; +} + +static int pagemap_scan_init_bounce_buffer(struct pagemap_scan_private *p) +{ + if (!p->arg.vec_len) { + /* + * An arbitrary non-page-aligned sentinel value for + * pagemap_scan_push_range(). + */ + p->cur_buf.start = p->cur_buf.end = ULLONG_MAX; + if (p->arg.vec) + p->vec_buf = ZERO_SIZE_PTR; + return 0; + } + + /* + * Allocate a smaller buffer to get output from inside the page + * walk functions and walk the range in PAGEMAP_WALK_SIZE chunks. + * The last range is always stored in p.cur_buf to allow coalescing + * consecutive ranges that have the same categories returned across + * walk_page_range() calls. + */ + p->vec_buf_len = min_t(size_t, PAGEMAP_WALK_SIZE >> PAGE_SHIFT, + p->arg.vec_len - 1); + p->vec_buf = kmalloc_array(p->vec_buf_len, sizeof(*p->vec_buf), + GFP_KERNEL); + if (!p->vec_buf) + return -ENOMEM; + + p->vec_out = (struct page_region __user *)p->arg.vec; + + return 0; +} + +static int pagemap_scan_flush_buffer(struct pagemap_scan_private *p) +{ + const struct page_region *buf = p->vec_buf; + int n = (int)p->vec_buf_index; + + if (!n) + return 0; + + if (copy_to_user(p->vec_out, buf, n * sizeof(*buf))) + return -EFAULT; + + p->arg.vec_len -= n; + p->vec_out += n; + + p->vec_buf_index = 0; + p->vec_buf_len = min_t(size_t, p->vec_buf_len, p->arg.vec_len - 1); + + return n; +} + +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) +{ + unsigned long walk_start, walk_end; + struct mmu_notifier_range range; + struct pagemap_scan_private p; + size_t n_ranges_out = 0; + int ret; + + memset(&p, 0, sizeof(p)); + ret = pagemap_scan_get_args(&p.arg, uarg); + if (ret) + return ret; + + ret = pagemap_scan_init_bounce_buffer(&p); + if (ret) + return ret; + + /* Protection change for the range is going to happen. */ + if (p.arg.flags & PM_SCAN_WP_MATCHING) { + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, + mm, p.arg.start, p.arg.end); + mmu_notifier_invalidate_range_start(&range); + } + + walk_start = walk_end = p.arg.start; + for (; walk_end != p.arg.end; walk_start = walk_end) { + int n_out; + + walk_end = min_t(unsigned long, + (walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, + p.arg.end); + + ret = mmap_read_lock_killable(mm); + if (ret) + break; + ret = walk_page_range(mm, walk_start, walk_end, + &pagemap_scan_ops, &p); + mmap_read_unlock(mm); + + n_out = pagemap_scan_flush_buffer(&p); + if (n_out < 0) + ret = n_out; + else + n_ranges_out += n_out; + + if (ret) + break; + } + + if (p.cur_buf.start != p.cur_buf.end) { + if (copy_to_user(p.vec_out, &p.cur_buf, sizeof(p.cur_buf))) + ret = -EFAULT; + else + ++n_ranges_out; + } + + /* ENOSPC signifies early stop (buffer full) from the walk. */ + if (!ret || ret == -ENOSPC) + ret = n_ranges_out; + + p.arg.walk_end = p.end_addr ? p.end_addr : walk_start; + if (pagemap_scan_writeback_args(&p.arg, uarg)) + ret = -EFAULT; + + if (p.arg.flags & PM_SCAN_WP_MATCHING) + mmu_notifier_invalidate_range_end(&range); + + kfree(p.vec_buf); + return ret; +} + +static long do_pagemap_cmd(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct mm_struct *mm = file->private_data; + + switch (cmd) { + case PAGEMAP_SCAN: + return do_pagemap_scan(mm, arg); + + default: + return -EINVAL; + } +} + const struct file_operations proc_pagemap_operations = { .llseek = mem_lseek, /* borrow this */ .read = pagemap_read, .open = pagemap_open, .release = pagemap_release, + .unlocked_ioctl = do_pagemap_cmd, + .compat_ioctl = do_pagemap_cmd, }; #endif /* CONFIG_PROC_PAGE_MONITOR */ diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 0a393bc02f25b..8f8ff07453f22 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long cp_flags); bool is_hugetlb_entry_migration(pte_t pte); +bool is_hugetlb_entry_hwpoisoned(pte_t pte); void hugetlb_unshare_all_pmds(struct vm_area_struct *vma); #else /* !CONFIG_HUGETLB_PAGE */ diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index b7b56871029c5..1bb3c625c2381 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -305,4 +305,62 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND) +/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) + +/* Bits are set in flags of the page_region and masks in pm_scan_args */ +#define PAGE_IS_WPALLOWED (1 << 0) +#define PAGE_IS_WRITTEN (1 << 1) +#define PAGE_IS_FILE (1 << 2) +#define PAGE_IS_PRESENT (1 << 3) +#define PAGE_IS_SWAPPED (1 << 4) +#define PAGE_IS_PFNZERO (1 << 5) + +/* + * struct page_region - Page region with flags + * @start: Start of the region + * @end: End of the region (exclusive) + * @categories: PAGE_IS_* category bitmask for the region + */ +struct page_region { + __u64 start; + __u64 end; + __u64 categories; +}; + +/* Flags for PAGEMAP_SCAN ioctl */ +#define PM_SCAN_WP_MATCHING (1 << 0) /* Write protect the pages matched. */ +#define PM_SCAN_CHECK_WPASYNC (1 << 1) /* Abort the scan when a non-WP-enabled page is found. */ + +/* + * struct pm_scan_arg - Pagemap ioctl argument + * @size: Size of the structure + * @flags: Flags for the IOCTL + * @start: Starting address of the region + * @end: Ending address of the region + * @walk_end: Ending address of the visited memory is returned + * (This helps if entire range hasn't been visited) + * @vec: Address of page_region struct array for output + * @vec_len: Length of the page_region struct array + * @max_pages: Optional limit for number of returned pages (0 = disabled) + * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1 + * @category_mask: Skip pages for which any category doesn't match + * @category_anyof_mask: Skip pages for which no category matches + * @return_mask: PAGE_IS_* categories that are to be reported in `page_region`s returned + */ +struct pm_scan_arg { + __u64 size; + __u64 flags; + __u64 start; + __u64 end; + __u64 walk_end; + __u64 vec; + __u64 vec_len; + __u64 max_pages; + __u64 category_inverted; + __u64 category_mask; + __u64 category_anyof_mask; + __u64 return_mask; +}; + #endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a073e6ed8900b..3b07db0a4f2d9 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5008,7 +5008,7 @@ bool is_hugetlb_entry_migration(pte_t pte) return false; } -static bool is_hugetlb_entry_hwpoisoned(pte_t pte) +bool is_hugetlb_entry_hwpoisoned(pte_t pte) { swp_entry_t swp;