This IOCTL, PAGEMAP_SCAN 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 are soft-dirty, file mapped, present
or swapped.
- Clear the soft-dirty PTE bit of the pages.
- Get and clear the soft-dirty PTE bit of the pages.
Only the soft-dirty bit can be read and cleared atomically. struct
pagemap_sd_args is used as the argument of the IOCTL. In this struct:
- The range is specified through start and len.
- The output buffer and size is specified as vec and vec_len.
- The optional maximum requested pages are specified in the max_pages.
- The flags can be specified in the flags field. The PAGEMAP_SD_CLEAR
and PAGEMAP_SD_NO_REUSED_REGIONS are supported.
- The masks are specified in rmask, amask, emask and return_mask.
This IOCTL can be extended to get information about more PTE bits.
This is based on a patch from Gabriel Krisman Bertazi.
Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
---
Changes in v4:
- Update the interface and implementation
Changes in v3:
- Tighten the user-kernel interface by using explicit types and add more
error checking
Changes in v2:
- Convert the interface from syscall to ioctl
- Remove pidfd support as it doesn't make sense in ioctl
---
fs/proc/task_mmu.c | 318 ++++++++++++++++++++++++++++++++++
include/uapi/linux/fs.h | 53 ++++++
tools/include/uapi/linux/fs.h | 53 ++++++
3 files changed, 424 insertions(+)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8235c536ac70..61892142cd5a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -19,6 +19,9 @@
#include <linux/shmem_fs.h>
#include <linux/uaccess.h>
#include <linux/pkeys.h>
+#include <uapi/linux/fs.h>
+#include <linux/vmalloc.h>
+#include <linux/minmax.h>
#include <asm/elf.h>
#include <asm/tlb.h>
@@ -1775,11 +1778,326 @@ static int pagemap_release(struct inode *inode, struct file *file)
return 0;
}
+#ifdef CONFIG_MEM_SOFT_DIRTY
+
+#define PAGEMAP_OP_MASK (PAGE_IS_SD | PAGE_IS_FILE | \
+ PAGE_IS_PRESENT | PAGE_IS_SWAPED)
+#define PAGEMAP_NON_SD_MASK (PAGE_IS_FILE | PAGE_IS_PRESENT | PAGE_IS_SWAPED)
+#define PAGEMAP_SD_FLAGS_MASK (PAGEMAP_SD_CLEAR | PAGEMAP_NO_REUSED_REGIONS)
+#define IS_CLEAR_OP(flags) (flags & PAGEMAP_SD_CLEAR)
+#define IS_GET_OP(vec) (vec)
+
+struct pagemap_scan_private {
+ struct page_region *vec;
+ unsigned long vec_len;
+ unsigned long index;
+ unsigned int max_pages;
+ unsigned int found_pages;
+ unsigned int flags;
+ unsigned int rmask;
+ unsigned int amask;
+ unsigned int emask;
+ unsigned int return_mask;
+};
+
+static int add_to_out(bool sd, bool file, bool pres, bool swap, struct pagemap_scan_private *p,
+ unsigned long addr, unsigned int len)
+{
+ unsigned int bitmap, cpy = true, cur = sd | file << 1 | pres << 2 | swap << 3;
+
+ if (p->rmask)
+ cpy = ((p->rmask & cur) == p->rmask) ? true : false;
+ if (cpy && p->amask)
+ cpy = (p->amask & cur) ? true : false;
+ if (cpy && p->emask)
+ cpy = (p->emask & cur) ? false : true;
+
+ bitmap = cur & p->return_mask;
+
+ if (cpy && bitmap) {
+ if (p->index && p->vec[p->index - 1].bitmap == bitmap &&
+ p->vec[p->index - 1].start + p->vec[p->index - 1].len * PAGE_SIZE == addr) {
+ p->vec[p->index - 1].len += len;
+ p->found_pages += len;
+ } else if (p->index < p->vec_len) {
+ p->vec[p->index].start = addr;
+ p->vec[p->index].len = len;
+ p->vec[p->index].bitmap = bitmap;
+ p->index++;
+ p->found_pages += len;
+ } else {
+ return -ENOMEM;
+ }
+ }
+
+ return 0;
+}
+
+static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long addr,
+ unsigned long end, struct mm_walk *walk)
+{
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ unsigned long start = addr;
+ int dirty, ret = 0;
+ spinlock_t *ptl;
+ pte_t *pte;
+ bool dirty_vma = (p->flags & PAGEMAP_NO_REUSED_REGIONS) ?
+ (false) : (vma->vm_flags & VM_SOFTDIRTY);
+
+ if ((walk->vma->vm_end < addr) || (p->max_pages && p->found_pages == p->max_pages))
+ return 0;
+
+ end = min(end, walk->vma->vm_end);
+
+ ptl = pmd_trans_huge_lock(pmd, vma);
+ if (ptl) {
+ if (dirty_vma || check_soft_dirty_pmd(vma, addr, pmd, false)) {
+ /*
+ * Break huge page into small pages if operation needs to be performed is
+ * on a portion of the huge page or the return buffer cannot store complete
+ * data.
+ */
+ if ((IS_CLEAR_OP(p->flags) && (end - addr < HPAGE_SIZE)) ||
+ (IS_GET_OP(p->vec) && p->max_pages &&
+ (p->found_pages + HPAGE_SIZE/PAGE_SIZE > p->max_pages))) {
+ spin_unlock(ptl);
+ split_huge_pmd(vma, pmd, addr);
+ goto process_smaller_pages;
+ } else {
+ dirty = check_soft_dirty_pmd(vma, addr, pmd, IS_CLEAR_OP(p->flags));
+ if (IS_GET_OP(p->vec))
+ add_to_out(dirty_vma || dirty, vma->vm_file,
+ pmd_present(*pmd), is_swap_pmd(*pmd), p,
+ addr, (end - addr)/PAGE_SIZE);
+ }
+ }
+ spin_unlock(ptl);
+ return 0;
+ }
+
+process_smaller_pages:
+ if (pmd_trans_unstable(pmd))
+ return 0;
+
+ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+ for (; addr < end && !ret; pte++, addr += PAGE_SIZE) {
+ dirty = check_soft_dirty(vma, addr, pte, IS_CLEAR_OP(p->flags));
+ if (IS_GET_OP(p->vec)) {
+ ret = add_to_out(dirty_vma || dirty, vma->vm_file, pte_present(*pte),
+ is_swap_pte(*pte), p, addr, 1);
+ if (p->max_pages && (p->found_pages == p->max_pages))
+ break;
+ }
+ }
+ pte_unmap_unlock(pte - 1, ptl);
+ cond_resched();
+
+ if (IS_CLEAR_OP(p->flags))
+ flush_tlb_mm_range(vma->vm_mm, start, end, PAGE_SHIFT, false);
+
+ return 0;
+}
+
+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;
+ unsigned int len;
+ bool sd;
+
+ if (vma) {
+ /* Individual pages haven't been allocated and written */
+ sd = (p->flags & PAGEMAP_NO_REUSED_REGIONS) ? (false) :
+ (vma->vm_flags & VM_SOFTDIRTY);
+
+ len = (end - addr)/PAGE_SIZE;
+ if (p->max_pages && p->max_pages - p->found_pages < len)
+ len = p->max_pages - p->found_pages;
+
+ add_to_out(sd, vma->vm_file, false, false, p, addr, len);
+ }
+
+ return 0;
+}
+
+static int pagemap_scan_pre_vma(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 end_cut = end;
+ int ret;
+
+ if (!(p->flags & PAGEMAP_NO_REUSED_REGIONS) && IS_CLEAR_OP(p->flags) &&
+ (vma->vm_flags & VM_SOFTDIRTY)) {
+ if (vma->vm_start < start) {
+ ret = split_vma(vma->vm_mm, vma, start, 1);
+ if (ret)
+ return ret;
+ }
+ /* Calculate end_cut because of max_pages */
+ if (IS_GET_OP(p->vec) && p->max_pages)
+ end_cut = min(start + (p->max_pages - p->found_pages) * PAGE_SIZE, end);
+
+ if (vma->vm_end > end_cut) {
+ ret = split_vma(vma->vm_mm, vma, end_cut, 0);
+ if (ret)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static void pagemap_scan_post_vma(struct mm_walk *walk)
+{
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+
+ if (!(p->flags & PAGEMAP_NO_REUSED_REGIONS) && IS_CLEAR_OP(p->flags) &&
+ (vma->vm_flags & VM_SOFTDIRTY)) {
+ vma->vm_flags &= ~VM_SOFTDIRTY;
+ vma_set_page_prot(vma);
+ }
+}
+
+static int pagemap_scan_pmd_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;
+
+ if (IS_GET_OP(p->vec) && p->max_pages && (p->found_pages == p->max_pages))
+ return -1;
+
+ if (vma->vm_flags & VM_PFNMAP)
+ return 1;
+
+ return 0;
+}
+
+static const struct mm_walk_ops pagemap_scan_ops = {
+ .test_walk = pagemap_scan_pmd_test_walk,
+ .pmd_entry = pagemap_scan_pmd_entry,
+ .pte_hole = pagemap_scan_pte_hole,
+
+ /* Only for clearing SD bit over VMAs */
+ .pre_vma = pagemap_scan_pre_vma,
+ .post_vma = pagemap_scan_post_vma,
+};
+
+static long do_pagemap_sd_cmd(struct mm_struct *mm, struct pagemap_scan_arg *arg)
+{
+ struct mmu_notifier_range range;
+ unsigned long __user start, end;
+ struct pagemap_scan_private p;
+ int ret;
+
+ start = (unsigned long)untagged_addr(arg->start);
+ if ((!IS_ALIGNED(start, PAGE_SIZE)) || (!access_ok((void __user *)start, arg->len)))
+ return -EINVAL;
+
+ if (IS_GET_OP(arg->vec) &&
+ ((arg->vec_len == 0) || (!access_ok((struct page_region *)arg->vec, arg->vec_len))))
+ return -ENOMEM;
+
+ if ((arg->flags & ~PAGEMAP_SD_FLAGS_MASK) || (arg->rmask & ~PAGEMAP_OP_MASK) ||
+ (arg->amask & ~PAGEMAP_OP_MASK) || (arg->emask & ~PAGEMAP_OP_MASK) ||
+ (arg->return_mask & ~PAGEMAP_OP_MASK))
+ return -EINVAL;
+
+ if ((!arg->rmask && !arg->amask && !arg->emask) || !arg->return_mask)
+ return -EINVAL;
+
+ if ((arg->flags & PAGEMAP_SD_FLAGS_MASK) && ((arg->rmask & PAGEMAP_NON_SD_MASK) ||
+ (arg->amask & PAGEMAP_NON_SD_MASK)))
+ return -EINVAL;
+
+ end = start + arg->len;
+ p.max_pages = arg->max_pages;
+ p.found_pages = 0;
+ p.flags = arg->flags;
+ p.rmask = arg->rmask;
+ p.amask = arg->amask;
+ p.emask = arg->emask;
+ p.return_mask = arg->return_mask;
+ p.index = 0;
+ p.vec_len = arg->vec_len;
+
+ if (IS_GET_OP(arg->vec)) {
+ p.vec = vzalloc(arg->vec_len * sizeof(struct page_region));
+ if (!p.vec)
+ return -ENOMEM;
+ } else {
+ p.vec = NULL;
+ }
+
+ if (IS_CLEAR_OP(arg->flags)) {
+ mmap_write_lock(mm);
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY, 0, NULL, mm, start, end);
+ mmu_notifier_invalidate_range_start(&range);
+ inc_tlb_flush_pending(mm);
+ } else {
+ mmap_read_lock(mm);
+ }
+
+ ret = walk_page_range(mm, start, end, &pagemap_scan_ops, &p);
+
+ if (IS_CLEAR_OP(arg->flags)) {
+ mmu_notifier_invalidate_range_end(&range);
+ dec_tlb_flush_pending(mm);
+
+ mmap_write_unlock(mm);
+ } else {
+ mmap_read_unlock(mm);
+ }
+
+ if (ret < 0)
+ goto free_data;
+
+ if (IS_GET_OP(arg->vec) && p.index) {
+ if (copy_to_user((struct page_region *)arg->vec, p.vec,
+ p.index * sizeof(struct page_region))) {
+ ret = -EFAULT;
+ goto free_data;
+ }
+ ret = p.index;
+ } else {
+ ret = 0;
+ }
+
+free_data:
+ if (IS_GET_OP(arg->vec))
+ vfree(p.vec);
+
+ return ret;
+}
+
+static long pagemap_sd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct pagemap_scan_arg __user *uarg = (struct pagemap_scan_arg __user *)arg;
+ struct mm_struct *mm = file->private_data;
+ struct pagemap_scan_arg argument;
+
+ if (cmd == PAGEMAP_SCAN) {
+ if (copy_from_user(&argument, uarg, sizeof(struct pagemap_scan_arg)))
+ return -EFAULT;
+ return do_pagemap_sd_cmd(mm, &argument);
+ }
+ return -EINVAL;
+}
+#endif /* CONFIG_MEM_SOFT_DIRTY */
+
const struct file_operations proc_pagemap_operations = {
.llseek = mem_lseek, /* borrow this */
.read = pagemap_read,
.open = pagemap_open,
.release = pagemap_release,
+#ifdef CONFIG_MEM_SOFT_DIRTY
+ .unlocked_ioctl = pagemap_sd_ioctl,
+ .compat_ioctl = pagemap_sd_ioctl,
+#endif /* CONFIG_MEM_SOFT_DIRTY */
};
#endif /* CONFIG_PROC_PAGE_MONITOR */
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index b7b56871029c..5d6c0d85dac4 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -305,4 +305,57 @@ 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 pagemap_scan_arg)
+
+/* Bits are set in the bitmap of the page_region and masks in pagemap_sd_args */
+#define PAGE_IS_SD (1 << 0)
+#define PAGE_IS_FILE (1 << 1)
+#define PAGE_IS_PRESENT (1 << 2)
+#define PAGE_IS_SWAPED (1 << 3)
+
+/*
+ * struct page_region - Page region with bitmap flags
+ * @start: Start of the region
+ * @len: Length of the region
+ * bitmap: Bits sets for the region
+ */
+struct page_region {
+ __u64 start;
+ __u64 len;
+ __u32 bitmap;
+ __u32 __reserved;
+};
+
+/*
+ * struct pagemap_scan_arg - Soft-dirty IOCTL argument
+ * @start: Starting address of the region
+ * @len: Length of the region (All the pages in this length are included)
+ * @vec: Address of page_region struct array for output
+ * @vec_len: Length of the page_region struct array
+ * @max_pages: Optional max return pages (It must be less than vec_len if specified)
+ * @flags: Special flags for the IOCTL
+ * @rmask: Required mask - All of these bits have to be set in the PTE
+ * @amask: Any mask - Any of these bits are set in the PTE
+ * @emask: Exclude mask - None of these bits are set in the PTE
+ * @return_mask: Bits that have to be reported to the user in page_region
+ */
+struct pagemap_scan_arg {
+ __u64 start;
+ __u64 len;
+ __u64 vec;
+ __u64 vec_len;
+ __u32 max_pages;
+ __u32 flags;
+ __u32 rmask;
+ __u32 amask;
+ __u32 emask;
+ __u32 return_mask;
+};
+
+/* Special flags */
+#define PAGEMAP_SD_CLEAR (1 << 0)
+/* Check the individual pages if they are soft-dirty to find dirty pages faster. */
+#define PAGEMAP_NO_REUSED_REGIONS (1 << 1)
+
#endif /* _UAPI_LINUX_FS_H */
diff --git a/tools/include/uapi/linux/fs.h b/tools/include/uapi/linux/fs.h
index b7b56871029c..5d6c0d85dac4 100644
--- a/tools/include/uapi/linux/fs.h
+++ b/tools/include/uapi/linux/fs.h
@@ -305,4 +305,57 @@ 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 pagemap_scan_arg)
+
+/* Bits are set in the bitmap of the page_region and masks in pagemap_sd_args */
+#define PAGE_IS_SD (1 << 0)
+#define PAGE_IS_FILE (1 << 1)
+#define PAGE_IS_PRESENT (1 << 2)
+#define PAGE_IS_SWAPED (1 << 3)
+
+/*
+ * struct page_region - Page region with bitmap flags
+ * @start: Start of the region
+ * @len: Length of the region
+ * bitmap: Bits sets for the region
+ */
+struct page_region {
+ __u64 start;
+ __u64 len;
+ __u32 bitmap;
+ __u32 __reserved;
+};
+
+/*
+ * struct pagemap_scan_arg - Soft-dirty IOCTL argument
+ * @start: Starting address of the region
+ * @len: Length of the region (All the pages in this length are included)
+ * @vec: Address of page_region struct array for output
+ * @vec_len: Length of the page_region struct array
+ * @max_pages: Optional max return pages (It must be less than vec_len if specified)
+ * @flags: Special flags for the IOCTL
+ * @rmask: Required mask - All of these bits have to be set in the PTE
+ * @amask: Any mask - Any of these bits are set in the PTE
+ * @emask: Exclude mask - None of these bits are set in the PTE
+ * @return_mask: Bits that have to be reported to the user in page_region
+ */
+struct pagemap_scan_arg {
+ __u64 start;
+ __u64 len;
+ __u64 vec;
+ __u64 vec_len;
+ __u32 max_pages;
+ __u32 flags;
+ __u32 rmask;
+ __u32 amask;
+ __u32 emask;
+ __u32 return_mask;
+};
+
+/* Special flags */
+#define PAGEMAP_SD_CLEAR (1 << 0)
+/* Check the individual pages if they are soft-dirty to find dirty pages faster. */
+#define PAGEMAP_NO_REUSED_REGIONS (1 << 1)
+
#endif /* _UAPI_LINUX_FS_H */
--
2.30.2
