diff mbox series

[uprobe,thp,2/4] uprobe: use original page when all uprobes are removed

Message ID 20190529212049.2413886-3-songliubraving@fb.com (mailing list archive)
State New, archived
Headers show
Series THP aware uprobe | expand

Commit Message

Song Liu May 29, 2019, 9:20 p.m. UTC 
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).

This patch allows uprobe to use original page when possible (all uprobes
on the page are already removed).

Signed-off-by: Song Liu <songliubraving@fb.com>
---
 kernel/events/uprobes.c | 43 ++++++++++++++++++++++++++++++++---------
 1 file changed, 34 insertions(+), 9 deletions(-)

Comments

Kirill A. Shutemov May 30, 2019, 11:17 a.m. UTC | #1 
On Wed, May 29, 2019 at 02:20:47PM -0700, Song Liu wrote:
> @@ -501,6 +512,20 @@ 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);
> +	if (orig_page) {
> +		if (memcmp(page_address(orig_page),
> +			   page_address(new_page), PAGE_SIZE) == 0) {

Does it work for highmem?
Song Liu May 30, 2019, 5:18 p.m. UTC | #2 
> On May 30, 2019, at 4:17 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> 
> On Wed, May 29, 2019 at 02:20:47PM -0700, Song Liu wrote:
>> @@ -501,6 +512,20 @@ 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);
>> +	if (orig_page) {
>> +		if (memcmp(page_address(orig_page),
>> +			   page_address(new_page), PAGE_SIZE) == 0) {
> 
> Does it work for highmem?

Good catch! I will fix it in v2. 

Thanks!
Song

> 
> 
> -- 
> Kirill A. Shutemov
diff mbox series

Patch

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 78f61bfc6b79..ba49da99d2a2 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -160,16 +160,19 @@  static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
 	int err;
 	struct mmu_notifier_range range;
 	struct mem_cgroup *memcg;
+	bool orig = new_page->mapping != NULL;  /* new_page == orig_page */
 
 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr,
 				addr + PAGE_SIZE);
 
 	VM_BUG_ON_PAGE(PageTransHuge(old_page), old_page);
 
-	err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
-			false);
-	if (err)
-		return err;
+	if (!orig) {
+		err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL,
+					    &memcg, false);
+		if (err)
+			return err;
+	}
 
 	/* For try_to_free_swap() and munlock_vma_page() below */
 	lock_page(old_page);
@@ -177,15 +180,22 @@  static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
 	mmu_notifier_invalidate_range_start(&range);
 	err = -EAGAIN;
 	if (!page_vma_mapped_walk(&pvmw)) {
-		mem_cgroup_cancel_charge(new_page, memcg, false);
+		if (!orig)
+			mem_cgroup_cancel_charge(new_page, memcg, false);
 		goto unlock;
 	}
 	VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
 
 	get_page(new_page);
-	page_add_new_anon_rmap(new_page, vma, addr, false);
-	mem_cgroup_commit_charge(new_page, memcg, false, false);
-	lru_cache_add_active_or_unevictable(new_page, vma);
+	if (orig) {
+		page_add_file_rmap(new_page, false);
+		inc_mm_counter(mm, mm_counter_file(new_page));
+		dec_mm_counter(mm, MM_ANONPAGES);
+	} else {
+		page_add_new_anon_rmap(new_page, vma, addr, false);
+		mem_cgroup_commit_charge(new_page, memcg, false, false);
+		lru_cache_add_active_or_unevictable(new_page, vma);
+	}
 
 	if (!PageAnon(old_page)) {
 		dec_mm_counter(mm, mm_counter_file(old_page));
@@ -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 +512,20 @@  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);
+	if (orig_page) {
+		if (memcmp(page_address(orig_page),
+			   page_address(new_page), PAGE_SIZE) == 0) {
+			/* if new_page matches orig_page, use orig_page */
+			put_page(new_page);
+			new_page = orig_page;
+		} else {
+			put_page(orig_page);
+			orig_page = NULL;
+		}
+	}
+
 	ret = __replace_page(vma, vaddr, old_page, new_page);
 	put_page(new_page);
 put_old: