[PATCH 9/9] x86/cet: Handle THP/HugeTLB shadow stack page copying

Yu-cheng Yu
2018-06-07T14:40:52Z

This patch implements THP shadow stack memory copying in the same
way as the previous patch for regular PTE.

In copy_huge_pmd(), we clear the dirty bit from the PMD. On the
next shadow stack access to the PMD, a page fault occurs. At
that time, the page is copied/re-used and the PMD is fixed.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
mm/huge_memory.c | 10 +++++++++-
mm/hugetlb.c | 2 +-
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a3a1815f8e11..c6e72ccc4274 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -600,6 +600,8 @@ static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,

entry = mk_huge_pmd(page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (is_shstk_mapping(vma->vm_flags))
+ entry = pmd_mkdirty_shstk(entry);
page_add_new_anon_rmap(page, vma, haddr, true);
mem_cgroup_commit_charge(page, memcg, false, true);
lru_cache_add_active_or_unevictable(page, vma);
@@ -976,7 +978,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
mm_inc_nr_ptes(dst_mm);
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);

- pmdp_set_wrprotect(src_mm, addr, src_pmd);
+ pmdp_set_wrprotect_flush(vma, addr, src_pmd);
pmd = pmd_mkold(pmd_wrprotect(pmd));
set_pmd_at(dst_mm, addr, dst_pmd, pmd);

@@ -1196,6 +1198,8 @@ static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
pte_t entry;
entry = mk_pte(pages[i], vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ if (is_shstk_mapping(vma->vm_flags))
+ entry = pte_mkdirty_shstk(entry);
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
@@ -1280,6 +1284,8 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
pmd_t entry;
entry = pmd_mkyoung(orig_pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (is_shstk_mapping(vma->vm_flags))
+ entry = pmd_mkdirty_shstk(entry);
if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
ret |= VM_FAULT_WRITE;
@@ -1350,6 +1356,8 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
pmd_t entry;
entry = mk_huge_pmd(new_page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (is_shstk_mapping(vma->vm_flags))
+ entry = pmd_mkdirty_shstk(entry);
pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
page_add_new_anon_rmap(new_page, vma, haddr, true);
mem_cgroup_commit_charge(new_page, memcg, false, true);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 218679138255..d694cfab9f90 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3293,7 +3293,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
*
* See Documentation/vm/mmu_notifier.txt
*/
- huge_ptep_set_wrprotect(src, addr, src_pte);
+ huge_ptep_set_wrprotect_flush(vma, addr, src_pte);
}
entry = huge_ptep_get(src_pte);
ptepage = pte_page(entry);
--
2.15.1