On 4/18/22 09:14, Tong Tiangen wrote:
> From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
>
> As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table
> check"), add some necessary page table check hooks into routines that
> modify user page tables.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/pgtable.h | 65 +++++++++++++++++++++++++++++---
> 2 files changed, 61 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index e80fd2372f02..7114d2d5155e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -92,6 +92,7 @@ config ARM64
> select ARCH_SUPPORTS_ATOMIC_RMW
> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> select ARCH_SUPPORTS_NUMA_BALANCING
> + select ARCH_SUPPORTS_PAGE_TABLE_CHECK
> select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
> select ARCH_WANT_DEFAULT_BPF_JIT
> select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 930077f7b572..9f8f97a7cc7c 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -33,6 +33,7 @@
> #include <linux/mmdebug.h>
> #include <linux/mm_types.h>
> #include <linux/sched.h>
> +#include <linux/page_table_check.h>
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
> @@ -96,6 +97,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
> #define pte_young(pte) (!!(pte_val(pte) & PTE_AF))
> #define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL))
> #define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE))
> +#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
> #define pte_user_exec(pte) (!(pte_val(pte) & PTE_UXN))
> #define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT))
> #define pte_devmap(pte) (!!(pte_val(pte) & PTE_DEVMAP))
> @@ -312,7 +314,7 @@ static inline void __check_racy_pte_update(struct mm_struct *mm, pte_t *ptep,
> __func__, pte_val(old_pte), pte_val(pte));
> }
>
> -static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> +static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
> pte_t *ptep, pte_t pte)
> {
> if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
> @@ -343,6 +345,13 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> set_pte(ptep, pte);
> }
>
> +static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> + pte_t *ptep, pte_t pte)
> +{
> + page_table_check_pte_set(mm, addr, ptep, pte);
> + return __set_pte_at(mm, addr, ptep, pte);
> +}
> +
> /*
> * Huge pte definitions.
> */
> @@ -454,6 +463,8 @@ static inline int pmd_trans_huge(pmd_t pmd)
> #define pmd_dirty(pmd) pte_dirty(pmd_pte(pmd))
> #define pmd_young(pmd) pte_young(pmd_pte(pmd))
> #define pmd_valid(pmd) pte_valid(pmd_pte(pmd))
> +#define pmd_user(pmd) pte_user(pmd_pte(pmd))
> +#define pmd_user_exec(pmd) pte_user_exec(pmd_pte(pmd))
> #define pmd_cont(pmd) pte_cont(pmd_pte(pmd))
> #define pmd_wrprotect(pmd) pte_pmd(pte_wrprotect(pmd_pte(pmd)))
> #define pmd_mkold(pmd) pte_pmd(pte_mkold(pmd_pte(pmd)))
> @@ -501,8 +512,19 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
> #define pud_pfn(pud) ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
> #define pfn_pud(pfn,prot) __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>
> -#define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
> -#define set_pud_at(mm, addr, pudp, pud) set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
> +static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
> + pmd_t *pmdp, pmd_t pmd)
> +{
> + page_table_check_pmd_set(mm, addr, pmdp, pmd);
> + return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
> +}
> +
> +static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
> + pud_t *pudp, pud_t pud)
> +{
> + page_table_check_pud_set(mm, addr, pudp, pud);
> + return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
> +}
>
> #define __p4d_to_phys(p4d) __pte_to_phys(p4d_pte(p4d))
> #define __phys_to_p4d_val(phys) __phys_to_pte_val(phys)
> @@ -643,6 +665,24 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
> #define pud_present(pud) pte_present(pud_pte(pud))
> #define pud_leaf(pud) pud_sect(pud)
> #define pud_valid(pud) pte_valid(pud_pte(pud))
> +#define pud_user(pud) pte_user(pud_pte(pud))
> +
> +#ifdef CONFIG_PAGE_TABLE_CHECK
> +static inline bool pte_user_accessible_page(pte_t pte)
> +{
> + return pte_present(pte) && (pte_user(pte) || pte_user_exec(pte));
> +}
> +
> +static inline bool pmd_user_accessible_page(pmd_t pmd)
> +{
> + return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> +}
> +
> +static inline bool pud_user_accessible_page(pud_t pud)
> +{
> + return pud_present(pud) && pud_user(pud);
> +}
> +#endif
>
> static inline void set_pud(pud_t *pudp, pud_t pud)
> {
> @@ -872,11 +912,21 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> +static inline pte_t __ptep_get_and_clear(struct mm_struct *mm,
> + unsigned long address, pte_t *ptep)
> +{
> + return __pte(xchg_relaxed(&pte_val(*ptep), 0));
> +}
> +
> #define __HAVE_ARCH_PTEP_GET_AND_CLEAR
> static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> unsigned long address, pte_t *ptep)
> {
> - return __pte(xchg_relaxed(&pte_val(*ptep), 0));
> + pte_t pte = __ptep_get_and_clear(mm, address, ptep);
> +
> + page_table_check_pte_clear(mm, address, pte);
> +
> + return pte;
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -884,7 +934,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
> unsigned long address, pmd_t *pmdp)
> {
> - return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
> + pmd_t pmd = pte_pmd(__ptep_get_and_clear(mm, address, (pte_t *)pmdp));
> +
> + page_table_check_pmd_clear(mm, address, pmd);
> +
> + return pmd;
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> @@ -918,6 +972,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
> static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> unsigned long address, pmd_t *pmdp, pmd_t pmd)
> {
> + page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd);
> return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd)));
> }
> #endif
Ran this series on arm64 platform after enabling
- CONFIG_PAGE_TABLE_CHECK
- CONFIG_PAGE_TABLE_CHECK_ENFORCED (avoiding kernel command line option)
After some time, the following error came up
[ 23.266013] ------------[ cut here ]------------
[ 23.266807] kernel BUG at mm/page_table_check.c:90!
[ 23.267609] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[ 23.268503] Modules linked in:
[ 23.269012] CPU: 1 PID: 30 Comm: khugepaged Not tainted 5.18.0-rc3-00004-g60aa8e363a91 #2
[ 23.270383] Hardware name: linux,dummy-virt (DT)
[ 23.271210] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 23.272445] pc : page_table_check_clear.isra.6+0x114/0x148
[ 23.273429] lr : page_table_check_clear.isra.6+0x64/0x148
[ 23.274395] sp : ffff80000afb3ca0
[ 23.274994] x29: ffff80000afb3ca0 x28: fffffc00022558e8 x27: ffff80000a27f628
[ 23.276260] x26: ffff800009f9f2b0 x25: ffff00008a8d5000 x24: ffff800009f09fa0
[ 23.277527] x23: 0000ffff89e00000 x22: ffff800009f09fb8 x21: ffff000089414cc0
[ 23.278798] x20: 0000000000000200 x19: fffffc00022a0000 x18: 0000000000000001
[ 23.280066] x17: 0000000000000001 x16: 0000000000000000 x15: 0000000000000003
[ 23.281331] x14: 0000000000000068 x13: 00000000000000c0 x12: 0000000000000010
[ 23.282602] x11: fffffc0002320008 x10: fffffc0002320000 x9 : ffff800009fa1000
[ 23.283868] x8 : 00000000ffffffff x7 : 0000000000000001 x6 : ffff800009fa1f08
[ 23.285135] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
[ 23.286406] x2 : 00000000ffffffff x1 : ffff000080f2800c x0 : ffff000080f28000
[ 23.287673] Call trace:
[ 23.288123] page_table_check_clear.isra.6+0x114/0x148
[ 23.289043] __page_table_check_pmd_clear+0x3c/0x50
[ 23.289918] pmdp_collapse_flush+0x114/0x370
[ 23.290692] khugepaged+0x1170/0x19e0
[ 23.291356] kthread+0x110/0x120
[ 23.291945] ret_from_fork+0x10/0x20
[ 23.292596] Code: 91001041 b8e80024 51000482 36fffd62 (d4210000)
[ 23.293678] ---[ end trace 0000000000000000 ]---
[ 23.294511] note: khugepaged[30] exited with preempt_count 2
Looking into file mm/page_table_check.c where this problem occured.
/*
* An enty is removed from the page table, decrement the counters for that page
* verify that it is of correct type and counters do not become negative.
*/
static void page_table_check_clear(struct mm_struct *mm, unsigned long addr,
unsigned long pfn, unsigned long pgcnt)
{
struct page_ext *page_ext;
struct page *page;
unsigned long i;
bool anon;
if (!pfn_valid(pfn))
return;
page = pfn_to_page(pfn);
page_ext = lookup_page_ext(page);
anon = PageAnon(page);
for (i = 0; i < pgcnt; i++) {
struct page_table_check *ptc = get_page_table_check(page_ext);
if (anon) {
BUG_ON(atomic_read(&ptc->file_map_count));
BUG_ON(atomic_dec_return(&ptc->anon_map_count) < 0);
} else {
BUG_ON(atomic_read(&ptc->anon_map_count));
Triggered here ====>> BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0);
}
page_ext = page_ext_next(page_ext);
}
}
Could you explain what was expected during pmdp_collapse_flush() which when
failed, triggered this BUG_ON() ? This counter seems to be page table check
specific, could it just go wrong ? I have not looked into the details about
page table check mechanism.
- Anshuman
