Re: [PATCH -next v7 5/6] arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK

[Anders Roxell]

On 2022-05-07 11:01, Tong Tiangen wrote:
> From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> 
> As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table check")
> , enable ARCH_SUPPORTS_PAGE_TABLE_CHECK on arm64.
> 
> Add additional page table check stubs for page table helpers, these stubs
> can be used to check the existing page table entries.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>

When building and booting an arm64 allmodconfig kernel on the next tree, branch next-20220516,
see the following kernel oops when booting in QEMU [1]:

T35] ------------[ cut here ]------------
[  578.695796][   T35] kernel BUG at mm/page_table_check.c:82!
[  578.697292][   T35] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[  578.704318][   T35] Modules linked in:
[  578.705907][   T35] CPU: 0 PID: 35 Comm: khugepaged Tainted: G                T 5.18.0-rc6-next-20220513 #1 893498a5d8159d9fb26e12492a93c07e83dd4b7f
[  578.711170][   T35] Hardware name: linux,dummy-virt (DT)
[  578.713315][   T35] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  578.716398][   T35] pc : page_table_check_clear.constprop.0+0x1f4/0x280
[  578.719107][   T35] lr : page_table_check_clear.constprop.0+0x1cc/0x280
[  578.721781][   T35] sp : ffff80000f3778b0
[  578.723446][   T35] x29: ffff80000f3778b0 x28: ffff80000b891218 x27: ffff000012dd55f0
[  578.726667][   T35] x26: 0000000000000008 x25: ffff80000c38cd80 x24: 0000000000000000
[  578.729870][   T35] x23: ffff80000c38c9c0 x22: 0000000000000000 x21: 0000000000000200
[  578.733079][   T35] x20: ffff000007bae000 x19: ffff000007bae008 x18: 0000000000000000
[  578.736299][   T35] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[  578.739505][   T35] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
[  578.742735][   T35] x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
[  578.745925][   T35] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
[  578.749145][   T35] x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff000007bae00c
[  578.752348][   T35] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 00000000ffffffff
[  578.755556][   T35] Call trace:
[  578.756877][   T35]  page_table_check_clear.constprop.0+0x1f4/0x280
[  578.759446][   T35]  __page_table_check_pmd_clear+0xc4/0x140
[  578.761757][   T35]  pmdp_collapse_flush+0xa4/0x1c0
[  578.763771][   T35]  collapse_huge_page+0x4e4/0xb00
[  578.765778][   T35]  khugepaged_scan_pmd+0xc18/0xd00
[  578.767840][   T35]  khugepaged_scan_mm_slot+0x580/0x780
[  578.770018][   T35]  khugepaged+0x2dc/0x400
[  578.771786][   T35]  kthread+0x164/0x180
[  578.773430][   T35]  ret_from_fork+0x10/0x20
[  578.775253][   T35] Code: 52800021 91001263 14000388 36f80040 (d4210000) 
[  578.777990][   T35] ---[ end trace 0000000000000000 ]---
[  578.778021][   T35] Kernel panic - not syncing: Oops - BUG: Fatal exception
[  578.782934][   T35] Kernel Offset: disabled
[  578.784642][   T35] CPU features: 0x000,00100010,00001086
[  578.786848][   T35] Memory Limit: none
[  578.788433][   T35] ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]---

Bisected down to this patch, see the bisect log [2].

When I revert this patch I don't see the issue anymore.

Cheers,
Anders
[1] https://people.linaro.org/~anders.roxell/output-next-20220513.log
[2] http://ix.io/3XZB

> ---
>  arch/arm64/Kconfig               |  1 +
>  arch/arm64/include/asm/pgtable.h | 61 ++++++++++++++++++++++++++++----
>  2 files changed, 56 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 272c75af9302..3055fb5b3fb4 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 8ebf1cec5d90..4e61cde27f9f 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))
> @@ -312,8 +314,8 @@ 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,
> -			      pte_t *ptep, pte_t pte)
> +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))
>  		__sync_icache_dcache(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_present(pud) && !pud_table(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)
>  {
> @@ -876,7 +916,11 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
>  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 = __pte(xchg_relaxed(&pte_val(*ptep), 0));
> +
> +	page_table_check_pte_clear(mm, address, pte);
> +
> +	return pte;
>  }
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -884,7 +928,11 @@ 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 = __pmd(xchg_relaxed(&pmd_val(*pmdp), 0));
> +
> +	page_table_check_pmd_clear(mm, address, pmd);
> +
> +	return pmd;
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  
> @@ -918,6 +966,7 @@ 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
> -- 
> 2.25.1
> 

-- 
Anders Roxell
anders.roxell@xxxxxxxxxx
M: +46 708 22 71 05 | IRC: roxell