Hi Ram,
On 31/07/2017 02:12, Ram Pai wrote:
> arch independent code calls arch_override_mprotect_pkey()
> to return a pkey that best matches the requested protection.
>
> This patch provides the implementation.
>
> Signed-off-by: Ram Pai <linux...@us.ibm.com>
> ---
> arch/powerpc/include/asm/mmu_context.h | 5 +++
> arch/powerpc/include/asm/pkeys.h | 17 ++++++++++-
> arch/powerpc/mm/pkeys.c | 47
> ++++++++++++++++++++++++++++++++
> 3 files changed, 67 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/mmu_context.h
> b/arch/powerpc/include/asm/mmu_context.h
> index 4705dab..7232484 100644
> --- a/arch/powerpc/include/asm/mmu_context.h
> +++ b/arch/powerpc/include/asm/mmu_context.h
> @@ -185,6 +185,11 @@ static inline bool arch_vma_access_permitted(struct
> vm_area_struct *vma,
> #ifndef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> #define pkey_initialize()
> #define pkey_mm_init(mm)
> +
> +static inline int vma_pkey(struct vm_area_struct *vma)
> +{
> + return 0;
> +}
> #endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
>
> #endif /* __KERNEL__ */
> diff --git a/arch/powerpc/include/asm/pkeys.h
> b/arch/powerpc/include/asm/pkeys.h
> index a715a08..03f7ea2 100644
> --- a/arch/powerpc/include/asm/pkeys.h
> +++ b/arch/powerpc/include/asm/pkeys.h
> @@ -46,6 +46,16 @@ static inline u64 pkey_to_vmflag_bits(u16 pkey)
> ((pkey & 0x10UL) ? VM_PKEY_BIT4 : 0x0UL));
> }
>
> +#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
> + VM_PKEY_BIT3 | VM_PKEY_BIT4)
> +
> +static inline int vma_pkey(struct vm_area_struct *vma)
> +{
> + if (!pkey_inited)
> + return 0;
> + return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
> +}
> +
> #define arch_max_pkey() pkeys_total
> #define AMR_RD_BIT 0x1UL
> #define AMR_WR_BIT 0x2UL
> @@ -146,11 +156,14 @@ static inline int execute_only_pkey(struct mm_struct
> *mm)
> return __execute_only_pkey(mm);
> }
>
> -
> +extern int __arch_override_mprotect_pkey(struct vm_area_struct *vma,
> + int prot, int pkey);
> static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
> int prot, int pkey)
> {
> - return 0;
> + if (!pkey_inited)
> + return 0;
> + return __arch_override_mprotect_pkey(vma, prot, pkey);
> }
>
> extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
> diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
> index 25749bf..edcbf48 100644
> --- a/arch/powerpc/mm/pkeys.c
> +++ b/arch/powerpc/mm/pkeys.c
> @@ -154,3 +154,50 @@ int __execute_only_pkey(struct mm_struct *mm)
> mm->context.execute_only_pkey = execute_only_pkey;
> return execute_only_pkey;
> }
> +
> +static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
> +{
> + /* Do this check first since the vm_flags should be hot */
> + if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
> + return false;
> +
> + return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
> +}
> +
> +/*
> + * This should only be called for *plain* mprotect calls.
> + */
> +int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
> + int pkey)
> +{
> + /*
> + * Is this an mprotect_pkey() call? If so, never
> + * override the value that came from the user.
> + */
> + if (pkey != -1)
> + return pkey;
This check should be moved in arch_override_mprotect_pkey() in
arch/powerpc/include/asm/pkeys.h
> +
> + /*
> + * If the currently associated pkey is execute-only,
> + * but the requested protection requires read or write,
> + * move it back to the default pkey.
> + */
> + if (vma_is_pkey_exec_only(vma) &&
> + (prot & (PROT_READ|PROT_WRITE)))
> + return 0;
> +
> + /*
> + * the requested protection is execute-only. Hence
> + * lets use a execute-only pkey.
> + */
> + if (prot == PROT_EXEC) {
> + pkey = execute_only_pkey(vma->vm_mm);
> + if (pkey > 0)
> + return pkey;
> + }
> +
> + /*
> + * nothing to override.
> + */
> + return vma_pkey(vma);
> +}
>
