From: Ram Pai <linuxram@us.ibm.com>
To: Balbir Singh <bsingharora@gmail.com>
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
benh@kernel.crashing.org, paulus@samba.org,
khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com,
hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com,
ebiederm@xmission.com
Subject: Re: [PATCH 13/25] powerpc: implementation for arch_override_mprotect_pkey()
Date: Wed, 18 Oct 2017 14:10:41 -0700 [thread overview]
Message-ID: <20171018211041.GI5617@ram.oc3035372033.ibm.com> (raw)
In-Reply-To: <20171018153635.1ab9765d@firefly.ozlabs.ibm.com>
On Wed, Oct 18, 2017 at 03:36:35PM +1100, Balbir Singh wrote:
> On Fri, 8 Sep 2017 15:45:01 -0700
> Ram Pai <linuxram@us.ibm.com> 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 <linuxram@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 c705a5d..8e5a87e 100644
> > --- a/arch/powerpc/include/asm/mmu_context.h
> > +++ b/arch/powerpc/include/asm/mmu_context.h
> > @@ -145,6 +145,11 @@ 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 f13e913..d2fffef 100644
> > --- a/arch/powerpc/include/asm/pkeys.h
> > +++ b/arch/powerpc/include/asm/pkeys.h
> > @@ -41,6 +41,16 @@ 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;
>
> We don't want pkey_inited to be present in all functions, why do we need
> a conditional branch for all functions. Even if we do, it should be a jump
> label. I would rather we just removed !pkey_inited unless really really
> required.
No. we really really need it. For example when we build a kernel with
PROTECTION_KEYS config enabled and run that kernel on a older processor
or on a system where the key feature is not enabled in the device tree,
we have fail all the calls that get called-in by the arch-neutral code.
Hence we need this check.
BTW: jump labels are awkward IMHO, unless absolutely needed.
>
> > + 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
> > @@ -142,11 +152,14 @@ 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 8a24983..fb1a76a 100644
> > --- a/arch/powerpc/mm/pkeys.c
> > +++ b/arch/powerpc/mm/pkeys.c
> > @@ -245,3 +245,50 @@ 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.
>
> What's a plain mprotect call?
there is sys_mprotect() and now there is a sys_pkey_mprotect() call.
The 'plain' one is the former.
>
> > + */
> > +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;
>
> If the user specified a key, we always use it? Presumably the user
> got it from pkey_alloc(), in other cases, the user was lazy and used
> -1 in the mprotect call?
in the plain sys_mprotect() key is not specified. In that case this
function gets called with a -1.
>
> > +
> > + /*
> > + * 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);
> > +}
>
> Balbir Singh.
--
Ram Pai
next prev parent reply other threads:[~2017-10-18 21:10 UTC|newest]
Thread overview: 134+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-08 22:44 [PATCH 0/7] powerpc: Free up RPAGE_RSV bits Ram Pai
2017-09-08 22:44 ` [PATCH 1/7] powerpc: introduce pte_set_hash_slot() helper Ram Pai
2017-09-13 7:55 ` Balbir Singh
2017-10-19 4:52 ` Michael Ellerman
2017-09-08 22:44 ` [PATCH 2/7] powerpc: introduce pte_get_hash_gslot() helper Ram Pai
2017-09-13 9:32 ` Balbir Singh
2017-09-13 20:10 ` Ram Pai
2017-09-08 22:44 ` [PATCH 3/7] powerpc: Free up four 64K PTE bits in 4K backed HPTE pages Ram Pai
2017-09-14 1:18 ` Balbir Singh
2017-10-19 3:25 ` Michael Ellerman
2017-10-19 17:02 ` Ram Pai
2017-10-23 8:47 ` Aneesh Kumar K.V
2017-10-23 16:29 ` Ram Pai
2017-10-25 9:18 ` Michael Ellerman
2017-10-26 6:08 ` Ram Pai
2017-09-08 22:44 ` [PATCH 4/7] powerpc: Free up four 64K PTE bits in 64K " Ram Pai
2017-09-14 1:44 ` Balbir Singh
2017-09-14 17:54 ` Ram Pai
2017-09-14 18:25 ` Ram Pai
2017-09-14 8:13 ` Benjamin Herrenschmidt
2017-10-23 8:52 ` Aneesh Kumar K.V
2017-10-23 23:42 ` Ram Pai
2017-10-23 19:22 ` Ram Pai
2017-10-24 3:37 ` Aneesh Kumar K.V
2017-09-08 22:44 ` [PATCH 5/7] powerpc: Swizzle around 4K PTE bits to free up bit 5 and bit 6 Ram Pai
2017-09-14 1:48 ` Balbir Singh
2017-09-14 17:23 ` Ram Pai
2017-09-08 22:44 ` [PATCH 6/7] powerpc: use helper functions to get and set hash slots Ram Pai
2017-09-08 22:44 ` [PATCH 7/7] powerpc: capture the PTE format changes in the dump pte report Ram Pai
2017-09-14 3:22 ` Balbir Singh
2017-09-14 17:19 ` Ram Pai
2017-09-08 22:44 ` [PATCH 00/25] powerpc: Memory Protection Keys Ram Pai
2017-09-08 22:44 ` [PATCH 01/25] powerpc: initial pkey plumbing Ram Pai
2017-09-14 3:32 ` Balbir Singh
2017-09-14 16:17 ` Ram Pai
2017-10-19 4:20 ` Michael Ellerman
2017-10-19 17:11 ` Ram Pai
2017-10-24 8:17 ` Michael Ellerman
2017-09-08 22:44 ` [PATCH 02/25] powerpc: define an additional vma bit for protection keys Ram Pai
2017-09-14 4:38 ` Balbir Singh
2017-09-14 8:11 ` Benjamin Herrenschmidt
2017-10-23 21:06 ` Ram Pai
2017-09-14 16:15 ` Ram Pai
2017-10-23 9:25 ` Aneesh Kumar K.V
2017-10-23 9:28 ` Aneesh Kumar K.V
2017-10-23 17:57 ` Ram Pai
2017-10-23 17:43 ` Ram Pai
2017-09-08 22:44 ` [PATCH 03/25] powerpc: track allocation status of all pkeys Ram Pai
2017-10-07 10:02 ` Michael Ellerman
2017-10-08 23:02 ` Ram Pai
2017-10-18 2:47 ` Balbir Singh
2017-10-23 9:41 ` Aneesh Kumar K.V
2017-10-23 18:14 ` Ram Pai
2017-10-24 6:28 ` Aneesh Kumar K.V
2017-10-24 7:23 ` Ram Pai
2017-09-08 22:44 ` [PATCH 04/25] powerpc: helper function to read, write AMR, IAMR, UAMOR registers Ram Pai
2017-10-18 3:17 ` [PATCH 04/25] powerpc: helper function to read,write AMR,IAMR,UAMOR registers Balbir Singh
2017-10-18 3:42 ` Ram Pai
2017-09-08 22:44 ` [PATCH 05/25] powerpc: helper functions to initialize AMR, IAMR and UAMOR registers Ram Pai
2017-10-18 3:24 ` Balbir Singh
2017-10-18 20:38 ` Ram Pai
2017-10-24 6:25 ` Aneesh Kumar K.V
2017-10-24 7:04 ` Ram Pai
2017-10-24 8:29 ` Michael Ellerman
2017-09-08 22:44 ` [PATCH 06/25] powerpc: cleaup AMR, iAMR when a key is allocated or freed Ram Pai
2017-10-18 3:34 ` [PATCH 06/25] powerpc: cleaup AMR,iAMR " Balbir Singh
2017-10-23 9:43 ` [PATCH 06/25] powerpc: cleaup AMR, iAMR " Aneesh Kumar K.V
2017-10-23 18:36 ` [PATCH 06/25] powerpc: cleaup AMR,iAMR " Ram Pai
2017-10-23 9:43 ` [PATCH 06/25] powerpc: cleaup AMR, iAMR " Aneesh Kumar K.V
2017-10-23 18:29 ` [PATCH 06/25] powerpc: cleaup AMR,iAMR " Ram Pai
2017-09-08 22:44 ` [PATCH 07/25] powerpc: implementation for arch_set_user_pkey_access() Ram Pai
2017-09-08 22:44 ` [PATCH 08/25] powerpc: sys_pkey_alloc() and sys_pkey_free() system calls Ram Pai
2017-10-24 15:48 ` Michael Ellerman
2017-10-24 18:34 ` Ram Pai
2017-10-25 9:26 ` Michael Ellerman
2017-09-08 22:44 ` [PATCH 09/25] powerpc: ability to create execute-disabled pkeys Ram Pai
2017-10-18 3:42 ` Balbir Singh
2017-10-18 5:15 ` Ram Pai
2017-10-24 6:58 ` Aneesh Kumar K.V
2017-10-24 7:20 ` Ram Pai
2017-10-24 4:36 ` Aneesh Kumar K.V
2017-10-28 23:18 ` Ram Pai
2017-09-08 22:44 ` [PATCH 10/25] powerpc: store and restore the pkey state across context switches Ram Pai
2017-10-18 3:49 ` Balbir Singh
2017-10-18 20:47 ` Ram Pai
2017-10-18 23:00 ` Balbir Singh
2017-10-19 0:52 ` Ram Pai
2017-09-08 22:44 ` [PATCH 11/25] powerpc: introduce execute-only pkey Ram Pai
2017-10-18 4:15 ` Balbir Singh
2017-10-18 20:57 ` Ram Pai
2017-10-18 23:02 ` Balbir Singh
2017-10-19 15:52 ` Ram Pai
2017-09-08 22:45 ` [PATCH 12/25] powerpc: ability to associate pkey to a vma Ram Pai
2017-10-18 4:27 ` Balbir Singh
2017-10-18 21:01 ` Ram Pai
2017-09-08 22:45 ` [PATCH 13/25] powerpc: implementation for arch_override_mprotect_pkey() Ram Pai
2017-10-18 4:36 ` Balbir Singh
2017-10-18 21:10 ` Ram Pai [this message]
2017-10-18 23:04 ` Balbir Singh
2017-10-19 16:39 ` Ram Pai
2017-09-08 22:45 ` [PATCH 14/25] powerpc: map vma key-protection bits to pte key bits Ram Pai
2017-10-18 4:39 ` Balbir Singh
2017-10-18 21:14 ` Ram Pai
2017-09-08 22:45 ` [PATCH 15/25] powerpc: sys_pkey_mprotect() system call Ram Pai
2017-09-08 22:45 ` [PATCH 16/25] powerpc: Program HPTE key protection bits Ram Pai
2017-10-18 4:43 ` Balbir Singh
2017-09-08 22:45 ` [PATCH 17/25] powerpc: helper to validate key-access permissions of a pte Ram Pai
2017-10-18 4:48 ` Balbir Singh
2017-10-18 21:19 ` Ram Pai
2017-09-08 22:45 ` [PATCH 18/25] powerpc: check key protection for user page access Ram Pai
2017-10-18 19:57 ` Balbir Singh
2017-10-18 21:29 ` Ram Pai
2017-10-18 23:08 ` Balbir Singh
2017-10-19 16:46 ` Ram Pai
2017-09-08 22:45 ` [PATCH 19/25] powerpc: implementation for arch_vma_access_permitted() Ram Pai
2017-10-18 23:20 ` Balbir Singh
2017-10-24 15:48 ` Michael Ellerman
2017-09-08 22:45 ` [PATCH 20/25] powerpc: Handle exceptions caused by pkey violation Ram Pai
2017-10-18 23:27 ` Balbir Singh
2017-10-19 16:53 ` Ram Pai
2017-10-24 15:47 ` Michael Ellerman
2017-10-24 18:26 ` Ram Pai
2017-10-29 14:03 ` Aneesh Kumar K.V
2017-10-30 0:37 ` Ram Pai
2017-09-08 22:45 ` [PATCH 21/25] powerpc: introduce get_pte_pkey() helper Ram Pai
2017-10-18 23:29 ` Balbir Singh
2017-10-19 16:55 ` Ram Pai
2017-09-08 22:45 ` [PATCH 22/25] powerpc: capture the violated protection key on fault Ram Pai
2017-10-24 15:46 ` Michael Ellerman
2017-09-08 22:45 ` [PATCH 23/25] powerpc: Deliver SEGV signal on pkey violation Ram Pai
2017-10-24 15:46 ` Michael Ellerman
2017-10-24 17:19 ` Ram Pai
2017-09-08 22:45 ` [PATCH 24/25] powerpc/ptrace: Add memory protection key regset Ram Pai
2017-09-08 22:45 ` [PATCH 25/25] powerpc: Enable pkey subsystem Ram Pai
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