From: Ram Pai <linuxram@us.ibm.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: mpe@ellerman.id.au, mingo@redhat.com, akpm@linux-foundation.org,
linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
x86@kernel.org, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, benh@kernel.crashing.org,
paulus@samba.org, khandual@linux.vnet.ibm.com,
aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com,
hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com,
ebiederm@xmission.com, corbet@lwn.net, arnd@arndb.de
Subject: Re: [PATCH v13 3/3] mm, powerpc, x86: introduce an additional vma bit for powerpc pkey
Date: Fri, 4 May 2018 18:12:43 -0700 [thread overview]
Message-ID: <20180505011243.GB5617@ram.oc3035372033.ibm.com> (raw)
In-Reply-To: <1e37895e-5a18-11c1-58f1-834f96dfd4d5@intel.com>
On Fri, May 04, 2018 at 03:57:33PM -0700, Dave Hansen wrote:
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 0c9e392..3ddddc7 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -679,6 +679,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> > [ilog2(VM_PKEY_BIT1)] = "",
> > [ilog2(VM_PKEY_BIT2)] = "",
> > [ilog2(VM_PKEY_BIT3)] = "",
> > + [ilog2(VM_PKEY_BIT4)] = "",
> > #endif /* CONFIG_ARCH_HAS_PKEYS */
> ...
> > +#if defined(CONFIG_PPC)
> > +# define VM_PKEY_BIT4 VM_HIGH_ARCH_4
> > +#else
> > +# define VM_PKEY_BIT4 0
> > +#endif
> > #endif /* CONFIG_ARCH_HAS_PKEYS */
>
> That new line boils down to:
>
> [ilog2(0)] = "",
>
> on x86. It wasn't *obvious* to me that it is OK to do that. The other
> possibly undefined bits (VM_SOFTDIRTY for instance) #ifdef themselves
> out of this array.
>
> I would just be a wee bit worried that this would overwrite the 0 entry
> ("??") with "".
Yes it would :-( and could potentially break anything that depends on
0th entry being "??"
Is the following fix acceptable?
#if VM_PKEY_BIT4
[ilog2(VM_PKEY_BIT4)] = "",
#endif
--
Ram Pai
next prev parent reply other threads:[~2018-05-05 1:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-04 21:59 [PATCH v13 0/3] mm, x86, powerpc: Enhancements to Memory Protection Keys Ram Pai
2018-05-04 21:59 ` [PATCH v13 1/3] mm, powerpc, x86: define VM_PKEY_BITx bits if CONFIG_ARCH_HAS_PKEYS is enabled Ram Pai
2018-05-04 21:59 ` [PATCH v13 3/3] mm, powerpc, x86: introduce an additional vma bit for powerpc pkey Ram Pai
2018-05-04 22:57 ` Dave Hansen
2018-05-05 1:12 ` Ram Pai [this message]
2018-05-05 4:42 ` Dave Hansen
2018-05-04 21:59 ` [PATCH v11 3/3] mm, x86, powerpc: display pkey in smaps only if arch supports pkeys Ram Pai
2018-05-08 14:39 ` [PATCH v13 0/3] mm, x86, powerpc: Enhancements to Memory Protection Keys Michael Ellerman
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