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Date:   Fri, 19 Jan 2018 08:50:50 -0800
From:   Ram Pai <linuxram@us.ibm.com>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     mpe@ellerman.id.au, mingo@redhat.com, akpm@linux-foundation.org,
        corbet@lwn.net, arnd@arndb.de, linuxppc-dev@lists.ozlabs.org,
        linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org, dave.hansen@intel.com,
        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
Subject: Re: [PATCH v10 27/27] mm: display pkey in smaps if
 arch_pkeys_enabled() is true
Reply-To: Ram Pai <linuxram@us.ibm.com>
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 <87shb1de4a.fsf@xmission.com>
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On Fri, Jan 19, 2018 at 10:09:41AM -0600, Eric W. Biederman wrote:
> Ram Pai <linuxram@us.ibm.com> writes:
> 
> > Currently the  architecture  specific code is expected to
> > display  the  protection  keys  in  smap  for a given vma.
> > This can lead to redundant code and possibly to divergent
> > formats in which the key gets displayed.
> >
> > This  patch  changes  the implementation. It displays the
> > pkey only if the architecture support pkeys.
> >
> > x86 arch_show_smap() function is not needed anymore.
> > Delete it.
> >
> > Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> > ---
> >  arch/x86/kernel/setup.c |    8 --------
> >  fs/proc/task_mmu.c      |   11 ++++++-----
> >  2 files changed, 6 insertions(+), 13 deletions(-)
> >
> > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> > index 8af2e8d..ddf945a 100644
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -1326,11 +1326,3 @@ static int __init register_kernel_offset_dumper(void)
> >  	return 0;
> >  }
> >  __initcall(register_kernel_offset_dumper);
> > -
> > -void arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
> > -{
> > -	if (!boot_cpu_has(X86_FEATURE_OSPKE))
> > -		return;
> > -
> > -	seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
> > -}
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 0edd4da..4b39a94 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/page_idle.h>
> >  #include <linux/shmem_fs.h>
> >  #include <linux/uaccess.h>
> > +#include <linux/pkeys.h>
> >  
> >  #include <asm/elf.h>
> >  #include <asm/tlb.h>
> > @@ -728,10 +729,6 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
> >  }
> >  #endif /* HUGETLB_PAGE */
> >  
> > -void __weak arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
> > -{
> > -}
> > -
> >  static int show_smap(struct seq_file *m, void *v, int is_pid)
> >  {
> >  	struct proc_maps_private *priv = m->private;
> > @@ -851,9 +848,13 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
> >  			   (unsigned long)(mss->pss >> (10 + PSS_SHIFT)));
> >  
> >  	if (!rollup_mode) {
> > -		arch_show_smap(m, vma);
> > +#ifdef CONFIG_ARCH_HAS_PKEYS
> > +		if (arch_pkeys_enabled())
> > +			seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
> > +#endif
> 
> Would it be worth it making vma_pkey a noop on architectures that don't
> support protection keys so that we don't need the #ifdef here?

You mean something like this?
	#define vma_pkey(vma)  
It will lead to compilation error.


I can make it
	#define vma_pkey(vma)  0

and that will work and get rid of the #ifdef

RP