linux-kernel - Re: [PATCH v10 27/27] mm: display pkey in smaps if arch_pkeys

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Message-Id: <20180119165050.GK5612@ram.oc3035372033.ibm.com>
Date:   Fri, 19 Jan 2018 08:50:50 -0800
From:   Ram Pai <linuxram@...ibm.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     mpe@...erman.id.au, mingo@...hat.com, akpm@...ux-foundation.org,
        corbet@....net, arnd@...db.de, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org, x86@...nel.org, linux-arch@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, dave.hansen@...el.com,
        benh@...nel.crashing.org, paulus@...ba.org,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, hbabu@...ibm.com, mhocko@...nel.org,
        bauerman@...ux.vnet.ibm.com
Subject: Re: [PATCH v10 27/27] mm: display pkey in smaps if
 arch_pkeys_enabled() is true

On Fri, Jan 19, 2018 at 10:09:41AM -0600, Eric W. Biederman wrote:
> Ram Pai <linuxram@...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@...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