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

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Message-ID: <87shb1de4a.fsf@xmission.com>
Date:   Fri, 19 Jan 2018 10:09:41 -0600
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Ram Pai <linuxram@...ibm.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

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?

Eric


>  		show_smap_vma_flags(m, vma);
>  	}
> +
>  	m_cache_vma(m, vma);
>  	return ret;
>  }