linux-kernel - Re: [PATCH 3/6] mm: display pkey in smaps if arch_pkeys

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Date:   Fri, 22 Sep 2017 16:02:49 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Ram Pai <linuxram@...ibm.com>
Cc:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, linux-doc@...r.kernel.org,
        arnd@...db.de, akpm@...ux-foundation.org, corbet@....net,
        mingo@...hat.com, benh@...nel.crashing.org, paulus@...ba.org,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        hbabu@...ibm.com, mhocko@...nel.org, bauerman@...ux.vnet.ibm.com,
        ebiederm@...ssion.com
Subject: Re: [PATCH 3/6] mm: display pkey in smaps if arch_pkeys_enabled()
 is true

On Fri, 15 Sep 2017 18:21:07 -0700
Ram Pai <linuxram@...ibm.com> wrote:

> 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 3486d04..1953bce 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1340,11 +1340,3 @@ 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 cf25306..667d44a 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -16,6 +16,7 @@
>  #include <linux/mmu_notifier.h>
>  #include <linux/page_idle.h>
>  #include <linux/shmem_fs.h>
> +#include <linux/pkeys.h>
>  
>  #include <asm/elf.h>
>  #include <linux/uaccess.h>
> @@ -714,10 +715,6 @@ 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 vm_area_struct *vma = v;
> @@ -803,7 +800,11 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
>  		   (vma->vm_flags & VM_LOCKED) ?
>  			(unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
>  
> -	arch_show_smap(m, vma);
> +#ifdef CONFIG_ARCH_HAS_PKEYS
> +	if (arch_pkeys_enabled())
> +		seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
> +#endif

Can CONFIG_ARCH_HAS_PKEYS be true, but the kernel compiled without
support for them or it's just not enabled? I think the
earlier per_arch function was better

Balbir