linux-kernel - Re: [PATCH 22/32] x86, pkeys: dump PTE pkey in /proc/pid/smaps

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Date:	Tue, 5 Jan 2016 14:32:42 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Dave Hansen <dave@...1.net>, linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, x86@...nel.org, dave.hansen@...ux.intel.com
Subject: Re: [PATCH 22/32] x86, pkeys: dump PTE pkey in /proc/pid/smaps

On 12/14/2015 08:06 PM, Dave Hansen wrote:
> From: Dave Hansen <dave.hansen@...ux.intel.com>

$SUBJ is a bit confusing in that it's dumping stuff from VMA, not PTE's?

It could be also useful to extend dump_vma() appropriately. Currently 
there are no string translations for the new "flags" (but one can figure 
it out from the raw value). But maybe we should print pkey separately in 
dump_vma() as you do here. I have a series in flight [1] that touches 
dump_vma() and the flags printing in general, so to avoid conflicts, 
handling pkeys there could wait. But mentioning it now for less chance 
of being forgotten...

[1] https://lkml.org/lkml/2015/12/18/178 - a previous version is in 
mmotm and this should replace it after 4.5-rc1

> The protection key can now be just as important as read/write
> permissions on a VMA.  We need some debug mechanism to help
> figure out if it is in play.  smaps seems like a logical
> place to expose it.
>
> arch/x86/kernel/setup.c is a bit of a weirdo place to put
> this code, but it already had seq_file.h and there was not
> a much better existing place to put it.
>
> We also use no #ifdef.  If protection keys is .config'd out
> we will get the same function as if we used the weak generic
> function.
>
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>
>   b/arch/x86/kernel/setup.c |    9 +++++++++
>   b/fs/proc/task_mmu.c      |   14 ++++++++++++++
>   2 files changed, 23 insertions(+)
>
> diff -puN arch/x86/kernel/setup.c~pkeys-40-smaps arch/x86/kernel/setup.c
> --- a/arch/x86/kernel/setup.c~pkeys-40-smaps	2015-12-14 10:42:48.777070739 -0800
> +++ b/arch/x86/kernel/setup.c	2015-12-14 10:42:48.782070963 -0800
> @@ -112,6 +112,7 @@
>   #include <asm/alternative.h>
>   #include <asm/prom.h>
>   #include <asm/microcode.h>
> +#include <asm/mmu_context.h>
>
>   /*
>    * max_low_pfn_mapped: highest direct mapped pfn under 4GB
> @@ -1282,3 +1283,11 @@ static int __init register_kernel_offset
>   	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 -puN fs/proc/task_mmu.c~pkeys-40-smaps fs/proc/task_mmu.c
> --- a/fs/proc/task_mmu.c~pkeys-40-smaps	2015-12-14 10:42:48.779070829 -0800
> +++ b/fs/proc/task_mmu.c	2015-12-14 10:42:48.783071008 -0800
> @@ -615,11 +615,20 @@ static void show_smap_vma_flags(struct s
>   		[ilog2(VM_MERGEABLE)]	= "mg",
>   		[ilog2(VM_UFFD_MISSING)]= "um",
>   		[ilog2(VM_UFFD_WP)]	= "uw",
> +#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
> +		/* These come out via ProtectionKey: */
> +		[ilog2(VM_PKEY_BIT0)]	= "",
> +		[ilog2(VM_PKEY_BIT1)]	= "",
> +		[ilog2(VM_PKEY_BIT2)]	= "",
> +		[ilog2(VM_PKEY_BIT3)]	= "",
> +#endif
>   	};
>   	size_t i;
>
>   	seq_puts(m, "VmFlags: ");
>   	for (i = 0; i < BITS_PER_LONG; i++) {
> +		if (!mnemonics[i][0])
> +			continue;
>   		if (vma->vm_flags & (1UL << i)) {
>   			seq_printf(m, "%c%c ",
>   				   mnemonics[i][0], mnemonics[i][1]);
> @@ -657,6 +666,10 @@ static int smaps_hugetlb_range(pte_t *pt
>   }
>   #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;
> @@ -713,6 +726,7 @@ static int show_smap(struct seq_file *m,
>   		   (vma->vm_flags & VM_LOCKED) ?
>   			(unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
>
> +	arch_show_smap(m, vma);
>   	show_smap_vma_flags(m, vma);
>   	m_cache_vma(m, vma);
>   	return 0;
> _
>
> --
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