From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave@sr71.net>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
dave.hansen@linux.intel.com
Subject: Re: [PATCH 16/34] x86, mm: simplify get_user_pages() PTE bit handling
Date: Tue, 8 Dec 2015 19:01:33 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1512081839471.3595@nanos> (raw)
In-Reply-To: <20151204011446.DDC6435F@viggo.jf.intel.com>
On Thu, 3 Dec 2015, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> The current get_user_pages() code is a wee bit more complicated
> than it needs to be for pte bit checking. Currently, it establishes
> a mask of required pte _PAGE_* bits and ensures that the pte it
> goes after has all those bits.
>
> This consolidates the three identical copies of this code.
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> ---
>
> b/arch/x86/mm/gup.c | 45 ++++++++++++++++++++++++++++-----------------
> 1 file changed, 28 insertions(+), 17 deletions(-)
>
> diff -puN arch/x86/mm/gup.c~pkeys-16-gup-swizzle arch/x86/mm/gup.c
> --- a/arch/x86/mm/gup.c~pkeys-16-gup-swizzle 2015-12-03 16:21:25.148649631 -0800
> +++ b/arch/x86/mm/gup.c 2015-12-03 16:21:25.151649767 -0800
> @@ -63,6 +63,30 @@ retry:
> #endif
> }
>
> +static inline int pte_allows_gup(pte_t pte, int write)
> +{
> + /*
> + * 'pte' can reall be a pte, pmd or pud. We only check
> + * _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which
> + * are the same value on all 3 types.
> + */
> + if (!(pte_flags(pte) & (_PAGE_PRESENT|_PAGE_USER)))
> + return 0;
> + if (write && !(pte_write(pte)))
> + return 0;
> + return 1;
> +}
> +
> +static inline int pmd_allows_gup(pmd_t pmd, int write)
> +{
> + return pte_allows_gup(*(pte_t *)&pmd, write);
> +}
> +
> +static inline int pud_allows_gup(pud_t pud, int write)
> +{
> + return pte_allows_gup(*(pte_t *)&pud, write);
> +}
This still puzzles me. And the only reason it compiles is because we
have -fno-strict-aliasing set ...
All this operates on the pteval or even just on the pte_flags(). Even
the new arch_pte_access_permitted() thingy which you add later is only
interrested in pte_flags() and its just a wrapper around
__pkru_allows_pkey().
So for readability and simplicity sake, can we please do something
like this (pkey check already added):
/*
* 'pteval' can reall be a pte, pmd or pud. We only check
* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which
* are the same value on all 3 types.
*/
static inline int pte_allows_gup(unsigned long pteval, int write)
{
unsigned long mask = _PAGE_PRESENT|_PAGE_USER;
if (write)
mask |= _PAGE_RW;
if ((pteval & mask) != mask)
return 0;
if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
return 0;
return 1;
}
and at the callsites do:
if (pte_allows_gup(pte_val(pte, write))
if (pte_allows_gup(pmd_val(pmd, write))
if (pte_allows_gup(pud_val(pud, write))
Hmm?
tglx
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave@sr71.net>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
dave.hansen@linux.intel.com
Subject: Re: [PATCH 16/34] x86, mm: simplify get_user_pages() PTE bit handling
Date: Tue, 8 Dec 2015 19:01:33 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1512081839471.3595@nanos> (raw)
In-Reply-To: <20151204011446.DDC6435F@viggo.jf.intel.com>
On Thu, 3 Dec 2015, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> The current get_user_pages() code is a wee bit more complicated
> than it needs to be for pte bit checking. Currently, it establishes
> a mask of required pte _PAGE_* bits and ensures that the pte it
> goes after has all those bits.
>
> This consolidates the three identical copies of this code.
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> ---
>
> b/arch/x86/mm/gup.c | 45 ++++++++++++++++++++++++++++-----------------
> 1 file changed, 28 insertions(+), 17 deletions(-)
>
> diff -puN arch/x86/mm/gup.c~pkeys-16-gup-swizzle arch/x86/mm/gup.c
> --- a/arch/x86/mm/gup.c~pkeys-16-gup-swizzle 2015-12-03 16:21:25.148649631 -0800
> +++ b/arch/x86/mm/gup.c 2015-12-03 16:21:25.151649767 -0800
> @@ -63,6 +63,30 @@ retry:
> #endif
> }
>
> +static inline int pte_allows_gup(pte_t pte, int write)
> +{
> + /*
> + * 'pte' can reall be a pte, pmd or pud. We only check
> + * _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which
> + * are the same value on all 3 types.
> + */
> + if (!(pte_flags(pte) & (_PAGE_PRESENT|_PAGE_USER)))
> + return 0;
> + if (write && !(pte_write(pte)))
> + return 0;
> + return 1;
> +}
> +
> +static inline int pmd_allows_gup(pmd_t pmd, int write)
> +{
> + return pte_allows_gup(*(pte_t *)&pmd, write);
> +}
> +
> +static inline int pud_allows_gup(pud_t pud, int write)
> +{
> + return pte_allows_gup(*(pte_t *)&pud, write);
> +}
This still puzzles me. And the only reason it compiles is because we
have -fno-strict-aliasing set ...
All this operates on the pteval or even just on the pte_flags(). Even
the new arch_pte_access_permitted() thingy which you add later is only
interrested in pte_flags() and its just a wrapper around
__pkru_allows_pkey().
So for readability and simplicity sake, can we please do something
like this (pkey check already added):
/*
* 'pteval' can reall be a pte, pmd or pud. We only check
* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which
* are the same value on all 3 types.
*/
static inline int pte_allows_gup(unsigned long pteval, int write)
{
unsigned long mask = _PAGE_PRESENT|_PAGE_USER;
if (write)
mask |= _PAGE_RW;
if ((pteval & mask) != mask)
return 0;
if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
return 0;
return 1;
}
and at the callsites do:
if (pte_allows_gup(pte_val(pte, write))
if (pte_allows_gup(pmd_val(pmd, write))
if (pte_allows_gup(pud_val(pud, write))
Hmm?
tglx
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next prev parent reply other threads:[~2015-12-08 18:02 UTC|newest]
Thread overview: 145+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-04 1:14 [PATCH 00/34] x86: Memory Protection Keys (v5) Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 01/34] mm, gup: introduce concept of "foreign" get_user_pages() Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 02/34] x86, fpu: add placeholder for Processor Trace XSAVE state Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 03/34] x86, pkeys: Add Kconfig option Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 04/34] x86, pkeys: cpuid bit definition Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 05/34] x86, pkeys: define new CR4 bit Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 06/34] x86, pkeys: add PKRU xsave fields and data structure(s) Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 07/34] x86, pkeys: PTE bits for storing protection key Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 08/34] x86, pkeys: new page fault error code bit: PF_PK Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 09/34] x86, pkeys: store protection in high VMA flags Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 14:17 ` Thomas Gleixner
2015-12-08 14:17 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 10/34] x86, pkeys: arch-specific protection bits Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 15:15 ` [PATCH 10/34] x86, pkeys: arch-specific protection bitsy Thomas Gleixner
2015-12-08 15:15 ` Thomas Gleixner
2015-12-08 16:34 ` Dave Hansen
2015-12-08 16:34 ` Dave Hansen
2015-12-08 17:24 ` Thomas Gleixner
2015-12-08 17:24 ` Thomas Gleixner
2015-12-08 18:06 ` Dave Hansen
2015-12-08 18:29 ` Thomas Gleixner
2015-12-08 18:29 ` Thomas Gleixner
2015-12-08 18:35 ` Thomas Gleixner
2015-12-08 18:35 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 11/34] x86, pkeys: pass VMA down in to fault signal generation code Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 12/34] signals, pkeys: notify userspace about protection key faults Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 13/34] x86, pkeys: fill in pkey field in siginfo Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 14/34] x86, pkeys: add functions to fetch PKRU Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 15:18 ` Thomas Gleixner
2015-12-08 15:18 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 15/34] mm: factor out VMA fault permission checking Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 17:26 ` Thomas Gleixner
2015-12-08 17:26 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 16/34] x86, mm: simplify get_user_pages() PTE bit handling Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:01 ` Thomas Gleixner [this message]
2015-12-08 18:01 ` Thomas Gleixner
2015-12-08 18:30 ` Dave Hansen
2015-12-08 18:30 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 17/34] x86, pkeys: check VMAs and PTEs for protection keys Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:11 ` Thomas Gleixner
2015-12-08 18:11 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 18/34] mm: add gup flag to indicate "foreign" mm access Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 19/34] x86, pkeys: optimize fault handling in access_error() Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:14 ` Thomas Gleixner
2015-12-08 18:14 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 20/34] x86, pkeys: differentiate instruction fetches Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:17 ` Thomas Gleixner
2015-12-08 18:17 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 21/34] x86, pkeys: dump PKRU with other kernel registers Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:19 ` Thomas Gleixner
2015-12-08 18:19 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 22/34] x86, pkeys: dump PTE pkey in /proc/pid/smaps Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:20 ` Thomas Gleixner
2015-12-08 18:20 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 23/34] x86, pkeys: add Kconfig prompt to existing config option Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:21 ` Thomas Gleixner
2015-12-08 18:21 ` Thomas Gleixner
2015-12-04 1:14 ` [PATCH 24/34] mm, multi-arch: pass a protection key in to calc_vm_flag_bits() Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-04 1:14 ` [PATCH 25/34] x86, pkeys: add arch_validate_pkey() Dave Hansen
2015-12-04 1:14 ` Dave Hansen
2015-12-08 18:39 ` Thomas Gleixner
2015-12-08 18:39 ` Thomas Gleixner
2015-12-04 1:15 ` [PATCH 26/34] mm: implement new mprotect_key() system call Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-05 6:50 ` Michael Kerrisk (man-pages)
2015-12-05 6:50 ` Michael Kerrisk (man-pages)
2015-12-05 6:50 ` Michael Kerrisk (man-pages)
2015-12-07 16:44 ` Dave Hansen
2015-12-07 16:44 ` Dave Hansen
2015-12-09 11:08 ` Michael Kerrisk (man-pages)
2015-12-09 11:08 ` Michael Kerrisk (man-pages)
2015-12-09 15:48 ` Dave Hansen
2015-12-09 15:48 ` Dave Hansen
2015-12-09 16:45 ` Michael Kerrisk (man-pages)
2015-12-09 16:45 ` Michael Kerrisk (man-pages)
2015-12-09 16:45 ` Michael Kerrisk (man-pages)
2015-12-09 17:05 ` Dave Hansen
2015-12-09 17:05 ` Dave Hansen
2015-12-09 17:05 ` Dave Hansen
2015-12-11 20:13 ` Michael Kerrisk (man-pages)
2015-12-11 20:13 ` Michael Kerrisk (man-pages)
2015-12-04 1:15 ` [PATCH 27/34] x86, pkeys: make mprotect_key() mask off additional vm_flags Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-08 18:41 ` Thomas Gleixner
2015-12-08 18:41 ` Thomas Gleixner
2015-12-04 1:15 ` [PATCH 28/34] x86: wire up mprotect_key() system call Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-08 18:44 ` Thomas Gleixner
2015-12-08 18:44 ` Thomas Gleixner
2015-12-08 18:44 ` Thomas Gleixner
2015-12-08 19:06 ` Dave Hansen
2015-12-08 19:06 ` Dave Hansen
2015-12-08 20:38 ` Thomas Gleixner
2015-12-08 20:38 ` Thomas Gleixner
2015-12-08 20:38 ` Thomas Gleixner
2015-12-04 1:15 ` [PATCH 29/34] x86: separate out LDT init from context init Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-08 18:45 ` Thomas Gleixner
2015-12-08 18:45 ` Thomas Gleixner
2015-12-04 1:15 ` [PATCH 30/34] x86, fpu: allow setting of XSAVE state Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-08 18:48 ` Thomas Gleixner
2015-12-08 18:48 ` Thomas Gleixner
2015-12-04 1:15 ` [PATCH 31/34] x86, pkeys: allocation/free syscalls Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-04 1:15 ` [PATCH 32/34] x86, pkeys: add pkey set/get syscalls Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-04 1:15 ` [PATCH 33/34] x86, pkeys: actually enable Memory Protection Keys in CPU Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-04 1:15 ` [PATCH 34/34] x86, pkeys: Documentation Dave Hansen
2015-12-04 1:15 ` Dave Hansen
2015-12-04 23:31 ` [PATCH 00/34] x86: Memory Protection Keys (v5) Andy Lutomirski
2015-12-04 23:31 ` Andy Lutomirski
2015-12-04 23:38 ` Dave Hansen
2015-12-04 23:38 ` Dave Hansen
2015-12-04 23:38 ` Dave Hansen
2015-12-11 20:16 ` Andy Lutomirski
2015-12-11 20:16 ` Andy Lutomirski
2015-12-11 20:16 ` Andy Lutomirski
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