From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
Cc: Calvin Owens <calvinowens@fb.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Al Viro <viro@zeniv.linux.org.uk>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Peter Feiner <pfeiner@google.com>,
Grant Likely <grant.likely@secretlab.ca>,
linux-kernel <linux-kernel@vger.kernel.org>,
kernel-team@fb.com
Subject: Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files
Date: Wed, 14 Jan 2015 15:53:16 +0100 [thread overview]
Message-ID: <87fvbdv2g3.fsf@rasmusvillemoes.dk> (raw)
In-Reply-To: <CAAHN_R0AhAc7zt3sfbKdXJEj3Ncd4Hao-1qr=X3mkSjB7F_fYg@mail.gmail.com> (Siddhesh Poyarekar's message of "Wed, 14 Jan 2015 20:07:06 +0530")
On Wed, Jan 14 2015, Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com> wrote:
> On 14 January 2015 at 19:43, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
>> Just thinking out loud: Could one simply mark a VMA as being used for
>> stack during the clone call (is there room in vm_flags, or does
>> VM_GROWSDOWN already tell the whole story?), and then write the TID into
>> a new field in the VMA - I think one could make a union with vm_pgoff so
>> as not to enlarge the structure.
>
> vm_flags does not have space IIRC (that was my first approach at
> implementing this) and VM_GROWSDOWN is not sufficient.
Looking at include/linux/mm.h:
#define VM_GROWSDOWN 0x00000100 /* general info on the segment */
#define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */
It would seem that 0x00000200 is available (unless defined and used
somewhere else).
> If we can make a union with vm_pgoff like you say, we probably don't
> need a flag value; a non-zero value could indicate that it is a thread
> stack.
Well, only when combined with checking vm_file for being NULL. One would
also need to ensure that vm_pgoff is 0 for any non-stack,
non-file-backed VMA. At which point it is somewhat ugly.
> One problem with caching the value on clone like this though is that
> the stack could change due to a setcontext, but AFAICT we don't care
> about that for the process stack either.
If it is important, I guess one could update the info when a task calls
setcontext.
Rasmus
next prev parent reply other threads:[~2015-01-14 14:53 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-14 0:20 [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files Calvin Owens
2015-01-14 0:23 ` Calvin Owens
2015-01-14 14:13 ` Rasmus Villemoes
2015-01-14 14:37 ` Siddhesh Poyarekar
2015-01-14 14:53 ` Rasmus Villemoes [this message]
2015-01-14 21:03 ` Calvin Owens
2015-01-14 22:45 ` Andrew Morton
2015-01-14 23:51 ` Rasmus Villemoes
2015-01-16 1:15 ` Andrew Morton
2015-01-16 11:00 ` Kirill A. Shutemov
2015-01-14 15:25 ` Kirill A. Shutemov
2015-01-14 15:33 ` Cyrill Gorcunov
2015-01-14 20:46 ` Calvin Owens
2015-01-14 21:16 ` Cyrill Gorcunov
2015-01-22 2:45 ` [RFC][PATCH] procfs: Always expose /proc/<pid>/map_files/ and make it readable Calvin Owens
2015-01-22 7:16 ` Cyrill Gorcunov
2015-01-22 11:02 ` Kirill A. Shutemov
2015-01-22 21:00 ` Calvin Owens
2015-01-22 21:27 ` Kirill A. Shutemov
2015-01-23 5:52 ` Calvin Owens
2015-01-24 3:15 ` [RFC][PATCH v2] " Calvin Owens
2015-01-26 12:47 ` Kirill A. Shutemov
2015-01-26 21:00 ` Cyrill Gorcunov
2015-01-26 23:43 ` Andrew Morton
2015-01-27 0:15 ` Kees Cook
2015-01-27 7:37 ` Cyrill Gorcunov
2015-01-27 19:53 ` Kees Cook
2015-01-27 21:35 ` Cyrill Gorcunov
2015-01-27 21:46 ` Pavel Emelyanov
2015-01-27 0:19 ` Kirill A. Shutemov
2015-01-27 6:46 ` Cyrill Gorcunov
2015-01-27 6:50 ` Andrew Morton
2015-01-27 7:23 ` Cyrill Gorcunov
2015-01-28 4:38 ` Calvin Owens
2015-01-30 1:30 ` Kees Cook
2015-01-31 1:58 ` Calvin Owens
2015-02-02 14:01 ` Austin S Hemmelgarn
2015-02-04 3:53 ` Calvin Owens
2015-02-02 20:16 ` Andy Lutomirski
2015-02-04 3:28 ` Calvin Owens
2015-02-12 2:29 ` [RFC][PATCH v3] " Calvin Owens
2015-02-12 7:45 ` Cyrill Gorcunov
2015-02-14 20:40 ` [RFC][PATCH v4] " Calvin Owens
2015-03-10 22:17 ` Cyrill Gorcunov
2015-04-28 22:23 ` Calvin Owens
2015-04-29 7:32 ` Cyrill Gorcunov
2015-05-19 3:10 ` [PATCH v5] " Calvin Owens
2015-05-19 3:29 ` Joe Perches
2015-05-19 18:04 ` Andy Lutomirski
2015-05-21 1:52 ` Calvin Owens
2015-05-21 2:10 ` Andy Lutomirski
2015-06-09 3:39 ` [PATCH v6] " Calvin Owens
2015-06-09 17:27 ` Kees Cook
2015-06-09 17:47 ` Andy Lutomirski
2015-06-09 18:15 ` Cyrill Gorcunov
2015-06-09 21:13 ` Andrew Morton
2015-06-10 1:39 ` Calvin Owens
2015-06-10 20:58 ` Andrew Morton
2015-06-11 11:10 ` Alexey Dobriyan
2015-06-11 18:49 ` Andrew Morton
2015-06-12 9:55 ` Alexey Dobriyan
2015-06-19 2:32 ` [PATCH v7] " Calvin Owens
2015-07-15 22:21 ` Andrew Morton
2015-07-15 23:39 ` Calvin Owens
2015-02-14 20:44 ` [PATCH] procfs: Return -ESRCH on /proc/N/fd/* when PID N doesn't exist Calvin Owens
2015-01-14 22:40 ` [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files Kirill A. Shutemov
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