[tip:x86/mpx] x86, mpx: Introduce VM_MPX to indicate that a VMA is MPX specific

From: tip-bot for Qiaowei Ren
Date: Mon Nov 17 2014 - 19:07:03 EST

Commit-ID: 4aae7e436fa51faf4bf5d11b175aea82cfe8224a
Gitweb: http://git.kernel.org/tip/4aae7e436fa51faf4bf5d11b175aea82cfe8224a
Author: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
AuthorDate: Fri, 14 Nov 2014 07:18:25 -0800
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 18 Nov 2014 00:58:53 +0100

x86, mpx: Introduce VM_MPX to indicate that a VMA is MPX specific

MPX-enabled applications using large swaths of memory can
potentially have large numbers of bounds tables in process
address space to save bounds information. These tables can take
up huge swaths of memory (as much as 80% of the memory on the
system) even if we clean them up aggressively. In the worst-case
scenario, the tables can be 4x the size of the data structure
being tracked. IOW, a 1-page structure can require 4 bounds-table

Being this huge, our expectation is that folks using MPX are
going to be keen on figuring out how much memory is being
dedicated to it. So we need a way to track memory use for MPX.

If we want to specifically track MPX VMAs we need to be able to
distinguish them from normal VMAs, and keep them from getting
merged with normal VMAs. A new VM_ flag set only on MPX VMAs does
both of those things. With this flag, MPX bounds-table VMAs can
be distinguished from other VMAs, and userspace can also walk
/proc/$pid/smaps to get memory usage for MPX.

In addition to this flag, we also introduce a special ->vm_ops
specific to MPX VMAs (see the patch "add MPX specific mmap
interface"), but currently different ->vm_ops do not by
themselves prevent VMA merging, so we still need this flag.

We understand that VM_ flags are scarce and are open to other

Signed-off-by: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: Dave Hansen <dave@xxxxxxxx>
Link: http://lkml.kernel.org/r/20141114151825.565625B3@xxxxxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
fs/proc/task_mmu.c | 3 +++
include/linux/mm.h | 6 ++++++
2 files changed, 9 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4e0388c..f6734c6 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -552,6 +552,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
[ilog2(VM_GROWSDOWN)] = "gd",
[ilog2(VM_PFNMAP)] = "pf",
[ilog2(VM_DENYWRITE)] = "dw",
+ [ilog2(VM_MPX)] = "mp",
[ilog2(VM_LOCKED)] = "lo",
[ilog2(VM_IO)] = "io",
[ilog2(VM_SEQ_READ)] = "sr",
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b464611..f7606d3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -128,6 +128,7 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */
#define VM_NONLINEAR 0x00800000 /* Is non-linear (remap_file_pages) */
#define VM_ARCH_1 0x01000000 /* Architecture-specific flag */
+#define VM_ARCH_2 0x02000000
#define VM_DONTDUMP 0x04000000 /* Do not include in the core dump */

@@ -155,6 +156,11 @@ extern unsigned int kobjsize(const void *objp);
# define VM_MAPPED_COPY VM_ARCH_1 /* T if mapped copy of data (nommu mmap) */

+#if defined(CONFIG_X86)
+/* MPX specific bounds table or bounds directory */
+# define VM_MPX VM_ARCH_2
#ifndef VM_GROWSUP
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