procfs: add VmFlags field in smaps output

During c/r sessions we've found that there is no way at the moment to
fetch some VMA associated flags, such as mlock() and madvise().

This leads us to a problem -- we don't know if we should call for mlock()
and/or madvise() after restore on the vma area we're bringing back to
life.

This patch intorduces a new field into "smaps" output called VmFlags,
where all set flags associated with the particular VMA is shown as two
letter mnemonics.

[ Strictly speaking for c/r we only need mlock/madvise bits but it has been
  said that providing just a few flags looks somehow inconsistent.  So all
  flags are here now. ]

This feature is made available on CONFIG_CHECKPOINT_RESTORE=n kernels, as
other applications may start to use these fields.

The data is encoded in a somewhat awkward two letters mnemonic form, to
encourage userspace to be prepared for fields being added or removed in
the future.

[a.p.zijlstra@chello.nl: props to use for_each_set_bit]
[sfr@canb.auug.org.au: props to use array instead of struct]
[akpm@linux-foundation.org: overall redesign and simplification]
[akpm@linux-foundation.org: remove unneeded braces per sfr, avoid using bloaty for_each_set_bit()]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4877562..448455b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -526,6 +526,57 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	return 0;
 }
 
+static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
+{
+	/*
+	 * Don't forget to update Documentation/ on changes.
+	 */
+	static const char mnemonics[BITS_PER_LONG][2] = {
+		/*
+		 * In case if we meet a flag we don't know about.
+		 */
+		[0 ... (BITS_PER_LONG-1)] = "??",
+
+		[ilog2(VM_READ)]	= "rd",
+		[ilog2(VM_WRITE)]	= "wr",
+		[ilog2(VM_EXEC)]	= "ex",
+		[ilog2(VM_SHARED)]	= "sh",
+		[ilog2(VM_MAYREAD)]	= "mr",
+		[ilog2(VM_MAYWRITE)]	= "mw",
+		[ilog2(VM_MAYEXEC)]	= "me",
+		[ilog2(VM_MAYSHARE)]	= "ms",
+		[ilog2(VM_GROWSDOWN)]	= "gd",
+		[ilog2(VM_PFNMAP)]	= "pf",
+		[ilog2(VM_DENYWRITE)]	= "dw",
+		[ilog2(VM_LOCKED)]	= "lo",
+		[ilog2(VM_IO)]		= "io",
+		[ilog2(VM_SEQ_READ)]	= "sr",
+		[ilog2(VM_RAND_READ)]	= "rr",
+		[ilog2(VM_DONTCOPY)]	= "dc",
+		[ilog2(VM_DONTEXPAND)]	= "de",
+		[ilog2(VM_ACCOUNT)]	= "ac",
+		[ilog2(VM_NORESERVE)]	= "nr",
+		[ilog2(VM_HUGETLB)]	= "ht",
+		[ilog2(VM_NONLINEAR)]	= "nl",
+		[ilog2(VM_ARCH_1)]	= "ar",
+		[ilog2(VM_DONTDUMP)]	= "dd",
+		[ilog2(VM_MIXEDMAP)]	= "mm",
+		[ilog2(VM_HUGEPAGE)]	= "hg",
+		[ilog2(VM_NOHUGEPAGE)]	= "nh",
+		[ilog2(VM_MERGEABLE)]	= "mg",
+	};
+	size_t i;
+
+	seq_puts(m, "VmFlags: ");
+	for (i = 0; i < BITS_PER_LONG; i++) {
+		if (vma->vm_flags & (1UL << i)) {
+			seq_printf(m, "%c%c ",
+				   mnemonics[i][0], mnemonics[i][1]);
+		}
+	}
+	seq_putc(m, '\n');
+}
+
 static int show_smap(struct seq_file *m, void *v, int is_pid)
 {
 	struct proc_maps_private *priv = m->private;
@@ -581,6 +632,8 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
 		seq_printf(m, "Nonlinear:      %8lu kB\n",
 				mss.nonlinear >> 10);
 
+	show_smap_vma_flags(m, vma);
+
 	if (m->count < m->size)  /* vma is copied successfully */
 		m->version = (vma != get_gate_vma(task->mm))
 			? vma->vm_start : 0;