[PATCH] NOMMU: add [stack] label to per-process maps output

[Mike Frysinger <vapier@gentoo.org>]

Add support to the NOMMU per-process proc maps file to show which mapping
is the stack.  This is largely based on the MMU code.

root:/> cat /proc/self/maps
02064000-02067ccc rw-p 0004d000 00:01 22         /bin/busybox
0206e000-0206f35c rw-p 00006000 00:01 295        /lib/ld-uClibc.so.0
025f0000-025f6f0c r-xs 00000000 00:01 295        /lib/ld-uClibc.so.0
02680000-026ba6b0 r-xs 00000000 00:01 297        /lib/libc.so.0
02700000-0274d384 r-xs 00000000 00:01 22         /bin/busybox
02816000-02817000 rw-p 00000000 00:00 0
02848000-0284c0d8 rw-p 00000000 00:00 0
02860000-02880000 rw-p 00000000 00:00 0          [stack]

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
it'd be cool if the global /proc/maps could display something like
[stack/<pid>], but i can't quite divine how to get a mm_struct out
of a vm_region without having to walk the entire process list.

 fs/proc/task_nommu.c |   20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 5d9fd64..283b5c0 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -121,11 +121,20 @@ int task_statm(struct mm_struct *mm, int *shared, int *text,
 	return size;
 }
 
+static void pad_len_spaces(struct seq_file *m, int len)
+{
+	len = 25 + sizeof(void*) * 6 - len;
+	if (len < 1)
+		len = 1;
+	seq_printf(m, "%*c", len, ' ');
+}
+
 /*
  * display a single VMA to a sequenced file
  */
 static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
 {
+	struct mm_struct *mm = vma->vm_mm;
 	unsigned long ino = 0;
 	struct file *file;
 	dev_t dev = 0;
@@ -154,11 +163,14 @@ static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
 		   MAJOR(dev), MINOR(dev), ino, &len);
 
 	if (file) {
-		len = 25 + sizeof(void *) * 6 - len;
-		if (len < 1)
-			len = 1;
-		seq_printf(m, "%*c", len, ' ');
+		pad_len_spaces(m, len);
 		seq_path(m, &file->f_path, "");
+	} else if (mm) {
+		if (vma->vm_start <= mm->start_brk &&
+				vma->vm_end >= mm->brk) {
+			pad_len_spaces(m, len);
+			seq_puts(m, "[stack]");
+		}
 	}
 
 	seq_putc(m, '\n');
-- 
1.6.5.5