procfs: provide stack information for threads

A patch to give a better overview of the userland application stack usage,
especially for embedded linux.

Currently you are only able to dump the main process/thread stack usage
which is showed in /proc/pid/status by the "VmStk" Value.  But you get no
information about the consumed stack memory of the the threads.

There is an enhancement in the /proc/<pid>/{task/*,}/*maps and which marks
the vm mapping where the thread stack pointer reside with "[thread stack
xxxxxxxx]".  xxxxxxxx is the maximum size of stack.  This is a value
information, because libpthread doesn't set the start of the stack to the
top of the mapped area, depending of the pthread usage.

A sample output of /proc/<pid>/task/<tid>/maps looks like:

08048000-08049000 r-xp 00000000 03:00 8312       /opt/z
08049000-0804a000 rw-p 00001000 03:00 8312       /opt/z
0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
a7d12000-a7d13000 ---p 00000000 00:00 0
a7d13000-a7f13000 rw-p 00000000 00:00 0          [thread stack: 001ff4b4]
a7f13000-a7f14000 ---p 00000000 00:00 0
a7f14000-a7f36000 rw-p 00000000 00:00 0
a7f36000-a8069000 r-xp 00000000 03:00 4222       /lib/libc.so.6
a8069000-a806b000 r--p 00133000 03:00 4222       /lib/libc.so.6
a806b000-a806c000 rw-p 00135000 03:00 4222       /lib/libc.so.6
a806c000-a806f000 rw-p 00000000 00:00 0
a806f000-a8083000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
a8083000-a8084000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
a8084000-a8085000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
a8085000-a8088000 rw-p 00000000 00:00 0
a8088000-a80a4000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
a80a4000-a80a5000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
a80a5000-a80a6000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
afaf5000-afb0a000 rw-p 00000000 00:00 0          [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]

Also there is a new entry "stack usage" in /proc/<pid>/{task/*,}/status
which will you give the current stack usage in kb.

A sample output of /proc/self/status looks like:

Name:	cat
State:	R (running)
Tgid:	507
Pid:	507
.
.
.
CapBnd:	fffffffffffffeff
voluntary_ctxt_switches:	0
nonvoluntary_ctxt_switches:	0
Stack usage:	12 kB

I also fixed stack base address in /proc/<pid>/{task/*,}/stat to the base
address of the associated thread stack and not the one of the main
process.  This makes more sense.

[akpm@linux-foundation.org: fs/proc/array.c now needs walk_page_range()]
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 84 insertions, 1 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 725a650bbbb8..0c6bc602e6c4 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -82,6 +82,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/ptrace.h>
 #include <linux/tracehook.h>
+#include <linux/swapops.h>
 
 #include <asm/pgtable.h>
 #include <asm/processor.h>
@@ -321,6 +322,87 @@ static inline void task_context_switch_counts(struct seq_file *m,
                         p->nivcsw);
 }
 
+struct stack_stats {
+        struct vm_area_struct *vma;
+        unsigned long   startpage;
+        unsigned long   usage;
+};
+
+static int stack_usage_pte_range(pmd_t *pmd, unsigned long addr,
+                                unsigned long end, struct mm_walk *walk)
+{
+        struct stack_stats *ss = walk->private;
+        struct vm_area_struct *vma = ss->vma;
+        pte_t *pte, ptent;
+        spinlock_t *ptl;
+        int ret = 0;
+
+        pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+        for (; addr != end; pte++, addr += PAGE_SIZE) {
+                ptent = *pte;
+
+#ifdef CONFIG_STACK_GROWSUP
+                if (pte_present(ptent) || is_swap_pte(ptent))
+                        ss->usage = addr - ss->startpage + PAGE_SIZE;
+#else
+                if (pte_present(ptent) || is_swap_pte(ptent)) {
+                        ss->usage = ss->startpage - addr + PAGE_SIZE;
+                        pte++;
+                        ret = 1;
+                        break;
+                }
+#endif
+        }
+        pte_unmap_unlock(pte - 1, ptl);
+        cond_resched();
+        return ret;
+}
+
+static inline unsigned long get_stack_usage_in_bytes(struct vm_area_struct *vma,
+                                struct task_struct *task)
+{
+        struct stack_stats ss;
+        struct mm_walk stack_walk = {
+                .pmd_entry = stack_usage_pte_range,
+                .mm = vma->vm_mm,
+                .private = &ss,
+        };
+
+        if (!vma->vm_mm || is_vm_hugetlb_page(vma))
+                return 0;
+
+        ss.vma = vma;
+        ss.startpage = task->stack_start & PAGE_MASK;
+        ss.usage = 0;
+
+#ifdef CONFIG_STACK_GROWSUP
+        walk_page_range(KSTK_ESP(task) & PAGE_MASK, vma->vm_end,
+                &stack_walk);
+#else
+        walk_page_range(vma->vm_start, (KSTK_ESP(task) & PAGE_MASK) + PAGE_SIZE,
+                &stack_walk);
+#endif
+        return ss.usage;
+}
+
+static inline void task_show_stack_usage(struct seq_file *m,
+                                                struct task_struct *task)
+{
+        struct vm_area_struct   *vma;
+        struct mm_struct        *mm = get_task_mm(task);
+
+        if (mm) {
+                down_read(&mm->mmap_sem);
+                vma = find_vma(mm, task->stack_start);
+                if (vma)
+                        seq_printf(m, "Stack usage:\t%lu kB\n",
+                                get_stack_usage_in_bytes(vma, task) >> 10);
+
+                up_read(&mm->mmap_sem);
+                mmput(mm);
+        }
+}
+
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
                         struct pid *pid, struct task_struct *task)
 {
@@ -340,6 +422,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
         task_show_regs(m, task);
 #endif
         task_context_switch_counts(m, task);
+        task_show_stack_usage(m, task);
         return 0;
 }
 
@@ -481,7 +564,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
                 rsslim,
                 mm ? mm->start_code : 0,
                 mm ? mm->end_code : 0,
-                (permitted && mm) ? mm->start_stack : 0,
+                (permitted) ? task->stack_start : 0,
                 esp,
                 eip,
                 /* The signal information here is obsolete.