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.