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>

7 files changed, 114 insertions, 4 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 75988ba26a51..b5aee7838a00 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -176,6 +176,7 @@ read the file /proc/PID/status:
   CapBnd: ffffffffffffffff
   voluntary_ctxt_switches:        0
   nonvoluntary_ctxt_switches:     1
+  Stack usage:    12 kB
 
 This shows you nearly the same information you would get if you viewed it with
 the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
@@ -229,6 +230,7 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
  Mems_allowed_list           Same as previous, but in "list format"
  voluntary_ctxt_switches     number of voluntary context switches
  nonvoluntary_ctxt_switches  number of non voluntary context switches
+ Stack usage:                stack usage high water mark (round up to page size)
 ..............................................................................
 
 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
@@ -307,7 +309,7 @@ address           perms offset  dev   inode      pathname
 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
 0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
 a7cb1000-a7cb2000 ---p 00000000 00:00 0
-a7cb2000-a7eb2000 rw-p 00000000 00:00 0
+a7cb2000-a7eb2000 rw-p 00000000 00:00 0          [threadstack:001ff4b4]
 a7eb2000-a7eb3000 ---p 00000000 00:00 0
 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
@@ -343,6 +345,7 @@ is not associated with a file:
  [stack]                  = the stack of the main process
  [vdso]                   = the "virtual dynamic shared object",
                             the kernel system call handler
+ [threadstack:xxxxxxxx]   = the stack of the thread, xxxxxxxx is the stack size
 
  or if empty, the mapping is anonymous.
 
diff --git a/fs/exec.c b/fs/exec.c
index 69bb9d899791..5c833c18d0d4 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1357,6 +1357,8 @@ int do_execve(char * filename,
         if (retval < 0)
                 goto out;
 
+        current->stack_start = current->mm->start_stack;
+
         /* execve succeeded */
         current->fs->in_exec = 0;
         current->in_execve = 0;
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.
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 366b1017a4f1..2a1bef9203c6 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -243,6 +243,25 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
                                 } else if (vma->vm_start <= mm->start_stack &&
                                            vma->vm_end >= mm->start_stack) {
                                         name = "[stack]";
+                                } else {
+                                        unsigned long stack_start;
+                                        struct proc_maps_private *pmp;
+
+                                        pmp = m->private;
+                                        stack_start = pmp->task->stack_start;
+
+                                        if (vma->vm_start <= stack_start &&
+                                            vma->vm_end >= stack_start) {
+                                                pad_len_spaces(m, len);
+                                                seq_printf(m,
+                                                 "[threadstack:%08lx]",
+#ifdef CONFIG_STACK_GROWSUP
+                                                 vma->vm_end - stack_start
+#else
+                                                 stack_start - vma->vm_start
+#endif
+                                                );
+                                        }
                                 }
                         } else {
                                 name = "[vdso]";
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6448bbc6406b..3cbc6c0be666 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1529,6 +1529,7 @@ struct task_struct {
         /* bitmask of trace recursion */
         unsigned long trace_recursion;
 #endif /* CONFIG_TRACING */
+        unsigned long stack_start;
 };
 
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
diff --git a/kernel/fork.c b/kernel/fork.c
index 7cf45812ce84..8f45b0ebdda7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1095,6 +1095,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 
         p->bts = NULL;
 
+        p->stack_start = stack_start;
+
         /* Perform scheduler related setup. Assign this task to a CPU. */
         sched_fork(p, clone_flags);
 
diff --git a/mm/Makefile b/mm/Makefile
index 728a9fde49d1..88193d73cd1a 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -11,10 +11,10 @@ obj-y			:= bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
                            maccess.o page_alloc.o page-writeback.o \
                            readahead.o swap.o truncate.o vmscan.o shmem.o \
                            prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
-                           page_isolation.o mm_init.o mmu_context.o $(mmu-y)
+                           page_isolation.o mm_init.o mmu_context.o \
+                           pagewalk.o $(mmu-y)
 obj-y += init-mm.o
 
-obj-$(CONFIG_PROC_PAGE_MONITOR) += pagewalk.o
 obj-$(CONFIG_BOUNCE)    += bounce.o
 obj-$(CONFIG_SWAP)      += page_io.o swap_state.o swapfile.o thrash.o
 obj-$(CONFIG_HAS_DMA)   += dmapool.o