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    Subject[patch 2/2] procfs: provide stack information for threads V0.8
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    Date
    This is the newest version of the formaly named "detailed stack info"
    patch which give you 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.

    Changes since last posting:

    - change maps/smaps output, displays now the max. stack size

    The patch is against 2.6.30-rc7 and tested with on intel and ppc
    architectures.

    ChangeLog:
    20. Jan 2009 V0.1
    - First Version for Kernel 2.6.28.1
    31. Mar 2009 V0.2
    - Ported to Kernel 2.6.29
    03. Jun 2009 V0.3
    - Ported to Kernel 2.6.30
    - Redesigned what was suggested by Ingo Molnar
    - the thread watch monitor is gone
    - the /proc/stackmon entry is also gone
    - slim down
    04. Jun 2009 V0.4
    - Redesigned everything that was suggested by Andrew Morton
    - slim down
    04. Jun 2009 V0.5
    - Code cleanup
    06. Jun 2009 V0.6
    - Fix missing mm->mmap_sem locking in function task_show_stack_usage()
    - Code cleanup
    10. Jun 2009 V0.7
    - update Documentation/filesystem/proc.txt

    Documentation/filesystems/proc.txt | 5 ++-
    fs/exec.c | 2 +
    fs/proc/array.c | 51 ++++++++++++++++++++++++++++++++++++-
    fs/proc/task_mmu.c | 19 +++++++++++++
    include/linux/sched.h | 1
    kernel/fork.c | 2 +
    6 files changed, 78 insertions(+), 2 deletions(-)

    Signed-off-by: Stefani Seibold <stefani@seibold.net>

    diff -u -N -r linux-2.6.30.orig/Documentation/filesystems/proc.txt linux-2.6.30/Documentation/filesystems/proc.txt
    --- linux-2.6.30.orig/Documentation/filesystems/proc.txt 2009-06-10 09:09:27.000000000 +0200
    +++ linux-2.6.30/Documentation/filesystems/proc.txt 2009-06-10 09:07:46.000000000 +0200
    @@ -176,6 +176,7 @@
    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 @@
    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 @@
    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 [thread stack: 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 @@
    [stack] = the stack of the main process
    [vdso] = the "virtual dynamic shared object",
    the kernel system call handler
    + [thread stack, xxxxxxxx] = the stack of the thread, xxxxxxxx is the stack size

    or if empty, the mapping is anonymous.

    diff -u -N -r linux-2.6.30.orig/fs/exec.c linux-2.6.30/fs/exec.c
    --- linux-2.6.30.orig/fs/exec.c 2009-06-04 09:29:47.000000000 +0200
    +++ linux-2.6.30/fs/exec.c 2009-06-04 09:32:35.000000000 +0200
    @@ -1328,6 +1328,8 @@
    if (retval < 0)
    goto out;

    + current->stack_start = current->mm->start_stack;
    +
    /* execve succeeded */
    current->fs->in_exec = 0;
    current->in_execve = 0;
    diff -u -N -r linux-2.6.30.orig/fs/proc/array.c linux-2.6.30/fs/proc/array.c
    --- linux-2.6.30.orig/fs/proc/array.c 2009-06-04 09:29:47.000000000 +0200
    +++ linux-2.6.30/fs/proc/array.c 2009-06-05 21:13:30.000000000 +0200
    @@ -321,6 +321,54 @@
    p->nivcsw);
    }

    +static inline unsigned long get_stack_usage_in_bytes(struct vm_area_struct *vma,
    + struct task_struct *p)
    +{
    + unsigned long i;
    + struct page *page;
    + unsigned long stkpage;
    +
    + stkpage = KSTK_ESP(p) & PAGE_MASK;
    +
    +#ifdef CONFIG_STACK_GROWSUP
    + for (i = vma->vm_end; i-PAGE_SIZE > stkpage; i -= PAGE_SIZE) {
    +
    + page = follow_page(vma, i-PAGE_SIZE, 0);
    +
    + if (!IS_ERR(page) && page)
    + break;
    + }
    + return i - (p->stack_start & PAGE_MASK);
    +#else
    + for (i = vma->vm_start; i+PAGE_SIZE <= stkpage; i += PAGE_SIZE) {
    +
    + page = follow_page(vma, i, 0);
    +
    + if (!IS_ERR(page) && page)
    + break;
    + }
    + return (p->stack_start & PAGE_MASK) - i + PAGE_SIZE;
    +#endif
    +}
    +
    +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 +388,7 @@
    task_show_regs(m, task);
    #endif
    task_context_switch_counts(m, task);
    + task_show_stack_usage(m, task);
    return 0;
    }

    @@ -481,7 +530,7 @@
    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 -u -N -r linux-2.6.30.orig/fs/proc/task_mmu.c linux-2.6.30/fs/proc/task_mmu.c
    --- linux-2.6.30.orig/fs/proc/task_mmu.c 2009-06-04 09:29:47.000000000 +0200
    +++ linux-2.6.30/fs/proc/task_mmu.c 2009-06-10 09:02:40.000000000 +0200
    @@ -242,6 +242,25 @@
    } 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,
    + "[thread stack: %08lx]",
    +#ifdef CONFIG_STACK_GROWSUP
    + vma->vm_end - stack_start
    +#else
    + stack_start - vma->vm_start
    +#endif
    + );
    + }
    }
    } else {
    name = "[vdso]";
    diff -u -N -r linux-2.6.30.orig/include/linux/sched.h linux-2.6.30/include/linux/sched.h
    --- linux-2.6.30.orig/include/linux/sched.h 2009-06-04 09:29:47.000000000 +0200
    +++ linux-2.6.30/include/linux/sched.h 2009-06-04 09:32:35.000000000 +0200
    @@ -1429,6 +1429,7 @@
    /* state flags for use by tracers */
    unsigned long trace;
    #endif
    + unsigned long stack_start;
    };

    /* Future-safe accessor for struct task_struct's cpus_allowed. */
    diff -u -N -r linux-2.6.30.orig/kernel/fork.c linux-2.6.30/kernel/fork.c
    --- linux-2.6.30.orig/kernel/fork.c 2009-06-04 09:29:47.000000000 +0200
    +++ linux-2.6.30/kernel/fork.c 2009-06-04 13:15:35.000000000 +0200
    @@ -1092,6 +1092,8 @@
    if (unlikely(current->ptrace))
    ptrace_fork(p, clone_flags);

    + p->stack_start = stack_start;
    +
    /* Perform scheduler related setup. Assign this task to a CPU. */
    sched_fork(p, clone_flags);




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