[patch] procfs: provide stack information for threads

Stefani Seibold
2009-06-04T20:21:41Z

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 start address of the stack.

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

- Code cleanup suggested by Andrew

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

fs/exec.c | 2 +
fs/proc/array.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++-
fs/proc/task_mmu.c | 14 +++++++++++++
include/linux/sched.h | 1
kernel/fork.c | 2 +
5 files changed, 70 insertions(+), 1 deletion(-)

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

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 2009-06-04 10:37:53.000000000 +0200
@@ -321,6 +321,55 @@
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 *p)
+{
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+
+ mm = get_task_mm(p);
+
+ if (mm) {
+ vma = find_vma(mm, p->stack_start);
+
+ if (vma)
+ seq_printf(m, "Stack usage:\t%lu kB\n",
+ get_stack_usage_in_bytes(vma, p) >> 10);
+
+ mmput(mm);
+ }
+}
+
int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
@@ -340,6 +389,7 @@
task_show_regs(m, task);
#endif
task_context_switch_counts(m, task);
+ task_show_stack_usage(m, task);
return 0;
}

@@ -481,7 +531,7 @@
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 2009-06-04 22:10:47.000000000 +0200
@@ -242,6 +242,20 @@
} 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]",
+ stack_start);
+ }
}
} 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);