[PATCH 3/4] NOMMU: Make it possible to get the per-task stack usagethrough /proc for NOMMU

From: David Howells
Date: Thu Sep 24 2009 - 07:35:42 EST


Make it possible to get the per-task stack usage through /proc on a NOMMU
system. This is required because walk_page_range() doesn't work on NOMMU.

# grep "Stack usage:" /proc/*/status
/proc/1/status:Stack usage: 2 kB
/proc/56/status:Stack usage: 2 kB
/proc/57/status:Stack usage: 1 kB
/proc/58/status:Stack usage: 2 kB
/proc/59/status:Stack usage: 5 kB
/proc/self/status:Stack usage: 1 kB

I've only tested it with ELF-FDPIC, though it should work with FLAT too.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Cc: Mike Frysinger <vapier@xxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: Robin Getz <rgetz@xxxxxxxxxxxxxxxxxxxx>
---

fs/proc/array.c | 30 ++++++++++++++++++++++++++++++
1 files changed, 30 insertions(+), 0 deletions(-)


diff --git a/fs/proc/array.c b/fs/proc/array.c
index 0c6bc60..4b8f9e5 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -328,6 +328,7 @@ struct stack_stats {
unsigned long usage;
};

+#ifdef CONFIG_MMU
static int stack_usage_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
@@ -403,6 +404,35 @@ static inline void task_show_stack_usage(struct seq_file *m,
}
}

+#else /* CONFIG_MMU */
+
+/*
+ * Calculate the size of a NOMMU process's stack
+ */
+static void task_show_stack_usage(struct seq_file *m, struct task_struct *task)
+{
+ struct mm_struct *mm = get_task_mm(task);
+ unsigned long sp, base, limit, size;
+
+ if (mm) {
+ down_read(&mm->mmap_sem);
+
+ /* we assume the stack grows down towards the brk point */
+ sp = KSTK_ESP(task);
+ base = roundup(mm->arg_start, sizeof(long));
+ limit = mm->context.end_brk;
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+
+ if (limit <= sp && sp <= base)
+ size = base - sp;
+ else
+ size = base - limit;
+ seq_printf(m, "Stack usage:\t%lu kB\n", (size + 1023) >> 10);
+ }
+}
+#endif /* CONFIG_MMU */
+
int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{

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