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Subject[PATCH 3/5 -mm] fault-injection: Clamp debugfs stacktrace-depth to MAX_STACK_TRACE_DEPTH
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Clamp /debug/fail*/stacktrace-depth to MAX_STACK_TRACE_DEPTH.
Ensures that a read of /debug/fail*/stacktrace-depth always
returns a truthful answer.

Signed-off-by: Don Mullis <dwm@meer.net>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
---
lib/fault-inject.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
Index: linux-2.6.18/lib/fault-inject.c
===================================================================
--- linux-2.6.18.orig/lib/fault-inject.c
+++ linux-2.6.18/lib/fault-inject.c
@@ -53,6 +53,8 @@ static bool fail_task(struct fault_attr
return !in_interrupt() && task->make_it_fail;
}

+#define MAX_STACK_TRACE_DEPTH 32
+
#ifdef CONFIG_STACK_UNWIND

static asmlinkage int fail_stacktrace_callback(struct unwind_frame_info *info,
@@ -98,8 +100,7 @@ static bool fail_stacktrace(struct fault

trace.nr_entries = 0;
trace.entries = entries;
- trace.max_entries = (depth < MAX_STACK_TRACE_DEPTH) ?
- depth : MAX_STACK_TRACE_DEPTH;
+ trace.max_entries = depth;
trace.skip = 1;
trace.all_contexts = 0;

@@ -179,6 +180,13 @@ static void debugfs_ul_set(void *data, u
*(unsigned long *)data = val;
}

+static void debugfs_ul_set_MAX_STACK_TRACE_DEPTH(void *data, u64 val)
+{
+ *(unsigned long *)data =
+ val < MAX_STACK_TRACE_DEPTH ?
+ val : MAX_STACK_TRACE_DEPTH;
+}
+
static u64 debugfs_ul_get(void *data)
{
return *(unsigned long *)data;
@@ -192,6 +200,17 @@ static struct dentry *debugfs_create_ul(
return debugfs_create_file(name, mode, parent, value, &fops_ul);
}

+DEFINE_SIMPLE_ATTRIBUTE(fops_ul_MAX_STACK_TRACE_DEPTH, debugfs_ul_get,
+ debugfs_ul_set_MAX_STACK_TRACE_DEPTH, "%llu\n");
+
+static struct dentry *debugfs_create_ul_MAX_STACK_TRACE_DEPTH(
+ const char *name, mode_t mode,
+ struct dentry *parent, unsigned long *value)
+{
+ return debugfs_create_file(name, mode, parent, value,
+ &fops_ul_MAX_STACK_TRACE_DEPTH);
+}
+
static void debugfs_atomic_t_set(void *data, u64 val)
{
atomic_set((atomic_t *)data, val);
@@ -284,8 +303,8 @@ int init_fault_attr_dentries(struct faul
mode, dir, &attr->task_filter);

attr->dentries.stacktrace_depth_file =
- debugfs_create_ul("stacktrace-depth", mode, dir,
- &attr->stacktrace_depth);
+ debugfs_create_ul_MAX_STACK_TRACE_DEPTH(
+ "stacktrace-depth", mode, dir, &attr->stacktrace_depth);

attr->dentries.require_start_file =
debugfs_create_ul("require-start", mode, dir, &attr->require_start);

-
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