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Subject[PATCH 09/18] vchecker: Support toggle on/off of callstack check
Date
From: Namhyung Kim <namhyung@kernel.org>

By default, callstack checker only collects callchains. When a user
writes 'on' to the callstack file in debugfs, it checks and reports new
callstacks. Writing 'off' to disable it again.

# cd /sys/kernel/debug/vchecker
# echo 0 8 > anon_vma/callstack
# echo 1 > anon_vma/enable

... (do some work to collect enough callstacks) ...

# echo on > anon_vma/callstack

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
mm/kasan/vchecker.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/mm/kasan/vchecker.c b/mm/kasan/vchecker.c
index 0c9a4fc..6b3824f 100644
--- a/mm/kasan/vchecker.c
+++ b/mm/kasan/vchecker.c
@@ -69,6 +69,7 @@ struct vchecker_value_arg {
struct vchecker_callstack_arg {
depot_stack_handle_t *handles;
atomic_t count;
+ bool enabled;
};

static struct dentry *debugfs_root;
@@ -698,8 +699,7 @@ static bool check_callstack(struct kmem_cache *s, struct vchecker_cb *cb,
if (idx < CALLSTACK_MAX_HANDLE)
arg->handles[idx] = handle;

- /* TODO: support reporting new callstack */
- return true;
+ return !arg->enabled;
}

static int callstack_show(struct seq_file *f, void *v)
@@ -712,9 +712,36 @@ static int callstack_open(struct inode *inode, struct file *file)
return single_open(file, callstack_show, inode->i_private);
}

+static void callstack_onoff(struct file *filp, bool enable)
+{
+ struct kmem_cache *s = file_inode(filp)->i_private;
+ struct vchecker_cb *cb;
+
+ mutex_lock(&vchecker_meta);
+ list_for_each_entry(cb, &s->vchecker_cache.checker->cb_list, list) {
+ if (cb->type == &vchecker_types[VCHECKER_TYPE_CALLSTACK]) {
+ struct vchecker_callstack_arg *arg = cb->arg;
+
+ arg->enabled = enable;
+ }
+ }
+ mutex_unlock(&vchecker_meta);
+}
+
static ssize_t callstack_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
+ char buf[4];
+
+ if (copy_from_user(buf, ubuf, 4))
+ return -EFAULT;
+
+ /* turn on/off existing callstack checkers */
+ if (!strncmp(buf, "on", 2) || !strncmp(buf, "off", 3)) {
+ callstack_onoff(filp, buf[1] == 'n');
+ return cnt;
+ }
+
/* add a new (disabled) callstack checker at the given offset */
return vchecker_type_write(filp, ubuf, cnt, ppos,
VCHECKER_TYPE_CALLSTACK);
--
2.7.4
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