// SPDX-License-Identifier: GPL-2.0-or-later
#define pr_fmt(fmt) "ref_tracker: " fmt
#include <linux/export.h>
#include <linux/list_sort.h>
#include <linux/ref_tracker.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/stackdepot.h>
#define REF_TRACKER_STACK_ENTRIES 16
#define STACK_BUF_SIZE 1024
struct ref_tracker {
struct list_head head; /* anchor into dir->list or dir->quarantine */
bool dead;
depot_stack_handle_t alloc_stack_handle;
depot_stack_handle_t free_stack_handle;
};
struct ref_tracker_dir_stats {
int total;
int count;
struct {
depot_stack_handle_t stack_handle;
unsigned int count;
} stacks[];
};
static struct ref_tracker_dir_stats *
ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
{
struct ref_tracker_dir_stats *stats;
struct ref_tracker *tracker;
stats = kmalloc(struct_size(stats, stacks, limit),
GFP_NOWAIT | __GFP_NOWARN);
if (!stats)
return ERR_PTR(-ENOMEM);
stats->total = 0;
stats->count = 0;
list_for_each_entry(tracker, &dir->list, head) {
depot_stack_handle_t stack = tracker->alloc_stack_handle;
int i;
++stats->total;
for (i = 0; i < stats->count; ++i)
if (stats->stacks[i].stack_handle == stack)
break;
if (i >= limit)
continue;
if (i >= stats->count) {
stats->stacks[i].stack_handle = stack;
stats->stacks[i].count = 0;
++stats->count;
}
++stats->stacks[i].count;
}
return stats;
}
struct ostream {
char *buf;
int size, used;
};
#define pr_ostream(stream, fmt, args...) \
({ \
struct ostream *_s = (stream); \
\
if (!_s->buf) { \
pr_err(fmt, ##args); \
} else { \
int ret, len = _s->size - _s->used; \
ret = snprintf(_s->buf + _s->used, len, pr_fmt(fmt), ##args); \
_s->used += min(ret, len); \
} \
})
static void
__ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
unsigned int display_limit, struct ostream *s)
{
struct ref_tracker_dir_stats *stats;
unsigned int i = 0, skipped;
depot_stack_handle_t stack;
char *sbuf;
lockdep_assert_held(&dir->lock);
if (list_empty(&dir->list))
return;
stats = ref_tracker_get_stats(dir, display_limit);
if (IS_ERR(stats)) {
pr_ostream(s, "%s@%pK: couldn't get stats, error %pe\n",
dir->name, dir, stats);
return;
}
sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN);
for (i = 0, skipped = stats->total; i < stats->count; ++i) {
stack = stats->stacks[i].stack_handle;
if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
sbuf[0] = 0;
pr_ostream(s, "%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
stats->stacks[i].count, stats->total, sbuf);
skipped -= stats->stacks[i].count;
}
if (skipped)
pr_ostream(s, "%s@%pK skipped reports about %d/%d users.\n",
dir->name, dir, skipped, stats->total);
kfree(sbuf);
kfree(stats);
}
void ref_tracker_dir_print_locked(struct ref_tracker_dir *dir,
unsigned int display_limit)
{
struct ostream os = {};
__ref_tracker_dir_pr_ostream(dir, display_limit, &os);
}
EXPORT_SYMBOL(ref_tracker_dir_print_locked);
void ref_tracker_dir_print(struct ref_tracker_dir *dir,
unsigned int display_limit)
{
unsigned long flags;
spin_lock_irqsave(&dir->lock, flags);
ref_tracker_dir_print_locked(dir, display_limit);
spin_unlock_irqrestore(&dir->lock, flags);
}
EXPORT_SYMBOL(ref_tracker_dir_print);
int ref_tracker_dir_snprint(struct ref_tracker_dir *dir, char *buf, size_t size)
{
struct ostream os = { .buf = buf, .size = size };
unsigned long flags;
spin_lock_irqsave(&dir->lock, flags);
__ref_tracker_dir_pr_ostream(dir, 16, &os);
spin_unlock_irqrestore(&dir->lock, flags);
return os.used;
}
EXPORT_SYMBOL(ref_tracker_dir_snprint);
void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
{
struct ref_tracker *tracker, *n;
unsigned long flags;
bool leak = false;
dir->dead = true;
spin_lock_irqsave(&dir->lock, flags);
list_for_each_entry_safe(tracker, n, &dir->quarantine, head) {
list_del(&tracker->head);
kfree(tracker);
dir->quarantine_avail++;
}
if (!list_empty(&dir->list)) {
ref_tracker_dir_print_locked(dir, 16);
leak = true;
list_for_each_entry_safe(tracker, n, &dir->list, head) {
list_del(&tracker->head);
kfree(tracker);
}
}
spin_unlock_irqrestore(&dir->lock, flags);
WARN_ON_ONCE(leak);
WARN_ON_ONCE(refcount_read(&dir->untracked) != 1);
WARN_ON_ONCE(refcount_read(&dir->no_tracker) != 1);
}
EXPORT_SYMBOL(ref_tracker_dir_exit);
int ref_tracker_alloc(struct ref_tracker_dir *dir,
struct ref_tracker **trackerp,
gfp_t gfp)
{
unsigned long entries[REF_TRACKER_STACK_ENTRIES];
struct ref_tracker *tracker;
unsigned int nr_entries;
gfp_t gfp_mask = gfp | __GFP_NOWARN;
unsigned long flags;
WARN_ON_ONCE(dir->dead);
if (!trackerp) {
refcount_inc(&dir->no_tracker);
return 0;
}
if (gfp & __GFP_DIRECT_RECLAIM)
gfp_mask |= __GFP_NOFAIL;
*trackerp = tracker = kzalloc(sizeof(*tracker), gfp_mask);
if (unlikely(!tracker)) {
pr_err_once("memory allocation failure, unreliable refcount tracker.\n");
refcount_inc(&dir->untracked);
return -ENOMEM;
}
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
tracker->alloc_stack_handle = stack_depot_save(entries, nr_entries, gfp);
spin_lock_irqsave(&dir->lock, flags);
list_add(&tracker->head, &dir->list);
spin_unlock_irqrestore(&dir->lock, flags);
return 0;
}
EXPORT_SYMBOL_GPL(ref_tracker_alloc);
int ref_tracker_free(struct ref_tracker_dir *dir,
struct ref_tracker **trackerp)
{
unsigned long entries[REF_TRACKER_STACK_ENTRIES];
depot_stack_handle_t stack_handle;
struct ref_tracker *tracker;
unsigned int nr_entries;
unsigned long flags;
WARN_ON_ONCE(dir->dead);
if (!trackerp) {
refcount_dec(&dir->no_tracker);
return 0;
}
tracker = *trackerp;
if (!tracker) {
refcount_dec(&dir->untracked);
return -EEXIST;
}
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
stack_handle = stack_depot_save(entries, nr_entries,
GFP_NOWAIT | __GFP_NOWARN);
spin_lock_irqsave(&dir->lock, flags);
if (tracker->dead) {
pr_err("reference already released.\n");
if (tracker->alloc_stack_handle) {
pr_err("allocated in:\n");
stack_depot_print(tracker->alloc_stack_handle);
}
if (tracker->free_stack_handle) {
pr_err("freed in:\n");
stack_depot_print(tracker->free_stack_handle);
}
spin_unlock_irqrestore(&dir->lock, flags);
WARN_ON_ONCE(1);
return -EINVAL;
}
tracker->dead = true;
tracker->free_stack_handle = stack_handle;
list_move_tail(&tracker->head, &dir->quarantine);
if (!dir->quarantine_avail) {
tracker = list_first_entry(&dir->quarantine, struct ref_tracker, head);
list_del(&tracker->head);
} else {
dir->quarantine_avail--;
tracker = NULL;
}
spin_unlock_irqrestore(&dir->lock, flags);
kfree(tracker);
return 0;
}
EXPORT_SYMBOL_GPL(ref_tracker_free);
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