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-rw-r--r--kernel/trace/trace.c111
1 files changed, 83 insertions, 28 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 13f2b84..f86efe9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3628,22 +3628,24 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp)
return 0;
}
-static int mark_printk(const char *fmt, ...)
-{
- int ret;
- va_list args;
- va_start(args, fmt);
- ret = trace_vprintk(0, fmt, args);
- va_end(args);
- return ret;
-}
-
static ssize_t
tracing_mark_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *fpos)
{
- char *buf;
- size_t written;
+ unsigned long addr = (unsigned long)ubuf;
+ struct ring_buffer_event *event;
+ struct ring_buffer *buffer;
+ struct print_entry *entry;
+ unsigned long irq_flags;
+ struct page *pages[2];
+ int nr_pages = 1;
+ ssize_t written;
+ void *page1;
+ void *page2;
+ int offset;
+ int size;
+ int len;
+ int ret;
if (tracing_disabled)
return -EINVAL;
@@ -3651,28 +3653,81 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
if (cnt > TRACE_BUF_SIZE)
cnt = TRACE_BUF_SIZE;
- buf = kmalloc(cnt + 2, GFP_KERNEL);
- if (buf == NULL)
- return -ENOMEM;
+ /*
+ * Userspace is injecting traces into the kernel trace buffer.
+ * We want to be as non intrusive as possible.
+ * To do so, we do not want to allocate any special buffers
+ * or take any locks, but instead write the userspace data
+ * straight into the ring buffer.
+ *
+ * First we need to pin the userspace buffer into memory,
+ * which, most likely it is, because it just referenced it.
+ * But there's no guarantee that it is. By using get_user_pages_fast()
+ * and kmap_atomic/kunmap_atomic() we can get access to the
+ * pages directly. We then write the data directly into the
+ * ring buffer.
+ */
+ BUILD_BUG_ON(TRACE_BUF_SIZE >= PAGE_SIZE);
- if (copy_from_user(buf, ubuf, cnt)) {
- kfree(buf);
- return -EFAULT;
+ /* check if we cross pages */
+ if ((addr & PAGE_MASK) != ((addr + cnt) & PAGE_MASK))
+ nr_pages = 2;
+
+ offset = addr & (PAGE_SIZE - 1);
+ addr &= PAGE_MASK;
+
+ ret = get_user_pages_fast(addr, nr_pages, 0, pages);
+ if (ret < nr_pages) {
+ while (--ret >= 0)
+ put_page(pages[ret]);
+ written = -EFAULT;
+ goto out;
}
- if (buf[cnt-1] != '\n') {
- buf[cnt] = '\n';
- buf[cnt+1] = '\0';
+
+ page1 = kmap_atomic(pages[0]);
+ if (nr_pages == 2)
+ page2 = kmap_atomic(pages[1]);
+
+ local_save_flags(irq_flags);
+ size = sizeof(*entry) + cnt + 2; /* possible \n added */
+ buffer = global_trace.buffer;
+ event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
+ irq_flags, preempt_count());
+ if (!event) {
+ /* Ring buffer disabled, return as if not open for write */
+ written = -EBADF;
+ goto out_unlock;
+ }
+
+ entry = ring_buffer_event_data(event);
+ entry->ip = _THIS_IP_;
+
+ if (nr_pages == 2) {
+ len = PAGE_SIZE - offset;
+ memcpy(&entry->buf, page1 + offset, len);
+ memcpy(&entry->buf[len], page2, cnt - len);
} else
- buf[cnt] = '\0';
+ memcpy(&entry->buf, page1 + offset, cnt);
- written = mark_printk("%s", buf);
- kfree(buf);
- *fpos += written;
+ if (entry->buf[cnt - 1] != '\n') {
+ entry->buf[cnt] = '\n';
+ entry->buf[cnt + 1] = '\0';
+ } else
+ entry->buf[cnt] = '\0';
+
+ ring_buffer_unlock_commit(buffer, event);
- /* don't tell userspace we wrote more - it might confuse them */
- if (written > cnt)
- written = cnt;
+ written = cnt;
+ *fpos += written;
+
+ out_unlock:
+ if (nr_pages == 2)
+ kunmap_atomic(page2);
+ kunmap_atomic(page1);
+ while (nr_pages > 0)
+ put_page(pages[--nr_pages]);
+ out:
return written;
}