diff options
| -rw-r--r-- | kernel/trace/trace.c | 111 |
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; } |
