Messages in this thread | | | Date | Fri, 11 May 2018 15:21:51 +0900 | From | Sergey Senozhatsky <> | Subject | Re: printk feature for syzbot? |
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On (05/11/18 11:38), Tetsuo Handa wrote: > > > > So you basically want to have one more con_msg_format_flags? Do > > you want to track a context which prints out a messages or the > > context which "generated" the message? A CPU/task that stores > > a logbuf entry - vprintk_emit() - is not always the same as the > > CPU/task that prints it to consoles - console_unlock(). > > > > Well, below is the (partial) patch.
Hi,
Tetsuo, I will take a look a bit later, but at glance, there are several ways to achieve what you are trying to do. The first one is the way you did it - add additional buffer and make that context tracking info part of the message body. Another one would be to extend struct printk_log and add pid/cpu/flag there, which you then can convert into text in msg_print_text(). So far we talked about extending printk_log. Yet another one could be - add vsprintf specifiers that would add pid/cpu/flag to the vsprintf-ed message. You then can re-define pr_fmt, for instance, in the code you want to track pr_fmt "%zZ" fmt, or somehow force printk to add that "%zZ" to every message.
> By the way, when I tried to make similar change for printk_safe_log_store(), > I noticed that printk_safe_log_store() is not safe because it is reusing > the va_list variable after "goto again;". We need to use va_copy(), or > we will get crash like an example shown below.
Oh, right. Can you send a patch?
-ss
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