On Thu, Feb 25, 2021 at 6:31 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> Here's nothing special about %s in TP_printk. It uses the same code as
> printk() and what other string formatters use.
>
> What is special is that the print is on data that is stored from a previous
> time.
Well, technically that's not actually limited to just %s, although
that's the common case.
All our magic "%p*" formats do the same thing: they print out not the
argument _value_, but something that the pointer value points to.
So "%pD" takes a "struct file *" pointer, and follows it to the
dentry, and then from the dentry to the name. So it will in fact
follow pointers even more than "%s" does.
It might indeed be worth having a warning for TP_printk() about any of
the formats that follow a pointer, exactly because of the whole "by
the time it actually prints, the pointer may be long gone".
Linus
