On Thu, 25 Feb 2021 09:49:15 -0800 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > 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. Correct, as I've told people about that as well. > > 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". > Just a comment? Or should we add some check that gives a warning for when one of these are used? That can be done at boot up or module load. (note, %s can be OK for some cases, as mentioned in a previous email). -- Steve
