Hello, On Mon, 20 May 2024, zhang warden wrote:
> > > > On May 20, 2024, at 14:46, Miroslav Benes <mbe...@suse.cz> wrote: > > > > Hi, > > > > On Mon, 20 May 2024, Wardenjohn wrote: > > > >> Livepatch module usually used to modify kernel functions. > >> If the patched function have bug, it may cause serious result > >> such as kernel crash. > >> > >> This is a kobject attribute of klp_func. Sysfs interface named > >> "called" is introduced to livepatch which will be set as true > >> if the patched function is called. > >> > >> /sys/kernel/livepatch/<patch>/<object>/<function,sympos>/called > >> > >> This value "called" is quite necessary for kernel stability > >> assurance for livepatching module of a running system. > >> Testing process is important before a livepatch module apply to > >> a production system. With this interface, testing process can > >> easily find out which function is successfully called. > >> Any testing process can make sure they have successfully cover > >> all the patched function that changed with the help of this interface. > > > > Even easier is to use the existing tracing infrastructure in the kernel > > (ftrace for example) to track the new function. You can obtain much more > > information with that than the new attribute provides. > > > > Regards, > > Miroslav > Hi Miroslav > > First, in most cases, testing process is should be automated, which make > using existing tracing infrastructure inconvenient. could you elaborate, please? We use ftrace exactly for this purpose and our testing process is also more or less automated. > Second, livepatch is > already use ftrace for functional replacement, I don’t think it is a > good choice of using kernel tracing tool to trace a patched function. Why? > At last, this attribute can be thought of as a state of a livepatch > function. It is a state, like the "patched" "transition" state of a > klp_patch. Adding this state will not break the state consistency of > livepatch. Yes, but the information you get is limited compared to what is available now. You would obtain the information that a patched function was called but ftrace could also give you the context and more. It would not hurt to add a new attribute per se but I am wondering about the reason and its usage. Once we have it, the commit message should be improved based on that. Regards, Miroslav
