Messages in this thread | | | Date | Wed, 23 Feb 2022 15:49:41 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 04/29] x86/livepatch: Validate __fentry__ location |
| |
On Wed, Feb 23, 2022 at 09:23:27AM -0500, Steven Rostedt wrote: > On Wed, 23 Feb 2022 07:41:39 -0500 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > > --- a/kernel/trace/ftrace.c > > > +++ b/kernel/trace/ftrace.c > > > @@ -1578,7 +1578,23 @@ unsigned long ftrace_location_range(unsi > > > */ > > > unsigned long ftrace_location(unsigned long ip) > > > { > > > - return ftrace_location_range(ip, ip); > > > + struct dyn_ftrace *rec; > > > + unsigned long offset; > > > + unsigned long size; > > > + > > > + rec = lookup_rec(ip, ip); > > > + if (!rec) { > > > + if (!kallsyms_lookup_size_offset(ip, &size, &offset)) > > > + goto out; > > > +
if (!offset)
> > > + rec = lookup_rec(ip - offset, (ip - offset) + size); > > > + } > > > + > > > > Please create a new function for this. Perhaps find_ftrace_location(). > > > > ftrace_location() is used to see if the address given is a ftrace > > nop or not. This change will make it always return true. > > Now we could do: > > return ip <= (rec->ip + MCOUNT_INSN_SIZE) ? rec->ip : 0;
I don't see the point of that MCOUNT_INSN_SIZE there, I've done the above. If +0 then find the entry, wherever it may be.
> Since we would want rec->ip if the pointer is before the ftrace > instruction. But we would need to audit all use cases and make sure this is > not called from any hot paths (in a callback). > > This will affect kprobes and BPF as they both use ftrace_location() as well.
Yes, I already fixed kprobes, still trying to (re)discover how to run the bpf-selftests, that stuff is too painful :-(
| |