On Mon, Aug 15, 2022 at 12:30:46PM +0200, Jiri Olsa wrote: > On Mon, Aug 15, 2022 at 12:13:39PM +0200, Peter Zijlstra wrote: > > On Thu, Aug 11, 2022 at 11:15:22AM +0200, Jiri Olsa wrote: > > > Keeping the resolved 'addr' in kallsyms_callback, instead of taking > > > ftrace_location value, because we depend on symbol address in the > > > cookie related code. > > > > > > With CONFIG_X86_KERNEL_IBT option the ftrace_location value differs > > > from symbol address, which screwes the symbol address cookies matching. > > > > > > There are 2 users of this function: > > > - bpf_kprobe_multi_link_attach > > > for which this fix is for > > > > Except you fail to explain what the problem is and how this helps > > anything. > > we search this array of resolved addresses later in cookie code > (bpf_kprobe_multi_cookie) for address returned by fprobe, which > is not 'ftrace_location' address What is fprobe? > so we want ftrace_lookup_symbols to return 'only' resolved address > at this point, not 'ftrace_location' address In general; I'm completely confused what any of this code is doing. Mostly I don't speak BPF *at*all*. And have very little clue as to what things are supposed to do, please help me along. But the thing is, we're likely going to change all this (function call abi) again in the very near future; it would be very nice if all this code could grow some what/why comments, because I've gotten lost multiple times in all this.
