On Tue, Jun 13, 2023 at 09:36:06AM -0400, Steven Rostedt wrote: > On Mon, 12 Jun 2023 22:04:28 -0700 > Yonghong Song <yhs@xxxxxxxx> wrote: > > > Thanks for explanation! It would be great if we can put more details in > > this email into the commit message! > > I agree. > > This is the patch I just pulled into my queue: great, thanks jirka > > From: Jiri Olsa <jolsa@xxxxxxxxxx> > Date: Sun, 11 Jun 2023 15:00:29 +0200 > Subject: [PATCH] ftrace: Show all functions with addresses in > available_filter_functions_addrs > > Adding new available_filter_functions_addrs file that shows all available > functions (same as available_filter_functions) together with addresses, > like: > > # cat available_filter_functions_addrs | head > ffffffff81000770 __traceiter_initcall_level > ffffffff810007c0 __traceiter_initcall_start > ffffffff81000810 __traceiter_initcall_finish > ffffffff81000860 trace_initcall_finish_cb > ... > > Note displayed address is the patch-site address and can differ from > /proc/kallsyms address. > > It's useful to have address avilable for traceable symbols, so we don't > need to allways cross check kallsyms with available_filter_functions > (or the other way around) and have all the data in single file. > > For backwards compatibility reasons we can't change the existing > available_filter_functions file output, but we need to add new file. > > The problem is that we need to do 2 passes: > > - through available_filter_functions and find out if the function is traceable > - through /proc/kallsyms to get the address for traceable function > > Having available_filter_functions symbols together with addresses allow > us to skip the kallsyms step and we are ok with the address in > available_filter_functions_addr not being the function entry, because > kprobe_multi uses fprobe and that handles both entry and patch-site > address properly. > > We have 2 interfaces how to create kprobe_multi link: > > a) passing symbols to kernel > > 1) user gathers symbols and need to ensure that they are > trace-able -> pass through available_filter_functions file > > 2) kernel takes those symbols and translates them to addresses > through kallsyms api > > 3) addresses are passed to fprobe/ftrace through: > > register_fprobe_ips > -> ftrace_set_filter_ips > > b) passing addresses to kernel > > 1) user gathers symbols and needs to ensure that they are > trace-able -> pass through available_filter_functions file > > 2) user takes those symbols and translates them to addresses > through /proc/kallsyms > > 3) addresses are passed to the kernel and kernel calls: > > register_fprobe_ips > -> ftrace_set_filter_ips > > The new available_filter_functions_addrs file helps us with option b), > because we can make 'b 1' and 'b 2' in one step - while filtering traceable > functions, we get the address directly. > > Link: https://lore.kernel.org/linux-trace-kernel/20230611130029.1202298-1-jolsa@xxxxxxxxxx > > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > Cc: Jackie Liu <liu.yun@xxxxxxxxx> > Suggested-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> > Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> > --- > Documentation/trace/ftrace.rst | 6 ++++++ > include/linux/ftrace.h | 1 + > kernel/trace/ftrace.c | 37 ++++++++++++++++++++++++++++++++++ > 3 files changed, 44 insertions(+) > > diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst > index df2d3e57a83f..b7308ab10c0e 100644 > --- a/Documentation/trace/ftrace.rst > +++ b/Documentation/trace/ftrace.rst > @@ -324,6 +324,12 @@ of ftrace. Here is a list of some of the key files: > "set_graph_function", or "set_graph_notrace". > (See the section "dynamic ftrace" below for more details.) > > + available_filter_functions_addrs: > + > + Similar to available_filter_functions, but with address displayed > + for each function. The displayed address is the patch-site address > + and can differ from /proc/kallsyms address. > + > dyn_ftrace_total_info: > > This file is for debugging purposes. The number of functions that > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index 49f279f4c3a1..8e59bd954153 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -633,6 +633,7 @@ enum { > FTRACE_ITER_MOD = (1 << 5), > FTRACE_ITER_ENABLED = (1 << 6), > FTRACE_ITER_TOUCHED = (1 << 7), > + FTRACE_ITER_ADDRS = (1 << 8), > }; > > void arch_ftrace_update_code(int command); > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 764668467155..b24c573934af 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -3861,6 +3861,9 @@ static int t_show(struct seq_file *m, void *v) > if (!rec) > return 0; > > + if (iter->flags & FTRACE_ITER_ADDRS) > + seq_printf(m, "%lx ", rec->ip); > + > if (print_rec(m, rec->ip)) { > /* This should only happen when a rec is disabled */ > WARN_ON_ONCE(!(rec->flags & FTRACE_FL_DISABLED)); > @@ -3996,6 +3999,30 @@ ftrace_touched_open(struct inode *inode, struct file *file) > return 0; > } > > +static int > +ftrace_avail_addrs_open(struct inode *inode, struct file *file) > +{ > + struct ftrace_iterator *iter; > + int ret; > + > + ret = security_locked_down(LOCKDOWN_TRACEFS); > + if (ret) > + return ret; > + > + if (unlikely(ftrace_disabled)) > + return -ENODEV; > + > + iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter)); > + if (!iter) > + return -ENOMEM; > + > + iter->pg = ftrace_pages_start; > + iter->flags = FTRACE_ITER_ADDRS; > + iter->ops = &global_ops; > + > + return 0; > +} > + > /** > * ftrace_regex_open - initialize function tracer filter files > * @ops: The ftrace_ops that hold the hash filters > @@ -5916,6 +5943,13 @@ static const struct file_operations ftrace_touched_fops = { > .release = seq_release_private, > }; > > +static const struct file_operations ftrace_avail_addrs_fops = { > + .open = ftrace_avail_addrs_open, > + .read = seq_read, > + .llseek = seq_lseek, > + .release = seq_release_private, > +}; > + > static const struct file_operations ftrace_filter_fops = { > .open = ftrace_filter_open, > .read = seq_read, > @@ -6377,6 +6411,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer) > trace_create_file("available_filter_functions", TRACE_MODE_READ, > d_tracer, NULL, &ftrace_avail_fops); > > + trace_create_file("available_filter_functions_addrs", TRACE_MODE_READ, > + d_tracer, NULL, &ftrace_avail_addrs_fops); > + > trace_create_file("enabled_functions", TRACE_MODE_READ, > d_tracer, NULL, &ftrace_enabled_fops); > > -- > 2.39.2 >
