Messages in this thread Patch in this message | | | Date | Thu, 24 Aug 2023 22:02:27 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [RFC PATCH v2 1/1] tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols |
| |
On Thu, 24 Aug 2023 12:37:34 +0200 Francis Laniel <flaniel@linux.microsoft.com> wrote:
> Previously to this commit, if func matches several symbols, a kprobe, being > either sysfs or PMU, would only be installed for the first matching address. > This could lead to some misunderstanding when some BPF code was never called > because it was attached to a function which was indeed not call, because the > effectively called one has no kprobes. > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > This way, user needs to use addr to remove the ambiguity.
Thanks for update the patch. I have some comments there.
> > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> > Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/ > --- > kernel/trace/trace_kprobe.c | 42 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 23dba01831f7..0c8dd6ba650b 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = { > .priority = 1 /* Invoked after kprobe module callback */ > }; > > +static int count_symbols(void *data, unsigned long unused) > +{ > + unsigned int *count = data; > + > + (*count)++; > + > + return 0; > +} > + > +static unsigned int func_name_several_symbols(char *func_name)
If this returns boolean, please use 'bool' for return type. Also, I think 'func_name_is_unique()' is more natural.
> +{ > + unsigned int count; > + > + count = 0; > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > + > + return count > 1; > +} > + > static int __trace_kprobe_create(int argc, const char *argv[]) > { > /* > @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const char *argv[]) > } > } > > + /* > + * If user specifies KSYM, we check it does not correspond to several > + * symbols. > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > + * he/she should use ADDR rather than KSYM to remove the ambiguity. > + */ > + if (symbol && func_name_several_symbols(symbol)) {
Then, here will be
if (symbol && !func_name_is_unique(symbol)) {
> + ret = -EADDRNOTAVAIL; > + > + goto error; > + } > + > trace_probe_log_set_index(0); > if (event) { > ret = traceprobe_parse_event_name(&event, &group, gbuf, > @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) > } > > #ifdef CONFIG_PERF_EVENTS > + > /* create a trace_kprobe, but don't add it to global lists */ > struct trace_event_call * > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > int ret; > char *event; > > + /* > + * If user specifies func, we check that function name does not > + * correspond to several symbols. > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > + * he/she should use addr and offs rather than func to remove the > + * ambiguity. > + */ > + if (func && func_name_several_symbols(func))
Ditto.
Thanks!
> + return ERR_PTR(-EADDRNOTAVAIL); > + > /* > * local trace_kprobes are not added to dyn_event, so they are never > * searched in find_trace_kprobe(). Therefore, there is no concern of > -- > 2.34.1 >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
| |