Messages in this thread | | | Date | Sat, 12 Nov 2022 14:23:39 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH 2/3] tracing/eprobe: Add eprobe filter support |
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On Wed, 9 Nov 2022 00:33:37 -0300 Rafael Mendonca <rafaelmendsr@gmail.com> wrote:
> Hi Masami, > I was playing around with the filter option and couldn't get it to work the way > I was expecting. For example, I'm getting the following output: > > root@localhost:/sys/kernel/tracing# echo 'e syscalls/sys_enter_openat \ > flags_rename=$flags:u32 if flags < 1000' >> dynamic_events > root@localhost:/sys/kernel/tracing# echo 1 > events/eprobes/sys_enter_openat/enable > [ 114.551550] event trace: Could not enable event sys_enter_openat > -bash: echo: write error: Invalid argument > > I was wondering if the trace_event_call passed to create_event_filter() > shouldn't be 'ep->event' instead of 'file->event_call' as such: > > diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c > index e888446d80fa..123d2c0a6b68 100644 > --- a/kernel/trace/trace_eprobe.c > +++ b/kernel/trace/trace_eprobe.c > @@ -643,7 +643,7 @@ new_eprobe_trigger(struct trace_eprobe *ep, struct > trace_event_file *file) > INIT_LIST_HEAD(&trigger->list); > > if (ep->filter_str) { > - ret = create_event_filter(file->tr, file->event_call, > + ret = create_event_filter(file->tr, ep->event, > ep->filter_str, false, &filter); > if (ret) > goto error;
Ah, OK. I got it. the "file->event_call" is for the eprobe's event itself, thus the filter doesn't work. ep->event is the event of the original event. Thus your fix is correct.
Thank you!
> > Applying the above change seems to make it work the way I was expecting: > > root@localhost:/sys/kernel/tracing# echo 'e syscalls/sys_enter_openat \ > flags_rename=$flags:u32 if flags < 1000' >> dynamic_events > root@localhost:/sys/kernel/tracing# echo 1 > events/eprobes/sys_enter_openat/enable > root@localhost:/sys/kernel/tracing# tail trace > cat-241 [000] ...1. 266.498449: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > cat-242 [000] ...1. 266.977640: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > cat-242 [000] ...1. 266.979883: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > bash-223 [000] ...1. 272.322714: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=577 > cat-243 [000] ...1. 273.630900: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > cat-243 [000] ...1. 273.633464: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > tail-244 [000] ...1. 300.013530: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > tail-244 [000] ...1. 300.018584: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > tail-245 [000] ...1. 301.237883: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > tail-245 [000] ...1. 301.243375: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0 > > I'm not familiar with the eprobe code, sorry if this is nonsense. > > > + ep->filter_str, false, &filter); > > + if (ret) > > + goto error; > > + } > > + RCU_INIT_POINTER(trigger->filter, filter); > > > > edata->file = file; > > edata->ep = ep; > > trigger->private_data = edata; > > > > return trigger; > > +error: > > + free_event_filter(filter); > > + kfree(edata); > > + kfree(trigger); > > + return ERR_PTR(ret); > > } > > > > static int enable_eprobe(struct trace_eprobe *ep, > > @@ -651,6 +667,7 @@ static int disable_eprobe(struct trace_eprobe *ep, > > { > > struct event_trigger_data *trigger = NULL, *iter; > > struct trace_event_file *file; > > + struct event_filter *filter; > > struct eprobe_data *edata; > > > > file = find_event_file(tr, ep->event_system, ep->event_name); > > @@ -677,6 +694,10 @@ static int disable_eprobe(struct trace_eprobe *ep, > > /* Make sure nothing is using the edata or trigger */ > > tracepoint_synchronize_unregister(); > > > > + filter = rcu_access_pointer(trigger->filter); > > + > > + if (filter) > > + free_event_filter(filter); > > kfree(edata); > > kfree(trigger); > > > > @@ -848,12 +869,62 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[ > > return ret; > > } > > > > +static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const char *argv[]) > > +{ > > + struct event_filter *dummy; > > + int i, ret, len = 0; > > + char *p; > > + > > + if (argc == 0) { > > + trace_probe_log_err(0, NO_EP_FILTER); > > + return -EINVAL; > > + } > > + > > + /* Recover the filter string */ > > + for (i = 0; i < argc; i++) > > + len += strlen(argv[i]) + 1; > > + > > + ep->filter_str = kzalloc(len, GFP_KERNEL); > > + if (!ep->filter_str) > > + return -ENOMEM; > > + > > + p = ep->filter_str; > > + for (i = 0; i < argc; i++) { > > + ret = snprintf(p, len, "%s ", argv[i]); > > + if (ret < 0) > > + goto error; > > + if (ret > len) { > > + ret = -E2BIG; > > + goto error; > > + } > > + p += ret; > > + len -= ret; > > + } > > + p[-1] = '\0'; > > + > > + /* > > + * Ensure the filter string can be parsed correctly. Note, this > > + * filter string is for the original event, not for the eprobe. > > + */ > > + ret = create_event_filter(top_trace_array(), ep->event, ep->filter_str, > > + true, &dummy); > > + free_event_filter(dummy); > > + if (ret) > > + goto error; > > + > > + return 0; > > +error: > > + kfree(ep->filter_str); > > + ep->filter_str = NULL; > > + return ret; > > +} > > + > > static int __trace_eprobe_create(int argc, const char *argv[]) > > { > > /* > > * Argument syntax: > > - * e[:[GRP/][ENAME]] SYSTEM.EVENT [FETCHARGS] > > - * Fetch args: > > + * e[:[GRP/][ENAME]] SYSTEM.EVENT [FETCHARGS] [if FILTER] > > + * Fetch args (no space): > > * <name>=$<field>[:TYPE] > > */ > > const char *event = NULL, *group = EPROBE_EVENT_SYSTEM; > > @@ -863,8 +934,8 @@ static int __trace_eprobe_create(int argc, const char *argv[]) > > char buf1[MAX_EVENT_NAME_LEN]; > > char buf2[MAX_EVENT_NAME_LEN]; > > char gbuf[MAX_EVENT_NAME_LEN]; > > - int ret = 0; > > - int i; > > + int ret = 0, filter_idx = 0; > > + int i, filter_cnt; > > > > if (argc < 2 || argv[0][0] != 'e') > > return -ECANCELED; > > @@ -894,6 +965,15 @@ static int __trace_eprobe_create(int argc, const char *argv[]) > > event = buf1; > > } > > > > + for (i = 2; i < argc; i++) { > > + if (!strcmp(argv[i], "if")) { > > + filter_idx = i + 1; > > + filter_cnt = argc - filter_idx; > > + argc = i; > > + break; > > + } > > + } > > + > > mutex_lock(&event_mutex); > > event_call = find_and_get_event(sys_name, sys_event); > > ep = alloc_event_probe(group, event, event_call, argc - 2); > > @@ -909,6 +989,14 @@ static int __trace_eprobe_create(int argc, const char *argv[]) > > goto error; > > } > > > > + if (filter_idx) { > > + trace_probe_log_set_index(filter_idx); > > + ret = trace_eprobe_parse_filter(ep, filter_cnt, argv + filter_idx); > > + if (ret) > > + goto parse_error; > > + } else > > + ep->filter_str = NULL; > > + > > argc -= 2; argv += 2; > > /* parse arguments */ > > for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { > > diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h > > index 3b3869ae8cfd..de38f1c03776 100644 > > --- a/kernel/trace/trace_probe.h > > +++ b/kernel/trace/trace_probe.h > > @@ -445,7 +445,8 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, > > C(SAME_PROBE, "There is already the exact same probe event"),\ > > C(NO_EVENT_INFO, "This requires both group and event name to attach"),\ > > C(BAD_ATTACH_EVENT, "Attached event does not exist"),\ > > - C(BAD_ATTACH_ARG, "Attached event does not have this field"), > > + C(BAD_ATTACH_ARG, "Attached event does not have this field"),\ > > + C(NO_EP_FILTER, "No filter rule after 'if'"), > > > > #undef C > > #define C(a, b) TP_ERR_##a > >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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