Messages in this thread | | | From | Francis Laniel <> | Subject | Re: [PATCH for-next] tracing/kprobes: Add symbol counting check when module loads | Date | Tue, 31 Oct 2023 23:24:43 +0200 |
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Hi!
Le dimanche 29 octobre 2023, 05:10:46 EET Masami Hiramatsu (Google) a écrit : > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > Check the number of probe target symbols in the target module when > the module is loaded. If the probe is not on the unique name symbols > in the module, it will be rejected at that point. > > Note that the symbol which has a unique name in the target module, > it will be accepted even if there are same-name symbols in the > kernel or other modules,
I am wondering about symbols which are only part of one specific module. I wrote a comment about it below, please let me know what you think about it.
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > --- > kernel/trace/trace_kprobe.c | 112 > ++++++++++++++++++++++++++----------------- 1 file changed, 68 > insertions(+), 44 deletions(-) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index e834f149695b..90cf2219adb4 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -670,6 +670,21 @@ static int register_trace_kprobe(struct trace_kprobe > *tk) return ret; > } > > +static int validate_module_probe_symbol(const char *modname, const char > *symbol); + > +static int register_module_trace_kprobe(struct module *mod, struct > trace_kprobe *tk) +{ > + const char *p; > + int ret = 0; > + > + p = strchr(trace_kprobe_symbol(tk), ':'); > + if (p) > + ret = validate_module_probe_symbol(module_name(mod), p++); > + if (!ret) > + ret = register_trace_kprobe(tk); > + return ret; > +} > + > /* Module notifier call back, checking event on the module */ > static int trace_kprobe_module_callback(struct notifier_block *nb, > unsigned long val, void *data) > @@ -688,7 +703,7 @@ static int trace_kprobe_module_callback(struct > notifier_block *nb, if (trace_kprobe_within_module(tk, mod)) { > /* Don't need to check busy - this should have gone. */ > __unregister_trace_kprobe(tk); > - ret = __register_trace_kprobe(tk); > + ret = register_module_trace_kprobe(mod, tk); > if (ret) > pr_warn("Failed to re-register probe %s on %s: %d\n", > trace_probe_name(&tk->tp), > @@ -729,17 +744,55 @@ static int count_mod_symbols(void *data, const char > *name, unsigned long unused) return 0; > } > > -static unsigned int number_of_same_symbols(char *func_name) > +static unsigned int number_of_same_symbols(const char *mod, const char > *func_name) { > struct sym_count_ctx ctx = { .count = 0, .name = func_name }; > > - kallsyms_on_each_match_symbol(count_symbols, func_name, &ctx.count); > + if (!mod) > + kallsyms_on_each_match_symbol(count_symbols, func_name, &ctx.count); > > - module_kallsyms_on_each_symbol(NULL, count_mod_symbols, &ctx); > + module_kallsyms_on_each_symbol(mod, count_mod_symbols, &ctx);
I may be missing something here or reviewing too quickly. Wouldn't this function return count to be 0 if func_name is only part of the module named mod? Indeed, if the function is not in kernel symbol, kallsyms_on_each_match_symbol() will not loop. And, by giving mod to module_kallsyms_on_each_symbol(), the corresponding module will be skipped, so count_mob_symbols() would not be called. Hence, we would have 0 as count, which would lead to ENOENT later.
> return ctx.count; > } > > +static int validate_module_probe_symbol(const char *modname, const char > *symbol) +{ > + unsigned int count = number_of_same_symbols(modname, symbol); > + > + if (count > 1) { > + /* > + * Users should use ADDR to remove the ambiguity of > + * using KSYM only. > + */ > + return -EADDRNOTAVAIL; > + } else if (count == 0) { > + /* > + * We can return ENOENT earlier than when register the > + * kprobe. > + */ > + return -ENOENT; > + } > + return 0; > +} > + > +static int validate_probe_symbol(char *symbol) > +{ > + char *mod = NULL, *p; > + int ret; > + > + p = strchr(symbol, ':'); > + if (p) { > + mod = symbol; > + symbol = p + 1; > + *p = '\0'; > + } > + ret = validate_module_probe_symbol(mod, symbol); > + if (p) > + *p = ':'; > + return ret; > +} > + > static int __trace_kprobe_create(int argc, const char *argv[]) > { > /* > @@ -859,6 +912,14 @@ static int __trace_kprobe_create(int argc, const char > *argv[]) trace_probe_log_err(0, BAD_PROBE_ADDR); > goto parse_error; > } > + ret = validate_probe_symbol(symbol); > + if (ret) { > + if (ret == -EADDRNOTAVAIL) > + trace_probe_log_err(0, NON_UNIQ_SYMBOL); > + else > + trace_probe_log_err(0, BAD_PROBE_ADDR); > + goto parse_error; > + } > if (is_return) > ctx.flags |= TPARG_FL_RETURN; > ret = kprobe_on_func_entry(NULL, symbol, offset); > @@ -871,31 +932,6 @@ static int __trace_kprobe_create(int argc, const char > *argv[]) } > } > > - if (symbol && !strchr(symbol, ':')) { > - unsigned int count; > - > - count = number_of_same_symbols(symbol); > - if (count > 1) { > - /* > - * Users should use ADDR to remove the ambiguity of > - * using KSYM only. > - */ > - trace_probe_log_err(0, NON_UNIQ_SYMBOL); > - ret = -EADDRNOTAVAIL; > - > - goto error; > - } else if (count == 0) { > - /* > - * We can return ENOENT earlier than when register the > - * kprobe. > - */ > - trace_probe_log_err(0, BAD_PROBE_ADDR); > - ret = -ENOENT; > - > - goto error; > - } > - } > - > trace_probe_log_set_index(0); > if (event) { > ret = traceprobe_parse_event_name(&event, &group, gbuf, > @@ -1767,21 +1803,9 @@ create_local_trace_kprobe(char *func, void *addr, > unsigned long offs, char *event; > > if (func) { > - unsigned int count; > - > - count = number_of_same_symbols(func); > - if (count > 1) > - /* > - * Users should use addr to remove the ambiguity of > - * using func only. > - */ > - return ERR_PTR(-EADDRNOTAVAIL); > - else if (count == 0) > - /* > - * We can return ENOENT earlier than when register the > - * kprobe. > - */ > - return ERR_PTR(-ENOENT); > + ret = validate_probe_symbol(func); > + if (ret) > + return ERR_PTR(ret); > } > > /*
Best regards.
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