Messages in this thread | | | Date | Wed, 1 Nov 2023 08:15:09 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH for-next] tracing/kprobes: Add symbol counting check when module loads |
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Hi,
On Tue, 31 Oct 2023 23:24:43 +0200 Francis Laniel <flaniel@linux.microsoft.com> wrote:
> > @@ -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?
No, please read below.
> 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.
Would you mean the case func_name is on the specific module? If 'mod' is specified, module_kallsyms_on_each_symbol() only loops on symbols in the module names 'mod'.
int module_kallsyms_on_each_symbol(const char *modname, int (*fn)(void *, const char *, unsigned long), void *data) { struct module *mod; unsigned int i; int ret = 0;
mutex_lock(&module_mutex); list_for_each_entry(mod, &modules, list) { struct mod_kallsyms *kallsyms;
if (mod->state == MODULE_STATE_UNFORMED) continue;
if (modname && strcmp(modname, mod->name)) continue; ...
So with above change, 'if mod is not specified, search the symbols in kernel and all modules. If mod is sepecified, search the symbol on the specific module'.
Thus, "if func_name is only part of the module named mod", the module_kallsyms_on_each_symbol() will count the 'func_name' in 'mod' module correctly.
Thank you,
Thank you,
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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