From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 115E7C4321E for ; Tue, 26 Apr 2022 10:25:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344509AbiDZK2q (ORCPT ); Tue, 26 Apr 2022 06:28:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348845AbiDZK2I (ORCPT ); Tue, 26 Apr 2022 06:28:08 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D642D5DE71; Tue, 26 Apr 2022 03:01:15 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 881C8B81D47; Tue, 26 Apr 2022 10:01:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F1A3C385A4; Tue, 26 Apr 2022 10:01:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650967273; bh=QpZImYLme4EiJQq5ruNv0+OY+uzOjs/YbCXzxSFuCCo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=XKRPriipnaberwU9XSsnbL9pNV4ANaq+YXwnl9ySmbeIqkTfRIb2jpiFpD4uWot2R tB1wUMnRCjynWi+JXceE/PNc+TrDbWbmflCL0UrHavtT2L50BoLaW8mMaeJeWsga/d 6aLwp/D1cGHrspOxDGgRGjAI0PtOnWSAjNayyLJ63WuWefF8bgZSUYZvYFPPxql1rK HESeX36K64XFebZRbpzB8Q17WKPC6W2dlhQaLDBGWtJccR0IpOmmf337IdHMt/G12t +PKM90yqiNd9Z8SX7I4DEUpJnHI02wQuIopVHv15F2G4GHzsyz/bdFDgTSaHZ140ci +sdwCrASZcyug== Date: Tue, 26 Apr 2022 19:01:08 +0900 From: Masami Hiramatsu To: Jiri Olsa Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , netdev@vger.kernel.org, bpf@vger.kernel.org, lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh Subject: Re: [PATCHv2 bpf-next 1/4] kallsyms: Add kallsyms_lookup_names function Message-Id: <20220426190108.d9c76f5ccff52e27dbef21af@kernel.org> In-Reply-To: References: <20220418124834.829064-1-jolsa@kernel.org> <20220418124834.829064-2-jolsa@kernel.org> <20220418233546.dfe0a1be12193c26b05cdd93@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Jiri, Sorry for replying late. On Fri, 22 Apr 2022 08:47:13 +0200 Jiri Olsa wrote: > On Tue, Apr 19, 2022 at 10:26:05AM +0200, Jiri Olsa wrote: > > SNIP > > > > > +static int kallsyms_callback(void *data, const char *name, > > > > + struct module *mod, unsigned long addr) > > > > +{ > > > > + struct kallsyms_data *args = data; > > > > + > > > > + if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp)) > > > > + return 0; > > > > + > > > > + addr = ftrace_location(addr); > > > > + if (!addr) > > > > + return 0; > > > > > > Ooops, wait. Did you do this last version? I missed this point. > > > This changes the meanings of the kernel function. > > > > yes, it was there before ;-) and you're right.. so some archs can > > return different address, I did not realize that > > > > > > > > > + > > > > + args->addrs[args->found++] = addr; > > > > + return args->found == args->cnt ? 1 : 0; > > > > +} > > > > + > > > > +/** > > > > + * kallsyms_lookup_names - Lookup addresses for array of symbols > > > > > > More correctly "Lookup 'ftraced' addresses for array of sorted symbols", right? > > > > > > I'm not sure, we can call it as a 'kallsyms' API, since this is using > > > kallsyms but doesn't return symbol address, but ftrace address. > > > I think this name misleads user to expect returning symbol address. > > > > > > > + * > > > > + * @syms: array of symbols pointers symbols to resolve, must be > > > > + * alphabetically sorted > > > > + * @cnt: number of symbols/addresses in @syms/@addrs arrays > > > > + * @addrs: array for storing resulting addresses > > > > + * > > > > + * This function looks up addresses for array of symbols provided in > > > > + * @syms array (must be alphabetically sorted) and stores them in > > > > + * @addrs array, which needs to be big enough to store at least @cnt > > > > + * addresses. > > > > > > Hmm, sorry I changed my mind. I rather like to expose kallsyms_on_each_symbol() > > > and provide this API from fprobe or ftrace, because this returns ftrace address > > > and thus this is only used from fprobe. > > > > ok, so how about: > > > > int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs); > > quick question.. is it ok if it stays in kalsyms.c object? I think if this is for the ftrace API, I think it should be in the ftrace.c, and it can remove unneeded #ifdefs in C code. > > so we don't need to expose kallsyms_on_each_symbol, > and it stays in 'kalsyms' place We don't need to expose it to modules, but just make it into a global scope. I don't think that doesn't cause a problem. Thank you, > > jirka > > > > diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h > index ce1bd2fbf23e..177e0b13c8c5 100644 > --- a/include/linux/kallsyms.h > +++ b/include/linux/kallsyms.h > @@ -72,6 +72,7 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, > #ifdef CONFIG_KALLSYMS > /* Lookup the address for a symbol. Returns 0 if not found. */ > unsigned long kallsyms_lookup_name(const char *name); > +int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs); > > extern int kallsyms_lookup_size_offset(unsigned long addr, > unsigned long *symbolsize, > @@ -103,6 +104,11 @@ static inline unsigned long kallsyms_lookup_name(const char *name) > return 0; > } > > +static inline int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs); > +{ > + return -ERANGE; > +} > + > static inline int kallsyms_lookup_size_offset(unsigned long addr, > unsigned long *symbolsize, > unsigned long *offset) > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index 79f2eb617a62..1e7136a765a9 100644 > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > > /* > * These will be re-linked against their real values > @@ -228,7 +229,7 @@ unsigned long kallsyms_lookup_name(const char *name) > return module_kallsyms_lookup_name(name); > } > > -#ifdef CONFIG_LIVEPATCH > +#if defined(CONFIG_LIVEPATCH) || defined(CONFIG_FPROBE) > /* > * Iterate over all symbols in vmlinux. For symbols from modules use > * module_kallsyms_on_each_symbol instead. > @@ -572,6 +573,73 @@ int sprint_backtrace_build_id(char *buffer, unsigned long address) > return __sprint_symbol(buffer, address, -1, 1, 1); > } > > +#ifdef CONFIG_FPROBE > +static int symbols_cmp(const void *a, const void *b) > +{ > + const char **str_a = (const char **) a; > + const char **str_b = (const char **) b; > + > + return strcmp(*str_a, *str_b); > +} > + > +struct kallsyms_data { > + unsigned long *addrs; > + const char **syms; > + size_t cnt; > + size_t found; > +}; > + > +static int kallsyms_callback(void *data, const char *name, > + struct module *mod, unsigned long addr) > +{ > + struct kallsyms_data *args = data; > + > + if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp)) > + return 0; > + > + addr = ftrace_location(addr); > + if (!addr) > + return 0; > + > + args->addrs[args->found++] = addr; > + return args->found == args->cnt ? 1 : 0; > +} > + > +/** > + * ftrace_lookup_symbols - Lookup addresses for array of symbols > + * > + * @sorted_syms: array of symbols pointers symbols to resolve, > + * must be alphabetically sorted > + * @cnt: number of symbols/addresses in @syms/@addrs arrays > + * @addrs: array for storing resulting addresses > + * > + * This function looks up addresses for array of symbols provided in > + * @syms array (must be alphabetically sorted) and stores them in > + * @addrs array, which needs to be big enough to store at least @cnt > + * addresses. > + * > + * This function returns 0 if all provided symbols are found, > + * -ESRCH otherwise. > + */ > +int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs) > +{ > + struct kallsyms_data args; > + > + args.addrs = addrs; > + args.syms = sorted_syms; > + args.cnt = cnt; > + args.found = 0; > + kallsyms_on_each_symbol(kallsyms_callback, &args); > + > + return args.found == args.cnt ? 0 : -ESRCH; > +} > +#else > +int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs) > +{ > + return -ERANGE; > +} > +#endif /* CONFIG_FPROBE */ > + > /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */ > struct kallsym_iter { > loff_t pos; -- Masami Hiramatsu