Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757780AbZCMJ3S (ORCPT ); Fri, 13 Mar 2009 05:29:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751517AbZCMJ3G (ORCPT ); Fri, 13 Mar 2009 05:29:06 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:58239 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750852AbZCMJ3D (ORCPT ); Fri, 13 Mar 2009 05:29:03 -0400 Message-ID: <49BA2704.9040404@cn.fujitsu.com> Date: Fri, 13 Mar 2009 17:27:32 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Lai Jiangshan CC: Paulo Marques , Ingo Molnar , Sam Ravnborg , Andrew Morton , Steven Rostedt , Frederic Weisbecker , LKML Subject: Re: [PATCH V3] kallsyms, tracing: output more proper symbol name References: <49B7863F.6020804@cn.fujitsu.com> <20090311094621.GA13543@elte.hu> <49B7B70F.5010908@grupopie.com> <49B876BB.50007@cn.fujitsu.com> <49B92B25.6020805@grupopie.com> <49BA06E2.7080807@cn.fujitsu.com> In-Reply-To: <49BA06E2.7080807@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4451 Lines: 146 Lai Jiangshan wrote: > Paulo Marques wrote: >> I would probably still place another test to compare the number of >> underscores, after both symbols are found to be equal in the "linker >> script provided" criteria. >> >> The way it is now, for my current kallsyms table: >> >>> ffffffff80200000 A _text >>> ffffffff80200000 T startup_64 >>> ffffffff80209000 T _stext >>> ffffffff80209000 t init_post >> a "startup_64" address would display as "_text" and a "init_post" >> address would display as "_stext". >> >> You can add all the stext/etext symbols as special cases to the >> "may_be_linker_script_provide_symbol" function (like it was on your v1 >> patch), but I'm just afraid that we'll find more cases in the future >> that are not automatically caught by these rules... >> > [resend, previous v3 has some mistakes] Subject: kallsyms, tracing: output more proper symbol name Impact: bugfix, output reliable result Debug tools(dump_stack(), ftrace...) are like to print out symbols. But it is always print out the first aliased symbol.(Aliased symbols are symbols with the same address), and the first aliased symbol is sometime not proper. # echo function_graph > current_tracer # cat trace ...... 1) 1.923 us | select_nohz_load_balancer(); 1) + 76.692 us | } 1) | default_idle() { 1) ==========> | __irqentry_text_start() { 1) 0.000 us | native_apic_mem_write(); 1) | irq_enter() { 1) 0.000 us | idle_cpu(); 1) | tick_check_idle() { 1) 0.000 us | tick_check_oneshot_broadcast(); 1) | tick_nohz_stop_idle() { ...... It's very embarrassing, it ouputs "__irqentry_text_start()", actually, it should output "smp_apic_timer_interrupt()". (these two symbol are the same address, but "__irqentry_text_start" is deemed to the first aliased symbol by scripts/kallsyms) This patch puts symbols like "__irqentry_text_start" to the second aliased symbols. And a more proper symbol name becomes the first. Aliased symbols mostly come from linker script. The solution is guessing "is this symbol defined in linker script", the symbols defined in linker script will not become the first aliased symbol. And if symbols are found to be equal in this "linker script provided" criteria, symbols are sorted by the number of prefix underscores. Signed-off-by: Lai Jiangshan --- diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index ad2434b..b187edc 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -500,6 +500,51 @@ static void optimize_token_table(void) optimize_result(); } +/* guess for "linker script provide" symbol */ +static int may_be_linker_script_provide_symbol(const struct sym_entry *se) +{ + const char *symbol = (char *)se->sym + 1; + int len = se->len - 1; + + if (len < 8) + return 0; + + if (symbol[0] != '_' || symbol[1] != '_') + return 0; + + /* __start_XXXXX */ + if (!memcmp(symbol + 2, "start_", 6)) + return 1; + + /* __stop_XXXXX */ + if (!memcmp(symbol + 2, "stop_", 5)) + return 1; + + /* __end_XXXXX */ + if (!memcmp(symbol + 2, "end_", 4)) + return 1; + + /* __XXXXX_start */ + if (!memcmp(symbol + len - 6, "_start", 6)) + return 1; + + /* __XXXXX_end */ + if (!memcmp(symbol + len - 4, "_end", 4)) + return 1; + + return 0; +} + +static int prefix_underscores_count(const char *str) +{ + const char *tail = str; + + while (*tail == '_') + tail++; + + return tail - str; +} + static int compare_symbols(const void *a, const void *b) { const struct sym_entry *sa; @@ -521,6 +566,18 @@ static int compare_symbols(const void *a, const void *b) if (wa != wb) return wa - wb; + /* sort by "linker script provide" type */ + wa = may_be_linker_script_provide_symbol(sa); + wb = may_be_linker_script_provide_symbol(sb); + if (wa != wb) + return wa - wb; + + /* sort by the number of prefix underscores */ + wa = prefix_underscores_count((const char *)sa->sym + 1); + wb = prefix_underscores_count((const char *)sb->sym + 1); + if (wa != wb) + return wa - wb; + /* sort by initial order, so that other symbols are left undisturbed */ return sa->start_pos - sb->start_pos; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/