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[2620:137:e000::1:20]) by mx.google.com with ESMTP id x4-20020a17090a9dc400b00229311676ecsi16143992pjv.49.2023.01.31.05.22.44; Tue, 31 Jan 2023 05:22:57 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=lwLEejvt; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231848AbjAaNQ6 (ORCPT + 99 others); Tue, 31 Jan 2023 08:16:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231726AbjAaNQw (ORCPT ); Tue, 31 Jan 2023 08:16:52 -0500 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 14670442EE; Tue, 31 Jan 2023 05:16:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1675171011; x=1706707011; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=buNnSEAE01t7rtwc1PFmnTIysYUAolAqo25T7Ol7MAM=; b=lwLEejvtrg4vLcqc2PrdZiEWiFZ3wyst1LRkGE3YeXCPUjXEGgxwr0Do YJiG1LtqZaf1eBkdZGMF/l7drdg2lFgQp8U+IZuyemFnNVF4bSUQMSXG0 gYabLir51Cls0y4WDiw9Vb5kmVa74y+hscS+eiYCbw4sGbdaV+PBXdkI0 88V3tc0mOostwgIs8esvlWlM5BD/IT8By8xAz4QRbgjdnolrri7+idIxW Rj3s28Ea04riNUpX7hYq+TGM1kL/QdT2k4KcGfZu4z6WxXjpb5YAg1GAz THSBQf/PzTR0u3w1FqX+f13z2dXhi9tNDx5/8EhwTQGyYQTxJUY9wHAna w==; X-IronPort-AV: E=McAfee;i="6500,9779,10606"; a="325534180" X-IronPort-AV: E=Sophos;i="5.97,261,1669104000"; d="scan'208";a="325534180" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jan 2023 05:16:50 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10606"; a="657864820" X-IronPort-AV: E=Sophos;i="5.97,261,1669104000"; d="scan'208";a="657864820" Received: from ahunter6-mobl1.ger.corp.intel.com (HELO ahunter-VirtualBox.home\044ger.corp.intel.com) ([10.252.47.218]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jan 2023 05:16:48 -0800 From: Adrian Hunter To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , Namhyung Kim , Ian Rogers , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH V2 5/9] perf symbols: Add support for IFUNC symbols for x86_64 Date: Tue, 31 Jan 2023 15:16:21 +0200 Message-Id: <20230131131625.6964-6-adrian.hunter@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230131131625.6964-1-adrian.hunter@intel.com> References: <20230131131625.6964-1-adrian.hunter@intel.com> MIME-Version: 1.0 Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki X-Spam-Status: No, score=-3.9 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_NONE,URI_NOVOWEL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1756544502719784168?= X-GMAIL-MSGID: =?utf-8?q?1756544502719784168?= For x86_64, the GNU linker is putting IFUNC information in the relocation addend, so use it to try to find a symbol for plt entries that refer to IFUNCs. Example: Before: $ cat tstpltlib.c void fn1(void) {} void fn2(void) {} void fn3(void) {} void fn4(void) {} $ cat tstpltifunc.c #include void thing1(void) { printf("thing1\n"); } void thing2(void) { printf("thing2\n"); } typedef void (*thing_fn_t)(void); thing_fn_t thing_ifunc(void) { int x; if (x & 1) return thing2; return thing1; } void thing(void) __attribute__ ((ifunc ("thing_ifunc"))); void fn1(void); void fn2(void); void fn3(void); void fn4(void); int main() { fn4(); fn1(); thing(); fn2(); fn3(); return 0; } $ gcc --version gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0 Copyright (C) 2021 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ gcc -Wall -Wextra -shared -o libtstpltlib.so tstpltlib.c $ gcc -Wall -Wextra -Wno-uninitialized -o tstpltifunc tstpltifunc.c -L . -ltstpltlib -Wl,-rpath="$(pwd)" $ readelf -rW tstpltifunc | grep -A99 plt Relocation section '.rela.plt' at offset 0x738 contains 8 entries: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000003f98 0000000300000007 R_X86_64_JUMP_SLOT 0000000000000000 puts@GLIBC_2.2.5 + 0 0000000000003fa8 0000000400000007 R_X86_64_JUMP_SLOT 0000000000000000 __stack_chk_fail@GLIBC_2.4 + 0 0000000000003fb0 0000000500000007 R_X86_64_JUMP_SLOT 0000000000000000 fn1 + 0 0000000000003fb8 0000000600000007 R_X86_64_JUMP_SLOT 0000000000000000 fn3 + 0 0000000000003fc0 0000000800000007 R_X86_64_JUMP_SLOT 0000000000000000 fn4 + 0 0000000000003fc8 0000000900000007 R_X86_64_JUMP_SLOT 0000000000000000 fn2 + 0 0000000000003fd0 0000000b00000007 R_X86_64_JUMP_SLOT 0000000000000000 getrandom@GLIBC_2.25 + 0 0000000000003fa0 0000000000000025 R_X86_64_IRELATIVE 125d $ perf record -e intel_pt//u --filter 'filter main @ ./tstpltifunc' ./tstpltifunc thing2 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.016 MB perf.data ] $ perf script --itrace=be --ns -F+flags,-event,+addr,-period,-comm,-tid,-cpu,-dso 21860.073683659: tr strt 0 [unknown] => 561e212c42be main+0x0 21860.073683659: tr end call 561e212c42c6 main+0x8 => 561e212c4110 fn4@plt+0x0 21860.073683661: tr strt 0 [unknown] => 561e212c42cb main+0xd 21860.073683661: tr end call 561e212c42cb main+0xd => 561e212c40f0 fn1@plt+0x0 21860.073683661: tr strt 0 [unknown] => 561e212c42d0 main+0x12 21860.073683661: tr end call 561e212c42d0 main+0x12 => 561e212c40d0 offset_0x10d0@plt+0x0 21860.073698451: tr strt 0 [unknown] => 561e212c42d5 main+0x17 21860.073698451: tr end call 561e212c42d5 main+0x17 => 561e212c4120 fn2@plt+0x0 21860.073698451: tr strt 0 [unknown] => 561e212c42da main+0x1c 21860.073698451: tr end call 561e212c42da main+0x1c => 561e212c4100 fn3@plt+0x0 21860.073698452: tr strt 0 [unknown] => 561e212c42df main+0x21 21860.073698452: tr end return 561e212c42e5 main+0x27 => 7fb51cc29d90 __libc_start_call_main+0x80 After: $ perf script --itrace=be --ns -F+flags,-event,+addr,-period,-comm,-tid,-cpu,-dso 21860.073683659: tr strt 0 [unknown] => 561e212c42be main+0x0 21860.073683659: tr end call 561e212c42c6 main+0x8 => 561e212c4110 fn4@plt+0x0 21860.073683661: tr strt 0 [unknown] => 561e212c42cb main+0xd 21860.073683661: tr end call 561e212c42cb main+0xd => 561e212c40f0 fn1@plt+0x0 21860.073683661: tr strt 0 [unknown] => 561e212c42d0 main+0x12 21860.073683661: tr end call 561e212c42d0 main+0x12 => 561e212c40d0 thing_ifunc@plt+0x0 21860.073698451: tr strt 0 [unknown] => 561e212c42d5 main+0x17 21860.073698451: tr end call 561e212c42d5 main+0x17 => 561e212c4120 fn2@plt+0x0 21860.073698451: tr strt 0 [unknown] => 561e212c42da main+0x1c 21860.073698451: tr end call 561e212c42da main+0x1c => 561e212c4100 fn3@plt+0x0 21860.073698452: tr strt 0 [unknown] => 561e212c42df main+0x21 21860.073698452: tr end return 561e212c42e5 main+0x27 => 7fb51cc29d90 __libc_start_call_main+0x80 Signed-off-by: Adrian Hunter --- tools/perf/util/symbol-elf.c | 38 +++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c index 07cfcf8f40e3..a002fc0bea03 100644 --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -381,6 +381,42 @@ static int sort_rel(struct rel_info *ri) return 0; } +/* + * For x86_64, the GNU linker is putting IFUNC information in the relocation + * addend. + */ +static bool addend_may_be_ifunc(GElf_Ehdr *ehdr, struct rel_info *ri) +{ + return ehdr->e_machine == EM_X86_64 && ri->is_rela && + GELF_R_TYPE(ri->rela.r_info) == R_X86_64_IRELATIVE; +} + +static bool get_ifunc_name(Elf *elf, struct dso *dso, GElf_Ehdr *ehdr, + struct rel_info *ri, char *buf, size_t buf_sz) +{ + u64 addr = ri->rela.r_addend; + struct symbol *sym; + GElf_Phdr phdr; + + if (!addend_may_be_ifunc(ehdr, ri)) + return false; + + if (elf_read_program_header(elf, addr, &phdr)) + return false; + + addr -= phdr.p_vaddr - phdr.p_offset; + + sym = dso__find_symbol_nocache(dso, addr); + + /* Expecting the address to be an IFUNC or IFUNC alias */ + if (!sym || sym->start != addr || (sym->type != STT_GNU_IFUNC && !sym->ifunc_alias)) + return false; + + snprintf(buf, buf_sz, "%s@plt", sym->name); + + return true; +} + static void exit_rel(struct rel_info *ri) { free(ri->sorted); @@ -560,7 +596,7 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) elf_name = demangled; if (*elf_name) snprintf(sympltname, sizeof(sympltname), "%s@plt", elf_name); - else + else if (!get_ifunc_name(elf, dso, &ehdr, &ri, sympltname, sizeof(sympltname))) snprintf(sympltname, sizeof(sympltname), "offset_%#" PRIx64 "@plt", plt_offset); free(demangled);