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[23.128.96.18]) by mx.google.com with ESMTP id h19si2795025ede.378.2021.06.16.12.26.02; Wed, 16 Jun 2021 12:26:26 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=mediatek.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234198AbhFPPb7 (ORCPT + 99 others); Wed, 16 Jun 2021 11:31:59 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:60337 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S233949AbhFPPb6 (ORCPT ); Wed, 16 Jun 2021 11:31:58 -0400 X-UUID: f2bd905068764510afb6cb637a10eb58-20210616 X-UUID: f2bd905068764510afb6cb637a10eb58-20210616 Received: from mtkcas06.mediatek.inc [(172.21.101.30)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 1351017316; Wed, 16 Jun 2021 23:29:47 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs08n2.mediatek.inc (172.21.101.56) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 16 Jun 2021 23:29:46 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Wed, 16 Jun 2021 23:29:46 +0800 From: Mark-PK Tsai To: CC: , , , , , , , , Subject: Re: [PATCH v3] recordmcount: Correct st_shndx handling Date: Wed, 16 Jun 2021 23:29:46 +0800 Message-ID: <20210616152946.2709-1-mark-pk.tsai@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Wed, Jun 16, 2021 at 12:23:13AM +0800, Mark-PK Tsai wrote: > > From: Peter Zijlstra > > > > One should only use st_shndx when >SHN_UNDEF and > SHN_XINDEX, then use .symtab_shndx. Otherwise use 0. > > > > This handles the case: st_shndx >= SHN_LORESERVE && st_shndx != SHN_XINDEX. > > > > Reported-by: Mark-PK Tsai > > Signed-off-by: Peter Zijlstra (Intel) > > Tested-by: Mark-PK Tsai > > [handle endianness of sym->st_shndx] > > Signed-off-by: Mark-PK Tsai > > --- > > scripts/recordmcount.h | 13 +++++++++---- > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h > > index f9b19524da11..ef9c3425f86b 100644 > > --- a/scripts/recordmcount.h > > +++ b/scripts/recordmcount.h > > @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, > > unsigned long offset; > > int index; > > > > + if (w2(sym->st_shndx) > SHN_UNDEF && > > + w2(sym->st_shndx) < SHN_LORESERVE) > > return w2(sym->st_shndx); > > > > + if (w2(sym->st_shndx) == SHN_XINDEX) { > > + offset = (unsigned long)sym - (unsigned long)symtab; > > + index = offset / sizeof(*sym); > > > > + return w(symtab_shndx[index]); > > + } > > + > > + return 0; > > } > > Thanks. However that leads to atrocious codegen because w2 is an > indirect function, something like the below seems much better. Oh, I didn't notice that. I'll update in v4. Thanks! > > 1d00: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d05: c0 eb 04 shr $0x4,%bl > 1d08: ff 15 7a 54 00 00 callq *0x547a(%rip) # 7188 > 1d0e: 85 c0 test %eax,%eax > 1d10: 74 16 je 1d28 > 1d12: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d17: ff 15 6b 54 00 00 callq *0x546b(%rip) # 7188 > 1d1d: 3d ff fe 00 00 cmp $0xfeff,%eax > 1d22: 0f 86 00 03 00 00 jbe 2028 > 1d28: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d2d: ff 15 55 54 00 00 callq *0x5455(%rip) # 7188 > > vs > > 1d0c: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d11: ff 15 71 54 00 00 callq *0x5471(%rip) # 7188 > > --- > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h > index f9b19524da11..b3e9d0563c03 100644 > --- a/scripts/recordmcount.h > +++ b/scripts/recordmcount.h > @@ -192,15 +192,23 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, > Elf32_Word const *symtab_shndx) > { > unsigned long offset; > + unsigned short shndx; > int index; > > - if (sym->st_shndx != SHN_XINDEX) > - return w2(sym->st_shndx); > + shndx = w2(sym->st_shndx); > > - offset = (unsigned long)sym - (unsigned long)symtab; > - index = offset / sizeof(*sym); > + if (shndx > SHN_UNDEF && > + shndx < SHN_LORESERVE) > + return shndx; > > - return w(symtab_shndx[index]); > + if (shndx == SHN_XINDEX) { > + offset = (unsigned long)sym - (unsigned long)symtab; > + index = offset / sizeof(*sym); > + > + return w(symtab_shndx[index]); > + } > + > + return 0; > } > > static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)