Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754786AbaLJKNg (ORCPT ); Wed, 10 Dec 2014 05:13:36 -0500 Received: from ozlabs.org ([103.22.144.67]:49008 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751380AbaLJKNf (ORCPT ); Wed, 10 Dec 2014 05:13:35 -0500 Message-ID: <1418206413.9279.9.camel@ellerman.id.au> Subject: Re: [RFC PATCH 6/8] perf tools powerpc: Fix PPC64 ELF ABIv2 symbol decoding From: Michael Ellerman To: "Naveen N. Rao" Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, acme@kernel.org, ananth@in.ibm.com Date: Wed, 10 Dec 2014 21:13:33 +1100 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2014-12-09 at 23:04 +0530, Naveen N. Rao wrote: > PPC64 ELF ABIv2 has a Global Entry Point (GEP) and a Local Entry Point > (LEP). For purposes of probing, we need the LEP. Offset to the LEP is > encoded in st_other. > > diff --git a/tools/perf/arch/powerpc/util/elf-sym-decode.c b/tools/perf/arch/powerpc/util/elf-sym-decode.c > new file mode 100644 > index 0000000..7434656 > --- /dev/null > +++ b/tools/perf/arch/powerpc/util/elf-sym-decode.c > @@ -0,0 +1,27 @@ > +/* > + * Decode offset from Global Entry Point to Local Entry Point on PPC64 > + * ELF ABIv2. > + * > + * Derived from definitions in arch/powerpc/kernel/module_64.c > + * > + * Copyright (C) 2014 Ananth N Mavinakayanahalli, IBM Corporation. > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; either version > + * 2 of the License, or (at your option) any later version. > + */ > + > +#include > +#include "elf_sym.h" > + > +/* PowerPC64 ABIv2 specific values for the ELF64_Sym st_other field. */ > +#define STO_PPC64_LOCAL_BIT 5 > +#define STO_PPC64_LOCAL_MASK (7 << STO_PPC64_LOCAL_BIT) > +#define PPC64_LOCAL_ENTRY_OFFSET(other) \ > + (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2) You're in userspace, you should be able to get these from elf.h > +unsigned int arch_elf_sym_decode_offset(GElf_Sym *sym) > +{ > + return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other); What happens on ABIv1 ? We hope st_other is zero? > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c > index 67e4392..92a424e 100644 > --- a/tools/perf/util/symbol-elf.c > +++ b/tools/perf/util/symbol-elf.c > @@ -10,6 +10,7 @@ > #include "vdso.h" > #include > #include "debug.h" > +#include "elf_sym.h" > > #ifndef HAVE_ELF_GETPHDRNUM_SUPPORT > static int elf_getphdrnum(Elf *elf, size_t *dst) > @@ -848,6 +849,13 @@ int dso__load_sym(struct dso *dso, struct map *map, > (sym.st_value & 1)) > --sym.st_value; > > + /* > + * PPC64 ELF ABIv2 encodes Local Entry Point offset in > + * the st_other field > + */ > + if ((map->type == MAP__FUNCTION) && sym.st_other) > + sym.st_value += arch_elf_sym_decode_offset(&sym); I guess no other arch has needed to do anything like this. But if they did it's unlikely they'll want to do the exact same logic, ie. check st_other and add some value to st_value. To make it more generically useful you could just make it: > + if (map->type == MAP__FUNCTION) > + arch_elf_sym_decode(&sym); And do any other checks in the arch routine. cheers -- 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/