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([2a01:cb14:499:3d00:cd47:f651:9d80:157a]) by smtp.gmail.com with ESMTPSA id s8sm2584112wrg.50.2020.06.02.00.36.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Jun 2020 00:36:49 -0700 (PDT) Subject: Re: [PATCH 2/2] objtool: Add support for relocations without addends To: Matt Helsley , linux-kernel@vger.kernel.org Cc: Josh Poimboeuf , Peter Zijlstra , Steven Rostedt References: From: Julien Thierry Message-ID: Date: Tue, 2 Jun 2020 08:36:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Matt, On 5/29/20 10:01 PM, Matt Helsley wrote: > Currently objtool only collects information about relocations with > addends. In recordmcount, which we are about to merge into objtool, > some supported architectures do not use rela relocations. > > Signed-off-by: Matt Helsley > --- > tools/objtool/elf.c | 146 +++++++++++++++++++++++++++++++++++----- > tools/objtool/elf.h | 7 +- > tools/objtool/orc_gen.c | 2 +- > 3 files changed, 135 insertions(+), 20 deletions(-) > > diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c > index c21e8417637b..5034918494b6 100644 > --- a/tools/objtool/elf.c > +++ b/tools/objtool/elf.c > @@ -490,6 +490,32 @@ void elf_add_reloc(struct elf *elf, struct reloc *reloc) > elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc)); > } > > +static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx) > +{ > + if (!gelf_getrel(sec->data, i, &reloc->rel)) { > + WARN_ELF("gelf_getrel"); > + return -1; > + } > + reloc->type = GELF_R_TYPE(reloc->rel.r_info); > + reloc->addend = 0; > + reloc->offset = reloc->rel.r_offset; > + *symndx = GELF_R_SYM(reloc->rel.r_info); > + return 0; > +} > + > +static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx) > +{ > + if (!gelf_getrela(sec->data, i, &reloc->rela)) { > + WARN_ELF("gelf_getrela"); > + return -1; > + } > + reloc->type = GELF_R_TYPE(reloc->rela.r_info); > + reloc->addend = reloc->rela.r_addend; > + reloc->offset = reloc->rela.r_offset; > + *symndx = GELF_R_SYM(reloc->rela.r_info); > + return 0; > +} > + > static int read_relocs(struct elf *elf) > { > struct section *sec; > @@ -499,7 +525,8 @@ static int read_relocs(struct elf *elf) > unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0; > > list_for_each_entry(sec, &elf->sections, list) { > - if (sec->sh.sh_type != SHT_RELA) > + if ((sec->sh.sh_type != SHT_RELA) && > + (sec->sh.sh_type != SHT_REL)) > continue; > > sec->base = find_section_by_index(elf, sec->sh.sh_info); > @@ -519,16 +546,17 @@ static int read_relocs(struct elf *elf) > return -1; > } > memset(reloc, 0, sizeof(*reloc)); > - > - if (!gelf_getrela(sec->data, i, &reloc->rela)) { > - WARN_ELF("gelf_getrela"); > - return -1; > + switch(sec->sh.sh_type) { > + case SHT_REL: > + if (read_rel_reloc(sec, i, reloc, &symndx)) > + return -1; > + break; > + case SHT_RELA: > + if (read_rela_reloc(sec, i, reloc, &symndx)) > + return -1; > + break; > + default: return -1; > } > - > - reloc->type = GELF_R_TYPE(reloc->rela.r_info); > - reloc->addend = reloc->rela.r_addend; > - reloc->offset = reloc->rela.r_offset; > - symndx = GELF_R_SYM(reloc->rela.r_info); > reloc->sym = find_symbol_by_index(elf, symndx); > reloc->sec = sec; > if (!reloc->sym) { > @@ -716,7 +744,38 @@ struct section *elf_create_section(struct elf *elf, const char *name, > return sec; > } > > -struct section *elf_create_reloc_section(struct elf *elf, struct section *base) > +static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base) > +{ > + char *relocname; > + struct section *sec; > + > + relocname = malloc(strlen(base->name) + strlen(".rel") + 1); > + if (!relocname) { > + perror("malloc"); > + return NULL; > + } > + strcpy(relocname, ".rel"); > + strcat(relocname, base->name); > + > + sec = elf_create_section(elf, relocname, sizeof(GElf_Rel), 0); > + free(relocname); > + if (!sec) > + return NULL; > + > + base->reloc = sec; > + sec->base = base; > + > + sec->sh.sh_type = SHT_REL; > + sec->sh.sh_addralign = 8; > + sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx; > + sec->sh.sh_info = base->idx; > + sec->sh.sh_flags = SHF_INFO_LINK; > + > + return sec; > +} > + > + Nit: Extra new line. Otherwise: Reviewed-by: Julien Thierry -- Julien Thierry