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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id w125sm3027860pgw.22.2020.04.21.13.11.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2020 13:11:48 -0700 (PDT) Date: Tue, 21 Apr 2020 13:11:47 -0700 From: Kees Cook To: Sami Tolvanen Cc: Josh Poimboeuf , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] objtool: use gelf_getsymshndx to handle >64k sections Message-ID: <202004211311.EF577DFD13@keescook> References: <20200421180724.245410-1-samitolvanen@google.com> <20200421180724.245410-2-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200421180724.245410-2-samitolvanen@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 21, 2020 at 11:07:22AM -0700, Sami Tolvanen wrote: > Currently, objtool fails to load the correct section for symbols when > the index is greater than SHN_LORESERVE. Use gelf_getsymshndx instead > of gelf_getsym to handle >64k sections. > > Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook -Kees > --- > tools/objtool/elf.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c > index 09ddc8f1def3..887445e87380 100644 > --- a/tools/objtool/elf.c > +++ b/tools/objtool/elf.c > @@ -327,12 +327,14 @@ static int read_sections(struct elf *elf) > > static int read_symbols(struct elf *elf) > { > - struct section *symtab, *sec; > + struct section *symtab, *symtab_shndx, *sec; > struct symbol *sym, *pfunc; > struct list_head *entry; > struct rb_node *pnode; > int symbols_nr, i; > char *coldstr; > + Elf_Data *shndx_data = NULL; > + Elf32_Word shndx; > > symtab = find_section_by_name(elf, ".symtab"); > if (!symtab) { > @@ -340,6 +342,10 @@ static int read_symbols(struct elf *elf) > return -1; > } > > + symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); > + if (symtab_shndx) > + shndx_data = symtab_shndx->data; > + > symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize; > > for (i = 0; i < symbols_nr; i++) { > @@ -353,8 +359,9 @@ static int read_symbols(struct elf *elf) > > sym->idx = i; > > - if (!gelf_getsym(symtab->data, i, &sym->sym)) { > - WARN_ELF("gelf_getsym"); > + if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym, > + &shndx)) { > + WARN_ELF("gelf_getsymshndx"); > goto err; > } > > @@ -368,10 +375,13 @@ static int read_symbols(struct elf *elf) > sym->type = GELF_ST_TYPE(sym->sym.st_info); > sym->bind = GELF_ST_BIND(sym->sym.st_info); > > - if (sym->sym.st_shndx > SHN_UNDEF && > - sym->sym.st_shndx < SHN_LORESERVE) { > - sym->sec = find_section_by_index(elf, > - sym->sym.st_shndx); > + if ((sym->sym.st_shndx > SHN_UNDEF && > + sym->sym.st_shndx < SHN_LORESERVE) || > + (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) { > + if (sym->sym.st_shndx != SHN_XINDEX) > + shndx = sym->sym.st_shndx; > + > + sym->sec = find_section_by_index(elf, shndx); > if (!sym->sec) { > WARN("couldn't find section for symbol %s", > sym->name); > -- > 2.26.1.301.g55bc3eb7cb9-goog > -- Kees Cook