Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964796AbWBEAUZ (ORCPT ); Sat, 4 Feb 2006 19:20:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964839AbWBEAUZ (ORCPT ); Sat, 4 Feb 2006 19:20:25 -0500 Received: from pasmtp.tele.dk ([193.162.159.95]:51207 "EHLO pasmtp.tele.dk") by vger.kernel.org with ESMTP id S964796AbWBEAUY (ORCPT ); Sat, 4 Feb 2006 19:20:24 -0500 Date: Sun, 5 Feb 2006 01:20:16 +0100 From: Sam Ravnborg To: Keith Owens , LKML Subject: Re: Check for references to discarded sections during build time Message-ID: <20060205002016.GA6105@mars.ravnborg.org> References: <20060204225025.GA21292@mars.ravnborg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060204225025.GA21292@mars.ravnborg.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4905 Lines: 173 On Sat, Feb 04, 2006 at 11:50:25PM +0100, Sam Ravnborg wrote: > Hi Keith. > > While doing some other modpost.c changes I thought about the > possibility to do the reference_init check during the modpost stage - so > it is done early and author can catch warning when he made the error. > Attached is first cut. > > It does a much more lousy job than reference_init because it identifies > the module and not the .o file. I hope to later identify the function > where the illegal reference hapens. > > I have only run it on a subset of the kernel and it found a few > warnings in ide-core.o + one warning in net/drivers/drgs.o. > I have not investigated if this is false positives yet. > > make allmodconfig running in background - will check the result when I > wake up again. That spew out several screenfull of stuff... So far by looking only positives.. Heading for a business trip and vacation the next 2 weeks so do not expect much response... Sam Corrected patch below: diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index d901095..01b482d 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -451,6 +451,101 @@ static char *get_modinfo(void *modinfo, return NULL; } +/** + * Is this section a true init section? + **/ +static int is_init_section(const char *name) +{ + if (strcmp(name, ".init") == 0) + return 1; + if (strncmp(name, ".init.", strlen(".init.")) == 0) + return 1; + return 0; +} + +/** + * Check name - identify sections which is discarded by vmlinux + * after module is loaded. Here we are fine referencing __init. + **/ +static int is_ref_init_ok(const char *name) +{ + const char **s; + /* Absolute section names */ + const char *namelist1[] = { + ".init", + ".stab", + ".rodata", + ".text.lock", + ".pci_fixup_header", + ".pci_fixup_final", + ".pdr", + "__param", + NULL + }; + /* Start of section names */ + const char *namelist2[] = { + ".init.", + ".altinstructions", + ".eh_frame", + ".debug", + NULL + }; + + for (s = namelist1; *s; s++) + if (strcmp(*s, name) == 0) + return 1; + for (s = namelist2; *s; s++) + if (strncmp(*s, name, strlen(*s)) == 0) + return 1; + return 0; +} + +/** + * Walk through all sections. + * All sections with references to a section identified as "init" + * needs to be int too - otherwise we have a reference to code marked + * __init and which is discarded by vmlinux + **/ +static void handle_checkinitref(struct module *mod, const char *modname, struct elf_info *elf) +{ + int i; + Elf_Sym *sym; + Elf_Ehdr *hdr = elf->hdr; + Elf_Shdr *sechdrs = elf->sechdrs; + const char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; + + /* Walk through all sections */ + for (i = 0; i < hdr->e_shnum; i++) { + const char *name = secstrings + sechdrs[i].sh_name + strlen(".rela"); + /* We want to process only relocation sections and not .init */ + if (is_ref_init_ok(name) || (sechdrs[i].sh_type != SHT_RELA)) + continue; + Elf_Rela *rela; + Elf_Rela *start = (void *)hdr + sechdrs[i].sh_offset; + Elf_Rela *stop = (void*)start + sechdrs[i].sh_size; + + for (rela = start; rela < stop; rela++) { + Elf_Rela r; + const char *symname; + r.r_offset = TO_NATIVE(rela->r_offset); + r.r_info = TO_NATIVE(rela->r_info); + sym = elf->symtab_start + ELF_R_SYM(r.r_info); + /* Skip special sections */ + if (sym->st_shndx >= SHN_LORESERVE) + continue; + symname = secstrings + sechdrs[sym->st_shndx].sh_name; + + if (is_init_section(symname)) { + warn("%s: Reference to %s section from " + "offset 0x%lx within section %s\n", + modname, symname, + (long)r.r_offset, + name); + } + } + } +} + static void read_symbols(char *modname) { const char *symname; @@ -476,6 +571,7 @@ static void read_symbols(char *modname) handle_modversions(mod, &info, sym, symname); handle_moddevtable(mod, &info, sym, symname); } + handle_checkinitref(mod, modname, &info); version = get_modinfo(info.modinfo, info.modinfo_len, "version"); if (version) diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h index c0de7b9..f7126c1 100644 --- a/scripts/mod/modpost.h +++ b/scripts/mod/modpost.h @@ -19,6 +19,9 @@ #define ELF_ST_BIND ELF32_ST_BIND #define ELF_ST_TYPE ELF32_ST_TYPE +#define Elf_Rela Elf32_Rela +#define ELF_R_SYM ELF32_R_SYM +#define ELF_R_TYPE ELF32_R_TYPE #else #define Elf_Ehdr Elf64_Ehdr @@ -27,6 +30,9 @@ #define ELF_ST_BIND ELF64_ST_BIND #define ELF_ST_TYPE ELF64_ST_TYPE +#define Elf_Rela Elf64_Rela +#define ELF_R_SYM ELF64_R_SYM +#define ELF_R_TYPE ELF64_R_TYPE #endif #if KERNEL_ELFDATA != HOST_ELFDATA - 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/