From patchwork Sun May 8 19:06:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 12842686 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6332C433FE for ; Sun, 8 May 2022 19:17:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229635AbiEHTVa (ORCPT ); Sun, 8 May 2022 15:21:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231245AbiEHTQO (ORCPT ); Sun, 8 May 2022 15:16:14 -0400 Received: from conuserg-09.nifty.com (conuserg-09.nifty.com [210.131.2.76]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B45EC12AE6; Sun, 8 May 2022 12:11:15 -0700 (PDT) Received: from grover.sesame (133-32-177-133.west.xps.vectant.ne.jp [133.32.177.133]) (authenticated) by conuserg-09.nifty.com with ESMTP id 248J8qSS030019; Mon, 9 May 2022 04:08:58 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conuserg-09.nifty.com 248J8qSS030019 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1652036939; bh=T233+M5ZMF8rUMgorj/Lt/jCSMW/kSv5PBB2geiLwtk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HmOzBgE3BoxE4R4Q7Sh2n7SmfRDEyYnct2UnMWmQ/7rUNGYpRokNfBQuzjOxfvp8f 7NJQWFEZeMSrR0edlDjDRcUIBg/q+/sXKhHi3dXuQmGpMEKls/R5wgXYG4WgfflY72 kMULh7OZW1HXprl7JuvEqAa2EyTZ6CJ6TPXIDkPH5JqMqV7/H2Mw0b74IxSvZEvsRJ xa/51ZJQERRXD0UOUoFcS4cXeFTDsE+5VdFRdTI9NrLeuO3jqjEAKIRsgy4Zgj4Gwi T/3fY8KAR/EkQb8r/vZ9nLijLWCvW+zCVLLj4jWkU5H1SozH6ERpFO0ASq247c8RXp ENYRkdOE7G7rw== X-Nifty-SrcIP: [133.32.177.133] From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Nathan Chancellor , Nick Desaulniers , Nicolas Schier , Peter Zijlstra , linux-modules@vger.kernel.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, clang-built-linux@googlegroups.com, Ard Biesheuvel , Sami Tolvanen , Masahiro Yamada Subject: [PATCH v4 05/14] modpost: extract symbol versions from *.cmd files Date: Mon, 9 May 2022 04:06:22 +0900 Message-Id: <20220508190631.2386038-6-masahiroy@kernel.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220508190631.2386038-1-masahiroy@kernel.org> References: <20220508190631.2386038-1-masahiroy@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol versions into ELF objects. Then, modpost extracts the version CRCs from them. The following figures show how it currently works, and how I am trying to change it. Current implementation ====================== |----------| embed CRC -------------------------->| final | $(CC) $(LD) / |---------| | link for | -----> *.o -------> *.o -->| modpost | | vmlinux | / / | |-- *.mod.c -->| or | / genksyms / |---------| | module | *.c ------> *.symversions |----------| Genksyms outputs the calculated CRCs in the form of linker script (*.symversions), which is used by $(LD) to update the object. If CONFIG_LTO_CLANG=y, the build process is much more complex. Embedding the CRCs is postponed until the LLVM bitcode is converted into ELF, creating another intermediate *.prelink.o. However, this complexity is unneeded. There is no reason why we must embed version CRCs in objects so early. There is final link stage for vmlinux (scripts/link-vmlinux.sh) and modules (scripts/Makefile.modfinal). We can link CRCs at the very last moment. New implementation ================== |----------| --------------------------------------->| final | $(CC) / |---------| | link for | -----> *.o ---->| | | vmlinux | / | modpost |--- .vmlinux.export.c -->| or | / genksyms | |--- *.mod.c ------------>| module | *.c ------> *.cmd -->|---------| |----------| Pass the symbol versions to modpost as separate text data, which are available in *.cmd files. This commit changes modpost to extract CRCs from *.cmd files instead of from ELF objects. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor Reviewed-by: Sami Tolvanen --- (no changes since v2) Changes in v2: - Simplify the implementation (parse .cmd files after ELF) scripts/mod/modpost.c | 177 ++++++++++++++++++++++++++++++------------ 1 file changed, 129 insertions(+), 48 deletions(-) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index fc5db1f73cf1..54f957952723 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -381,19 +381,10 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod, return s; } -static void sym_set_crc(const char *name, unsigned int crc) +static void sym_set_crc(struct symbol *sym, unsigned int crc) { - struct symbol *s = find_symbol(name); - - /* - * Ignore stand-alone __crc_*, which might be auto-generated symbols - * such as __*_veneer in ARM ELF. - */ - if (!s) - return; - - s->crc = crc; - s->crc_valid = true; + sym->crc = crc; + sym->crc_valid = true; } static void *grab_file(const char *filename, size_t *size) @@ -616,33 +607,6 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname) return 0; } -static void handle_modversion(const struct module *mod, - const struct elf_info *info, - const Elf_Sym *sym, const char *symname) -{ - unsigned int crc; - - if (sym->st_shndx == SHN_UNDEF) { - warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" - "Is \"%s\" prototyped in ?\n", - symname, mod->name, mod->is_vmlinux ? "" : ".ko", - symname); - - return; - } - - if (sym->st_shndx == SHN_ABS) { - crc = sym->st_value; - } else { - unsigned int *crcp; - - /* symbol points to the CRC in the ELF object */ - crcp = sym_get_data(info, sym); - crc = TO_NATIVE(*crcp); - } - sym_set_crc(symname, crc); -} - static void handle_symbol(struct module *mod, struct elf_info *info, const Elf_Sym *sym, const char *symname) { @@ -760,6 +724,102 @@ static char *remove_dot(char *s) return s; } +/* + * The CRCs are recorded in .*.cmd files in the form of: + * #SYMVER + */ +static void extract_crcs_for_object(const char *object, struct module *mod) +{ + char cmd_file[PATH_MAX]; + char *buf, *p; + const char *base; + int dirlen, ret; + + base = strrchr(object, '/'); + if (base) { + base++; + dirlen = base - object; + } else { + dirlen = 0; + base = object; + } + + ret = snprintf(cmd_file, sizeof(cmd_file), "%.*s.%s.cmd", + dirlen, object, base); + if (ret >= sizeof(cmd_file)) { + error("%s: too long path was truncated\n", cmd_file); + return; + } + + buf = read_text_file(cmd_file); + p = buf; + + while ((p = strstr(p, "\n#SYMVER "))) { + char *name; + size_t namelen; + unsigned int crc; + struct symbol *sym; + + name = p + strlen("\n#SYMVER "); + + p = strchr(name, ' '); + if (!p) + break; + + namelen = p - name; + p++; + + if (!isdigit(*p)) + continue; /* skip this line */ + + crc = strtol(p, &p, 0); + if (*p != '\n') + continue; /* skip this line */ + + name[namelen] = '\0'; + + sym = sym_find_with_module(name, mod); + if (!sym) { + warn("Skip the version for unexported symbol \"%s\" [%s%s]\n", + name, mod->name, mod->is_vmlinux ? "" : ".ko"); + continue; + } + sym_set_crc(sym, crc); + } + + free(buf); +} + +/* + * The symbol versions (CRC) are recorded in the .*.cmd files. + * Parse them to retrieve CRCs for the current module. + */ +static void mod_set_crcs(struct module *mod) +{ + char objlist[PATH_MAX]; + char *buf, *p, *obj; + int ret; + + if (mod->is_vmlinux) { + strcpy(objlist, ".vmlinux.objs"); + } else { + /* objects for a module are listed in the *.mod file. */ + ret = snprintf(objlist, sizeof(objlist), "%s.mod", mod->name); + if (ret >= sizeof(objlist)) { + error("%s: too long path was truncated\n", objlist); + return; + } + } + + buf = read_text_file(objlist); + p = buf; + + while ((obj = strsep(&p, "\n")) && obj[0]) + extract_crcs_for_object(obj, mod); + + free(buf); +} + static void read_symbols(const char *modname) { const char *symname; @@ -820,9 +880,6 @@ static void read_symbols(const char *modname) if (strstarts(symname, "__kstrtabns_")) sym_update_namespace(symname + strlen("__kstrtabns_"), sym_get_data(&info, sym)); - if (strstarts(symname, "__crc_")) - handle_modversion(mod, &info, sym, - symname + strlen("__crc_")); } // check for static EXPORT_SYMBOL_* functions && global vars @@ -850,12 +907,17 @@ static void read_symbols(const char *modname) parse_elf_finish(&info); - /* Our trick to get versioning for module struct etc. - it's - * never passed as an argument to an exported function, so - * the automatic versioning doesn't pick it up, but it's really - * important anyhow */ - if (modversions) + if (modversions) { + /* + * Our trick to get versioning for module struct etc. - it's + * never passed as an argument to an exported function, so + * the automatic versioning doesn't pick it up, but it's really + * important anyhow + */ sym_add_unresolved("module_layout", mod, false); + + mod_set_crcs(mod); + } } static void read_symbols_from_files(const char *filename) @@ -1012,6 +1074,23 @@ static void add_header(struct buffer *b, struct module *mod) buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n"); } +static void check_symversions(struct module *mod) +{ + struct symbol *sym; + + if (!modversions) + return; + + list_for_each_entry(sym, &mod->exported_symbols, list) { + if (!sym->crc_valid) { + warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" + "Is \"%s\" prototyped in ?\n", + sym->name, mod->name, mod->is_vmlinux ? "" : ".ko", + sym->name); + } + } +} + /** * Record CRCs for unresolved symbols **/ @@ -1227,7 +1306,7 @@ static void read_dump(const char *fname) } s = sym_add_exported(symname, mod, gpl_only); s->is_static = false; - sym_set_crc(symname, crc); + sym_set_crc(s, crc); sym_update_namespace(symname, namespace); } free(buf); @@ -1353,6 +1432,8 @@ int main(int argc, char **argv) if (mod->from_dump) continue; + check_symversions(mod); + if (!mod->is_vmlinux) write_mod_c_file(mod); }