From mboxrd@z Thu Jan 1 00:00:00 1970 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 C4029C32771 for ; Wed, 28 Sep 2022 06:43:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233381AbiI1GnM (ORCPT ); Wed, 28 Sep 2022 02:43:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232599AbiI1Gl6 (ORCPT ); Wed, 28 Sep 2022 02:41:58 -0400 Received: from conuserg-08.nifty.com (conuserg-08.nifty.com [210.131.2.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D1E01D05E0; Tue, 27 Sep 2022 23:41:54 -0700 (PDT) Received: from zoe.. (133-32-182-133.west.xps.vectant.ne.jp [133.32.182.133]) (authenticated) by conuserg-08.nifty.com with ESMTP id 28S6e0G9004120; Wed, 28 Sep 2022 15:40:08 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conuserg-08.nifty.com 28S6e0G9004120 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1664347209; bh=ZH9B9GLn1QpV0HvmQtr5Na/EeHUXAOG5jwJoV2sRUOk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LXREac42ecbunylv8eHPu7VSrlvxzMCNsrRxzXMEptfo32vPENb6qBHDr18EkPUbZ jSvWaVeDVRTUXXxOAHtMRAowlCngyvAza5F/CdepHRWShBXlAkWF5UiS2xE+Ok/Iyt Ko0YZ8ZSWf+ZVULZ/vZcNdIWziDTMoWNdtyO29z39e7/wGgCeYd5ia9tEJWHyvwzeJ 98OZjrHesd69F9shnQ3v2cxA/cGBYlCHQ1xTPDD2Y4HY1bxygvD0OWpK5nvSQFyqxM dOl/nlZpqd8T6iHiqKlMmdxr4oDMLdoOTL88Gjy3TcpMkT+aIQC6BI/ycLD5nkvQhR ry5tljC7FeEyg== X-Nifty-SrcIP: [133.32.182.133] From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, Al Viro , Ard Biesheuvel , Nicolas Pitre , Masahiro Yamada , Michal Marek , Nathan Chancellor , Nick Desaulniers , Tom Rix , llvm@lists.linux.dev Subject: [PATCH v3 8/8] kbuild: implement CONFIG_TRIM_UNUSED_KSYMS without recursion Date: Wed, 28 Sep 2022 15:39:47 +0900 Message-Id: <20220928063947.299333-9-masahiroy@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220928063947.299333-1-masahiroy@kernel.org> References: <20220928063947.299333-1-masahiroy@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses the directory tree to determine which EXPORT_SYMBOL to trim. If an EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the second traverse, where some source files are recompiled with their EXPORT_SYMBOL() tuned into a no-op. Linus stated a negative opinion about this slowness in commits: - 5cf0fd591f2e ("Kbuild: disable TRIM_UNUSED_KSYMS option") - a555bdd0c58c ("Kbuild: enable TRIM_UNUSED_KSYMS again, with some guarding") We can do this better now. The final data structures of EXPORT_SYMBOL are generated by the modpost stage, so modpost can selectively emit KSYMTAB entries that are really used by modules. Commit 2cce989f8461 ("kbuild: unify two modpost invocations") is another ground-work to do this in a one-pass algorithm. With the list of modules, modpost sets sym->used if it is used by a module. modpost emits KSYMTAB only for symbols with sym->used==true. BTW, Nicolas explained why the trimming was implemented with recursion: https://lore.kernel.org/all/2o2rpn97-79nq-p7s2-nq5-8p83391473r@syhkavp.arg/ Actually, we never achieved that level of optimization where the chain reaction of trimming comes into play because: - CONFIG_LTO_CLANG cannot remove any unused symbols - CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled only for vmlinux, but not modules If deeper trimming is required, we need to revisit this, but I guess that is unlikely to happen. Signed-off-by: Masahiro Yamada --- Changes in v3: - Some cleanups Changes in v2: - New patch .gitignore | 1 - Makefile | 19 +--------- include/linux/export.h | 41 --------------------- scripts/Makefile.build | 7 ---- scripts/Makefile.modpost | 8 +++- scripts/adjust_autoksyms.sh | 73 ------------------------------------- scripts/basic/fixdep.c | 3 +- scripts/gen_autoksyms.sh | 62 ------------------------------- scripts/gen_ksymdeps.sh | 30 --------------- scripts/mod/modpost.c | 54 ++++++++++++++++++++++++--- scripts/remove-stale-files | 2 + 11 files changed, 61 insertions(+), 239 deletions(-) delete mode 100755 scripts/adjust_autoksyms.sh delete mode 100755 scripts/gen_autoksyms.sh delete mode 100755 scripts/gen_ksymdeps.sh diff --git a/.gitignore b/.gitignore index 265959544978..a9b44cd36066 100644 --- a/.gitignore +++ b/.gitignore @@ -103,7 +103,6 @@ modules.order # /include/config/ /include/generated/ -/include/ksym/ /arch/*/include/generated/ # stgit generated dirs diff --git a/Makefile b/Makefile index 79488f155fae..31dcde4c7fc5 100644 --- a/Makefile +++ b/Makefile @@ -1120,28 +1120,13 @@ endif export KBUILD_VMLINUX_LIBS export KBUILD_LDS := arch/$(SRCARCH)/kernel/vmlinux.lds -# Recurse until adjust_autoksyms.sh is satisfied -PHONY += autoksyms_recursive ifdef CONFIG_TRIM_UNUSED_KSYMS # For the kernel to actually contain only the needed exported symbols, # we have to build modules as well to determine what those symbols are. # (this can be evaluated only once include/config/auto.conf has been included) KBUILD_MODULES := 1 - -autoksyms_recursive: $(build-dir) modules.order - $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \ - "$(MAKE) -f $(srctree)/Makefile autoksyms_recursive" endif -autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h) - -quiet_cmd_autoksyms_h = GEN $@ - cmd_autoksyms_h = mkdir -p $(dir $@); \ - $(CONFIG_SHELL) $(srctree)/scripts/gen_autoksyms.sh $@ - -$(autoksyms_h): - $(call cmd,autoksyms_h) - # '$(AR) mPi' needs 'T' to workaround the bug of llvm-ar <= 14 quiet_cmd_ar_vmlinux.a = AR $@ cmd_ar_vmlinux.a = \ @@ -1154,7 +1139,7 @@ vmlinux.a: $(KBUILD_VMLINUX_OBJS) scripts/head-object-list.txt FORCE $(call if_changed,ar_vmlinux.a) PHONY += vmlinux_o -vmlinux_o: autoksyms_recursive vmlinux.a $(KBUILD_VMLINUX_LIBS) +vmlinux_o: vmlinux.a $(KBUILD_VMLINUX_LIBS) $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux_o vmlinux.o modules.builtin.modinfo modules.builtin: vmlinux_o @@ -1191,7 +1176,7 @@ scripts: scripts_basic scripts_dtc PHONY += prepare archprepare archprepare: outputmakefile archheaders archscripts scripts include/config/kernel.release \ - asm-generic $(version_h) $(autoksyms_h) include/generated/utsrelease.h \ + asm-generic $(version_h) include/generated/utsrelease.h \ include/generated/compile.h include/generated/autoconf.h remove-stale-files prepare0: archprepare diff --git a/include/linux/export.h b/include/linux/export.h index 0c71577cf8bb..d9fb1ebb535c 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -63,47 +63,6 @@ extern struct module __this_module; */ #define __EXPORT_SYMBOL(sym, sec, ns) -#elif defined(CONFIG_TRIM_UNUSED_KSYMS) - -#include - -/* - * For fine grained build dependencies, we want to tell the build system - * about each possible exported symbol even if they're not actually exported. - * We use a symbol pattern __ksym_marker_ that the build system filters - * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are - * discarded in the final link stage. - */ - -#ifdef __ASSEMBLY__ - -#define __ksym_marker(sym) \ - .section ".discard.ksym","a" ; \ -__ksym_marker_##sym: ; \ - .previous - -#else - -#define __ksym_marker(sym) \ - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used - -#endif - -#define __EXPORT_SYMBOL(sym, sec, ns) \ - __ksym_marker(sym); \ - __cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym)) -#define __cond_export_sym(sym, sec, ns, conf) \ - ___cond_export_sym(sym, sec, ns, conf) -#define ___cond_export_sym(sym, sec, ns, enabled) \ - __cond_export_sym_##enabled(sym, sec, ns) -#define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) - -#ifdef __GENKSYMS__ -#define __cond_export_sym_0(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) -#else -#define __cond_export_sym_0(sym, sec, ns) /* nothing */ -#endif - #else #define __EXPORT_SYMBOL(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 4c1d0bd1bc03..64f652b03d29 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -218,16 +218,10 @@ is-standard-object = $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(basetar $(obj)/%.o: objtool-enabled = $(if $(is-standard-object),$(if $(delay-objtool),$(is-single-obj-m),y)) -ifdef CONFIG_TRIM_UNUSED_KSYMS -cmd_gen_ksymdeps = \ - $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd -endif - cmd_check_local_export = $(srctree)/scripts/check-local-export $@ define rule_cc_o_c $(call cmd_and_fixdep,cc_o_c) - $(call cmd,gen_ksymdeps) $(call cmd,check_local_export) $(call cmd,checksrc) $(call cmd,checkdoc) @@ -238,7 +232,6 @@ endef define rule_as_o_S $(call cmd_and_fixdep,as_o_S) - $(call cmd,gen_ksymdeps) $(call cmd,check_local_export) $(call cmd,gen_objtooldep) $(call cmd,gen_symversions_S) diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index 7740ce3b29e8..555b9e741a01 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -86,6 +86,12 @@ output-symdump := $(if $(vmlinux.o-if-present), Module.symvers, modules-only.sym missing-input := $(filter-out $(vmlinux.o-if-present),vmlinux.o) endif +ifdef CONFIG_TRIM_UNUSED_KSYMS +ksym-wl := $(CONFIG_UNUSED_KSYMS_WHITELIST) +ksym-wl := $(if $(filter-out /%, $(ksym-wl)),$(srctree)/)$(ksym-wl) +modpost-args += -t $(addprefix -W, $(ksym-wl)) +endif + else # set src + obj - they may be used in the modules's Makefile @@ -122,7 +128,7 @@ quiet_cmd_modpost = MODPOST $@ sed 's/ko$$/o/' $(or $(modorder-if-needed), /dev/null) | $(MODPOST) $(modpost-args) $(vmlinux.o-if-present) -T - targets += $(output-symdump) -$(output-symdump): $(modorder-if-needed) $(vmlinux.o-if-present) $(moudle.symvers-if-present) $(MODPOST) FORCE +$(output-symdump): $(modorder-if-needed) $(vmlinux.o-if-present) $(moudle.symvers-if-present) $(MODPOST) $(ksym-wl) FORCE $(call if_changed,modpost) __modpost: $(output-symdump) diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh deleted file mode 100755 index f1b5ac818411..000000000000 --- a/scripts/adjust_autoksyms.sh +++ /dev/null @@ -1,73 +0,0 @@ -#!/bin/sh -# SPDX-License-Identifier: GPL-2.0-only - -# Script to update include/generated/autoksyms.h and dependency files -# -# Copyright: (C) 2016 Linaro Limited -# Created by: Nicolas Pitre, January 2016 -# - -# Update the include/generated/autoksyms.h file. -# -# For each symbol being added or removed, the corresponding dependency -# file's timestamp is updated to force a rebuild of the affected source -# file. All arguments passed to this script are assumed to be a command -# to be exec'd to trigger a rebuild of those files. - -set -e - -cur_ksyms_file="include/generated/autoksyms.h" -new_ksyms_file="include/generated/autoksyms.h.tmpnew" - -info() { - if [ "$quiet" != "silent_" ]; then - printf " %-7s %s\n" "$1" "$2" - fi -} - -info "CHK" "$cur_ksyms_file" - -# Use "make V=1" to debug this script. -case "$KBUILD_VERBOSE" in -*1*) - set -x - ;; -esac - -# Generate a new symbol list file -$CONFIG_SHELL $srctree/scripts/gen_autoksyms.sh --modorder "$new_ksyms_file" - -# Extract changes between old and new list and touch corresponding -# dependency files. -changed=$( -count=0 -sort "$cur_ksyms_file" "$new_ksyms_file" | uniq -u | -sed -n 's/^#define __KSYM_\(.*\) 1/\1/p' | -while read sympath; do - if [ -z "$sympath" ]; then continue; fi - depfile="include/ksym/${sympath}" - mkdir -p "$(dirname "$depfile")" - touch "$depfile" - # Filesystems with coarse time precision may create timestamps - # equal to the one from a file that was very recently built and that - # needs to be rebuild. Let's guard against that by making sure our - # dep files are always newer than the first file we created here. - while [ ! "$depfile" -nt "$new_ksyms_file" ]; do - touch "$depfile" - done - echo $((count += 1)) -done | tail -1 ) -changed=${changed:-0} - -if [ $changed -gt 0 ]; then - # Replace the old list with tne new one - old=$(grep -c "^#define __KSYM_" "$cur_ksyms_file" || true) - new=$(grep -c "^#define __KSYM_" "$new_ksyms_file" || true) - info "KSYMS" "symbols: before=$old, after=$new, changed=$changed" - info "UPD" "$cur_ksyms_file" - mv -f "$new_ksyms_file" "$cur_ksyms_file" - # Then trigger a rebuild of affected source files - exec $@ -else - rm -f "$new_ksyms_file" -fi diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c index 2328f9a641da..e7db12140d87 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -243,8 +243,7 @@ static void *read_file(const char *filename) /* Ignore certain dependencies */ static int is_ignored_file(const char *s, int len) { - return str_ends_with(s, len, "include/generated/autoconf.h") || - str_ends_with(s, len, "include/generated/autoksyms.h"); + return str_ends_with(s, len, "include/generated/autoconf.h"); } /* diff --git a/scripts/gen_autoksyms.sh b/scripts/gen_autoksyms.sh deleted file mode 100755 index 653fadbad302..000000000000 --- a/scripts/gen_autoksyms.sh +++ /dev/null @@ -1,62 +0,0 @@ -#!/bin/sh -# SPDX-License-Identifier: GPL-2.0-only - -# Create an autoksyms.h header file from the list of all module's needed symbols -# as recorded in *.usyms files and the user-provided symbol whitelist. - -set -e - -# Use "make V=1" to debug this script. -case "$KBUILD_VERBOSE" in -*1*) - set -x - ;; -esac - -read_modorder= - -if [ "$1" = --modorder ]; then - shift - read_modorder=1 -fi - -output_file="$1" - -needed_symbols= - -# Special case for modversions (see modpost.c) -if grep -q "^CONFIG_MODVERSIONS=y$" include/config/auto.conf; then - needed_symbols="$needed_symbols module_layout" -fi - -ksym_wl=$(sed -n 's/^CONFIG_UNUSED_KSYMS_WHITELIST=\(.*\)$/\1/p' include/config/auto.conf) -if [ -n "$ksym_wl" ]; then - [ "${ksym_wl}" != "${ksym_wl#/}" ] || ksym_wl="$abs_srctree/$ksym_wl" - if [ ! -f "$ksym_wl" ] || [ ! -r "$ksym_wl" ]; then - echo "ERROR: '$ksym_wl' whitelist file not found" >&2 - exit 1 - fi -fi - -# Generate a new ksym list file with symbols needed by the current -# set of modules. -cat > "$output_file" << EOT -/* - * Automatically generated file; DO NOT EDIT. - */ - -EOT - -{ - [ -n "${read_modorder}" ] && sed 's/ko$/usyms/' modules.order | xargs cat - echo "$needed_symbols" - [ -n "$ksym_wl" ] && cat "$ksym_wl" -} | sed -e 's/ /\n/g' | sed -n -e '/^$/!p' | -# Remove the dot prefix for ppc64; symbol names with a dot (.) hold entry -# point addresses. -sed -e 's/^\.//' | -sort -u | -# Ignore __this_module. It's not an exported symbol, and will be resolved -# when the final .ko's are linked. -grep -v '^__this_module$' | -sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$output_file" diff --git a/scripts/gen_ksymdeps.sh b/scripts/gen_ksymdeps.sh deleted file mode 100755 index 8ee533f33659..000000000000 --- a/scripts/gen_ksymdeps.sh +++ /dev/null @@ -1,30 +0,0 @@ -#!/bin/sh -# SPDX-License-Identifier: GPL-2.0 - -set -e - -# List of exported symbols -# -# If the object has no symbol, $NM warns 'no symbols'. -# Suppress the stderr. -# TODO: -# Use -q instead of 2>/dev/null when we upgrade the minimum version of -# binutils to 2.37, llvm to 13.0.0. -ksyms=$($NM $1 2>/dev/null | sed -n 's/.*__ksym_marker_\(.*\)/\1/p') - -if [ -z "$ksyms" ]; then - exit 0 -fi - -echo -echo "ksymdeps_$1 := \\" - -for s in $ksyms -do - printf ' $(wildcard include/ksym/%s) \\\n' "$s" -done - -echo -echo "$1: \$(ksymdeps_$1)" -echo -echo "\$(ksymdeps_$1):" diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 90733664a602..1e9eba0a6cec 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -34,6 +34,9 @@ static bool warn_unresolved; static int sec_mismatch_count; static bool sec_mismatch_warn_only = true; +/* Trim EXPORT_SYMBOLs that are unused by in-tree modules */ +static bool trim_unused_exports; + /* ignore missing files */ static bool ignore_missing_files; /* If set to 1, only warn (instead of error) about missing ns imports */ @@ -216,6 +219,7 @@ struct symbol { bool weak; bool is_func; bool is_gpl_only; /* exported by EXPORT_SYMBOL_GPL */ + bool used; /* there exists a user of this symbol */ char name[]; }; @@ -1872,6 +1876,7 @@ static void check_exports(struct module *mod) continue; } + exp->used = true; s->module = exp->module; s->crc_valid = exp->crc_valid; s->crc = exp->crc; @@ -1895,6 +1900,23 @@ static void check_exports(struct module *mod) } } +static void handle_white_list_exports(const char *white_list) +{ + char *buf, *p, *name; + + buf = read_text_file(white_list); + p = buf; + + while ((name = strsep(&p, "\n"))) { + struct symbol *sym = find_symbol(name); + + if (sym) + sym->used = true; + } + + free(buf); +} + static void check_modname_len(struct module *mod) { const char *mod_name; @@ -1965,10 +1987,14 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod) /* generate struct for exported symbols */ buf_printf(buf, "\n"); - list_for_each_entry(sym, &mod->exported_symbols, list) + list_for_each_entry(sym, &mod->exported_symbols, list) { + if (trim_unused_exports && !sym->used) + continue; + buf_printf(buf, "KSYMTAB_%s(%s, \"%s\", \"%s\");\n", sym->is_func ? "FUNC" : "DATA", sym->name, sym->is_gpl_only ? "_gpl" : "", sym->namespace); + } if (!modversions) return; @@ -1976,6 +2002,9 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod) /* record CRCs for exported symbols */ buf_printf(buf, "\n"); list_for_each_entry(sym, &mod->exported_symbols, list) { + if (trim_unused_exports && !sym->used) + continue; + if (!sym->crc_valid) warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n" "Is \"%s\" prototyped in ?\n", @@ -2139,9 +2168,6 @@ static void write_mod_c_file(struct module *mod) char fname[PATH_MAX]; int ret; - check_modname_len(mod); - check_exports(mod); - add_header(&buf, mod); add_exported_symbols(&buf, mod); add_versions(&buf, mod); @@ -2275,12 +2301,13 @@ int main(int argc, char **argv) { struct module *mod; char *missing_namespace_deps = NULL; + char *unused_exports_white_list = NULL; char *dump_write = NULL, *files_source = NULL; int opt; LIST_HEAD(dump_lists); struct dump_list *dl, *dl2; - while ((opt = getopt(argc, argv, "ei:mnT:o:awENd:")) != -1) { + while ((opt = getopt(argc, argv, "ei:mntT:tW:o:awENd:")) != -1) { switch (opt) { case 'e': external_module = true; @@ -2305,6 +2332,12 @@ int main(int argc, char **argv) case 'T': files_source = optarg; break; + case 't': + trim_unused_exports = true; + break; + case 'W': + unused_exports_white_list = optarg; + break; case 'w': warn_unresolved = true; break; @@ -2334,6 +2367,17 @@ int main(int argc, char **argv) if (files_source) read_symbols_from_files(files_source); + list_for_each_entry(mod, &modules, list) { + if (mod->from_dump || mod->is_vmlinux) + continue; + + check_modname_len(mod); + check_exports(mod); + } + + if (unused_exports_white_list) + handle_white_list_exports(unused_exports_white_list); + list_for_each_entry(mod, &modules, list) { if (mod->from_dump) continue; diff --git a/scripts/remove-stale-files b/scripts/remove-stale-files index ccadfa3afb2b..d2009eda270a 100755 --- a/scripts/remove-stale-files +++ b/scripts/remove-stale-files @@ -47,3 +47,5 @@ rm -f arch/riscv/purgatory/kexec-purgatory.c rm -f scripts/extract-cert rm -f arch/x86/purgatory/kexec-purgatory.c + +rm -rf include/ksym -- 2.34.1