From patchwork Sat May 13 20:45:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 13240334 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 774A7C77B7F for ; Sat, 13 May 2023 20:46:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230061AbjEMUq6 (ORCPT ); Sat, 13 May 2023 16:46:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234322AbjEMUqb (ORCPT ); Sat, 13 May 2023 16:46:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C1B440D1; Sat, 13 May 2023 13:46:02 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 983C761558; Sat, 13 May 2023 20:45:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B53FC433D2; Sat, 13 May 2023 20:45:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684010758; bh=EwZN3U3/2rCml/YtnBIQ1znO5pjexIvWP+wO2NdA8u0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b/iitFoI3Dkmks1eI/ieehxh8KaCAiGd4/ILGHwJ0ssbZ6Tae2qHY/kj3JPX1sNDW twiwtsDfR44JnG4J3d9wx/raefVHoX/tkCQpq6NTKJQ8CGDTYkVw4eBPm/7qTJ+pbJ B4bQIJ6sIxuA9vvoAv38j7uccg4P4jVnAdxZeIVU+rlrdxsEYPGJ++dxWFrNYeVkcd FDLlEkLv7TqHQ8+PUpYiBSG9QQDbTECzXDNSwCVttZrewSPqk3CEGGvGr9CMaG/naZ 6WxKlKSWYUFoBG4pkQRCDNH1XhZ/7fAeGkagEvcpPadA3kQyP0NZrN0qNO3Ykwqn0/ JBHMqp8+PuYXw== From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Nathan Chancellor , Nick Desaulniers , Nicolas Pitre , Nicolas Schier , Masahiro Yamada Subject: [PATCH v4 21/21] kbuild: implement CONFIG_TRIM_UNUSED_KSYMS without recursion Date: Sun, 14 May 2023 05:45:02 +0900 Message-Id: <20230513204502.1593923-22-masahiroy@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230513204502.1593923-1-masahiroy@kernel.org> References: <20230513204502.1593923-1-masahiroy@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@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 negative opinions 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 --- .gitignore | 1 - Makefile | 19 +--------- include/linux/export.h | 41 --------------------- scripts/Makefile.build | 7 ---- scripts/Makefile.modpost | 7 ++++ scripts/adjust_autoksyms.sh | 73 ------------------------------------- scripts/basic/fixdep.c | 3 +- scripts/gen_ksymdeps.sh | 30 --------------- scripts/mod/modpost.c | 54 ++++++++++++++++++++++++--- scripts/remove-stale-files | 2 + 10 files changed, 61 insertions(+), 176 deletions(-) delete mode 100755 scripts/adjust_autoksyms.sh delete mode 100755 scripts/gen_ksymdeps.sh diff --git a/.gitignore b/.gitignore index 7f86e0837909..172e3874adfd 100644 --- a/.gitignore +++ b/.gitignore @@ -112,7 +112,6 @@ modules.order # /include/config/ /include/generated/ -/include/ksym/ /arch/*/include/generated/ # stgit generated dirs diff --git a/Makefile b/Makefile index 9d765ebcccf1..2a081f2e9911 100644 --- a/Makefile +++ b/Makefile @@ -1193,28 +1193,13 @@ 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 = \ @@ -1223,7 +1208,7 @@ quiet_cmd_ar_vmlinux.a = AR $@ $(AR) mPiT $$($(AR) t $@ | sed -n 1p) $@ $$($(AR) t $@ | grep -F -f $(srctree)/scripts/head-object-list.txt) targets += vmlinux.a -vmlinux.a: $(KBUILD_VMLINUX_OBJS) scripts/head-object-list.txt autoksyms_recursive FORCE +vmlinux.a: $(KBUILD_VMLINUX_OBJS) scripts/head-object-list.txt FORCE $(call if_changed,ar_vmlinux.a) PHONY += vmlinux_o @@ -1279,7 +1264,7 @@ 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 4335a17a1ea7..0b9f85628fba 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -65,47 +65,6 @@ 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 94b3323dcea7..dc0b27d1a500 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -215,18 +215,12 @@ 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 $@ >> $(dot-target).cmd -endif - ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) cmd_warn_shared_object = $(if $(word 2, $(modname-multi)),$(warning $(kbuild-file): $*.o is added to multiple modules: $(modname-multi))) endif define rule_cc_o_c $(call cmd_and_fixdep,cc_o_c) - $(call cmd,gen_ksymdeps) $(call cmd,checksrc) $(call cmd,checkdoc) $(call cmd,gen_objtooldep) @@ -237,7 +231,6 @@ endef define rule_as_o_S $(call cmd_and_fixdep,as_o_S) - $(call cmd,gen_ksymdeps) $(call cmd,gen_objtooldep) $(call cmd,gen_symversions_S) $(call cmd,warn_shared_object) diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index 0980c58d8afc..1e0b47cbabd9 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -90,6 +90,13 @@ targets += .vmlinux.objs .vmlinux.objs: vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE $(call if_changed,vmlinux_objs) +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)) +modpost-deps += $(ksym-wl) +endif + ifeq ($(wildcard vmlinux.o),) missing-input := vmlinux.o output-symdump := modules-only.symvers 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 fa562806c2be..84b6efa849f4 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -246,8 +246,7 @@ 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"); } /* Do not parse these files */ 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 bb9510f9645f..4d77b83b1338 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -35,6 +35,9 @@ 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 */ @@ -217,6 +220,7 @@ 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[]; }; @@ -1758,6 +1762,7 @@ 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; @@ -1781,6 +1786,23 @@ 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; @@ -1851,10 +1873,14 @@ 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; @@ -1862,6 +1888,9 @@ 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", @@ -2025,9 +2054,6 @@ 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); @@ -2161,12 +2187,13 @@ 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; @@ -2191,6 +2218,12 @@ 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; @@ -2220,6 +2253,17 @@ 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 7f432900671a..8502a17d47df 100755 --- a/scripts/remove-stale-files +++ b/scripts/remove-stale-files @@ -33,3 +33,5 @@ rm -f rust/target.json rm -f scripts/bin2c rm -f .scmversion + +rm -rf include/ksym