From bbda5ec671d3fe62faefa1cab7270aa586042a4b Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 30 Nov 2018 10:05:26 +0900 Subject: [PATCH] kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS My main motivation of this commit is to clean up scripts/Kbuild.include and scripts/Makefile.build. Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick; possibly exported symbols are detected by letting $(CPP) replace EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is post-processed by sed, and passed to fixdep. The extra preprocessing is costly, and hacking cmd_and_fixdep is ugly. I came up with a new way to find exported symbols; insert a dummy symbol __ksym_marker_* to each potentially exported symbol. Those dummy symbols are picked up by $(NM), post-processed by sed, then appended to .*.cmd files. I collected the post-process part to a new shell script scripts/gen_ksymdeps.sh for readability. The dummy symbols are put into the .discard.* section so that the linker script rips them off the final vmlinux or modules. A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will be much faster. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Pitre --- include/asm-generic/export.h | 13 ++++++++----- include/linux/export.h | 22 +++++++++++----------- scripts/Kbuild.include | 28 ---------------------------- scripts/Makefile.build | 7 +++++++ scripts/basic/fixdep.c | 31 ++++--------------------------- scripts/gen_ksymdeps.sh | 25 +++++++++++++++++++++++++ 6 files changed, 55 insertions(+), 71 deletions(-) create mode 100755 scripts/gen_ksymdeps.sh diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h index 4d73e6e3c66c..294d6ae785d4 100644 --- a/include/asm-generic/export.h +++ b/include/asm-generic/export.h @@ -59,16 +59,19 @@ __kcrctab_\name: .endm #undef __put -#if defined(__KSYM_DEPS__) - -#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym === - -#elif defined(CONFIG_TRIM_UNUSED_KSYMS) +#if defined(CONFIG_TRIM_UNUSED_KSYMS) #include #include +.macro __ksym_marker sym + .section ".discard.ksym","a" +__ksym_marker_\sym: + .previous +.endm + #define __EXPORT_SYMBOL(sym, val, sec) \ + __ksym_marker sym; \ __cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym)) #define __cond_export_sym(sym, val, sec, conf) \ ___cond_export_sym(sym, val, sec, conf) diff --git a/include/linux/export.h b/include/linux/export.h index ce764a5d2ee4..fd8711ed9ac4 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -92,22 +92,22 @@ struct kernel_symbol { */ #define __EXPORT_SYMBOL(sym, sec) -#elif defined(__KSYM_DEPS__) - -/* - * 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 string pattern that is unlikely to be valid code that the build - * system filters out from the preprocessor output (see ksym_dep_filter - * in scripts/Kbuild.include). - */ -#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym === - #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. + */ +#define __ksym_marker(sym) \ + static int __ksym_marker_##sym[0] __section(".discard.ksym") __used + #define __EXPORT_SYMBOL(sym, sec) \ + __ksym_marker(sym); \ __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym)) #define __cond_export_sym(sym, sec, conf) \ ___cond_export_sym(sym, sec, conf) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 6cf6a8b83b97..4b943f4d2226 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -260,39 +260,11 @@ if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ), \ @set -e; \ $(cmd_and_fixdep), @:) -ifndef CONFIG_TRIM_UNUSED_KSYMS - cmd_and_fixdep = \ $(echo-cmd) $(cmd_$(1)); \ scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\ rm -f $(depfile); -else - -# Filter out exported kernel symbol names from the preprocessor output. -# See also __KSYM_DEPS__ in include/linux/export.h. -# We disable the depfile generation here, so as not to overwrite the existing -# depfile while fixdep is parsing it. -flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1))) -ksym_dep_filter = \ - case "$(1)" in \ - cc_*_c|cpp_i_c) \ - $(CPP) $(call flags_nodeps,c_flags) -D__KSYM_DEPS__ $< ;; \ - as_*_S|cpp_s_S) \ - $(CPP) $(call flags_nodeps,a_flags) -D__KSYM_DEPS__ $< ;; \ - boot*|build*|cpp_its_S|*cpp_lds_S|dtc|host*|vdso*) : ;; \ - *) echo "Don't know how to preprocess $(1)" >&2; false ;; \ - esac | tr ";" "\n" | sed -n 's/^.*=== __KSYM_\(.*\) ===.*$$/_\1/p' - -cmd_and_fixdep = \ - $(echo-cmd) $(cmd_$(1)); \ - $(ksym_dep_filter) | \ - scripts/basic/fixdep -e $(depfile) $@ '$(make-cmd)' \ - > $(dot-target).cmd; \ - rm -f $(depfile); - -endif - # Usage: $(call if_changed_rule,foo) # Will check if $(cmd_foo) or any of the prerequisites changed, # and if so will execute $(rule_foo). diff --git a/scripts/Makefile.build b/scripts/Makefile.build index cdb25d163b42..23ebf2508234 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -254,9 +254,15 @@ objtool_dep = $(objtool_obj) \ $(wildcard include/config/orc/unwinder.h \ include/config/stack/validation.h) +ifdef CONFIG_TRIM_UNUSED_KSYMS +cmd_gen_ksymdeps = \ + $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd; +endif + define rule_cc_o_c $(call echo-cmd,checksrc) $(cmd_checksrc) \ $(call cmd_and_fixdep,cc_o_c) \ + $(cmd_gen_ksymdeps) \ $(cmd_checkdoc) \ $(call echo-cmd,objtool) $(cmd_objtool) \ $(cmd_modversions_c) \ @@ -265,6 +271,7 @@ endef define rule_as_o_S $(call cmd_and_fixdep,as_o_S) \ + $(cmd_gen_ksymdeps) \ $(call echo-cmd,objtool) $(cmd_objtool) \ $(cmd_modversions_S) endef diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c index 850966f3d602..facbd603adf6 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -105,8 +105,7 @@ static void usage(void) { - fprintf(stderr, "Usage: fixdep [-e] \n"); - fprintf(stderr, " -e insert extra dependencies given on stdin\n"); + fprintf(stderr, "Usage: fixdep \n"); exit(1); } @@ -131,21 +130,6 @@ static void print_dep(const char *m, int slen, const char *dir) printf(".h) \\\n"); } -static void do_extra_deps(void) -{ - char buf[80]; - - while (fgets(buf, sizeof(buf), stdin)) { - int len = strlen(buf); - - if (len < 2 || buf[len - 1] != '\n') { - fprintf(stderr, "fixdep: bad data on stdin\n"); - exit(1); - } - print_dep(buf, len - 1, "include/ksym"); - } -} - struct item { struct item *next; unsigned int len; @@ -293,7 +277,7 @@ static int is_ignored_file(const char *s, int len) * assignments are parsed not only by make, but also by the rather simple * parser in scripts/mod/sumversion.c. */ -static void parse_dep_file(char *m, const char *target, int insert_extra_deps) +static void parse_dep_file(char *m, const char *target) { char *p; int is_last, is_target; @@ -369,9 +353,6 @@ static void parse_dep_file(char *m, const char *target, int insert_extra_deps) exit(1); } - if (insert_extra_deps) - do_extra_deps(); - printf("\n%s: $(deps_%s)\n\n", target, target); printf("$(deps_%s):\n", target); } @@ -379,13 +360,9 @@ static void parse_dep_file(char *m, const char *target, int insert_extra_deps) int main(int argc, char *argv[]) { const char *depfile, *target, *cmdline; - int insert_extra_deps = 0; void *buf; - if (argc == 5 && !strcmp(argv[1], "-e")) { - insert_extra_deps = 1; - argv++; - } else if (argc != 4) + if (argc != 4) usage(); depfile = argv[1]; @@ -395,7 +372,7 @@ int main(int argc, char *argv[]) printf("cmd_%s := %s\n\n", target, cmdline); buf = read_file(depfile); - parse_dep_file(buf, target, insert_extra_deps); + parse_dep_file(buf, target); free(buf); return 0; diff --git a/scripts/gen_ksymdeps.sh b/scripts/gen_ksymdeps.sh new file mode 100755 index 000000000000..1324986e1362 --- /dev/null +++ b/scripts/gen_ksymdeps.sh @@ -0,0 +1,25 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +set -e + +# List of exported symbols +ksyms=$($NM $1 | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z) + +if [ -z "$ksyms" ]; then + exit 0 +fi + +echo +echo "ksymdeps_$1 := \\" + +for s in $ksyms +do + echo $s | sed -e 's:^_*: $(wildcard include/ksym/:' \ + -e 's:__*:/:g' -e 's/$/.h) \\/' +done + +echo +echo "$1: \$(ksymdeps_$1)" +echo +echo "\$(ksymdeps_$1):"