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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 <yamada.masahiro@socionext.com> Reviewed-by: Nicolas Pitre <nico@linaro.org>
This commit is contained in:
Masahiro Yamada
parent
ee3e46b7ef
commit
bbda5ec671
@ -59,16 +59,19 @@ __kcrctab_\name:
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.endm
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#undef __put
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#if defined(__KSYM_DEPS__)
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#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
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#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
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#if defined(CONFIG_TRIM_UNUSED_KSYMS)
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#include <linux/kconfig.h>
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#include <generated/autoksyms.h>
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.macro __ksym_marker sym
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.section ".discard.ksym","a"
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__ksym_marker_\sym:
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.previous
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.endm
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#define __EXPORT_SYMBOL(sym, val, sec) \
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__ksym_marker sym; \
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__cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
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#define __cond_export_sym(sym, val, sec, conf) \
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___cond_export_sym(sym, val, sec, conf)
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@ -92,22 +92,22 @@ struct kernel_symbol {
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*/
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#define __EXPORT_SYMBOL(sym, sec)
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#elif defined(__KSYM_DEPS__)
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/*
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* For fine grained build dependencies, we want to tell the build system
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* about each possible exported symbol even if they're not actually exported.
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* We use a string pattern that is unlikely to be valid code that the build
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* system filters out from the preprocessor output (see ksym_dep_filter
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* in scripts/Kbuild.include).
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*/
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#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym ===
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#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
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#include <generated/autoksyms.h>
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/*
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* For fine grained build dependencies, we want to tell the build system
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* about each possible exported symbol even if they're not actually exported.
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* We use a symbol pattern __ksym_marker_<symbol> that the build system filters
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* from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
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* discarded in the final link stage.
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*/
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#define __ksym_marker(sym) \
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static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
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#define __EXPORT_SYMBOL(sym, sec) \
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__ksym_marker(sym); \
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__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
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#define __cond_export_sym(sym, sec, conf) \
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___cond_export_sym(sym, sec, conf)
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@ -260,39 +260,11 @@ if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ), \
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@set -e; \
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$(cmd_and_fixdep), @:)
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ifndef CONFIG_TRIM_UNUSED_KSYMS
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cmd_and_fixdep = \
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$(echo-cmd) $(cmd_$(1)); \
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scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
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rm -f $(depfile);
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else
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# Filter out exported kernel symbol names from the preprocessor output.
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# See also __KSYM_DEPS__ in include/linux/export.h.
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# We disable the depfile generation here, so as not to overwrite the existing
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# depfile while fixdep is parsing it.
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flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1)))
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ksym_dep_filter = \
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case "$(1)" in \
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cc_*_c|cpp_i_c) \
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$(CPP) $(call flags_nodeps,c_flags) -D__KSYM_DEPS__ $< ;; \
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as_*_S|cpp_s_S) \
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$(CPP) $(call flags_nodeps,a_flags) -D__KSYM_DEPS__ $< ;; \
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boot*|build*|cpp_its_S|*cpp_lds_S|dtc|host*|vdso*) : ;; \
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*) echo "Don't know how to preprocess $(1)" >&2; false ;; \
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esac | tr ";" "\n" | sed -n 's/^.*=== __KSYM_\(.*\) ===.*$$/_\1/p'
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cmd_and_fixdep = \
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$(echo-cmd) $(cmd_$(1)); \
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$(ksym_dep_filter) | \
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scripts/basic/fixdep -e $(depfile) $@ '$(make-cmd)' \
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> $(dot-target).cmd; \
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rm -f $(depfile);
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endif
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# Usage: $(call if_changed_rule,foo)
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# Will check if $(cmd_foo) or any of the prerequisites changed,
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# and if so will execute $(rule_foo).
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@ -254,9 +254,15 @@ objtool_dep = $(objtool_obj) \
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$(wildcard include/config/orc/unwinder.h \
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include/config/stack/validation.h)
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ifdef CONFIG_TRIM_UNUSED_KSYMS
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cmd_gen_ksymdeps = \
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$(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd;
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endif
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define rule_cc_o_c
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$(call echo-cmd,checksrc) $(cmd_checksrc) \
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$(call cmd_and_fixdep,cc_o_c) \
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$(cmd_gen_ksymdeps) \
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$(cmd_checkdoc) \
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$(call echo-cmd,objtool) $(cmd_objtool) \
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$(cmd_modversions_c) \
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@ -265,6 +271,7 @@ endef
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define rule_as_o_S
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$(call cmd_and_fixdep,as_o_S) \
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$(cmd_gen_ksymdeps) \
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$(call echo-cmd,objtool) $(cmd_objtool) \
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$(cmd_modversions_S)
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endef
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@ -105,8 +105,7 @@
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static void usage(void)
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{
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fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n");
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fprintf(stderr, " -e insert extra dependencies given on stdin\n");
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fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
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exit(1);
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}
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@ -131,21 +130,6 @@ static void print_dep(const char *m, int slen, const char *dir)
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printf(".h) \\\n");
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}
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static void do_extra_deps(void)
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{
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char buf[80];
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while (fgets(buf, sizeof(buf), stdin)) {
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int len = strlen(buf);
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if (len < 2 || buf[len - 1] != '\n') {
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fprintf(stderr, "fixdep: bad data on stdin\n");
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exit(1);
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}
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print_dep(buf, len - 1, "include/ksym");
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}
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}
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struct item {
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struct item *next;
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unsigned int len;
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@ -293,7 +277,7 @@ static int is_ignored_file(const char *s, int len)
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* assignments are parsed not only by make, but also by the rather simple
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* parser in scripts/mod/sumversion.c.
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*/
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static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
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static void parse_dep_file(char *m, const char *target)
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{
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char *p;
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int is_last, is_target;
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@ -369,9 +353,6 @@ static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
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exit(1);
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}
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if (insert_extra_deps)
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do_extra_deps();
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printf("\n%s: $(deps_%s)\n\n", target, target);
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printf("$(deps_%s):\n", target);
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}
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@ -379,13 +360,9 @@ static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
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int main(int argc, char *argv[])
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{
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const char *depfile, *target, *cmdline;
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int insert_extra_deps = 0;
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void *buf;
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if (argc == 5 && !strcmp(argv[1], "-e")) {
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insert_extra_deps = 1;
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argv++;
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} else if (argc != 4)
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if (argc != 4)
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usage();
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depfile = argv[1];
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@ -395,7 +372,7 @@ int main(int argc, char *argv[])
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printf("cmd_%s := %s\n\n", target, cmdline);
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buf = read_file(depfile);
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parse_dep_file(buf, target, insert_extra_deps);
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parse_dep_file(buf, target);
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free(buf);
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return 0;
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25
scripts/gen_ksymdeps.sh
Executable file
25
scripts/gen_ksymdeps.sh
Executable file
@ -0,0 +1,25 @@
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#!/bin/sh
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# SPDX-License-Identifier: GPL-2.0
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set -e
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# List of exported symbols
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ksyms=$($NM $1 | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
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if [ -z "$ksyms" ]; then
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exit 0
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fi
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echo
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echo "ksymdeps_$1 := \\"
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for s in $ksyms
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do
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echo $s | sed -e 's:^_*: $(wildcard include/ksym/:' \
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-e 's:__*:/:g' -e 's/$/.h) \\/'
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done
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echo
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echo "$1: \$(ksymdeps_$1)"
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echo
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echo "\$(ksymdeps_$1):"
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