Re: [PATCH 1/2] strip generated symbols from *.ko

From: Sam Ravnborg
Date: Thu Sep 27 2007 - 07:34:55 EST

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(private reply)

Being occupied by non-linux stuff lately but will review your patches soon.
non-linux stuff includes too little sleep because my baby girl having
yet another new teeth and it hurst...

I hope to go over it during the weekend so Ican include it in next merge window.

Sam

On Wed, Sep 19, 2007 at 03:57:07PM +0100, Jan Beulich wrote:
> This patch changes the way __crc_ symbols are being resolved from
> using ld to do so to using the assembler, thus allowing these symbols
> to be marked local (the linker creates then as global ones) and hence
> allow stripping (for modules) or ignoring (for vmlinux) them. While at
> this, also strip other generated symbols during module installation.
>
> One potentially debatable point is the handling of the flags passeed
> to gcc when translating the intermediate assembly file into an object:
> passing $(c_flags) unchanged doesn't work as gcc passes --gdwarf2 to
> gas whenever is sees any -g* option, even for -g0, and despite the
> fact that the compiler would have already produced all necessary debug
> info in the C->assembly translation phase. I took the approach of just
> filtering out all -g* options, but an alternative to such negative
> filtering might be to have a positive filter which might, in the ideal
> case allow just all the -Wa,* options to pass through.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
>
> ---
> Makefile | 15 ++++++------
> scripts/Makefile.build | 51 +++++++++++++++++++++++++++-----------------
> scripts/Makefile.modinst | 2 -
> scripts/genksyms/genksyms.c | 23 ++++++++++++++-----
> scripts/mksysmap | 6 +----
> scripts/strip-syms.lst | 19 ++++++++++++++++
> 6 files changed, 78 insertions(+), 38 deletions(-)
>
> --- 2.6.23-rc6-strip.orig/Makefile
> +++ 2.6.23-rc6-strip/Makefile
> @@ -542,19 +542,18 @@ MODLIB = $(INSTALL_MOD_PATH)/lib/modules
> export MODLIB
>
> #
> -# INSTALL_MOD_STRIP, if defined, will cause modules to be
> -# stripped after they are installed. If INSTALL_MOD_STRIP is '1', then
> -# the default option --strip-debug will be used. Otherwise,
> -# INSTALL_MOD_STRIP will used as the options to the strip command.
> -
> +# INSTALL_MOD_STRIP, if defined, will cause modules to be stripped while
> +# they get installed. If INSTALL_MOD_STRIP is '1', then the default
> +# options (see below) will be used. Otherwise, INSTALL_MOD_STRIP will
> +# be used as the option(s) to the objcopy command.
> ifdef INSTALL_MOD_STRIP
> ifeq ($(INSTALL_MOD_STRIP),1)
> -mod_strip_cmd = $(STRIP) --strip-debug
> +mod_strip_cmd = $(OBJCOPY) --strip-debug --strip-symbols $(srctree)/scripts/strip-syms.lst --wildcard
> else
> -mod_strip_cmd = $(STRIP) $(INSTALL_MOD_STRIP)
> +mod_strip_cmd = $(OBJCOPY) $(INSTALL_MOD_STRIP)
> endif # INSTALL_MOD_STRIP=1
> else
> -mod_strip_cmd = true
> +mod_strip_cmd = false
> endif # INSTALL_MOD_STRIP
> export mod_strip_cmd
>
> --- 2.6.23-rc6-strip.orig/scripts/Makefile.build
> +++ 2.6.23-rc6-strip/scripts/Makefile.build
> @@ -176,30 +176,38 @@ cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $
>
> else
> # When module versioning is enabled the following steps are executed:
> -# o compile a .tmp_<file>.o from <file>.c
> -# o if .tmp_<file>.o doesn't contain a __ksymtab version, i.e. does
> -# not export symbols, we just rename .tmp_<file>.o to <file>.o and
> +# o compile a .tmp_<file>.s from <file>.c
> +# o if .tmp_<file>.s doesn't contain a __ksymtab version, i.e. does
> +# not export symbols, we just assemble .tmp_<file>.s to <file>.o and
> # are done.
> # o otherwise, we calculate symbol versions using the good old
> # genksyms on the preprocessed source and postprocess them in a way
> -# that they are usable as a linker script
> -# o generate <file>.o from .tmp_<file>.o using the linker to
> -# replace the unresolved symbols __crc_exported_symbol with
> -# the actual value of the checksum generated by genksyms
> +# that they are usable as assembly source
> +# o assemble <file>.o from .tmp_<file>.s forcing inclusion of directives
> +# defining the actual values of __crc_*, followed by objcopy-ing them
> +# to force these symbols to be local to permit stripping them later.
>
> -cmd_cc_o_c = $(CC) $(c_flags) -c -o $(@D)/.tmp_$(@F) $<
> +cmd_cc_o_c = $(CC) $(c_flags) -S -o $(@D)/.tmp_$(@F:.o=.s) $<
> cmd_modversions = \
> - if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then \
> - $(CPP) -D__GENKSYMS__ $(c_flags) $< \
> - | $(GENKSYMS) $(if $(KBUILD_SYMTYPES), \
> - -T $(@D)/$(@F:.o=.symtypes)) -a $(ARCH) \
> - > $(@D)/.tmp_$(@F:.o=.ver); \
> - \
> - $(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) \
> - -T $(@D)/.tmp_$(@F:.o=.ver); \
> - rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver); \
> + if grep -q __ksymtab $(@D)/.tmp_$(@F:.o=.s); then \
> + if $(CPP) -D__GENKSYMS__ $(c_flags) $< \
> + | $(GENKSYMS) -A $(if $(KBUILD_SYMTYPES), \
> + -T $(@D)/$(@F:.o=.symtypes)) -a $(ARCH) \
> + > $(@D)/.tmp_$(@F:.o=.v) \
> + && $(CC) $(filter-out -g%,$(c_flags)) -c \
> + -Wa,$(@D)/.tmp_$(@F:.o=.v) \
> + -o $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.s) \
> + && $(OBJCOPY) -L '__crc_*' -L '___crc_*' -w \
> + $(@D)/.tmp_$(@F) $@; \
> + then \
> + : ; \
> + else \
> + rm -f $@; exit 1; \
> + fi; \
> else \
> - mv -f $(@D)/.tmp_$(@F) $@; \
> + rm -f $(@D)/.tmp_$(@F:.o=.v); \
> + $(CC) $(filter-out -g%,$(c_flags)) -c \
> + -o $@ $(@D)/.tmp_$(@F:.o=.s); \
> fi;
> endif
>
> @@ -209,7 +217,12 @@ define rule_cc_o_c
> $(cmd_modversions) \
> scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' > \
> $(dot-target).tmp; \
> - rm -f $(depfile); \
> + if [ -r $(@D)/.tmp_$(@F:.o=.v) ]; then \
> + echo >> $(dot-target).tmp; \
> + echo '$@: $(GENKSYMS)' >> $(dot-target).tmp; \
> + echo '$(GENKSYMS):: ;' >> $(dot-target).tmp; \
> + fi; \
> + rm -f $(depfile) $(@D)/.tmp_$(@F:.o=.?); \
> mv -f $(dot-target).tmp $(dot-target).cmd
> endef
>
> --- 2.6.23-rc6-strip.orig/scripts/Makefile.modinst
> +++ 2.6.23-rc6-strip/scripts/Makefile.modinst
> @@ -17,7 +17,7 @@ __modinst: $(modules)
> @:
>
> quiet_cmd_modules_install = INSTALL $@
> - cmd_modules_install = mkdir -p $(2); cp $@ $(2) ; $(mod_strip_cmd) $(2)/$(notdir $@)
> + cmd_modules_install = mkdir -p $(2); $(mod_strip_cmd) $@ $(2)/$(notdir $@) || cp $@ $(2)
>
> # Modules built outside the kernel source tree go into extra by default
> INSTALL_MOD_DIR ?= extra
> --- 2.6.23-rc6-strip.orig/scripts/genksyms/genksyms.c
> +++ 2.6.23-rc6-strip/scripts/genksyms/genksyms.c
> @@ -42,7 +42,7 @@ static FILE *debugfile;
> int cur_line = 1;
> char *cur_filename;
>
> -static int flag_debug, flag_dump_defs, flag_dump_types, flag_warnings;
> +static int flag_debug, flag_dump_defs, flag_dump_types, flag_warnings, flag_asm;
> static const char *arch = "";
> static const char *mod_prefix = "";
>
> @@ -415,8 +415,11 @@ void export_symbol(const char *name)
> if (flag_dump_defs)
> fputs(">\n", debugfile);
>
> - /* Used as a linker script. */
> - printf("%s__crc_%s = 0x%08lx ;\n", mod_prefix, name, crc);
> + /* Used as inline assembly or a linker script. */
> + printf(flag_asm
> + ? ".equiv %s__crc_%s, 0x%08lx\n"
> + : "%s__crc_%s = 0x%08lx ;\n",
> + mod_prefix, name, crc);
> }
> }
>
> @@ -440,8 +443,10 @@ void error_with_pos(const char *fmt, ...
>
> static void genksyms_usage(void)
> {
> - fputs("Usage:\n" "genksyms [-dDwqhV] > /path/to/.tmp_obj.ver\n" "\n"
> + fputs("Usage:\n" "genksyms [-aAdDwqhV] > /path/to/.tmp_obj.ver\n" "\n"
> #ifdef __GNU_LIBRARY__
> + " -a, --arch Specify target architecture\n"
> + " -A, --asm Generate inline assembly rather than linker script\n"
> " -d, --debug Increment the debug level (repeatable)\n"
> " -D, --dump Dump expanded symbol defs (for debugging only)\n"
> " -w, --warnings Enable warnings\n"
> @@ -449,6 +454,8 @@ static void genksyms_usage(void)
> " -h, --help Print this message\n"
> " -V, --version Print the release version\n"
> #else /* __GNU_LIBRARY__ */
> + " -a Specify target architecture\n"
> + " -A Generate inline assembly rather than linker script\n"
> " -d Increment the debug level (repeatable)\n"
> " -D Dump expanded symbol defs (for debugging only)\n"
> " -w Enable warnings\n"
> @@ -467,6 +474,7 @@ int main(int argc, char **argv)
> #ifdef __GNU_LIBRARY__
> struct option long_opts[] = {
> {"arch", 1, 0, 'a'},
> + {"asm", 0, 0, 'A'},
> {"debug", 0, 0, 'd'},
> {"warnings", 0, 0, 'w'},
> {"quiet", 0, 0, 'q'},
> @@ -477,10 +485,10 @@ int main(int argc, char **argv)
> {0, 0, 0, 0}
> };
>
> - while ((o = getopt_long(argc, argv, "a:dwqVDT:k:p:",
> + while ((o = getopt_long(argc, argv, "a:dwqVADT:k:p:",
> &long_opts[0], NULL)) != EOF)
> #else /* __GNU_LIBRARY__ */
> - while ((o = getopt(argc, argv, "a:dwqVDT:k:p:")) != EOF)
> + while ((o = getopt(argc, argv, "a:dwqVADT:k:p:")) != EOF)
> #endif /* __GNU_LIBRARY__ */
> switch (o) {
> case 'a':
> @@ -498,6 +506,9 @@ int main(int argc, char **argv)
> case 'V':
> fputs("genksyms version 2.5.60\n", stderr);
> break;
> + case 'A':
> + flag_asm = 1;
> + break;
> case 'D':
> flag_dump_defs = 1;
> break;
> --- 2.6.23-rc6-strip.orig/scripts/mksysmap
> +++ 2.6.23-rc6-strip/scripts/mksysmap
> @@ -36,9 +36,7 @@
>
> # readprofile starts reading symbols when _stext is found, and
> # continue until it finds a symbol which is not either of 'T', 't',
> -# 'W' or 'w'. __crc_ are 'A' and placed in the middle
> -# so we just ignore them to let readprofile continue to work.
> -# (At least sparc64 has __crc_ in the middle).
> +# 'W' or 'w'.
>
> -$NM -n $1 | grep -v '$ [aUw] $\|$__crc_$\|$ \$[adt]$' > $2
> +$NM -n $1 | grep -v '$ [aUw] $\|$ \$[adt]$' > $2
>
> --- /dev/null
> +++ 2.6.23-rc6-strip/scripts/strip-syms.lst
> @@ -0,0 +1,19 @@
> +<*>
> +*.h
> +__compound_literal[$.][0-9]*
> +__crc_[a-zA-Z_]*
> +__exitcall_[a-zA-Z_]*
> +__func__[$.][0-9]*
> +__FUNCTION__[$.][0-9]*
> +gcc[0-9]_compiled[$.]
> +__initcall_[a-zA-Z_]*
> +__kcrctab_[a-zA-Z_]*
> +__kstrtab_[a-zA-Z_]*
> +__ksymtab_[a-zA-Z_]*
> +__mod_[a-zA-Z_]*[0-9]
> +__module_depends
> +__param_[a-zA-Z_]*
> +__pci_fixup_[A-Z]*
> +__PRETTY_FUNCTION__[$.][0-9]*
> +__setup_[a-zA-Z_]*
> +____versions
>
>
-
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Next message: Arnd Bergmann: "Re: [PATCH 3/5] ibmebus: Add device creation and bus probing based on of_device"
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