On Fri, Dec 4, 2020 at 3:46 AM 'Sami Tolvanen' via Clang Built Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote: > > Hi Masahiro, > > On Thu, Dec 3, 2020 at 9:56 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > > > "xargs echo" is not a safe way to remove line breaks because the input > > may exceed the command line limit and xargs may break it up into > > multiple invocations of echo. This should never happen because > > scripts/gen_autoksyms.sh expects all undefined symbols are placed in > > the second line of .mod files. > > > > One possible way is to replace "xargs echo" with > > "sed ':x;N;$!bx;s/\n/ /g'" or something, but I rewrote the code by > > using awk because it is more readable. > > > > This issue was reported by Sami Tolvanen; in his Clang LTO patch set, > > $(multi-used-m) is no longer an ELF object, but a thin archive that > > contains LLVM bitcode files. llvm-nm prints out symbols for each > > archive member separately, which results a lot of dupications, in some > > places, beyond the system-defined limit. > > > > This problem must be fixed irrespective of LTO, and we must ensure > > zero possibility of having this issue. > > > > Link: https://lkml.org/lkml/2020/12/1/1658 > > Reported-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > > --- > > > > scripts/Makefile.build | 12 ++++-------- > > 1 file changed, 4 insertions(+), 8 deletions(-) > > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > > index ae647379b579..4c058f12dd73 100644 > > --- a/scripts/Makefile.build > > +++ b/scripts/Makefile.build > > @@ -252,6 +252,9 @@ objtool_dep = $(objtool_obj) \ > > ifdef CONFIG_TRIM_UNUSED_KSYMS > > cmd_gen_ksymdeps = \ > > $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd > > + > > +# List module undefined symbols > > +undefined_syms = $(NM) $< | $(AWK) '$$1 == "U" { printf("%s%s", x++ ? " " : "", $$2) }'; > > endif > > > > define rule_cc_o_c > > @@ -271,13 +274,6 @@ define rule_as_o_S > > $(call cmd,modversions_S) > > endef > > > > -# List module undefined symbols (or empty line if not enabled) > > -ifdef CONFIG_TRIM_UNUSED_KSYMS > > -cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | xargs echo > > -else > > -cmd_undef_syms = echo > > -endif > > - > > # Built-in and composite module parts > > $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE > > $(call if_changed_rule,cc_o_c) > > @@ -285,7 +281,7 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE > > > > cmd_mod = { \ > > echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \ > > - $(cmd_undef_syms); \ > > + $(undefined_syms) echo; \ > > } > $@ > > > > $(obj)/%.mod: $(obj)/%.o FORCE > > Thanks for the patch! I confirmed that this works with llvm-nm and > bitcode files, but it does still produce plenty of duplicates, Actually, the duplication does not matter because scripts/gen_autoksyms.sh line 46 calls 'sort -u' anyway. Only the problem is we have bigger .mod files, though. We do not have a good reason to move 'sort -u' for now. > even > though they now stay on one line. I'm not sure if the readability of > the .mod file matters though. Please feel free to add: > > Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > > Sami > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CABCJKufyBcN-foh0kj5kUsn-wiZMJ_a8ZjB72jaTmN2GEVzVNA%40mail.gmail.com. -- Best Regards Masahiro Yamada
