| Message ID | 20201013003203.4168817-15-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for Clang LTO | expand |
On Mon, Oct 12, 2020 at 05:31:52PM -0700, Sami Tolvanen wrote: > With LTO, llvm-nm prints out symbols for each archive member > separately, which results in a lot of duplicate dependencies in the > .mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module > consists of several compilation units, the output can exceed the > default xargs command size limit and split the dependency list to > multiple lines, which results in used symbols getting trimmed. > > This change removes duplicate dependencies, which will reduce the > probability of this happening and makes .mod files smaller and > easier to read. > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > Reviewed-by: Kees Cook <keescook@chromium.org> Hi Masahiro, This appears to be a general improvement as well. This looks like it can land without depending on the rest of the series. -Kees > --- > scripts/Makefile.build | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > index ab0ddf4884fd..96d6c9e18901 100644 > --- a/scripts/Makefile.build > +++ b/scripts/Makefile.build > @@ -266,7 +266,7 @@ 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 > +cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | sort -u | xargs echo > else > cmd_undef_syms = echo > endif > -- > 2.28.0.1011.ga647a8990f-goog >
On Thu, Oct 15, 2020 at 7:50 AM Kees Cook <keescook@chromium.org> wrote: > > On Mon, Oct 12, 2020 at 05:31:52PM -0700, Sami Tolvanen wrote: > > With LTO, llvm-nm prints out symbols for each archive member > > separately, which results in a lot of duplicate dependencies in the > > .mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module > > consists of several compilation units, the output can exceed the > > default xargs command size limit and split the dependency list to > > multiple lines, which results in used symbols getting trimmed. > > > > This change removes duplicate dependencies, which will reduce the > > probability of this happening and makes .mod files smaller and > > easier to read. > > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > Hi Masahiro, > > This appears to be a general improvement as well. This looks like it can > land without depending on the rest of the series. It cannot. Adding "sort -u" is pointless without the rest of the series since the symbol duplication happens only with Clang LTO. This is not a solution. "reduce the probability of this happening" well describes it. I wrote a different patch. > -Kees > > > --- > > scripts/Makefile.build | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > > index ab0ddf4884fd..96d6c9e18901 100644 > > --- a/scripts/Makefile.build > > +++ b/scripts/Makefile.build > > @@ -266,7 +266,7 @@ 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 > > +cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | sort -u | xargs echo > > else > > cmd_undef_syms = echo > > endif > > -- > > 2.28.0.1011.ga647a8990f-goog > > > > -- > Kees Cook > > -- > 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@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/202010141549.412F2BF0%40keescook.
On Thu, Dec 3, 2020 at 10:00 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Thu, Oct 15, 2020 at 7:50 AM Kees Cook <keescook@chromium.org> wrote: > > > > On Mon, Oct 12, 2020 at 05:31:52PM -0700, Sami Tolvanen wrote: > > > With LTO, llvm-nm prints out symbols for each archive member > > > separately, which results in a lot of duplicate dependencies in the > > > .mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module > > > consists of several compilation units, the output can exceed the > > > default xargs command size limit and split the dependency list to > > > multiple lines, which results in used symbols getting trimmed. > > > > > > This change removes duplicate dependencies, which will reduce the > > > probability of this happening and makes .mod files smaller and > > > easier to read. > > > > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > > Reviewed-by: Kees Cook <keescook@chromium.org> > > > > Hi Masahiro, > > > > This appears to be a general improvement as well. This looks like it can > > land without depending on the rest of the series. > > It cannot. > Adding "sort -u" is pointless without the rest of the series > since the symbol duplication happens only with Clang LTO. > > This is not a solution. > "reduce the probability of this happening" well describes it. > > I wrote a different patch. Great, thanks for looking into this. I'll drop this patch from the next version. Sami
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index ab0ddf4884fd..96d6c9e18901 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -266,7 +266,7 @@ 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 +cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | sort -u | xargs echo else cmd_undef_syms = echo endif