(minus Chengbin due to bounces) On Thu, Dec 3, 2020 at 5:11 PM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an > explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a > way that's forward compatible with existing configs, and makes adding > future versions more straightforward. > > Suggested-by: Fangrui Song <maskray@xxxxxxxxxx> > Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > Makefile | 14 ++++++++------ > lib/Kconfig.debug | 21 ++++++++++++++++----- > 2 files changed, 24 insertions(+), 11 deletions(-) > > diff --git a/Makefile b/Makefile > index a2ded5029084..2430e1ee7c44 100644 > --- a/Makefile > +++ b/Makefile > @@ -826,12 +826,14 @@ else > DEBUG_CFLAGS += -g > endif > > -ifneq ($(LLVM_IAS),1) > -KBUILD_AFLAGS += -Wa,-gdwarf-2 > -endif > - > -ifdef CONFIG_DEBUG_INFO_DWARF4 > -DEBUG_CFLAGS += -gdwarf-4 > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2 > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4 > +DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) > +ifneq ($(dwarf-version-y)$(LLVM_IAS),21) > +# Binutils 2.35+ required for -gdwarf-4+ support. > +dwarf-aflag := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y)) > +DEBUG_CFLAGS += $(dwarf-aflag) > +KBUILD_AFLAGS += $(dwarf-aflag) > endif > > ifdef CONFIG_DEBUG_INFO_REDUCED > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 0c7380e36370..04719294a7a3 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -256,14 +256,25 @@ config DEBUG_INFO_SPLIT > to know about the .dwo files and include them. > Incompatible with older versions of ccache. > > +choice > + prompt "DWARF version" > + help > + Which version of DWARF debug info to emit. > + > +config DEBUG_INFO_DWARF2 > + bool "Generate DWARF Version 2 debuginfo" > + help > + Generate DWARF v2 debug info. > + > config DEBUG_INFO_DWARF4 > - bool "Generate dwarf4 debuginfo" > + bool "Generate DWARF Version 4 debuginfo" > depends on $(cc-option,-gdwarf-4) > help > - Generate dwarf4 debug info. This requires recent versions > - of gcc and gdb. It makes the debug information larger. > - But it significantly improves the success of resolving > - variables in gdb on optimized code. > + Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+. > + It makes the debug information larger, but it significantly > + improves the success of resolving variables in gdb on optimized code. ^ I kept the previous help text, but while this may have been the case when DWARF v4 support was first introduced in GCC, by my (lone) measure of x86_64 defconfig with gcc 10.2, this doesn't or no longer seems to be the case. See patch 2 for measurements: https://lore.kernel.org/lkml/20201204011129.2493105-2-ndesaulniers@xxxxxxxxxx/. (also, missed the cover letter, here it is: https://lore.kernel.org/lkml/CAKwvOdkZEiHK01OD420USb0j=F0LcrnRbauv9Yw26tu-GRbYkg@xxxxxxxxxxxxxx/) > + > +endchoice # "DWARF version" > > config DEBUG_INFO_BTF > bool "Generate BTF typeinfo" > -- > 2.29.2.576.ga3fc446d84-goog > -- Thanks, ~Nick Desaulniers
