Hi Masahiro,
I wondered why my generated linux-image-db Debian packages were so big
when I use GCC toolchain instead of LLVM toolchain.
It turned out I mixed both...
KBUILD_AFLAGS += -Wa,-gdwarf-2
...together with...
DEBUG_CFLAGS += -gdwarf-4
...when CONFIG_DEBUG_INFO_DWARF4=y is set.
So I hacked up something like the following to prevent this:
diff --git a/Makefile b/Makefile
index 24a4c1b97bb0..e7a8e47b0e34 100644
--- a/Makefile
+++ b/Makefile
@@ -815,7 +815,11 @@ DEBUG_CFLAGS += -gsplit-dwarf
else
DEBUG_CFLAGS += -g
endif
+ifdef CONFIG_DEBUG_INFO_AS_DWARF2
KBUILD_AFLAGS += -Wa,-gdwarf-2
+else ifdef CONFIG_DEBUG_INFO_AS_DWARF4
+KBUILD_AFLAGS += -Wa,-gdwarf-4
+endif
endif
ifdef CONFIG_DEBUG_INFO_DWARF4
DEBUG_CFLAGS += -gdwarf-4
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ad9210d70a1..9f11fc71462c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -257,10 +257,23 @@ config DEBUG_INFO_SPLIT
to know about the .dwo files and include them.
Incompatible with older versions of ccache.
+config DEBUG_INFO_AS_DWARF2
+ bool "Use DWARF-2 assembler option with debuginfo"
+ depends on $(cc-option,-Wa$(comma)-gdwarf-2)
+ help
+ Set DWARF-2 assembler option with debuginfo
+
+config DEBUG_INFO_AS_DWARF4
+ bool "Use DWARF-4 assembler option with debuginfo"
+ depends on $(cc-option,-Wa$(comma)-gdwarf-4)
+ help
+ Set DWARF-4 assembler option with debuginfo
+
config DEBUG_INFO_DWARF4
bool "Generate dwarf4 debuginfo"
depends on DEBUG_INFO
depends on $(cc-option,-gdwarf-4)
+ select DEBUG_INFO_AS_DWARF4
help
Generate dwarf4 debug info. This requires recent versions
of gcc and gdb. It makes the debug information larger.
NOTE: This is on top of Linux v5.8 vanilla.
NOTE-2: When building with LLVM toolchain v11.0.0-rc1+ and especially
with LLVM_IAS=1 (and LLVM=1) DWARF version 4 is a good choice.
For details see below links.
Thoughts?
Regards,
- Sedat -
[1] https://github.com/ClangBuiltLinux/linux/issues/1086
[2] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674503335
[3] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674517876
