[PATCH v8 1/2] Kbuild: make DWARF version a choice

From: Nick Desaulniers
Date: Thu Feb 04 2021 - 01:41:47 EST


Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice which is
the default. Does so in a way that's forward compatible with existing
configs, and makes adding future versions more straightforward.

GCC since ~4.8 has defaulted to this DWARF version implicitly.

Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Suggested-by: Arvind Sankar <nivedita@xxxxxxxxxxxx>
Suggested-by: Fangrui Song <maskray@xxxxxxxxxx>
Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
Makefile | 5 ++---
lib/Kconfig.debug | 16 +++++++++++-----
2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index 407816375983..bed5cc150009 100644
--- a/Makefile
+++ b/Makefile
@@ -830,9 +830,8 @@ ifneq ($(LLVM_IAS),1)
KBUILD_AFLAGS += -Wa,-gdwarf-2
endif

-ifdef CONFIG_DEBUG_INFO_DWARF4
-DEBUG_CFLAGS += -gdwarf-4
-endif
+dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
+DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y)

ifdef CONFIG_DEBUG_INFO_REDUCED
DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e906ea906cb7..94c1a7ed6306 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -256,13 +256,19 @@ 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_DWARF4
- bool "Generate dwarf4 debuginfo"
+ bool "Generate DWARF Version 4 debuginfo"
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.
+
+endchoice # "DWARF version"

config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
--
2.30.0.365.g02bc693789-goog