Re: [PATCH v5 2/3] Kbuild: make DWARF version a choice

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On 2021-01-15, Sedat Dilek wrote:
On Fri, Jan 15, 2021 at 10:06 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: Arvind Sankar <nivedita@xxxxxxxxxxxx>
Suggested-by: Fangrui Song <maskray@xxxxxxxxxx>
Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
 Makefile          | 13 ++++++-------
 lib/Kconfig.debug | 21 ++++++++++++++++-----
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index d49c3f39ceb4..4eb3bf7ee974 100644
--- a/Makefile
+++ b/Makefile
@@ -826,13 +826,12 @@ else
 DEBUG_CFLAGS   += -g
 endif

-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_DWARF2) := 2
+dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
+DEBUG_CFLAGS   += -gdwarf-$(dwarf-version-y)
+# Binutils 2.35+ required for -gdwarf-4+ support.
+dwarf-aflag    := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y))
+KBUILD_AFLAGS  += $(dwarf-aflag)

 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 dd7d8d35b2a5..e80770fac4f0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -256,13 +256,24 @@ config DEBUG_INFO_SPLIT
          to know about the .dwo files and include them.
          Incompatible with older versions of ccache.

+choice
+       prompt "DWARF version"

Here you use "DWARF version" so keep this for v2 and v4.

+       help
+         Which version of DWARF debug info to emit.
+
+config DEBUG_INFO_DWARF2
+       bool "Generate DWARF Version 2 debuginfo"

s/DWARF Version/DWARF version

+       help
+         Generate DWARF v2 debug info.
+
 config DEBUG_INFO_DWARF4
-       bool "Generate dwarf4 debuginfo"
+       bool "Generate DWARF Version 4 debuginfo"

Same here: s/DWARF Version/DWARF version

DWARF Version 2 is fine and preferable.

I have checked DWARF Version 2/3/4/5 specifications.
"DWARF Version 2" is the official way that version is referred to...


- Sedat -

        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"
--
2.30.0.284.gd98b1dd5eaa7-goog




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