On Wed, Jan 20, 2021 at 9:40 PM Nathan Chancellor
[off-list ref] wrote:

On Fri, Jan 15, 2021 at 01:06:15PM -0800, Nick Desaulniers wrote:

quoted

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 <redacted>
Suggested-by: Fangrui Song <redacted>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <redacted>
---
 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

Aren't you regressing this with this patch? Why is the hunk from 3/3
that adds

ifdef CONFIG_CC_IS_CLANG
ifneq ($(LLVM_IAS),1)

not in this patch?

Nice catch Nathan.

Just FYI:

The patch...

"kbuild: Remove $(cc-option,-gdwarf-4) dependency from DEBUG_INFO_DWARF4"

... has now entered kbuild-next.
( This patch is included in this patch-series. )

So should we point to this one and add a comment?
Thinking of a next version of this DWARF5 support patch-series.

- Sedat -

[1] https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=3f4d8ce271c7082be75bacbcbd2048aa78ce2b44

quoted

-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"
+     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"
      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