From e96f326803e59ce0bca4af22334e4035d532ebbd Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@google.com>
Date: Mon, 19 Sep 2022 10:45:47 -0700
Subject: [PATCH] Makefile.debug: re-enable debug info for .S files

References: git-fixes
Patch-mainline: v6.0-rc7
Git-commit: 32ef9e5054ec0321b9336058c58ec749e9c6b0fe

Alexey reported that the fraction of unknown filename instances in
kallsyms grew from ~0.3% to ~10% recently; Bill and Greg tracked it down
to assembler defined symbols, which regressed as a result of:

commit b8a9092330da ("Kbuild: do not emit debug info for assembly with LLVM_IAS=1")

In that commit, I allude to restoring debug info for assembler defined
symbols in a follow up patch, but it seems I forgot to do so in

commit a66049e2cf0e ("Kbuild: make DWARF version a choice")

Link: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=31bf18645d98b4d3d7357353be840e320649a67d
Fixes: b8a9092330da ("Kbuild: do not emit debug info for assembly with LLVM_IAS=1")
Reported-by: Alexey Alexandrov <aalexand@google.com>
Reported-by: Bill Wendling <morbo@google.com>
Reported-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
[adjust for context: DEBUG_CFLAGS   := added upstream is already before
ifdef CONFIG_DEBUG_INFO in the old makefile]
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 Makefile          | 22 +++++++++++-----------
 lib/Kconfig.debug |  4 +++-
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c9a885f6c98e..f880c84f151f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -286,8 +286,10 @@ config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
 
 config DEBUG_INFO_DWARF4
 	bool "Generate DWARF Version 4 debuginfo"
+	depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
 	help
-	  Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
+	  Generate DWARF v4 debug info. This requires gcc 4.5+, binutils 2.35.2
+	  if using clang without clang's integrated assembler, and gdb 7.0+.
 
 	  If you have consumers of DWARF debug info that are not ready for
 	  newer revisions of DWARF, you may wish to choose this or have your
diff --git a/Makefile b/Makefile
index bfbac35bbb8b..b9b2be937f83 100644
--- a/Makefile
+++ b/Makefile
@@ -869,21 +869,21 @@ endif
 
 ifdef CONFIG_DEBUG_INFO
 
+debug-flags-y	:= -g
+
 ifdef CONFIG_DEBUG_INFO_SPLIT
 DEBUG_CFLAGS	+= -gsplit-dwarf
-else
-DEBUG_CFLAGS	+= -g
-endif
-
-ifneq ($(LLVM_IAS),1)
-KBUILD_AFLAGS	+= -Wa,-gdwarf-2
 endif
 
-ifndef CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
-dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
-dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5
-DEBUG_CFLAGS	+= -gdwarf-$(dwarf-version-y)
+debug-flags-$(CONFIG_DEBUG_INFO_DWARF4)	+= -gdwarf-4
+debug-flags-$(CONFIG_DEBUG_INFO_DWARF5)	+= -gdwarf-5
+ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_AS_IS_GNU),yy)
+# Clang does not pass -g or -gdwarf-* option down to GAS.
+# Add -Wa, prefix to explicitly specify the flags.
+KBUILD_AFLAGS	+= $(addprefix -Wa$(comma), $(debug-flags-y))
 endif
+DEBUG_CFLAGS	+= $(debug-flags-y)
+KBUILD_AFLAGS	+= $(debug-flags-y)
 
 ifdef CONFIG_DEBUG_INFO_REDUCED
 DEBUG_CFLAGS	+= $(call cc-option, -femit-struct-debug-baseonly) \
@@ -898,7 +898,7 @@ endif
 
 endif # CONFIG_DEBUG_INFO
 
-KBUILD_CFLAGS += $(DEBUG_CFLAGS)
+KBUILD_CFLAGS	+= $(DEBUG_CFLAGS)
 export DEBUG_CFLAGS
 
 ifdef CONFIG_FUNCTION_TRACER