[PATCH 5.19 198/207] Makefile.debug: re-enable debug info for .S files

Greg Kroah-Hartman
2022-09-26T12:42:30Z

From: Nick Desaulniers <ndesaulniers@google.com>

[ Upstream 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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/Kconfig.debug | 4 +++-
scripts/Makefile.debug | 21 +++++++++++----------
2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2e24db4bff19..c399ab486557 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -264,8 +264,10 @@ config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
config DEBUG_INFO_DWARF4
bool "Generate DWARF Version 4 debuginfo"
select DEBUG_INFO
+ 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/scripts/Makefile.debug b/scripts/Makefile.debug
index 26d6a9d97a20..8cf1cb22dd93 100644
--- a/scripts/Makefile.debug
+++ b/scripts/Makefile.debug
@@ -1,18 +1,19 @@
-DEBUG_CFLAGS := -g
+DEBUG_CFLAGS :=
+debug-flags-y := -g

ifdef CONFIG_DEBUG_INFO_SPLIT
DEBUG_CFLAGS += -gsplit-dwarf
endif

-ifndef CONFIG_AS_IS_LLVM
-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 += -fno-var-tracking
@@ -27,5 +28,5 @@ KBUILD_AFLAGS += -gz=zlib
KBUILD_LDFLAGS += --compress-debug-sections=zlib
endif

-KBUILD_CFLAGS += $(DEBUG_CFLAGS)
+KBUILD_CFLAGS += $(DEBUG_CFLAGS)
export DEBUG_CFLAGS
--
2.35.1