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@xxxxxxxxxx>
Reported-by: Bill Wendling <morbo@xxxxxxxxxx>
Reported-by: Greg Thelen <gthelen@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
Changes v2 -> v3:
* Replace diff outright with Masahiro's suggestion in
https://lore.kernel.org/llvm/CAK7LNATWDH01=ZKLnsxc0vcib1zGDbEq8jLQwhWP7HkkmSb_Mw@xxxxxxxxxxxxxx/2-dwarf.diff
with some modifications, PTAL.
* Pick up Nathan's RB tag and Masahiro's SB tag.
* Cut down commit message.
Changes v1 -> v2:
* Use newly added compiler-specific macros, as per Bill.
lib/Kconfig.debug | 4 +++-
scripts/Makefile.debug | 19 ++++++++++---------
2 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index bcbe60d6c80c..d3e5f36bb01e 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 9f39b0130551..2845145c1220 100644
--- a/scripts/Makefile.debug
+++ b/scripts/Makefile.debug
@@ -3,17 +3,16 @@ DEBUG_CFLAGS :=
ifdef CONFIG_DEBUG_INFO_SPLIT
DEBUG_CFLAGS += -gsplit-dwarf
else
-DEBUG_CFLAGS += -g
+debug-cflags-y += -g
endif
-ifndef CONFIG_AS_IS_LLVM
-KBUILD_AFLAGS += -Wa,-gdwarf-2
-endif
+debug-flags-$(CONFIG_DEBUG_INFO_DWARF4) += -gdwarf-4
+debug-flags-$(CONFIG_DEBUG_INFO_DWARF5) += -gdwarf-5
-ifndef CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
-dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
-dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5
-DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y)
+ifeq ($(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
ifdef CONFIG_DEBUG_INFO_REDUCED
@@ -29,5 +28,7 @@ KBUILD_AFLAGS += -gz=zlib
KBUILD_LDFLAGS += --compress-debug-sections=zlib
endif
-KBUILD_CFLAGS += $(DEBUG_CFLAGS)
+DEBUG_CFLAGS += $(debug-flags-y)
+KBUILD_AFLAGS += $(debug-flags-y)
+KBUILD_CFLAGS += $(DEBUG_CFLAGS)
export DEBUG_CFLAGS
--
2.37.2.789.g6183377224-goog
