Makefile.debug: re-enable debug info for .S files

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>

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index bcbe60d6c80c1a7cfd3bf4f595b26b14c5579883..d3e5f36bb01e0d75c2d855119d8f471b892014b8 100644 (file)
--- 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 26d6a9d97a20ed201941a7dda0b1637b1e92b5e3..8cf1cb22dd934365658eef08b135789458f7dce9 100644 (file)
--- 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