Kbuild: Add a option to enable dwarf4 v2

I found that a lot of unresolvable variables when using gdb on the
kernel become resolvable when dwarf4 is enabled. So add a Kconfig flag
to enable it.

It definitely increases the debug information size, but on the other
hand this isn't so bad when debug fusion is used.

v2: Use cc-option
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

2 files changed, 12 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index e5a269465f99..2fd21a58f5cf 100644
--- a/Makefile
+++ b/Makefile
@@ -691,6 +691,9 @@ KBUILD_CFLAGS	+= -g
 endif
 KBUILD_AFLAGS   += -Wa,-gdwarf-2
 endif
+ifdef CONFIG_DEBUG_INFO_DWARF4
+KBUILD_CFLAGS   += $(call cc-option, -gdwarf-4,)
+endif
 
 ifdef CONFIG_DEBUG_INFO_REDUCED
 KBUILD_CFLAGS   += $(call cc-option, -femit-struct-debug-baseonly) \
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 910355da9d14..d70f203ce710 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -158,6 +158,15 @@ config DEBUG_INFO_SPLIT
           to know about the .dwo files and include them.
           Incompatible with older versions of ccache.
 
+config DEBUG_INFO_DWARF4
+        bool "Generate dwarf4 debuginfo"
+        depends on DEBUG_INFO
+        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.
+
 config ENABLE_WARN_DEPRECATED
         bool "Enable __deprecated logic"
         default y