Commit 866ced95 authored by Andi Kleen's avatar Andi Kleen Committed by Michal Marek
Browse files

kbuild: Support split debug info v4

This is an alternative approach to lower the overhead of debug info
(as we discussed a few days ago)

gcc 4.7+ and newer binutils have a new "split debug info" debug info
model where the debug info is only written once into central ".dwo" files.

This avoids having to copy it around multiple times, from the object
files to the final executable. It lowers the disk space
requirements. In addition it defaults to compressed debug data.

More details here:

This patch adds a new option to enable it. It has to be an option,
because it'll undoubtedly break everyone's debuginfo packaging scheme.
gdb/objdump/etc. all still work, if you have new enough versions.

I don't see big compile wins (maybe a second or two faster or so), but the
object dirs with debuginfo get significantly smaller. My standard kernel
config (slightly bigger than defconfig) shrinks from 2.9G disk space
to 1.1G objdir (with non reduced debuginfo). I presume if you are IO...
parent 011bf125
......@@ -34,6 +34,7 @@
# Top-level generic files
......@@ -684,7 +684,11 @@ endif
KBUILD_CFLAGS += $(call cc-option, -gsplit-dwarf, -g)
KBUILD_AFLAGS += -Wa,-gdwarf-2
......@@ -1372,6 +1376,7 @@ clean: $(clean-dirs)
\( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \
-o -name '*.ko.*' \
-o -name '*.dwo' \
-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
-o -name '*.symtypes' -o -name 'modules.order' \
-o -name modules.builtin -o -name '.tmp_*.o.*' \
......@@ -143,6 +143,21 @@ config DEBUG_INFO_REDUCED
DEBUG_INFO build and compile times are reduced too.
Only works with newer gcc versions.
bool "Produce split debuginfo in .dwo files"
depends on DEBUG_INFO
Generate debug info into separate .dwo files. This significantly
reduces the build directory size for builds with DEBUG_INFO,
because it stores the information only once on disk in .dwo
files instead of multiple times in object files and executables.
In addition the debug information is also compressed.
Requires recent gcc (4.7+) and recent gdb/binutils.
Any tool that packages or reads debug information would need
to know about the .dwo files and include them.
Incompatible with older versions of ccache.
bool "Enable __deprecated logic"
default y
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