========
$ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }'
115710691
$ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10
./drivers/gpu/drm/i915/i915.ko 570570
./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 520240
./drivers/gpu/drm/radeon/radeon.ko 503849
./drivers/infiniband/hw/mlx5/mlx5_ib.ko 491777
./fs/xfs/xfs.ko 411544
./drivers/net/ethernet/intel/i40e/i40e.ko 403904
./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 398754
./drivers/infiniband/core/ib_core.ko 397224
./fs/cifs/cifs.ko 386249
./fs/nfsd/nfsd.ko 379738
SPLIT BTF
=========
$ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }'
5194047
$ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10
./drivers/gpu/drm/i915/i915.ko 293206
./drivers/gpu/drm/radeon/radeon.ko 282103
./fs/xfs/xfs.ko 222150
./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 198503
./drivers/infiniband/hw/mlx5/mlx5_ib.ko 198356
./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 113444
./fs/cifs/cifs.ko 109379
./arch/x86/kvm/kvm.ko 100225
./drivers/gpu/drm/drm.ko 94827
./drivers/infiniband/core/ib_core.ko 91188
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
lib/Kconfig.debug | 10 ++++++++++
scripts/Makefile.modfinal | 20 ++++++++++++++++++--
2 files changed, 28 insertions(+), 2 deletions(-)
@@ -265,6 +265,9 @@ config DEBUG_INFO_DWARF4
But it significantly improves the success of resolving
variables in gdb on optimized code.
+config PAHOLE_HAS_SPLIT_BTF
+ def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
+
config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
@@ -274,6 +277,13 @@ config DEBUG_INFO_BTF
Turning this on expects presence of pahole tool, which will convert
DWARF type info into equivalent deduplicated BTF type info.
+config DEBUG_INFO_BTF_MODULES
+ bool "Generate BTF for kernel modules"
+ def_bool y
+ depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
+ help
+ Generate compact split BTF type information for kernel modules.
+
config GDB_SCRIPTS
bool "Provide GDB scripts for kernel debugging"
help
@@ -6,6 +6,7 @@
PHONY := __modfinal
__modfinal:
+include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
# for c_flags
@@ -36,8 +37,23 @@ quiet_cmd_ld_ko_o = LD [M] $@
-T scripts/module.lds -o $@ $(filter %.o, $^); \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
-$(modules): %.ko: %.o %.mod.o scripts/module.lds FORCE
- +$(call if_changed,ld_ko_o)
+quiet_cmd_btf_ko = BTF [M] $@
+ cmd_btf_ko = LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@
+
+# Same as newer-prereqs, but allows to exclude specified extra dependencies
+newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
+
+# Same as if_changed, but allows to exclude specified extra dependencies
+if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
+ $(cmd); \
+ printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
+
+# Re-generate module BTFs if either module's .ko or vmlinux changed
+$(modules): %.ko: %.o %.mod.o scripts/module.lds vmlinux FORCE
+ +$(call if_changed_except,ld_ko_o,vmlinux)
+ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+ +$(if $(newer-prereqs),$(call cmd,btf_ko))
+endif
targets += $(modules) $(modules:.ko=.mod.o)