On 31/05/2024 20:06, Andrii Nakryiko wrote: > On Tue, May 28, 2024 at 5:25 AM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote: >> >> Support creation of module BTF along with distilled base BTF; >> the latter is stored in a .BTF.base ELF section and supplements >> split BTF references to base BTF with information about base types, >> allowing for later relocation of split BTF with a (possibly >> changed) base. resolve_btfids detects the presence of a .BTF.base >> section and will use it instead of the base BTF it is passed in >> BTF id resolution. >> >> Modules will be built with a distilled .BTF.base section for external >> module build, i.e. >> >> make -C. -M=path2/module >> >> ...while in-tree module build as part of a normal kernel build will >> not generate distilled base BTF; this is because in-tree modules >> change with the kernel and do not require BTF relocation for the >> running vmlinux. >> >> Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx> >> --- >> scripts/Makefile.btf | 5 +++++ >> scripts/Makefile.modfinal | 2 +- >> 2 files changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf >> index bca8a8f26ea4..191b4903e864 100644 >> --- a/scripts/Makefile.btf >> +++ b/scripts/Makefile.btf >> @@ -21,8 +21,13 @@ else >> # Switch to using --btf_features for v1.26 and later. >> pahole-flags-$(call test-ge, $(pahole-ver), 126) = -j --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func >> >> +ifneq ($(KBUILD_EXTMOD),) >> +module-pahole-flags-$(call test-ge, $(pahole-ver), 126) += --btf_features=distilled_base > > Remind me, please. What's the state of pahole patches? Are they > waiting on these libbpf changes to land first, right? > Exactly. The idea would be this; we land the libbpf patches first, and then update the dependent commit in the dwarves repo to point at one with the relocation APIs. In the interim - where we have the code in the library but not in pahole - everything continues to work as before. It's just that the above --btf_feature creating distilled BTF is ignored, which means we don't generate any distilled BTF in any modules until that support is in the pahole used. Thanks! Alan >> +endif >> + >> endif >> >> pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust >> >> export PAHOLE_FLAGS := $(pahole-flags-y) >> +export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y) >> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal >> index 79fcf2731686..6d2b8da98ee5 100644 >> --- a/scripts/Makefile.modfinal >> +++ b/scripts/Makefile.modfinal >> @@ -39,7 +39,7 @@ quiet_cmd_btf_ko = BTF [M] $@ >> if [ ! -f vmlinux ]; then \ >> printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \ >> else \ >> - LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) --btf_base vmlinux $@; \ >> + LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) $(MODULE_PAHOLE_FLAGS) --btf_base vmlinux $@; \ >> $(RESOLVE_BTFIDS) -b vmlinux $@; \ >> fi; >> >> -- >> 2.31.1 >>
