On Fri, Feb 18, 2022 at 11:44 AM Mauricio Vásquez Bernal <mauricio@xxxxxxxxxx> wrote: > > On Fri, Feb 18, 2022 at 11:20 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote: > > > > 2022-02-15 17:58 UTC-0500 ~ Mauricio Vásquez <mauricio@xxxxxxxxxx> > > > This commit implements the logic for the gen min_core_btf command. > > > Specifically, it implements the following functions: > > > > > > - minimize_btf(): receives the path of a source and destination BTF > > > files and a list of BPF objects. This function records the relocations > > > for all objects and then generates the BTF file by calling > > > btfgen_get_btf() (implemented in the following commit). > > > > > > - btfgen_record_obj(): loads the BTF and BTF.ext sections of the BPF > > > objects and loops through all CO-RE relocations. It uses > > > bpf_core_calc_relo_insn() from libbpf and passes the target spec to > > > btfgen_record_reloc(), that calls one of the following functions > > > depending on the relocation kind. > > > > > > - btfgen_record_field_relo(): uses the target specification to mark all > > > the types that are involved in a field-based CO-RE relocation. In this > > > case types resolved and marked recursively using btfgen_mark_type(). > > > Only the struct and union members (and their types) involved in the > > > relocation are marked to optimize the size of the generated BTF file. > > > > > > - btfgen_record_type_relo(): marks the types involved in a type-based > > > CO-RE relocation. In this case no members for the struct and union types > > > are marked as libbpf doesn't use them while performing this kind of > > > relocation. Pointed types are marked as they are used by libbpf in this > > > case. > > > > > > - btfgen_record_enumval_relo(): marks the whole enum type for enum-based > > > relocations. > > > > > > Signed-off-by: Mauricio Vásquez <mauricio@xxxxxxxxxx> > > > Signed-off-by: Rafael David Tinoco <rafael.tinoco@xxxxxxxxxxx> > > > Signed-off-by: Lorenzo Fontana <lorenzo.fontana@xxxxxxxxxx> > > > Signed-off-by: Leonardo Di Donato <leonardo.didonato@xxxxxxxxxx> > > > --- > > > tools/bpf/bpftool/Makefile | 8 +- > > > tools/bpf/bpftool/gen.c | 455 ++++++++++++++++++++++++++++++++++++- > > > 2 files changed, 457 insertions(+), 6 deletions(-) > > > > > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > > > index 94b2c2f4ad43..a137db96bd56 100644 > > > --- a/tools/bpf/bpftool/Makefile > > > +++ b/tools/bpf/bpftool/Makefile > > > @@ -34,10 +34,10 @@ LIBBPF_BOOTSTRAP_INCLUDE := $(LIBBPF_BOOTSTRAP_DESTDIR)/include > > > LIBBPF_BOOTSTRAP_HDRS_DIR := $(LIBBPF_BOOTSTRAP_INCLUDE)/bpf > > > LIBBPF_BOOTSTRAP := $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a > > > > > > -# We need to copy hashmap.h and nlattr.h which is not otherwise exported by > > > -# libbpf, but still required by bpftool. > > > -LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,hashmap.h nlattr.h) > > > -LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hashmap.h) > > > +# We need to copy hashmap.h, nlattr.h, relo_core.h and libbpf_internal.h > > > +# which are not otherwise exported by libbpf, but still required by bpftool. > > > +LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,hashmap.h nlattr.h relo_core.h libbpf_internal.h) > > > +LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hashmap.h relo_core.h libbpf_internal.h) > > > > > > $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR): > > > $(QUIET_MKDIR)mkdir -p $@ > > > diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c > > > index 8e066c747691..806001020841 100644 > > > --- a/tools/bpf/bpftool/gen.c > > > +++ b/tools/bpf/bpftool/gen.c > > > @@ -14,6 +14,7 @@ > > > #include <unistd.h> > > > #include <bpf/bpf.h> > > > #include <bpf/libbpf.h> > > > +#include <bpf/libbpf_internal.h> > > > #include <sys/types.h> > > > #include <sys/stat.h> > > > #include <sys/mman.h> > > > > Mauricio, did you try this patch on a system with an old Glibc (< 2.26) > > by any chance? Haven't tried yet but I expect this might break bpftool's > > build when COMPAT_NEED_REALLOCARRAY is set, because in that case gen.c > > pulls <bpf/libbpf_internal.h>, and then <tools/libc_compat.h> (through > > main.h). And libc_compat.h defines reallocarray(), which > > libbpf_internal.h poisons with a GCC pragma. > > > > I just tried on Ubuntu 16.04 with Glibc 2.23 and got the error you mentioned. > > > At least this is what I observe when trying to add your patches to the > > kernel mirror, where reallocarray() is redefined unconditionally. I'm > > trying to figure out if we should fix this mirror-side, or kernel-side. > > (I suppose we still need this compatibility layer, Ubuntu 16.04 seems to > > use Glibc 2.23). > > > > I suppose this should be fixed kernel-side, I don't think it's a > particular problem with the mirror. What about only including > `<tools/libc_compat.h>` in the places where reallocarray() is used: > prog.c and xlated_dumper.c? libbpf abandoned feature probing for this and just uses its own libbpf_reallocarray() implementation. Simple and reliable. Detecting reallocarray() is PITA and isn't worth it.
