2022-02-18 11:48 UTC-0800 ~ Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > 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. Thanks a lot for testing! >> >>> 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. We can do the same for bpftool, its mirror already does it [0]. We could have this in bpftool's sources and use "bpftool_reallocarray()" instead of "reallocarray()", and get rid of this probing. Mauricio are you willing to take this? [0] https://github.com/libbpf/bpftool/blob/master/include/tools/libc_compat.h#L25 Quentin
