On 9/8/21 11:32 PM, Andrii Nakryiko wrote:
From: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Introduce a macro LIBBPF_DEPRECATED_SINCE(major, minor, message) to prepare
the deprecation of two API functions. This macro marks functions as deprecated
when libbpf's version reaches the values passed as an argument.
As part of this change libbpf_version.h header is added with recorded major
(LIBBPF_MAJOR_VERSION) and minor (LIBBPF_MINOR_VERSION) libbpf version macros.
They are now part of libbpf public API and can be relied upon by user code.
libbpf_version.h is installed system-wide along other libbpf public headers.
Due to this new build-time auto-generated header, in-kernel applications
relying on libbpf (resolve_btfids, bpftool, bpf_preload) are updated to
include libbpf's output directory as part of a list of include search paths.
Better fix would be to use libbpf's make_install target to install public API
headers, but that clean up is left out as a future improvement. The build
changes were tested by building kernel (with KBUILD_OUTPUT and O= specified
explicitly), bpftool, libbpf, selftests/bpf, and resolve_btfids builds. No
problems were detected.
Note that because of the constraints of the C preprocessor we have to write
a few lines of macro magic for each version used to prepare deprecation (0.6
for now).
Also, use LIBBPF_DEPRECATED_SINCE() to schedule deprecation of
btf__get_from_id() and btf__load(), which are replaced by
btf__load_from_kernel_by_id() and btf__load_into_kernel(), respectively,
starting from future libbpf v0.6. This is part of libbpf 1.0 effort ([0]).
[0] Closes: https://github.com/libbpf/libbpf/issues/278
Co-developed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
v2->v3:
- adding `sleep 10` revealed two more missing dependencies in resolve_btfids
and selftest/bpf's bench, which were fixed (BPF CI);
v1->v2:
- fix bpf_preload build by adding dependency for iterators/iterators.o on
libbpf.a generation (caught by BPF CI);
kernel/bpf/preload/Makefile | 7 +++++--
tools/bpf/bpftool/Makefile | 4 ++++
tools/bpf/resolve_btfids/Makefile | 6 ++++--
tools/lib/bpf/Makefile | 24 +++++++++++++++++-------
tools/lib/bpf/btf.h | 2 ++
tools/lib/bpf/libbpf_common.h | 19 +++++++++++++++++++
tools/testing/selftests/bpf/Makefile | 4 ++--
7 files changed, 53 insertions(+), 13 deletions(-)
diff --git a/kernel/bpf/preload/Makefile b/kernel/bpf/preload/Makefile
index 1951332dd15f..ac29d4e9a384 100644
--- a/kernel/bpf/preload/Makefile
+++ b/kernel/bpf/preload/Makefile
@@ -10,12 +10,15 @@ LIBBPF_OUT = $(abspath $(obj))
$(LIBBPF_A):
$(Q)$(MAKE) -C $(LIBBPF_SRCS) O=$(LIBBPF_OUT)/ OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a
-userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
+userccflags += -I$(LIBBPF_OUT) -I $(srctree)/tools/include/ \
+ -I $(srctree)/tools/include/uapi \
-I $(srctree)/tools/lib/ -Wno-unused-result
userprogs := bpf_preload_umd
-clean-files := $(userprogs) bpf_helper_defs.h FEATURE-DUMP.libbpf staticobjs/ feature/
+clean-files := $(userprogs) libbpf_version.h bpf_helper_defs.h FEATURE-DUMP.libbpf staticobjs/ feature/
+
+$(obj)/iterators/iterators.o: $(LIBBPF_A)
bpf_preload_umd-objs := iterators/iterators.o
bpf_preload_umd-userldlibs := $(LIBBPF_A) -lelf -lz
One small issue I ran into by accident while testing:
[root@linux bpf-next]# make -j8 kernel/bpf/
SYNC include/config/auto.conf.cmd
DESCEND objtool
CALL scripts/atomic/check-atomics.sh
CALL scripts/checksyscalls.sh
CC kernel/bpf/syscall.o
AR kernel/bpf/preload/built-in.a
CC [M] kernel/bpf/preload/bpf_preload_kern.o
CC [U] kernel/bpf/preload/iterators/iterators.o
In file included from ./tools/lib/bpf/libbpf.h:20,
from kernel/bpf/preload/iterators/iterators.c:10:
./tools/lib/bpf/libbpf_common.h:13:10: fatal error: libbpf_version.h: No such file or directory
13 | #include "libbpf_version.h"
| ^~~~~~~~~~~~~~~~~~
compilation terminated.
make[3]: *** [scripts/Makefile.userprogs:43: kernel/bpf/preload/iterators/iterators.o] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [scripts/Makefile.build:540: kernel/bpf/preload] Error 2
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [scripts/Makefile.build:540: kernel/bpf] Error 2
make: *** [Makefile:1872: kernel] Error 2
For me it was the case where tools/lib/bpf/ was already built _before_ this patch
was applied, then I applied it, and just ran make -j8 kernel/bpf/ where the above
can then be reproduced. I'd assume that as-is, this would affect many folks on update.
Thanks,
Daniel
