Hi everyone.
I built and ran selftests/bpf with GCC 15-20241229, and would like to
share my findings.
Building required small adjustments in the Makefile, besides -std=gnu17
With the following change we can mitigate int64_t issue:
+progs/test_cls_redirect.c-CFLAGS := -nostdinc
+progs/test_cls_redirect_dynptr.c-CFLAGS := -nostdinc
+progs/test_cls_redirect_subprogs.c-CFLAGS := -nostdinc
Then, the compiler complains about an uninitialized variable in
progs/verifier_bpf_fastcall.c and progs/verifier_search_pruning.c
(full log at [1]):
In file included from progs/verifier_bpf_fastcall.c:7:
progs/verifier_bpf_fastcall.c: In function ‘may_goto_interaction’:
progs/bpf_misc.h:153:42: error: ‘<Uc098>’ is used uninitialized
[-Werror=uninitialized]
153 | #define __imm_insn(name, expr) [name]"i"(*(long *)&(expr))
| ^~~~~~~~~~~~~~~~
progs/verifier_bpf_fastcall.c:652:11: note: in expansion of macro
‘__imm_insn’
652 | __imm_insn(may_goto, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0,
0, +1 /* offset */, 0))
| ^~~~~~~~~~
/ci/workspace/tools/testing/selftests/bpf/../../../include/linux/filter.h:299:28:
note: ‘({anonymous})’ declared here
299 | ((struct bpf_insn) { \
| ^
progs/bpf_misc.h:153:53: note: in definition of macro ‘__imm_insn’
153 | #define __imm_insn(name, expr) [name]"i"(*(long *)&(expr))
| ^~~~
progs/verifier_bpf_fastcall.c:652:32: note: in expansion of macro
‘BPF_RAW_INSN’
652 | __imm_insn(may_goto, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0,
0, +1 /* offset */, 0))
BPF_RAW_INSN expands into struct init expr (include/linux/filter.h):
#define BPF_RAW_INSN(CODE, DST, SRC, OFF, IMM) \
((struct bpf_insn) { \
.code = CODE, \
.dst_reg = DST, \
.src_reg = SRC, \
.off = OFF, \
.imm = IMM })
This can be silenced with:
+progs/verifier_bpf_fastcall.c-CFLAGS := -Wno-error
+progs/verifier_search_pruning.c-CFLAGS := -Wno-error
Then the selftests/bpf build completes successfully, although libbpf
prints a lot of warnings like these on GEN-SKEL:
[...]
libbpf: elf: skipping section(3) .data (size 0)
libbpf: elf: skipping section(4) .data (size 0)
libbpf: elf: skipping unrecognized data section(13) .comment
libbpf: elf: skipping unrecognized data section(9) .comment
libbpf: elf: skipping unrecognized data section(12) .comment
libbpf: elf: skipping unrecognized data section(7) .comment
[...]
Test .bpf.o files are compiled regardless. Full log at [2].
Running all tests at once, as is usually done on CI, produces a too
cluttered log. I wrote a script to run each test individually in a
separate qemu instance and collect the logs.
187/581 of toplevel tests fail on current bpf-next [3]. Many tests
have subtests: toplevel test passes if all of its subtests pass.
You can find the archive with per-test logs at [4].
[1] https://gist.github.com/theihor/10b2425e6780fcfebb80aeceafba7678
[2] https://gist.github.com/theihor/9e96643ca730365cf79cea8445e40aeb
[3]
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=96ea081ed52bf077cad6d00153b6fba68e510767
[4]
https://github.com/kernel-patches/bpf/blob/8f2e62702ee17675464ab00d97d89d599922de20/tools/testing/selftests/bpf/gcc-bpf-selftests-logs.tgz
