On 1/4/25 1:17 AM, Ihor Solodrai wrote:
Various compilation errors happen when BPF programs in selftests/bpf
are built with GCC BPF. For more details see the discussion at [1].
Thanks for the patch!
The changes only affect test_progs-bpf_gcc, which is built only if
BPF_GCC is set:
* Pass -std=gnu17 when to avoid errors on bool
types declarations in vmlinux.h
* Pass -nostdinc for tests that trigger int64_t declaration
collision due to a difference between gcc and clang stdint.h
* Pass -Wno-error for tests that trigger uninitialized variable
warning pm BPF_RAW_INSNS
[1] https://lore.kernel.org/bpf/EYcXjcKDCJY7Yb0GGtAAb7nLKPEvrgWdvWpuNzXm2qi6rYMZDixKv5KwfVVMBq17V55xyC-A1wIjrqG3aw-Imqudo9q9X7D7nLU2gWgbN0w=@pm.me/
Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxx>
[ pls also add Jose to Cc (done here) ]
---
tools/testing/selftests/bpf/Makefile | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 9e870e519c30..2e1fe53efa83 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -103,6 +103,15 @@ progs/btf_dump_test_case_packing.c-bpf_gcc-CFLAGS := -Wno-error
progs/btf_dump_test_case_padding.c-bpf_gcc-CFLAGS := -Wno-error
progs/btf_dump_test_case_syntax.c-bpf_gcc-CFLAGS := -Wno-error
+# Uninitialized variable warning on BPF_RAW_INSN
+progs/verifier_bpf_fastcall.c-CFLAGS := -Wno-error
+progs/verifier_search_pruning.c-CFLAGS := -Wno-error
See previous feedback from Jose:
Ignoring the warning doesn't cure the resulting undefined behavior.
These selftests seems to be violating strict aliasing rules, so it is
better to either change the testcase to work well with anti-aliasing
rules or to disable strict aliasing, like it is done for many other
tests already:
progs/verifier_bpf_fastcall.c-CFLAGS := -fno-strict-aliasing
progs/verifier_search_pruning.c-CFLAGS := -fno-strict-aliasing
+# int64_t declaration collision
+progs/test_cls_redirect.c-CFLAGS := -nostdinc
+progs/test_cls_redirect_dynptr.c-CFLAGS := -nostdinc
+progs/test_cls_redirect_subprogs.c-CFLAGS := -nostdinc
iiuc, this hunk is not needed given [1] got merged which addresses the
collision issue already?
[0] https://lore.kernel.org/bpf/87pll3c8bt.fsf@xxxxxxxxxx/
[1] https://gcc.gnu.org/pipermail/gcc-patches/2025-January/672508.html
# The following tests do type-punning, via the __imm_insn macro, from
# `struct bpf_insn' to long and then uses the value. This triggers an
# "is used uninitialized" warning in GCC due to strict-aliasing
@@ -507,7 +516,7 @@ endef
# Build BPF object using GCC
define GCC_BPF_BUILD_RULE
$(call msg,GCC-BPF,$4,$2)
- $(Q)$(BPF_GCC) $3 -DBPF_NO_PRESERVE_ACCESS_INDEX -Wno-attributes -O2 -c $1 -o $2
+ $(Q)$(BPF_GCC) $3 -DBPF_NO_PRESERVE_ACCESS_INDEX -Wno-attributes -O2 -std=gnu17 -c $1 -o $2
endef
SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
