On Mon, 2025-01-06 at 18:54 +0000, 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]. > > The changes only affect test_progs-bpf_gcc, which is built only if > BPF_GCC is set: > * Pass -std=gnu17 to gcc in order to avoid errors on bool types > declarations in vmlinux.h > * Pass -fno-strict-aliasing for tests that trigger uninitialized > variable warning on BPF_RAW_INSNS [2] > > [1] https://lore.kernel.org/bpf/EYcXjcKDCJY7Yb0GGtAAb7nLKPEvrgWdvWpuNzXm2qi6rYMZDixKv5KwfVVMBq17V55xyC-A1wIjrqG3aw-Imqudo9q9X7D7nLU2gWgbN0w=@pm.me/ > [2] https://lore.kernel.org/bpf/87pll3c8bt.fsf@xxxxxxxxxx/ > > CC: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> > Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxx> > > --- > > v1: https://lore.kernel.org/bpf/20250104001751.1869849-1-ihor.solodrai@xxxxx/ > > tools/testing/selftests/bpf/Makefile | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile > index eb4d21651aa7..b043791fe6db 100644 > --- a/tools/testing/selftests/bpf/Makefile > +++ b/tools/testing/selftests/bpf/Makefile > @@ -69,6 +69,10 @@ progs/timer_crash.c-CFLAGS := -fno-strict-aliasing > progs/test_global_func9.c-CFLAGS := -fno-strict-aliasing > progs/verifier_nocsr.c-CFLAGS := -fno-strict-aliasing > > +# Uninitialized variable warning on BPF_RAW_INSN > +progs/verifier_bpf_fastcall.c-CFLAGS := -fno-strict-aliasing > +progs/verifier_search_pruning.c-CFLAGS := -fno-strict-aliasing Specifying -fno-strict-aliasing for a sub-set of tests is not convenient, as this list would have to be extended each time __imm_insn macro is used. Either this flag should be used for test_progs compilation as a whole, or the macro should be updated to use union as it was suggested previously. Personally, I don't like the aliasing rules and would prefer -fno-strict-aliasing, but changing macro is a simple and non-intrusive update, so I think it's a better option. > # Some utility functions use LLVM libraries > jit_disasm_helpers.c-CFLAGS = $(LLVM_CFLAGS) > > @@ -507,7 +511,7 @@ 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
