2023-01-14 18:00 UTC-0500 ~ Peter Foley <pefoley2@xxxxxxxxxxx>
> Avoid build errors on distros that force the stack protector on by
> default.
> e.g.
> CLANG /home/peter/linux/work/tools/bpf/bpftool/pid_iter.bpf.o
> skeleton/pid_iter.bpf.c:53:5: error: A call to built-in function '__stack_chk_fail' is not supported.
> int iter(struct bpf_iter__task_file *ctx)
> ^
> 1 error generated.
>
> Signed-off-by: Peter Foley <pefoley2@xxxxxxxxxxx>
> ---
> tools/bpf/bpftool/Makefile | 1 +
> tools/bpf/runqslower/Makefile | 5 +++--
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index f610e184ce02a..36ac0002e386f 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -215,6 +215,7 @@ $(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF_BOOTSTRAP)
> -I$(or $(OUTPUT),.) \
> -I$(srctree)/tools/include/uapi/ \
> -I$(LIBBPF_BOOTSTRAP_INCLUDE) \
> + -fno-stack-protector \
> -g -O2 -Wall -target bpf -c $< -o $@
> $(Q)$(LLVM_STRIP) -g $@
>
For bpftool, a similar patch was already submitted and merged to the
bpf-next tree last Friday: 878625e1c7a1 ("bpftool: Always disable stack
protection for BPF objects").
> diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
> index 8b3d87b82b7a2..f7313cc966a04 100644
> --- a/tools/bpf/runqslower/Makefile
> +++ b/tools/bpf/runqslower/Makefile
> @@ -60,8 +60,9 @@ $(OUTPUT)/%.skel.h: $(OUTPUT)/%.bpf.o | $(BPFTOOL)
> $(QUIET_GEN)$(BPFTOOL) gen skeleton $< > $@
>
> $(OUTPUT)/%.bpf.o: %.bpf.c $(BPFOBJ) | $(OUTPUT)
> - $(QUIET_GEN)$(CLANG) -g -O2 -target bpf $(INCLUDES) \
> - -c $(filter %.c,$^) -o $@ && \
> + $(QUIET_GEN)$(CLANG) -g -O2 -target bpf $(INCLUDES) \
> + -fno-stack-protector \
> + -c $(filter %.c,$^) -o $@ && \
> $(LLVM_STRIP) -g $@
>
> $(OUTPUT)/%.o: %.c | $(OUTPUT)
This one looks good, thanks!
I note a few more places in the repository where we compile to BPF using
clang. Given that there have been patches to add -fno-stack-protector at
several locations already, have you checked if any of these also need
the flag, by any chance, so we could fix this once and for all?
$ git grep -l 'target bpf ' | egrep -v '(Documentation|bpftool)'
kernel/bpf/preload/iterators/Makefile
samples/bpf/Makefile
samples/bpf/test_lwt_bpf.sh
tools/bpf/runqslower/Makefile
tools/build/feature/Makefile
tools/perf/Makefile.perf
tools/perf/util/llvm-utils.c
tools/testing/selftests/bpf/Makefile
tools/testing/selftests/net/bpf/Makefile
tools/testing/selftests/tc-testing/Makefile
