[PATCH 5.5 143/399] samples/bpf: Set -fno-stack-protector when building BPF programs

From: Greg Kroah-Hartman
Date: Fri Feb 21 2020 - 02:49:49 EST

From: Toke HÃiland-JÃrgensen <toke@xxxxxxxxxx>

[ Upstream commit 450278977acbf494a20367c22fbb38729772d1fc ]

It seems Clang can in some cases turn on stack protection by default, which
doesn't work with BPF. This was reported once before[0], but it seems the
flag to explicitly turn off the stack protector wasn't added to the
Makefile, so do that now.

The symptom of this is compile errors like the following:

error: <unknown>:0:0: in function bpf_prog1 i32 (%struct.__sk_buff*): A call to built-in function '__stack_chk_fail' is not supported.

[0] https://www.spinics.net/lists/netdev/msg556400.html

Signed-off-by: Toke HÃiland-JÃrgensen <toke@xxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20191216103819.359535-1-toke@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
samples/bpf/Makefile | 1 +
1 file changed, 1 insertion(+)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index c0147a8cf1882..06ebe3104cc03 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -236,6 +236,7 @@ BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
readelf -S ./llvm_btf_verify.o | grep BTF; \
/bin/rm -f ./llvm_btf_verify.o)

+BPF_EXTRA_CFLAGS += -fno-stack-protector
ifneq ($(BTF_LLVM_PROBE),)