From 3d717fad5081b8e3bda76d86907fad95398cbde8 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 28 Sep 2021 16:09:45 -0700 Subject: bpf: Replace "want address" users of BPF_CAST_CALL with BPF_CALL_IMM In order to keep ahead of cases in the kernel where Control Flow Integrity (CFI) may trip over function call casts, enabling -Wcast-function-type is helpful. To that end, BPF_CAST_CALL causes various warnings and is one of the last places in the kernel triggering this warning. Most places using BPF_CAST_CALL actually just want a void * to perform math on. It's not actually performing a call, so just use a different helper to get the void *, by way of the new BPF_CALL_IMM() helper, which can clean up a common copy/paste idiom as well. This change results in no object code difference. Signed-off-by: Kees Cook Signed-off-by: Alexei Starovoitov Reviewed-by: Gustavo A. R. Silva Acked-by: Andrii Nakryiko Link: https://github.com/KSPP/linux/issues/20 Link: https://lore.kernel.org/lkml/CAEf4Bzb46=-J5Fxc3mMZ8JQPtK1uoE0q6+g6WPz53Cvx=CBEhw@mail.gmail.com Link: https://lore.kernel.org/bpf/20210928230946.4062144-2-keescook@chromium.org --- lib/test_bpf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib/test_bpf.c') diff --git a/lib/test_bpf.c b/lib/test_bpf.c index 08f438e6fe9e..21ea1ab253a1 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -12439,7 +12439,7 @@ static __init int prepare_tail_call_tests(struct bpf_array **pprogs) err = -EFAULT; goto out_err; } - *insn = BPF_EMIT_CALL(BPF_CAST_CALL(addr)); + *insn = BPF_EMIT_CALL(addr); if ((long)__bpf_call_base + insn->imm != addr) *insn = BPF_JMP_A(0); /* Skip: NOP */ break; -- cgit v1.2.3