Commit 9c019e2b authored Nov 12, 2017 by Yonghong Song Committed by David S. Miller Nov 14, 2017

bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO



The helper bpf_probe_read arg2 type is changed
from ARG_CONST_SIZE to ARG_CONST_SIZE_OR_ZERO to permit
size-0 buffer. Together with newer ARG_CONST_SIZE_OR_ZERO
semantics which allows non-NULL buffer with size 0,
this allows simpler bpf programs with verifier acceptance.
The previous commit which changes ARG_CONST_SIZE_OR_ZERO semantics
has details on examples.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 9fd29c08

kernel/trace/bpf_trace.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -78,12 +78,16 @@ EXPORT_SYMBOL_GPL(trace_call_bpf);

		BPF_CALL_3(bpf_probe_read, void , dst, u32, size, const void , unsafe_ptr)
		{
		int ret;
		int ret = 0;

		if (unlikely(size == 0))
		goto out;

		ret = probe_kernel_read(dst, unsafe_ptr, size);
		if (unlikely(ret < 0))
		memset(dst, 0, size);

		out:
		return ret;
		}

		@@ -92,7 +96,7 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
		.gpl_only = true,
		.ret_type = RET_INTEGER,
		.arg1_type = ARG_PTR_TO_UNINIT_MEM,
		.arg2_type = ARG_CONST_SIZE,
		.arg2_type = ARG_CONST_SIZE_OR_ZERO,
		.arg3_type = ARG_ANYTHING,
		};

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