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bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO

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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>
This commit is contained in:
Yonghong Song 2017-11-12 14:49:10 -08:00 committed by David S. Miller
parent 9fd29c08e5
commit 9c019e2bc4
1 changed files with 6 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
kernel/trace/bpf_trace.c
View file

@ -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,
};