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Date: Tue, 18 Aug 2020 18:42:22 -0700 From: Yonghong Song <yhs@...com> To: Andrii Nakryiko <andriin@...com>, <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>, <daniel@...earbox.net> CC: <andrii.nakryiko@...il.com>, <kernel-team@...com> Subject: Re: [PATCH bpf-next 4/7] libbpf: sanitize BPF program code for bpf_probe_read_{kernel,user}[_str] On 8/18/20 2:33 PM, Andrii Nakryiko wrote: > Add BPF program code sanitization pass, replacing calls to BPF > bpf_probe_read_{kernel,user}[_str]() helpers with bpf_probe_read[_str](), if > libbpf detects that kernel doesn't support new variants. I know this has been merged. The whole patch set looks good to me. A few nit or questions below. > > Signed-off-by: Andrii Nakryiko <andriin@...com> > --- > tools/lib/bpf/libbpf.c | 80 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 80 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index ab0c3a409eea..bdc08f89a5c0 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -180,6 +180,8 @@ enum kern_feature_id { > FEAT_ARRAY_MMAP, > /* kernel support for expected_attach_type in BPF_PROG_LOAD */ > FEAT_EXP_ATTACH_TYPE, > + /* bpf_probe_read_{kernel,user}[_str] helpers */ > + FEAT_PROBE_READ_KERN, > __FEAT_CNT, > }; > > @@ -3591,6 +3593,27 @@ static int probe_kern_exp_attach_type(void) > return probe_fd(bpf_load_program_xattr(&attr, NULL, 0)); > } > [...] > > +static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id) > +{ > + __u8 class = BPF_CLASS(insn->code); > + > + if ((class == BPF_JMP || class == BPF_JMP32) && Do we support BPF_JMP32 + BPF_CALL ... as a helper call? I am not aware of this. > + BPF_OP(insn->code) == BPF_CALL && > + BPF_SRC(insn->code) == BPF_K && > + insn->src_reg == 0 && insn->dst_reg == 0) { > + if (func_id) > + *func_id = insn->imm; looks like func_id is always non-NULL. Unless this is to support future usage where func_id may be NULL, the above condition probably not needed. > + return true; > + } > + return false; > +} > + [...]
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