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From: Yonghong Song <yhs@fb.com>
To: Andrii Nakryiko <andriin@fb.com>, <bpf@vger.kernel.org>,
	<netdev@vger.kernel.org>, <ast@fb.com>, <daniel@iogearbox.net>
Cc: <andrii.nakryiko@gmail.com>, <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next 4/7] libbpf: sanitize BPF program code for bpf_probe_read_{kernel,user}[_str]
Date: Tue, 18 Aug 2020 18:42:22 -0700	[thread overview]
Message-ID: <e37c5162-3c94-4c73-d598-f2a048b2ff27@fb.com> (raw)
In-Reply-To: <20200818213356.2629020-5-andriin@fb.com>



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@fb.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;
> +}
> +
[...]

  reply	other threads:[~2020-08-19  1:42 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-18 21:33 [PATCH bpf-next 0/7] libbpf feature probing and sanitization improvements Andrii Nakryiko
2020-08-18 21:33 ` [PATCH bpf-next 1/7] libbpf: disable -Wswitch-enum compiler warning Andrii Nakryiko
2020-08-19  1:23   ` Yonghong Song
2020-08-19  1:39     ` Andrii Nakryiko
2020-08-19  5:44       ` Yonghong Song
2020-08-18 21:33 ` [PATCH bpf-next 2/7] libbpf: make kernel feature probing lazy Andrii Nakryiko
2020-08-18 21:33 ` [PATCH bpf-next 3/7] libbpf: factor out common logic of testing and closing FD Andrii Nakryiko
2020-08-18 21:33 ` [PATCH bpf-next 4/7] libbpf: sanitize BPF program code for bpf_probe_read_{kernel,user}[_str] Andrii Nakryiko
2020-08-19  1:42   ` Yonghong Song [this message]
2020-08-19 20:11     ` Andrii Nakryiko
2020-08-19 20:15       ` Alexei Starovoitov
2020-08-19 20:23         ` Andrii Nakryiko
2020-08-18 21:33 ` [PATCH bpf-next 5/7] selftests/bpf: fix test_vmlinux test to use bpf_probe_read_user() Andrii Nakryiko
2020-08-18 21:33 ` [PATCH bpf-next 6/7] libbpf: switch tracing and CO-RE helper macros to bpf_probe_read_kernel() Andrii Nakryiko
2020-08-18 21:33 ` [PATCH bpf-next 7/7] libbpf: detect minimal BTF support and skip BTF loading, if missing Andrii Nakryiko
2020-08-19  0:24 ` [PATCH bpf-next 0/7] libbpf feature probing and sanitization improvements Alexei Starovoitov

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