linux-kernel - Re: [PATCH bpf-next 4/4] selftests/bpf: add reason of rejection in ld

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Date:   Tue, 24 May 2022 12:49:02 +0800
From:   Shung-Hsi Yu <shung-hsi.yu@...e.com>
To:     Yonghong Song <yhs@...com>
Cc:     linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>
Subject: Re: [PATCH bpf-next 4/4] selftests/bpf: add reason of rejection in
 ld_imm64

On Fri, May 20, 2022 at 05:27:12PM -0700, Yonghong Song wrote:
> 
> 
> On 5/20/22 4:37 AM, Shung-Hsi Yu wrote:
> > It may not be immediately clear why that ld_imm64 test cases are
> > rejected, especially for test1 and test2 where JMP to the 2nd
> > instruction of BPF_LD_IMM64 is performed.
> > 
> > Add brief explaination of why each test case in verifier/ld_imm64.c
> > should be rejected.
> > 
> > Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@...e.com>
> > ---
> >   .../testing/selftests/bpf/verifier/ld_imm64.c | 20 ++++++++++---------
> >   1 file changed, 11 insertions(+), 9 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/bpf/verifier/ld_imm64.c b/tools/testing/selftests/bpf/verifier/ld_imm64.c
> > index f9297900cea6..021312641aaf 100644
> > --- a/tools/testing/selftests/bpf/verifier/ld_imm64.c
> > +++ b/tools/testing/selftests/bpf/verifier/ld_imm64.c
> > @@ -1,5 +1,6 @@
> > +/* Note: BPF_LD_IMM64 is composed of two instructions of class BPF_LD */
> 
> > [...]LD | BPF_IMM | BPF_DW, 0, 0, 0, 0),
> > @@ -42,7 +43,7 @@
> >   	.result = REJECT,
> >   },
> >   {
> > -	"test4 ld_imm64",
> > +	"test4 ld_imm64: reject incomplete BPF_LD_IMM64 instruction",
> >   	.insns = {
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 0),
> >   	BPF_EXIT_INSN(),
> > @@ -70,7 +71,7 @@
> >   	.retval = 1,
> >   },
> >   {
> > -	"test8 ld_imm64",
> > +	"test8 ld_imm64: reject 1st off!=0",
> 
> Let add some space like 'off != 0'. The same for
> some of later test names.

Okay, will do that in the next version. Thanks!

> >   	.insns = {
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 1, 1),
> >   	BPF_RAW_INSN(0, 0, 0, 0, 1),
> > @@ -80,7 +81,7 @@
> >   	.result = REJECT,
> >   },
> >   {
> > -	"test9 ld_imm64",
> > +	"test9 ld_imm64: reject 2nd off!=0",
> >   	.insns = {
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 1),
> >   	BPF_RAW_INSN(0, 0, 0, 1, 1),
> > @@ -90,7 +91,7 @@
> >   	.result = REJECT,
> >   },
> >   {
> > -	"test10 ld_imm64",
> > +	"test10 ld_imm64: reject 2nd dst_reg!=0",
> >   	.insns = {
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 1),
> >   	BPF_RAW_INSN(0, BPF_REG_1, 0, 0, 1),
> > @@ -100,7 +101,7 @@
> >   	.result = REJECT,
> >   },
> >   {
> > -	"test11 ld_imm64",
> > +	"test11 ld_imm64: reject 2nd src_reg!=0",
> >   	.insns = {
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 1),
> >   	BPF_RAW_INSN(0, 0, BPF_REG_1, 0, 1),
> > @@ -113,6 +114,7 @@
> >   	"test12 ld_imm64",
> >   	.insns = {
> >   	BPF_MOV64_IMM(BPF_REG_1, 0),
> > +	/* BPF_REG_1 is interpreted as BPF_PSEUDO_MAP_FD */
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, BPF_REG_1, 0, 1),
> >   	BPF_RAW_INSN(0, 0, 0, 0, 0),
> >   	BPF_EXIT_INSN(),
> > @@ -121,7 +123,7 @@
> >   	.result = REJECT,
> >   },
> >   {
> > -	"test13 ld_imm64",
> > +	"test13 ld_imm64: 2nd src_reg!=0",
> >   	.insns = {
> >   	BPF_MOV64_IMM(BPF_REG_1, 0),
> >   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, BPF_REG_1, 0, 1),
>