linux-kernel - Re: [PATCH bpf-next v4 2/3] selftests/bpf: activate the OP_NE login in range

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Message-ID: <CADxym3bOgnU84Xngx_H3cwxzEqsaK8JkaYDY3F4dSr74R492ug@mail.gmail.com>
Date: Mon, 18 Dec 2023 11:56:18 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Eddy Z <eddyz87@...il.com>, 
	Yonghong Song <yonghong.song@...ux.dev>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 2/3] selftests/bpf: activate the OP_NE login
 in range_cond()

On Mon, Dec 18, 2023 at 2:20 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Sun, Dec 17, 2023 at 5:18 AM Menglong Dong <menglong8.dong@...il.com> wrote:
> >
> > The edge range checking for the registers is supported by the verifier
> > now, so we can activate the extended login in
> > tools/testing/selftests/bpf/prog_tests/reg_bounds.c/range_cond() to test
> > such logic.
> >
> > Besides, I added some cases to the "crafted_cases" array for this logic.
> > These cases are mainly used to test the edge of the src reg and dst reg.
> >
> > All reg bounds testings has passed in the SLOW_TESTS mode:
> >
> > $ export SLOW_TESTS=1 && ./test_progs -t reg_bounds -j
> > Summary: 65/18959832 PASSED, 0 SKIPPED, 0 FAILED
> >
> > Signed-off-by: Menglong Dong <menglong8.dong@...il.com>
> > ---
> > v3:
> > - do some adjustment to the crafted cases that we added
> > v2:
> > - add some cases to the "crafted_cases"
> > ---
> >  .../selftests/bpf/prog_tests/reg_bounds.c     | 20 +++++++++++++------
> >  1 file changed, 14 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> > index 0c9abd279e18..c9dc9fe73211 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> > @@ -590,12 +590,7 @@ static void range_cond(enum num_t t, struct range x, struct range y,
> >                 *newy = range(t, max_t(t, x.a, y.a), min_t(t, x.b, y.b));
> >                 break;
> >         case OP_NE:
> > -               /* generic case, can't derive more information */
> > -               *newx = range(t, x.a, x.b);
> > -               *newy = range(t, y.a, y.b);
> > -               break;
> > -
> > -               /* below extended logic is not supported by verifier just yet */
> > +               /* below logic is supported by the verifier now */
> >                 if (x.a == x.b && x.a == y.a) {
> >                         /* X is a constant matching left side of Y */
> >                         *newx = range(t, x.a, x.b);
> > @@ -2101,6 +2096,19 @@ static struct subtest_case crafted_cases[] = {
> >         {S32, S64, {(u32)(s32)S32_MIN, (u32)(s32)-255}, {(u32)(s32)-2, 0}},
> >         {S32, S64, {0, 1}, {(u32)(s32)S32_MIN, (u32)(s32)S32_MIN}},
> >         {S32, U32, {(u32)(s32)S32_MIN, (u32)(s32)S32_MIN}, {(u32)(s32)S32_MIN, (u32)(s32)S32_MIN}},
> > +
> > +       /* edge overlap testings for BPF_NE, skipped some cases that already
> > +        * exist above.
> > +        */
> > +       {U64, U64, {0, U64_MAX}, {U64_MAX, U64_MAX}},
> > +       {U64, U64, {0, U64_MAX}, {0, 0}},
> > +       {S64, U64, {S64_MIN, 0}, {S64_MIN, S64_MIN}},
> > +       {S64, U64, {S64_MIN, 0}, {0, 0}},
> > +       {S64, U64, {S64_MIN, S64_MAX}, {S64_MAX, S64_MAX}},
> > +       {U32, U32, {0, U32_MAX}, {0, 0}},
> > +       {S32, U32, {(u32)(s32)S32_MIN, 0}, {0, 0}},
> > +       {S32, U32, {(u32)(s32)S32_MIN, 0}, {(u32)(s32)S32_MIN, (u32)(s32)S32_MIN}},
> > +       {S32, U32, {(u32)(s32)S32_MIN, S32_MAX}, {S32_MAX, S32_MAX}},
>
> I think you're copying the style of the casts from few lines above,
> but (s32)S32_MIN is unnecessary. S32_MIN includes the cast already.
> Please remove and fix the above lines too.

Enn...yes, I simulated the usage of S32_MIN from the lines above.
You are right, the s32 casting is unnecessary, I'll just keep the
u32 casting.

I'll wait a while before sending the next version to see if
someone else any comments on this series.

Thanks!
Menglong Dong