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

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Date: Mon, 18 Dec 2023 21:52:25 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: andrii@...nel.org, eddyz87@...il.com, yonghong.song@...ux.dev, 
	alexei.starovoitov@...il.com, ast@...nel.org, daniel@...earbox.net, 
	john.fastabend@...il.com, martin.lau@...ux.dev, song@...nel.org, 
	kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org, 
	bpf@...r.kernel.org, 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 6:22 PM Menglong Dong <menglong8.dong@...il.com> wrote:
>
> On Tue, Dec 19, 2023 at 1:58 AM Andrii Nakryiko
> <andrii.nakryiko@...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}},
> >
> > missing case where we compare against U32_MAX constant?
> >
>
> Hello,
>
> There seems to already be one existing above:
>
> {U32, S32, {0, U32_MAX}, {U32_MAX, U32_MAX}},
>

This one is doing S32 comparisons. For == and != it doesn't matter,
but it is a different use case. So I'd add U32, U32 case nevertheless.

> > > +       {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}},
> > >  };
> > >
> > >  /* Go over crafted hard-coded cases. This is fast, so we do it as part of
> > > --
> > > 2.39.2
> > >