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Message-ID: <20210921231320.pgmbhmh4bjgvxwvp@apollo.localdomain>
Date: Wed, 22 Sep 2021 04:43:20 +0530
From: Kumar Kartikeya Dwivedi <memxor@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: bpf <bpf@...r.kernel.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>, Yonghong Song <yhs@...com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Toke Høiland-Jørgensen <toke@...hat.com>,
Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 11/11] bpf: selftests: Add selftests for
module kfunc support
On Wed, Sep 22, 2021 at 04:30:32AM IST, Andrii Nakryiko wrote:
> On Mon, Sep 20, 2021 at 7:16 AM Kumar Kartikeya Dwivedi
> <memxor@...il.com> wrote:
> >
> > This adds selftests that tests the success and failure path for modules
> > kfuncs (in presence of invalid kfunc calls) for both libbpf and
> > gen_loader. It also adds a prog_test kfunc_btf_id_list so that we can
> > add module BTF ID set from bpf_testmod.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > ---
> > include/linux/btf.h | 2 +
> > kernel/bpf/btf.c | 2 +
> > net/bpf/test_run.c | 5 +-
> > tools/testing/selftests/bpf/Makefile | 5 +-
> > .../selftests/bpf/bpf_testmod/bpf_testmod.c | 26 ++++++-
> > .../selftests/bpf/prog_tests/ksyms_module.c | 52 ++++++++++----
> > .../bpf/prog_tests/ksyms_module_libbpf.c | 44 ++++++++++++
> > .../selftests/bpf/progs/test_ksyms_module.c | 41 ++++++++---
> > .../bpf/progs/test_ksyms_module_fail.c | 29 ++++++++
> > .../progs/test_ksyms_module_fail_toomany.c | 19 +++++
> > .../bpf/progs/test_ksyms_module_libbpf.c | 71 +++++++++++++++++++
> > .../bpf/progs/test_ksyms_module_util.h | 48 +++++++++++++
> > 12 files changed, 317 insertions(+), 27 deletions(-)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c
> > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_module_fail.c
> > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_module_fail_toomany.c
> > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_module_libbpf.c
> > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_module_util.h
> >
>
> [...]
>
> > @@ -243,7 +244,9 @@ BTF_SET_END(test_sk_kfunc_ids)
> >
> > bool bpf_prog_test_check_kfunc_call(u32 kfunc_id, struct module *owner)
> > {
> > - return btf_id_set_contains(&test_sk_kfunc_ids, kfunc_id);
> > + if (btf_id_set_contains(&test_sk_kfunc_ids, kfunc_id))
> > + return true;
> > + return __bpf_check_prog_test_kfunc_call(kfunc_id, owner);
> > }
> >
> > static void *bpf_test_init(const union bpf_attr *kattr, u32 size,
> > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > index 326ea75ce99e..d20ff0563120 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -174,6 +174,7 @@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_tes
> > $(Q)$(RM) bpf_testmod/bpf_testmod.ko # force re-compilation
> > $(Q)$(MAKE) $(submake_extras) -C bpf_testmod
> > $(Q)cp bpf_testmod/bpf_testmod.ko $@
> > + $(Q)$(RESOLVE_BTFIDS) -s ../../../../vmlinux bpf_testmod.ko
>
> $(VMLINUX_BTF) instead of "../../../../vmlinux", it will break
>
> >
> > $(OUTPUT)/test_stub.o: test_stub.c $(BPFOBJ)
> > $(call msg,CC,,$@)
> > @@ -315,8 +316,8 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \
> > linked_vars.skel.h linked_maps.skel.h
> >
> > LSKELS := kfunc_call_test.c fentry_test.c fexit_test.c fexit_sleep.c \
> > - test_ksyms_module.c test_ringbuf.c atomics.c trace_printk.c \
> > - trace_vprintk.c
> > + test_ksyms_module.c test_ksyms_module_fail.c test_ksyms_module_fail_toomany.c \
> > + test_ringbuf.c atomics.c trace_printk.c trace_vprintk.c
> > SKEL_BLACKLIST += $$(LSKELS)
> >
>
> [...]
>
> > diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_module_util.h b/tools/testing/selftests/bpf/progs/test_ksyms_module_util.h
> > new file mode 100644
> > index 000000000000..3afa74841ae0
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_ksyms_module_util.h
> > @@ -0,0 +1,48 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#ifndef __KSYMS_MODULE_UTIL_H__
> > +#define __KSYMS_MODULE_UTIL_H__
> > +
> > +#define __KFUNC_NR_EXP(Y) \
> > +Y(0) Y(1) Y(2) Y(3) Y(4) Y(5) Y(6) Y(7) Y(8) Y(9) Y(10) Y(11) Y(12) \
> > +Y(13) Y(14) Y(15) Y(16) Y(17) Y(18) Y(19) Y(20) Y(21) Y(22) Y(23) \
> > +Y(24) Y(25) Y(26) Y(27) Y(28) Y(29) Y(30) Y(31) Y(32) Y(33) Y(34) \
> > +Y(35) Y(36) Y(37) Y(38) Y(39) Y(40) Y(41) Y(42) Y(43) Y(44) Y(45) \
> > +Y(46) Y(47) Y(48) Y(49) Y(50) Y(51) Y(52) Y(53) Y(54) Y(55) Y(56) \
> > +Y(57) Y(58) Y(59) Y(60) Y(61) Y(62) Y(63) Y(64) Y(65) Y(66) Y(67) \
> > +Y(68) Y(69) Y(70) Y(71) Y(72) Y(73) Y(74) Y(75) Y(76) Y(77) Y(78) \
> > +Y(79) Y(80) Y(81) Y(82) Y(83) Y(84) Y(85) Y(86) Y(87) Y(88) Y(89) \
> > +Y(90) Y(91) Y(92) Y(93) Y(94) Y(95) Y(96) Y(97) Y(98) Y(99) Y(100) \
> > +Y(101) Y(102) Y(103) Y(104) Y(105) Y(106) Y(107) Y(108) Y(109) Y(110) \
> > +Y(111) Y(112) Y(113) Y(114) Y(115) Y(116) Y(117) Y(118) Y(119) Y(120) \
> > +Y(121) Y(122) Y(123) Y(124) Y(125) Y(126) Y(127) Y(128) Y(129) Y(130) \
> > +Y(131) Y(132) Y(133) Y(134) Y(135) Y(136) Y(137) Y(138) Y(139) Y(140) \
> > +Y(141) Y(142) Y(143) Y(144) Y(145) Y(146) Y(147) Y(148) Y(149) Y(150) \
> > +Y(151) Y(152) Y(153) Y(154) Y(155) Y(156) Y(157) Y(158) Y(159) Y(160) \
> > +Y(161) Y(162) Y(163) Y(164) Y(165) Y(166) Y(167) Y(168) Y(169) Y(170) \
> > +Y(171) Y(172) Y(173) Y(174) Y(175) Y(176) Y(177) Y(178) Y(179) Y(180) \
> > +Y(181) Y(182) Y(183) Y(184) Y(185) Y(186) Y(187) Y(188) Y(189) Y(190) \
> > +Y(191) Y(192) Y(193) Y(194) Y(195) Y(196) Y(197) Y(198) Y(199) Y(200) \
> > +Y(201) Y(202) Y(203) Y(204) Y(205) Y(206) Y(207) Y(208) Y(209) Y(210) \
> > +Y(211) Y(212) Y(213) Y(214) Y(215) Y(216) Y(217) Y(218) Y(219) Y(220) \
> > +Y(221) Y(222) Y(223) Y(224) Y(225) Y(226) Y(227) Y(228) Y(229) Y(230) \
> > +Y(231) Y(232) Y(233) Y(234) Y(235) Y(236) Y(237) Y(238) Y(239) Y(240) \
> > +Y(241) Y(242) Y(243) Y(244) Y(245) Y(246) Y(247) Y(248) Y(249) Y(250) \
> > +Y(251) Y(252) Y(253) Y(254) Y(255)
> > +
> > +#define __KFUNC_A(nr) bpf_testmod_test_mod_kfunc_##nr();
> > +#define KFUNC_VALID_DISTINCT_256 __KFUNC_NR_EXP(__KFUNC_A)
> > +
> > +#define __KFUNC_B(nr) extern void bpf_testmod_test_mod_kfunc_##nr(void) __ksym;
> > +#define KFUNC_KSYM_DECLARE_VALID_DISTINCT_256 __KFUNC_NR_EXP(__KFUNC_B)
> > +
> > +#define __KFUNC_C(nr) noinline void bpf_testmod_test_mod_kfunc_##nr(void) {};
> > +#define KFUNC_DEFINE_VALID_DISTINCT_256 __KFUNC_NR_EXP(__KFUNC_C)
> > +
> > +#define __KFUNC_D(nr) BTF_ID(func, bpf_testmod_test_mod_kfunc_##nr)
> > +#define KFUNC_BTF_ID_VALID_DISTINCT_256 __KFUNC_NR_EXP(__KFUNC_D)
> > +
> > +#define __KFUNC_E(nr) bpf_testmod_test_mod_kfunc(nr);
> > +#define KFUNC_VALID_SAME_ONE __KFUNC_E(0)
> > +#define KFUNC_VALID_SAME_256 __KFUNC_NR_EXP(__KFUNC_E)
> > +
>
> This is pretty horrible... Wouldn't it be better to test limits like
Yeah, I actually thought about this a bit yesterday, we could also do:
(untested)
#define X_0(x)
#define X_1(x) x X_0(x)
#define X_2(x) x X_1(x)
#define X_3(x) x X_2(x)
#define X_4(x) x X_3(x)
#define X_5(x) x X_4(x)
#define X_6(x) x X_5(x)
#define X_7(x) x X_6(x)
#define X_8(x) x X_7(x)
#define X_9(x) x X_8(x)
#define X_10(x) x X_9(x)
Then, for generating 256 items
X_2(X_10(X_10(foo))) X_5(X_10(foo)) X_6(foo)
... which looks much better.
> this using the test_verifier approach, where we can craft a *short*
> sequence of instructions that will test all these limits?...
>
Hmm, good idea, I'd just need to fill in the BTF id dynamically at runtime,
but that should be possible.
Though we still need to craft distinct calls (I am trying to test the limit
where insn->off is different for each case). Since we try to reuse index in both
gen_loader and libbpf, just generating same call 256 times would not be enough.
Let me know which one of the two you prefer.
>
> > +#endif
> > --
> > 2.33.0
> >
--
Kartikeya
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