Re: Re: [PATCH bpf-next v2 2/2] selftests/bpf: Add cross-subprog gotox target coverage

["Nuoqi Gui" <gnq25@mails.tsinghua.edu.cn>]

> -----Original Messages-----
> From: "Anton Protopopov" <a.s.protopopov@gmail.com>
> Send time:Monday, 22/06/2026 22:40:01
> To: "Nuoqi Gui" <gnq25@mails.tsinghua.edu.cn>
> Cc: bpf@vger.kernel.org, "Alexei Starovoitov" <ast@kernel.org>, "Daniel Borkmann" <daniel@iogearbox.net>, "Andrii Nakryiko" <andrii@kernel.org>, "Eduard Zingerman" <eddyz87@gmail.com>, "Shuah Khan" <shuah@kernel.org>, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
> Subject: Re: [PATCH bpf-next v2 2/2] selftests/bpf: Add cross-subprog gotox target coverage
> 
> On 26/06/13 05:33PM, Nuoqi Gui wrote:
> > Add a gotox regression test with two one-entry INSN_ARRAY maps. CFG can
> > model a map whose target stays in the main subprog, while the verified path
> > can load a different map whose target is the first instruction of another
> > subprog.
> > 
> > That second target is outside the subprog that contains this gotox
> > instruction, so program load must be rejected with -EINVAL.
> > 
> > Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
> 
> Sorry, was AFK the last week. The looks better now. A few small nits.
> 
> > ---
> >  tools/testing/selftests/bpf/prog_tests/bpf_gotox.c | 73 ++++++++++++++++++++++
> >  1 file changed, 73 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_gotox.c b/tools/testing/selftests/bpf/prog_tests/bpf_gotox.c
> > index 73dc63882b7d..5252ca09689c 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/bpf_gotox.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_gotox.c
> > @@ -255,6 +255,30 @@ static int create_jt_map(__u32 max_entries)
> >  			      key_size, value_size, max_entries, NULL);
> >  }
> >  
> > +static int create_jt_map_with_target(__u32 target)
> > +{
> > +	struct bpf_insn_array_value val = { .orig_off = target };
> > +	__u32 key = 0;
> > +	int map_fd;
> > +
> > +	map_fd = create_jt_map(1);
> > +	if (!ASSERT_GE(map_fd, 0, "create_jt_map"))
> > +		return -1;
> > +
> > +	if (!ASSERT_EQ(bpf_map_update_elem(map_fd, &key, &val, 0),
> > +		       0, "bpf_map_update_elem")) {
> > +		close(map_fd);
> > +		return -1;
> > +	}
> > +
> > +	if (!ASSERT_EQ(bpf_map_freeze(map_fd), 0, "bpf_map_freeze")) {
> > +		close(map_fd);
> > +		return -1;
> > +	}
> > +
> > +	return map_fd;
> > +}
> > +
> >  static int prog_load(struct bpf_insn *insns, __u32 insn_cnt)
> >  {
> >  	return bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
> > @@ -393,6 +417,52 @@ reject_offsets(struct bpf_insn *insns, __u32 insn_cnt, int off1, int off2, int o
> >  		close(prog_fd);
> >  }
> >  
> > +static void
> > +check_cross_subprog_gotox_target(struct bpf_gotox *skel __always_unused)
> 
> Why to pass the skel pointer at all?
> 
> > +{
> > +	struct bpf_insn insns[] = {
> > +		/* main subprog [0,14) */
> > +		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
> > +		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_CALL, 0, 12),
> > +		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6, 0),
> > +		BPF_JMP_IMM(BPF_JEQ, BPF_REG_7, 0, 4),
> > +		BPF_LD_IMM64_RAW(BPF_REG_2, BPF_PSEUDO_MAP_VALUE, 0),
> > +		BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_2, 0),
> > +		BPF_JMP_A(3),
> > +		BPF_LD_IMM64_RAW(BPF_REG_2, BPF_PSEUDO_MAP_VALUE, 0),
> > +		BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_2, 0),
> > +		BPF_RAW_INSN(BPF_JMP | BPF_JA | BPF_X, BPF_REG_2, 0, 0, 0),
> > +		BPF_MOV64_IMM(BPF_REG_0, 1),
> > +		BPF_EXIT_INSN(),
> > +
> > +		/* static subprog [14,16) */
> > +		BPF_MOV64_IMM(BPF_REG_0, 42),
> > +		BPF_EXIT_INSN(),
> > +	};
> > +	int good_fd, bad_fd, prog_fd;
> > +
> > +	good_fd = create_jt_map_with_target(12);
> > +	if (!ASSERT_GE(good_fd, 0, "create_good_jt_map"))
> > +		return;
> > +
> > +	bad_fd = create_jt_map_with_target(14);
> > +	if (!ASSERT_GE(bad_fd, 0, "create_bad_jt_map")) {
> > +		close(good_fd);
> > +		return;
> > +	}
> > +
> > +	insns[4].imm = bad_fd;
> > +	insns[8].imm = good_fd;
> > +
> > +	prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL",
> > +				insns, ARRAY_SIZE(insns), NULL);
> > +	if (!ASSERT_EQ(prog_fd, -EINVAL, "cross_subprog_gotox_prog_load"))
> > +		close(prog_fd);
> > +
> > +	close(bad_fd);
> > +	close(good_fd);
> > +}
> > +
> >  /*
> >   * Verify a bit more complex programs which include indirect jumps
> >   * and with jump tables loaded with a non-zero offset
> > @@ -538,6 +608,9 @@ void test_bpf_gotox(void)
> >  	if (test__start_subtest("check-ldimm64-off-gotox"))
> >  		__subtest(skel, check_ldimm64_off_gotox);
> >  
> > +	if (test__start_subtest("check-cross-subprog-gotox-target"))
> > +		check_cross_subprog_gotox_target(skel);
> > +
> >  	if (test__start_subtest("check-ldimm64-off-gotox-llvm"))
> >  		__subtest(skel, check_ldimm64_off_gotox_llvm);
> >  
> 
> Why haven't you add the test as the last one? Especially that it
> doesn't use the __subtest() helper.
> 
> > -- 
> > 2.34.1
> > 

I will drop the unused skel argument and keep this raw-insn
test independent from the skeleton-based __subtest() path.