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

[Anton Protopopov <a.s.protopopov@gmail.com>]

On 26/06/09 11:03PM, 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 absent from the CFG jump table for this gotox
> instruction, so program load must be rejected.
> 
> Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
> ---
>  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..866b4a14ccb7 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)
> +{
> +	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, -EACCES, "cross_subprog_gotox_prog_load"))
> +		close(prog_fd);

Robots are right, of course:

    ...
    check_cross_subprog_gotox_target:PASS:create_bad_jt_map 0 nsec
    check_cross_subprog_gotox_target:FAIL:cross_subprog_gotox_prog_load unexpected cross_subprog_gotox_prog_load: actual -22 != expected -13
    #20/14   bpf_gotox/check-cross-subprog-gotox-target:FAIL
    ...

Please the next time actually run selftests before sending patches.

> +
> +	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"))
> +		__subtest(skel, check_cross_subprog_gotox_target);
> +
>  	if (test__start_subtest("check-ldimm64-off-gotox-llvm"))
>  		__subtest(skel, check_ldimm64_off_gotox_llvm);
>  
> 
> -- 
> 2.34.1
>