On Mon, Nov 4, 2024 at 9:46 AM Mikko Ylinen
<mikko.ylinen@xxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> I was experimenting with struct_ops for my use-case but the programs
> would not load because of "program of this type cannot use helper
> xyz" error. However, [1] suggests that the ones I tried *are* supported.
> Is the doc outdated or my steps are simply wrong here?
>
> Andrii suggested to report the case here with reproduce steps so here
> it goes.
>
> with:
>
> diff --git a/tools/testing/selftests/bpf/progs/dummy_st_ops_success.c b/tools/testing/selftests/bpf/progs/dummy_st_ops_success.c
> index ec0c595d47af..c3ca873957f0 100644
> --- a/tools/testing/selftests/bpf/progs/dummy_st_ops_success.c
> +++ b/tools/testing/selftests/bpf/progs/dummy_st_ops_success.c
> @@ -39,6 +39,7 @@ int BPF_PROG(test_2, struct bpf_dummy_ops_state *state, int a1, unsigned short a
> test_2_args[2] = a2;
> test_2_args[3] = a3;
> test_2_args[4] = a4;
> + bpf_printk("struct_ops/test_2");
> return 0;
> }
>
> and:
> tools/testing/selftests/bpf/vmtest.sh -- ./test_progs -t dummy_st_ops/dummy_st_ops_attach
>
> I get:
>
> [build + VM boot cut out]
> ./test_progs -t dummy_st_ops/dummy_st_ops_attach
> [ 1.068102] bpf_testmod: loading out-of-tree module taints kernel.
> [ 1.068733] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
> tester_init:PASS:tester_log_buf 0 nsec
> process_subtest:PASS:obj_open_mem 0 nsec
> process_subtest:PASS:specs_alloc 0 nsec
> libbpf: prog 'test_2': BPF program load failed: Invalid argument
> libbpf: prog 'test_2': -- BEGIN PROG LOAD LOG --
> 0: R1=ctx() R10=fp0
> ; int BPF_PROG(test_2, struct bpf_dummy_ops_state *state, int a1, unsigned short a2, @ dummy_st_ops_success.c:40
> 0: (79) r2 = *(u64 *)(r1 +0)
> func 'test_2' arg0 has btf_id 83075 type STRUCT 'bpf_dummy_ops_state'
> 1: R1=ctx() R2_w=trusted_ptr_bpf_dummy_ops_state()
> ; test_2_args[0] = state->val; @ dummy_st_ops_success.c:43
> 1: (61) r2 = *(u32 *)(r2 +0) ; R2_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
> ; int BPF_PROG(test_2, struct bpf_dummy_ops_state *state, int a1, unsigned short a2, @ dummy_st_ops_success.c:40
> 2: (79) r3 = *(u64 *)(r1 +8) ; R1=ctx() R3_w=scalar()
> 3: (79) r4 = *(u64 *)(r1 +16) ; R1=ctx() R4_w=scalar()
> 4: (79) r5 = *(u64 *)(r1 +24) ; R1=ctx() R5_w=scalar()
> 5: (79) r1 = *(u64 *)(r1 +32) ; R1_w=scalar()
> ; test_2_args[0] = state->val; @ dummy_st_ops_success.c:43
> 6: (18) r0 = 0xffffb456400f6000 ; R0_w=map_value(map=dummy_st.bss,ks=4,vs=40)
> ; test_2_args[4] = a4; @ dummy_st_ops_success.c:47
> 8: (7b) *(u64 *)(r0 +32) = r1 ; R0_w=map_value(map=dummy_st.bss,ks=4,vs=40) R1_w=scalar()
> ; test_2_args[3] = a3; @ dummy_st_ops_success.c:46
> 9: (67) r5 <<= 56 ; R5_w=scalar(smax=0x7f00000000000000,umax=0xff00000000000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xff00000000000000))
> 10: (c7) r5 s>>= 56 ; R5_w=scalar(smin=smin32=-128,smax=smax32=127)
> 11: (7b) *(u64 *)(r0 +24) = r5 ; R0_w=map_value(map=dummy_st.bss,ks=4,vs=40) R5_w=scalar(smin=smin32=-128,smax=smax32=127)
> ; int BPF_PROG(test_2, struct bpf_dummy_ops_state *state, int a1, unsigned short a2, @ dummy_st_ops_success.c:40
> 12: (57) r4 &= 65535 ; R4_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=0xffff,var_off=(0x0; 0xffff))
> ; test_2_args[2] = a2; @ dummy_st_ops_success.c:45
> 13: (7b) *(u64 *)(r0 +16) = r4 ; R0_w=map_value(map=dummy_st.bss,ks=4,vs=40) R4_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=0xffff,var_off=(0x0; 0xffff))
> ; test_2_args[1] = a1; @ dummy_st_ops_success.c:44
> 14: (67) r3 <<= 32 ; R3_w=scalar(smax=0x7fffffff00000000,umax=0xffffffff00000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xffffffff00000000))
> 15: (c7) r3 s>>= 32 ; R3_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff)
> 16: (7b) *(u64 *)(r0 +8) = r3 ; R0_w=map_value(map=dummy_st.bss,ks=4,vs=40) R3_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff)
> ; test_2_args[0] = state->val; @ dummy_st_ops_success.c:43
> 17: (67) r2 <<= 32 ; R2_w=scalar(smax=0x7fffffff00000000,umax=0xffffffff00000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xffffffff00000000))
> 18: (c7) r2 s>>= 32 ; R2_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff)
> 19: (7b) *(u64 *)(r0 +0) = r2 ; R0_w=map_value(map=dummy_st.bss,ks=4,vs=40) R2_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff)
> ; bpf_printk("struct_ops/test_2"); @ dummy_st_ops_success.c:48
> 20: (18) r1 = 0xffff9481c114e5d8 ; R1_w=map_value(map=dummy_st.rodata,ks=4,vs=18)
> 22: (b4) w2 = 18 ; R2_w=18
> 23: (85) call bpf_trace_printk#6
> program of this type cannot use helper bpf_trace_printk#6
> processed 22 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
> -- END PROG LOAD LOG --
> libbpf: prog 'test_2': failed to load: -22
> libbpf: failed to load object 'dummy_st_ops_success'
> libbpf: failed to load BPF skeleton 'dummy_st_ops_success': -22
> test_dummy_st_ops_attach:FAIL:dummy_st_ops_load unexpected error: -22
> #84/1 dummy_st_ops/dummy_st_ops_attach:FAIL
> #84 dummy_st_ops:FAIL
>
This is expected.
Each struct_ops has its own .get_func_proto callback.
This is a dummy struct_ops for testing. It doesn't allow
calling any helpers. get_func_proto is not set:
static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
.is_valid_access = bpf_dummy_ops_is_valid_access,
.btf_struct_access = bpf_dummy_ops_btf_struct_access,
};
