Re: [PATCH bpf-next 4/4] selftests/bpf: add reason of rejection in ld_imm64

[Yonghong Song]

On 5/20/22 4:37 AM, Shung-Hsi Yu wrote:
> It may not be immediately clear why that ld_imm64 test cases are
> rejected, especially for test1 and test2 where JMP to the 2nd
> instruction of BPF_LD_IMM64 is performed.
>
> Add brief explaination of why each test case in verifier/ld_imm64.c
> should be rejected.
>
> Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@xxxxxxxx>
> ---
>   .../testing/selftests/bpf/verifier/ld_imm64.c | 20 ++++++++++---------
>   1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/verifier/ld_imm64.c b/tools/testing/selftests/bpf/verifier/ld_imm64.c
> index f9297900cea6..021312641aaf 100644
> --- a/tools/testing/selftests/bpf/verifier/ld_imm64.c
> +++ b/tools/testing/selftests/bpf/verifier/ld_imm64.c
> @@ -1,5 +1,6 @@
> +/* Note: BPF_LD_IMM64 is composed of two instructions of class BPF_LD */

> [...]LD | BPF_IMM | BPF_DW, 0, 0, 0, 0),
> @@ -42,7 +43,7 @@
>   	.result = REJECT,
>   },
>   {
> -	"test4 ld_imm64",
> +	"test4 ld_imm64: reject incomplete BPF_LD_IMM64 instruction",
>   	.insns = {
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 0),
>   	BPF_EXIT_INSN(),
> @@ -70,7 +71,7 @@
>   	.retval = 1,
>   },
>   {
> -	"test8 ld_imm64",
> +	"test8 ld_imm64: reject 1st off!=0",

Let add some space like 'off != 0'. The same for
some of later test names.

>   	.insns = {
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 1, 1),
>   	BPF_RAW_INSN(0, 0, 0, 0, 1),
> @@ -80,7 +81,7 @@
>   	.result = REJECT,
>   },
>   {
> -	"test9 ld_imm64",
> +	"test9 ld_imm64: reject 2nd off!=0",
>   	.insns = {
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 1),
>   	BPF_RAW_INSN(0, 0, 0, 1, 1),
> @@ -90,7 +91,7 @@
>   	.result = REJECT,
>   },
>   {
> -	"test10 ld_imm64",
> +	"test10 ld_imm64: reject 2nd dst_reg!=0",
>   	.insns = {
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 1),
>   	BPF_RAW_INSN(0, BPF_REG_1, 0, 0, 1),
> @@ -100,7 +101,7 @@
>   	.result = REJECT,
>   },
>   {
> -	"test11 ld_imm64",
> +	"test11 ld_imm64: reject 2nd src_reg!=0",
>   	.insns = {
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 1),
>   	BPF_RAW_INSN(0, 0, BPF_REG_1, 0, 1),
> @@ -113,6 +114,7 @@
>   	"test12 ld_imm64",
>   	.insns = {
>   	BPF_MOV64_IMM(BPF_REG_1, 0),
> +	/* BPF_REG_1 is interpreted as BPF_PSEUDO_MAP_FD */
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, BPF_REG_1, 0, 1),
>   	BPF_RAW_INSN(0, 0, 0, 0, 0),
>   	BPF_EXIT_INSN(),
> @@ -121,7 +123,7 @@
>   	.result = REJECT,
>   },
>   {
> -	"test13 ld_imm64",
> +	"test13 ld_imm64: 2nd src_reg!=0",
>   	.insns = {
>   	BPF_MOV64_IMM(BPF_REG_1, 0),
>   	BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, BPF_REG_1, 0, 1),