LoongArch: BPF: No support of struct argument in trampoline programs

The current implementation does not support struct argument.
This cause a oops when running bpf selftest:

    $ ./test_progs -a tracing_struct
    CPU -1 Unable to handle kernel paging request at virtual address 0000000000000018, era == 90000000845659f4, ra == 90000000845659e8
    Oops[#1]:
    CPU -1 Unable to handle kernel paging request at virtual address 0000000000000018, era == 9000000085bef268, ra == 90000000844f3938
    rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
    rcu:     1-...0: (19 ticks this GP) idle=1094/1/0x4000000000000000 softirq=1380/1382 fqs=801
    rcu:     (detected by 0, t=5252 jiffies, g=1197, q=52 ncpus=4)
    Sending NMI from CPU 0 to CPUs 1:
    rcu: rcu_preempt kthread starved for 2495 jiffies! g1197 f0x0 RCU_GP_DOING_FQS(6) ->state=0x0 ->cpu=2
    rcu:     Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
    rcu: RCU grace-period kthread stack dump:
    task:rcu_preempt     state:I stack:0     pid:15    tgid:15    ppid:2      task_flags:0x208040 flags:0x00000800
    Stack : 9000000100423e80 0000000000000402 0000000000000010 90000001003b0680
            9000000085d88000 0000000000000000 0000000000000040 9000000087159350
            9000000085c2b9b0 0000000000000001 900000008704a000 0000000000000005
            00000000ffff355b 00000000ffff355b 0000000000000000 0000000000000004
            9000000085d90510 0000000000000000 0000000000000002 7b5d998f8281e86e
            00000000ffff355c 7b5d998f8281e86e 000000000000003f 9000000087159350
            900000008715bf98 0000000000000005 9000000087036000 900000008704a000
            9000000100407c98 90000001003aff80 900000008715c4c0 9000000085c2b9b0
            00000000ffff355b 9000000085c33d3c 00000000000000b4 0000000000000000
            9000000007002150 00000000ffff355b 9000000084615480 0000000007000002
            ...
    Call Trace:
    [<9000000085c2a868>] __schedule+0x410/0x1520
    [<9000000085c2b9ac>] schedule+0x34/0x190
    [<9000000085c33d38>] schedule_timeout+0x98/0x140
    [<90000000845e9120>] rcu_gp_fqs_loop+0x5f8/0x868
    [<90000000845ed538>] rcu_gp_kthread+0x260/0x2e0
    [<900000008454e8a4>] kthread+0x144/0x238
    [<9000000085c26b60>] ret_from_kernel_thread+0x28/0xc8
    [<90000000844f20e4>] ret_from_kernel_thread_asm+0xc/0x88

    rcu: Stack dump where RCU GP kthread last ran:
    Sending NMI from CPU 0 to CPUs 2:
    NMI backtrace for cpu 2 skipped: idling at idle_exit+0x0/0x4

Reject it for now.

Fixes: f9b6b41 ("LoongArch: BPF: Add basic bpf trampoline support")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Acked-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn>

Author: chenhengqi

arch/loongarch/net/bpf_jit.c

@@ -1516,6 +1516,12 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
 	if (m->nr_args > LOONGARCH_MAX_REG_ARGS)
 		return -ENOTSUPP;
 
+	/* don't support struct argument */
+	for (i = 0; i < m->nr_args; i++) {
+		if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
+			return -ENOTSUPP;
+	}
+
 	if (flags & (BPF_TRAMP_F_ORIG_STACK | BPF_TRAMP_F_SHARE_IPMODIFY))
 		return -ENOTSUPP;