LoongArch: BPF: Implement bpf_addr_space_cast instruction

LLVM generates bpf_addr_space_cast instruction while translating pointers
between native (zero) address space and __attribute__((address_space(N))).
The addr_space=0 is reserved as bpf_arena address space.

rY = addr_space_cast(rX, 0, 1) is processed by the verifier and converted
to normal 32-bit move: wX = wY

rY = addr_space_cast(rX, 1, 0) has to be converted by JIT.

With this, the following test cases passed:

$ ./test_progs -a arena_htab,arena_list,arena_strsearch,verifier_arena,verifier_arena_large
#4/1 arena_htab/arena_htab_llvm:OK
#4/2 arena_htab/arena_htab_asm:OK
#4 arena_htab:OK
#5/1 arena_list/arena_list_1:OK
#5/2 arena_list/arena_list_1000:OK
#5 arena_list:OK
#7/1 arena_strsearch/arena_strsearch:OK
#7 arena_strsearch:OK
#507/1 verifier_arena/basic_alloc1:OK
#507/2 verifier_arena/basic_alloc2:OK
#507/3 verifier_arena/basic_alloc3:OK
#507/4 verifier_arena/basic_reserve1:OK
#507/5 verifier_arena/basic_reserve2:OK
#507/6 verifier_arena/reserve_twice:OK
#507/7 verifier_arena/reserve_invalid_region:OK
#507/8 verifier_arena/iter_maps1:OK
#507/9 verifier_arena/iter_maps2:OK
#507/10 verifier_arena/iter_maps3:OK
#507 verifier_arena:OK
#508/1 verifier_arena_large/big_alloc1:OK
#508/2 verifier_arena_large/access_reserved:OK
#508/3 verifier_arena_large/request_partially_reserved:OK
#508/4 verifier_arena_large/free_reserved:OK
#508/5 verifier_arena_large/big_alloc2:OK
#508 verifier_arena_large:OK
Summary: 5/20 PASSED, 0 SKIPPED, 0 FAILED

Acked-by: Tiezhu Yang <[e-mail]>
Tested-by: Vincent Li <[e-mail]>
Signed-off-by: Hengqi Chen <[e-mail]>
Signed-off-by: Huacai Chen <[e-mail]>

arch/loongarch/net/bpf_jit.c

···
 	/* dst = src */
 	case BPF_ALU | BPF_MOV | BPF_X:
 	case BPF_ALU64 | BPF_MOV | BPF_X:
+		if (insn_is_cast_user(insn)) {
+			move_reg(ctx, t1, src);
+			emit_zext_32(ctx, t1, true);
+			move_imm(ctx, dst, (ctx->user_vm_start >> 32) << 32, false);
+			emit_insn(ctx, beq, t1, LOONGARCH_GPR_ZERO, 1);
+			emit_insn(ctx, or, t1, dst, t1);
+			move_reg(ctx, dst, t1);
+			break;
+		}
 		switch (off) {
 		case 0:
 			move_reg(ctx, dst, src);
···
 	memset(&ctx, 0, sizeof(ctx));
 	ctx.prog = prog;
 	ctx.arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena);
+	ctx.user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena);
 
 	ctx.offset = kvcalloc(prog->len + 1, sizeof(u32), GFP_KERNEL);
 	if (ctx.offset == NULL) {
···
 }
 
 bool bpf_jit_bypass_spec_v4(void)
+{
+	return true;
+}
+
+bool bpf_jit_supports_arena(void)
 {
 	return true;
 }

arch/loongarch/net/bpf_jit.h

···
 	union loongarch_instruction *ro_image;
 	u32 stack_size;
 	u64 arena_vm_start;
+	u64 user_vm_start;
 };
 
 struct jit_data {