bpf, arm64: Use emit_addr_mov_i64() for BPF_PSEUDO_FUNC

The following error is reported when running "./test_progs -t for_each"
under arm64:

  bpf_jit: multi-func JIT bug 58 != 56
  [...]
  JIT doesn't support bpf-to-bpf calls

The root cause is the size of BPF_PSEUDO_FUNC instruction increases
from 2 to 3 after the address of called bpf-function is settled and
there are two bpf-to-bpf calls in test_pkt_access. The generated
instructions are shown below:

  0x48:  21 00 C0 D2    movz x1, #0x1, lsl #32
  0x4c:  21 00 80 F2    movk x1, #0x1

  0x48:  E1 3F C0 92    movn x1, #0x1ff, lsl #32
  0x4c:  41 FE A2 F2    movk x1, #0x17f2, lsl #16
  0x50:  81 70 9F F2    movk x1, #0xfb84

Fixing it by using emit_addr_mov_i64() for BPF_PSEUDO_FUNC, so
the size of jited image will not change.

Fixes: 69c087ba ("bpf: Add bpf_for_each_map_elem() helper")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211231151018.3781550-1-houtao1@huawei.com

arch/arm64/net/bpf_jit_comp.c

@@ -792,7 +792,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 		u64 imm64;
 
 		imm64 = (u64)insn1.imm << 32 | (u32)imm;
-		emit_a64_mov_i64(dst, imm64, ctx);
+		if (bpf_pseudo_func(insn))
+			emit_addr_mov_i64(dst, imm64, ctx);
+		else
+			emit_a64_mov_i64(dst, imm64, ctx);
 
 		return 1;
 	}