bpf, arm64: Add support for signed arena loads

Add support for signed loads from arena which are internally converted
to loads with mode set BPF_PROBE_MEM32SX by the verifier. The
implementation is similar to BPF_PROBE_MEMSX and BPF_MEMSX but for
BPF_PROBE_MEM32SX, arena_vm_base is added to the src register to form
the address.

Signed-off-by: Puranjay Mohan <[email protected]>

Author: puranjaymohan

arch/arm64/net/bpf_jit_comp.c

@@ -3073,11 +3073,6 @@ bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)
 		if (!bpf_atomic_is_load_store(insn) &&
 		    !cpus_have_cap(ARM64_HAS_LSE_ATOMICS))
 			return false;
-		break;
-	case BPF_LDX | BPF_MEMSX | BPF_B:
-	case BPF_LDX | BPF_MEMSX | BPF_H:
-	case BPF_LDX | BPF_MEMSX | BPF_W:
-		return false;
 	}
 	return true;
 }