bpf: arm64: Add support for indirect jumps

Add support for a new instruction	BPF_JMP|BPF_X|BPF_JA, SRC=0, DST=Rx, off=0, imm=0 which does an indirect jump to a location stored in Rx. The register Rx should have type PTR_TO_INSN. This new type assures that the Rx register contains a value (or a range of values) loaded from a correct jump table – map of type instruction array. ARM64 JIT supports indirect jumps to all registers through the A64_BR() macro, use it to implement this new instruction. Signed-off-by: Puranjay Mohan <puranjay@kernel.org> Reviewed-by: Anton Protopopov <a.s.protopopov@gmail.com> Acked-by: Xu Kuohai <xukuohai@huawei.com> Link: https://lore.kernel.org/r/20251117130732.11107-3-puranjay@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: puranjaymohan

arch/arm64/net/bpf_jit_comp.c

@@ -1452,6 +1452,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 emit(A64_ASR(is64, dst, dst, imm), ctx);
 break;
 
+/* JUMP reg */
+case BPF_JMP | BPF_JA | BPF_X:
+emit(A64_BR(dst), ctx);
+break;
 /* JUMP off */
 case BPF_JMP | BPF_JA:
 case BPF_JMP32 | BPF_JA: