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>

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 4a2afc0cefc42aef6427ff3a5446700b396cd79b..4cfb549f2b4395d532e22d177d0c667fc3323377 100644 (file)
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1452,6 +1452,10 @@ emit_bswap_uxt:
                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: