[RFC PATCH 2/3] LoongArch: BPF: Add support for indirect jumps

[Tiezhu Yang]

In order to implement JIT support for the indirect jump instruction
(BPF_JMP | BPF_JA | BPF_X), emit a jirl instruction to jump to the
target address held in rd without saving PC+4 into return address.

This is similar to commit f4a66cf1cb14 ("bpf: arm64: Add support for
indirect jumps").

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
 arch/loongarch/net/bpf_jit.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 26904010d9b5..64abebd9c950 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1184,6 +1184,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
 			goto toofar;
 		break;
 
+	case BPF_JMP | BPF_JA | BPF_X:
+		emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, rd, 0);
+		break;
+
 	/* PC += off */
 	case BPF_JMP | BPF_JA:
 		jmp_offset = bpf2la_offset(i, off, ctx);
-- 
2.42.0