bpf: disasm: add support for BPF_JMP|BPF_JA|BPF_X

Add support for indirect jump instruction.

Example output from bpftool:

   0: (79) r3 = *(u64 *)(r1 +0)
   1: (25) if r3 > 0x4 goto pc+666
   2: (67) r3 <<= 3
   3: (18) r1 = 0xffffbeefspameggs
   5: (0f) r1 += r3
   6: (79) r1 = *(u64 *)(r1 +0)
   7: (0d) gotox r1

Signed-off-by: Anton Protopopov <[email protected]>

Author: aspsk

kernel/bpf/disasm.c

@@ -183,6 +183,13 @@ static inline bool is_mov_percpu_addr(const struct bpf_insn *insn)
 	return insn->code == (BPF_ALU64 | BPF_MOV | BPF_X) && insn->off == BPF_ADDR_PERCPU;
 }
 
+static void print_bpf_ja_indirect(bpf_insn_print_t verbose,
+				  void *private_data,
+				  const struct bpf_insn *insn)
+{
+	verbose(private_data, "(%02x) gotox r%d\n", insn->code, insn->dst_reg);
+}
+
 void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 		    const struct bpf_insn *insn,
 		    bool allow_ptr_leaks)
@@ -358,6 +365,9 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 		} else if (insn->code == (BPF_JMP | BPF_JA)) {
 			verbose(cbs->private_data, "(%02x) goto pc%+d\n",
 				insn->code, insn->off);
+		} else if (insn->code == (BPF_JMP | BPF_JA | BPF_X) ||
+			   insn->code == (BPF_JMP32 | BPF_JA | BPF_X)) {
+			print_bpf_ja_indirect(verbose, cbs->private_data, insn);
 		} else if (insn->code == (BPF_JMP | BPF_JCOND) &&
 			   insn->src_reg == BPF_MAY_GOTO) {
 			verbose(cbs->private_data, "(%02x) may_goto pc%+d\n",