bpf: Disasm support for addr_space_cast instruction.

LLVM generates rX = addr_space_cast(rY, dst_addr_space, src_addr_space)
instruction when pointers in non-zero address space are used by the bpf
program. Recognize this insn in uapi and in bpf disassembler.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-3-alexei.starovoitov@gmail.com

Author: Alexei Starovoitov

include/uapi/linux/bpf.h

@@ -1339,6 +1339,10 @@ enum {
  */
 #define BPF_PSEUDO_KFUNC_CALL	2
 
+enum bpf_addr_space_cast {
+	BPF_ADDR_SPACE_CAST = 1,
+};
+
 /* flags for BPF_MAP_UPDATE_ELEM command */
 enum {
 	BPF_ANY		= 0, /* create new element or update existing */

kernel/bpf/disasm.c

@@ -166,6 +166,12 @@ static bool is_movsx(const struct bpf_insn *insn)
 	       (insn->off == 8 || insn->off == 16 || insn->off == 32);
 }
 
+static bool is_addr_space_cast(const struct bpf_insn *insn)
+{
+	return insn->code == (BPF_ALU64 | BPF_MOV | BPF_X) &&
+		insn->off == BPF_ADDR_SPACE_CAST;
+}
+
 void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 		    const struct bpf_insn *insn,
 		    bool allow_ptr_leaks)
@@ -184,6 +190,10 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 				insn->code, class == BPF_ALU ? 'w' : 'r',
 				insn->dst_reg, class == BPF_ALU ? 'w' : 'r',
 				insn->dst_reg);
+		} else if (is_addr_space_cast(insn)) {
+			verbose(cbs->private_data, "(%02x) r%d = addr_space_cast(r%d, %d, %d)\n",
+				insn->code, insn->dst_reg,
+				insn->src_reg, ((u32)insn->imm) >> 16, (u16)insn->imm);
 		} else if (BPF_SRC(insn->code) == BPF_X) {
 			verbose(cbs->private_data, "(%02x) %c%d %s %s%c%d\n",
 				insn->code, class == BPF_ALU ? 'w' : 'r',

tools/include/uapi/linux/bpf.h

@@ -1339,6 +1339,10 @@ enum {
  */
 #define BPF_PSEUDO_KFUNC_CALL	2
 
+enum bpf_addr_space_cast {
+	BPF_ADDR_SPACE_CAST = 1,
+};
+
 /* flags for BPF_MAP_UPDATE_ELEM command */
 enum {
 	BPF_ANY		= 0, /* create new element or update existing */