[PATCH v2 bpf-next 06/20] bpf: Disasm support for cast_kern/user instructions.

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

From: Alexei Starovoitov <ast@kernel.org>

LLVM generates rX = bpf_cast_kern/_user(rY, address_space) instructions
when pointers in non-zero address space are used by the bpf program.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 include/uapi/linux/bpf.h       |  5 +++++
 kernel/bpf/disasm.c            | 11 +++++++++++
 tools/include/uapi/linux/bpf.h |  5 +++++
 3 files changed, 21 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f6648851eae6..3de1581379d4 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1313,6 +1313,11 @@ enum {
  */
 #define BPF_PSEUDO_KFUNC_CALL	2
 
+enum bpf_arena_cast_kinds {
+	BPF_ARENA_CAST_KERN = 1,
+	BPF_ARENA_CAST_USER = 2,
+};
+
 /* flags for BPF_MAP_UPDATE_ELEM command */
 enum {
 	BPF_ANY		= 0, /* create new element or update existing */
diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
index 49940c26a227..37d9b37b34f7 100644
--- a/kernel/bpf/disasm.c
+++ b/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_arena_cast(const struct bpf_insn *insn)
+{
+	return insn->code == (BPF_ALU64 | BPF_MOV | BPF_X) &&
+		(insn->off == BPF_ARENA_CAST_KERN || insn->off == BPF_ARENA_CAST_USER);
+}
+
 void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 		    const struct bpf_insn *insn,
 		    bool allow_ptr_leaks)
@@ -184,6 +190,11 @@ 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_arena_cast(insn)) {
+			verbose(cbs->private_data, "(%02x) r%d = cast_%s(r%d, %d)\n",
+				insn->code, insn->dst_reg,
+				insn->off == BPF_ARENA_CAST_KERN ? "kern" : "user",
+				insn->src_reg, 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',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index f6648851eae6..3de1581379d4 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1313,6 +1313,11 @@ enum {
  */
 #define BPF_PSEUDO_KFUNC_CALL	2
 
+enum bpf_arena_cast_kinds {
+	BPF_ARENA_CAST_KERN = 1,
+	BPF_ARENA_CAST_USER = 2,
+};
+
 /* flags for BPF_MAP_UPDATE_ELEM command */
 enum {
 	BPF_ANY		= 0, /* create new element or update existing */
-- 
2.34.1