[PATCH bpf-next 14/16] bpf: Add helper macro bpf_arena_cast()

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

From: Alexei Starovoitov <ast@kernel.org>

Introduce helper macro bpf_arena_cast() that emits:
rX = rX
instruction with off = BPF_ARENA_CAST_KERN or off = BPF_ARENA_CAST_USER
and encodes address_space into imm32.

It's useful with older LLVM that doesn't emit this insn automatically.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 .../testing/selftests/bpf/bpf_experimental.h  | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 0d749006d107..e73b7d48439f 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -331,6 +331,47 @@ l_true:												\
 	asm volatile("%[reg]=%[reg]"::[reg]"r"((short)var))
 #endif
 
+/* emit instruction: rX=rX .off = mode .imm32 = address_space */
+#ifndef bpf_arena_cast
+#define bpf_arena_cast(var, mode, addr_space)	\
+	({					\
+	typeof(var) __var = var;		\
+	asm volatile(".byte 0xBF;		\
+		     .ifc %[reg], r0;		\
+		     .byte 0x00;		\
+		     .endif;			\
+		     .ifc %[reg], r1;		\
+		     .byte 0x11;		\
+		     .endif;			\
+		     .ifc %[reg], r2;		\
+		     .byte 0x22;		\
+		     .endif;			\
+		     .ifc %[reg], r3;		\
+		     .byte 0x33;		\
+		     .endif;			\
+		     .ifc %[reg], r4;		\
+		     .byte 0x44;		\
+		     .endif;			\
+		     .ifc %[reg], r5;		\
+		     .byte 0x55;		\
+		     .endif;			\
+		     .ifc %[reg], r6;		\
+		     .byte 0x66;		\
+		     .endif;			\
+		     .ifc %[reg], r7;		\
+		     .byte 0x77;		\
+		     .endif;			\
+		     .ifc %[reg], r8;		\
+		     .byte 0x88;		\
+		     .endif;			\
+		     .ifc %[reg], r9;		\
+		     .byte 0x99;		\
+		     .endif;			\
+		     .short %[off]; .long %[as]"	\
+		     :: [reg]"r"(__var), [off]"i"(mode), [as]"i"(addr_space)); __var; \
+	})
+#endif
+
 /* Description
  *	Assert that a conditional expression is true.
  * Returns
-- 
2.34.1