bpf: allocate 0x06 to new eBPF instruction class JMP32

The new eBPF instruction class JMP32 uses the reserved class number 0x6.
Kernel BPF ISA documentation updated accordingly.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Documentation/networking/filter.txt

@@ -865,7 +865,7 @@ Three LSB bits store instruction class which is one of:
   BPF_STX   0x03          BPF_STX   0x03
   BPF_ALU   0x04          BPF_ALU   0x04
   BPF_JMP   0x05          BPF_JMP   0x05
-  BPF_RET   0x06          [ class 6 unused, for future if needed ]
+  BPF_RET   0x06          BPF_JMP32 0x06
   BPF_MISC  0x07          BPF_ALU64 0x07
 
 When BPF_CLASS(code) == BPF_ALU or BPF_JMP, 4th bit encodes source operand ...
@@ -902,9 +902,9 @@ If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of:
   BPF_ARSH  0xc0  /* eBPF only: sign extending shift right */
   BPF_END   0xd0  /* eBPF only: endianness conversion */
 
-If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of:
+If BPF_CLASS(code) == BPF_JMP or BPF_JMP32 [ in eBPF ], BPF_OP(code) is one of:
 
-  BPF_JA    0x00
+  BPF_JA    0x00  /* BPF_JMP only */
   BPF_JEQ   0x10
   BPF_JGT   0x20
   BPF_JGE   0x30
@@ -912,8 +912,8 @@ If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of:
   BPF_JNE   0x50  /* eBPF only: jump != */
   BPF_JSGT  0x60  /* eBPF only: signed '>' */
   BPF_JSGE  0x70  /* eBPF only: signed '>=' */
-  BPF_CALL  0x80  /* eBPF only: function call */
-  BPF_EXIT  0x90  /* eBPF only: function return */
+  BPF_CALL  0x80  /* eBPF BPF_JMP only: function call */
+  BPF_EXIT  0x90  /* eBPF BPF_JMP only: function return */
   BPF_JLT   0xa0  /* eBPF only: unsigned '<' */
   BPF_JLE   0xb0  /* eBPF only: unsigned '<=' */
   BPF_JSLT  0xc0  /* eBPF only: signed '<' */
@@ -936,8 +936,9 @@ Classic BPF wastes the whole BPF_RET class to represent a single 'ret'
 operation. Classic BPF_RET | BPF_K means copy imm32 into return register
 and perform function exit. eBPF is modeled to match CPU, so BPF_JMP | BPF_EXIT
 in eBPF means function exit only. The eBPF program needs to store return
-value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is currently
-unused and reserved for future use.
+value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is used as
+BPF_JMP32 to mean exactly the same operations as BPF_JMP, but with 32-bit wide
+operands for the comparisons instead.
 
 For load and store instructions the 8-bit 'code' field is divided as:
 

include/uapi/linux/bpf.h

@@ -14,6 +14,7 @@
 /* Extended instruction set based on top of classic BPF */
 
 /* instruction classes */
+#define BPF_JMP32	0x06	/* jmp mode in word width */
 #define BPF_ALU64	0x07	/* alu mode in double word width */
 
 /* ld/ldx fields */

tools/include/uapi/linux/bpf.h

@@ -14,6 +14,7 @@
 /* Extended instruction set based on top of classic BPF */
 
 /* instruction classes */
+#define BPF_JMP32	0x06	/* jmp mode in word width */
 #define BPF_ALU64	0x07	/* alu mode in double word width */
 
 /* ld/ldx fields */