| /* |
| * Copyright 2018, The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef ANDROID_APF_APF_H |
| #define ANDROID_APF_APF_H |
| |
| // A brief overview of APF: |
| // |
| // APF machine is composed of: |
| // 1. A read-only program consisting of bytecodes as described below. |
| // 2. Two 32-bit registers, called R0 and R1. |
| // 3. Sixteen 32-bit temporary memory slots (cleared between packets). |
| // 4. A read-only packet. |
| // The program is executed by the interpreter below and parses the packet |
| // to determine if the application processor (AP) should be woken up to |
| // handle the packet or if can be dropped. |
| // |
| // APF bytecode description: |
| // |
| // The APF interpreter uses big-endian byte order for loads from the packet |
| // and for storing immediates in instructions. |
| // |
| // Each instruction starts with a byte composed of: |
| // Top 5 bits form "opcode" field, see *_OPCODE defines below. |
| // Next 2 bits form "size field", which indicate the length of an immediate |
| // value which follows the first byte. Values in this field: |
| // 0 => immediate value is 0 and no bytes follow. |
| // 1 => immediate value is 1 byte big. |
| // 2 => immediate value is 2 bytes big. |
| // 3 => immediate value is 4 bytes big. |
| // Bottom bit forms "register" field, which indicates which register this |
| // instruction operates on. |
| // |
| // There are three main categories of instructions: |
| // Load instructions |
| // These instructions load byte(s) of the packet into a register. |
| // They load either 1, 2 or 4 bytes, as determined by the "opcode" field. |
| // They load into the register specified by the "register" field. |
| // The immediate value that follows the first byte of the instruction is |
| // the byte offset from the beginning of the packet to load from. |
| // There are "indexing" loads which add the value in R1 to the byte offset |
| // to load from. The "opcode" field determines which loads are "indexing". |
| // Arithmetic instructions |
| // These instructions perform simple operations, like addition, on register |
| // values. The result of these instructions is always written into R0. One |
| // argument of the arithmetic operation is R0's value. The other argument |
| // of the arithmetic operation is determined by the "register" field: |
| // If the "register" field is 0 then the immediate value following |
| // the first byte of the instruction is used as the other argument |
| // to the arithmetic operation. |
| // If the "register" field is 1 then R1's value is used as the other |
| // argument to the arithmetic operation. |
| // Conditional jump instructions |
| // These instructions compare register R0's value with another value, and if |
| // the comparison succeeds, jump (i.e. adjust the program counter). The |
| // immediate value that follows the first byte of the instruction |
| // represents the jump target offset, i.e. the value added to the program |
| // counter if the comparison succeeds. The other value compared is |
| // determined by the "register" field: |
| // If the "register" field is 0 then another immediate value |
| // follows the jump target offset. This immediate value is of the |
| // same size as the jump target offset, and represents the value |
| // to compare against. |
| // If the "register" field is 1 then register R1's value is |
| // compared against. |
| // The type of comparison (e.g. equal to, greater than etc) is determined |
| // by the "opcode" field. The comparison interprets both values being |
| // compared as unsigned values. |
| // |
| // Miscellaneous details: |
| // |
| // Pre-filled temporary memory slot values |
| // When the APF program begins execution, three of the sixteen memory slots |
| // are pre-filled by the interpreter with values that may be useful for |
| // programs: |
| // Slot #11 contains the size (in bytes) of the APF program. |
| // Slot #12 contains the total size of the APF buffer (program + data). |
| // Slot #13 is filled with the IPv4 header length. This value is calculated |
| // by loading the first byte of the IPv4 header and taking the |
| // bottom 4 bits and multiplying their value by 4. This value is |
| // set to zero if the first 4 bits after the link layer header are |
| // not 4, indicating not IPv4. |
| // Slot #14 is filled with size of the packet in bytes, including the |
| // link-layer header if any. |
| // Slot #15 is filled with the filter age in seconds. This is the number of |
| // seconds since the AP sent the program to the chipset. This may |
| // be used by filters that should have a particular lifetime. For |
| // example, it can be used to rate-limit particular packets to one |
| // every N seconds. |
| // Special jump targets: |
| // When an APF program executes a jump to the byte immediately after the last |
| // byte of the progam (i.e., one byte past the end of the program), this |
| // signals the program has completed and determined the packet should be |
| // passed to the AP. |
| // When an APF program executes a jump two bytes past the end of the program, |
| // this signals the program has completed and determined the packet should |
| // be dropped. |
| // Jump if byte sequence doesn't match: |
| // This is a special instruction to facilitate matching long sequences of |
| // bytes in the packet. Initially it is encoded like a conditional jump |
| // instruction with two exceptions: |
| // The first byte of the instruction is always followed by two immediate |
| // fields: The first immediate field is the jump target offset like other |
| // conditional jump instructions. The second immediate field specifies the |
| // number of bytes to compare. |
| // These two immediate fields are followed by a sequence of bytes. These |
| // bytes are compared with the bytes in the packet starting from the |
| // position specified by the value of the register specified by the |
| // "register" field of the instruction. |
| |
| // Number of temporary memory slots, see ldm/stm instructions. |
| #define MEMORY_ITEMS 16 |
| // Upon program execution, some temporary memory slots are prefilled: |
| #define MEMORY_OFFSET_PROGRAM_SIZE 11 // Size of program (in bytes) |
| #define MEMORY_OFFSET_DATA_SIZE 12 // Total size of program + data |
| #define MEMORY_OFFSET_IPV4_HEADER_SIZE 13 // 4*([APF_FRAME_HEADER_SIZE]&15) |
| #define MEMORY_OFFSET_PACKET_SIZE 14 // Size of packet in bytes. |
| #define MEMORY_OFFSET_FILTER_AGE 15 // Age since filter installed in seconds. |
| |
| // Leave 0 opcode unused as it's a good indicator of accidental incorrect execution (e.g. data). |
| #define LDB_OPCODE 1 // Load 1 byte from immediate offset, e.g. "ldb R0, [5]" |
| #define LDH_OPCODE 2 // Load 2 bytes from immediate offset, e.g. "ldh R0, [5]" |
| #define LDW_OPCODE 3 // Load 4 bytes from immediate offset, e.g. "ldw R0, [5]" |
| #define LDBX_OPCODE 4 // Load 1 byte from immediate offset plus register, e.g. "ldbx R0, [5+R0]" |
| #define LDHX_OPCODE 5 // Load 2 byte from immediate offset plus register, e.g. "ldhx R0, [5+R0]" |
| #define LDWX_OPCODE 6 // Load 4 byte from immediate offset plus register, e.g. "ldwx R0, [5+R0]" |
| #define ADD_OPCODE 7 // Add, e.g. "add R0,5" |
| #define MUL_OPCODE 8 // Multiply, e.g. "mul R0,5" |
| #define DIV_OPCODE 9 // Divide, e.g. "div R0,5" |
| #define AND_OPCODE 10 // And, e.g. "and R0,5" |
| #define OR_OPCODE 11 // Or, e.g. "or R0,5" |
| #define SH_OPCODE 12 // Left shift, e.g, "sh R0, 5" or "sh R0, -5" (shifts right) |
| #define LI_OPCODE 13 // Load signed immediate, e.g. "li R0,5" |
| #define JMP_OPCODE 14 // Unconditional jump, e.g. "jmp label" |
| #define JEQ_OPCODE 15 // Compare equal and branch, e.g. "jeq R0,5,label" |
| #define JNE_OPCODE 16 // Compare not equal and branch, e.g. "jne R0,5,label" |
| #define JGT_OPCODE 17 // Compare greater than and branch, e.g. "jgt R0,5,label" |
| #define JLT_OPCODE 18 // Compare less than and branch, e.g. "jlt R0,5,label" |
| #define JSET_OPCODE 19 // Compare any bits set and branch, e.g. "jset R0,5,label" |
| #define JNEBS_OPCODE 20 // Compare not equal byte sequence, e.g. "jnebs R0,5,label,0x1122334455" |
| #define EXT_OPCODE 21 // Immediate value is one of *_EXT_OPCODE |
| #define LDDW_OPCODE 22 // Load 4 bytes from data address (register + simm): "lddw R0, [5+R1]" |
| #define STDW_OPCODE 23 // Store 4 bytes to data address (register + simm): "stdw R0, [5+R1]" |
| |
| // Extended opcodes. These all have an opcode of EXT_OPCODE |
| // and specify the actual opcode in the immediate field. |
| #define LDM_EXT_OPCODE 0 // Load from temporary memory, e.g. "ldm R0,5" |
| // Values 0-15 represent loading the different temporary memory slots. |
| #define STM_EXT_OPCODE 16 // Store to temporary memory, e.g. "stm R0,5" |
| // Values 16-31 represent storing to the different temporary memory slots. |
| #define NOT_EXT_OPCODE 32 // Not, e.g. "not R0" |
| #define NEG_EXT_OPCODE 33 // Negate, e.g. "neg R0" |
| #define SWAP_EXT_OPCODE 34 // Swap, e.g. "swap R0,R1" |
| #define MOV_EXT_OPCODE 35 // Move, e.g. "move R0,R1" |
| |
| #define EXTRACT_OPCODE(i) (((i) >> 3) & 31) |
| #define EXTRACT_REGISTER(i) ((i) & 1) |
| #define EXTRACT_IMM_LENGTH(i) (((i) >> 1) & 3) |
| |
| #endif // ANDROID_APF_APF_H |
