diff options
Diffstat (limited to 'apf_interpreter.c')
| -rw-r--r-- | apf_interpreter.c | 146 |
1 files changed, 1 insertions, 145 deletions
diff --git a/apf_interpreter.c b/apf_interpreter.c index abe4c5e..924b23e 100644 --- a/apf_interpreter.c +++ b/apf_interpreter.c @@ -18,151 +18,7 @@ #include <string.h> // For memcmp -// 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 memory slots. -// 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 begining 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 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 #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 send 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 memory slots, see ldm/stm instructions. -#define MEMORY_ITEMS 16 -// Upon program execution starting some memory slots are prefilled: -#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 immediate, e.g. "li R0,5" (immediate encoded as signed value) -#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 -// 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 memory, e.g. "ldm R0,5" - // Values 0-15 represent loading the different memory slots. -#define STM_EXT_OPCODE 16 // Store to memory, e.g. "stm R0,5" - // Values 16-31 represent storing to the different 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) +#include "apf.h" // Return code indicating "packet" should accepted. #define PASS_PACKET 1 |