1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef SANDBOX_LINUX_SECCOMP_BPF_INSTRUCTION_H__
6 #define SANDBOX_LINUX_SECCOMP_BPF_INSTRUCTION_H__
14 // The fields in this structure have the same meaning as the corresponding
15 // fields in "struct sock_filter". See <linux/filter.h> for a lot more
17 // code -- Opcode of the instruction. This is typically a bitwise
18 // combination BPF_XXX values.
19 // k -- Operand; BPF instructions take zero or one operands. Operands
20 // are 32bit-wide constants, if present. They can be immediate
21 // values (if BPF_K is present in "code_"), addresses (if BPF_ABS
22 // is present in "code_"), or relative jump offsets (if BPF_JMP
23 // and BPF_JA are present in "code_").
24 // jt, jf -- all conditional jumps have a 8bit-wide jump offset that allows
25 // jumps of up to 256 instructions forward. Conditional jumps are
26 // identified by BPF_JMP in "code_", but the lack of BPF_JA.
27 // Conditional jumps have a "t"rue and "f"alse branch.
29 // Constructor for an non-jumping instruction or for an unconditional
31 Instruction(uint16_t c, uint32_t parm, Instruction* n)
32 : code(c), jt(0), jf(0), jt_ptr(NULL), jf_ptr(NULL), next(n), k(parm) {}
34 // Constructor for a conditional jump instruction.
35 Instruction(uint16_t c, uint32_t parm, Instruction* jt, Instruction* jf)
36 : code(c), jt(0), jf(0), jt_ptr(jt), jf_ptr(jf), next(NULL), k(parm) {}
40 // When code generation is complete, we will have computed relative
41 // branch targets that are in the range 0..255.
44 // While assembling the BPF program, we use pointers for branch targets.
45 // Once we have computed basic blocks, these pointers will be entered as
46 // keys in a TargetsToBlocks map and should no longer be dereferenced
48 Instruction* jt_ptr, *jf_ptr;
50 // While assembling the BPF program, non-jumping instructions are linked
51 // by the "next_" pointer. This field is no longer needed when we have
52 // computed basic blocks.
58 } // namespace sandbox
60 #endif // SANDBOX_LINUX_SECCOMP_BPF_INSTRUCTION_H__