227 lines
6.4 KiB
C
227 lines
6.4 KiB
C
/* bpf.h
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* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*
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* Berkeley Packet Filter functions.
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*/
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#ifndef BPF_H
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#define BPF_H
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#include <asm/bitsperlong.h> /* for __BITS_PER_LONG */
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#include <endian.h>
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#include <linux/audit.h>
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#include <linux/filter.h>
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#include <stddef.h>
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#include <sys/user.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "arch.h"
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#if __BITS_PER_LONG == 32 || defined(__ILP32__)
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#define BITS32
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#elif __BITS_PER_LONG == 64
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#define BITS64
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#endif
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/* Constants for comparison operators. */
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#define MIN_OPERATOR 128
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enum {
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EQ = MIN_OPERATOR,
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NE,
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LT,
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LE,
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GT,
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GE,
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SET,
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IN
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};
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/*
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* BPF return values and data structures,
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* since they're not yet in the kernel.
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* TODO(crbug.com/1147037): Replace this with an #include.
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*/
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#define SECCOMP_RET_KILL_PROCESS 0x80000000U /* kill the entire process */
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#define SECCOMP_RET_KILL_THREAD 0x00000000U /* kill the thread */
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#define SECCOMP_RET_KILL SECCOMP_RET_KILL_THREAD
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#define SECCOMP_RET_TRAP 0x00030000U /* return SIGSYS */
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#define SECCOMP_RET_ERRNO 0x00050000U /* return -1 and set errno */
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#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */
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#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
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#define SECCOMP_RET_DATA 0x0000ffffU /* mask for return value */
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struct seccomp_data {
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int nr;
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__u32 arch;
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__u64 instruction_pointer;
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__u64 args[6];
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};
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#define syscall_nr (offsetof(struct seccomp_data, nr))
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#define arch_nr (offsetof(struct seccomp_data, arch))
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/* Size-dependent defines. */
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#if defined(BITS32)
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/*
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* On 32 bits, comparisons take 2 instructions: 1 for loading the argument,
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* 1 for the actual comparison.
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*/
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#define BPF_LOAD_ARG_LEN 1U
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#define BPF_COMP_LEN 1U
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#define BPF_SHORT_GT_GE_COMP_LEN 1U
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#define BPF_GT_GE_COMP_LEN 1U
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#define BPF_ARG_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_COMP_LEN)
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#define BPF_ARG_SHORT_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_SHORT_GT_GE_COMP_LEN)
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#define BPF_ARG_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_GT_GE_COMP_LEN)
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#define bpf_comp_jeq bpf_comp_jeq32
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#define bpf_comp_jgt bpf_comp_jgt32
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#define bpf_comp_jge bpf_comp_jge32
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#define bpf_comp_jset bpf_comp_jset32
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#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
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#elif defined(BITS64)
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/*
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* On 64 bits, comparisons take 7-8 instructions: 4 for loading the argument,
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* and 3-4 for the actual comparison.
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*/
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#define BPF_LOAD_ARG_LEN 4U
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#define BPF_COMP_LEN 3U
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#define BPF_SHORT_GT_GE_COMP_LEN 3U
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#define BPF_GT_GE_COMP_LEN 4U
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#define BPF_ARG_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_COMP_LEN)
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#define BPF_ARG_SHORT_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_SHORT_GT_GE_COMP_LEN)
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#define BPF_ARG_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_GT_GE_COMP_LEN)
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#define bpf_comp_jeq bpf_comp_jeq64
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#define bpf_comp_jgt bpf_comp_jgt64
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#define bpf_comp_jge bpf_comp_jge64
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#define bpf_comp_jset bpf_comp_jset64
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/* Ensure that we load the logically correct offset. */
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#if defined(__LITTLE_ENDIAN__) || __BYTE_ORDER == __LITTLE_ENDIAN
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#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
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#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
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#else
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#error "Unsupported endianness"
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#endif
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#else
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#error "Unknown bit width"
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#endif
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/* Common jump targets. */
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#define NEXT 0
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#define SKIP 1
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#define SKIPN(_n) (_n)
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/* Support for labels in BPF programs. */
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#define JUMP_JT 0xff
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#define JUMP_JF 0xff
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#define LABEL_JT 0xfe
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#define LABEL_JF 0xfe
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#define MAX_BPF_LABEL_LEN 32
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#define BPF_LABELS_MAX 512U /* Each syscall could have an argument block. */
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struct bpf_labels {
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size_t count;
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struct __bpf_label {
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const char *label;
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unsigned int location;
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} labels[BPF_LABELS_MAX];
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};
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/* BPF instruction manipulation functions and macros. */
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static inline size_t set_bpf_instr(struct sock_filter *instr,
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unsigned short code, unsigned int k,
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unsigned char jt, unsigned char jf)
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{
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instr->code = code;
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instr->k = k;
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instr->jt = jt;
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instr->jf = jf;
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return 1U;
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}
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#define set_bpf_stmt(_block, _code, _k) \
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set_bpf_instr((_block), (_code), (_k), 0, 0)
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#define set_bpf_jump(_block, _code, _k, _jt, _jf) \
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set_bpf_instr((_block), (_code), (_k), (_jt), (_jf))
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#define set_bpf_lbl(_block, _lbl_id) \
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set_bpf_jump((_block), BPF_JMP+BPF_JA, (_lbl_id), \
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LABEL_JT, LABEL_JF)
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#define set_bpf_jump_lbl(_block, _lbl_id) \
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set_bpf_jump((_block), BPF_JMP+BPF_JA, (_lbl_id), \
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JUMP_JT, JUMP_JF)
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#define set_bpf_ret_kill(_block) \
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set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_KILL)
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#define set_bpf_ret_kill_process(_block) \
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set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_KILL_PROCESS)
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#define set_bpf_ret_trap(_block) \
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set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_TRAP)
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#define set_bpf_ret_errno(_block, _errno) \
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set_bpf_stmt((_block), BPF_RET+BPF_K, \
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SECCOMP_RET_ERRNO | ((_errno) & SECCOMP_RET_DATA))
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#define set_bpf_ret_log(_block) \
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set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_LOG)
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#define set_bpf_ret_allow(_block) \
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set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
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#define bpf_load_syscall_nr(_filter) \
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set_bpf_stmt((_filter), BPF_LD+BPF_W+BPF_ABS, syscall_nr)
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/* BPF label functions. */
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int bpf_resolve_jumps(struct bpf_labels *labels,
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struct sock_filter *filter, size_t count);
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int bpf_label_id(struct bpf_labels *labels, const char *label);
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void free_label_strings(struct bpf_labels *labels);
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/* BPF helper functions. */
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size_t bpf_load_arg(struct sock_filter *filter, int argidx);
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size_t bpf_comp_jeq(struct sock_filter *filter, unsigned long c,
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unsigned char jt, unsigned char jf);
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size_t bpf_comp_jgt(struct sock_filter *filter, unsigned long c,
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unsigned char jt, unsigned char jf);
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size_t bpf_comp_jge(struct sock_filter *filter, unsigned long c,
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unsigned char jt, unsigned char jf);
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size_t bpf_comp_jset(struct sock_filter *filter, unsigned long mask,
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unsigned char jt, unsigned char jf);
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size_t bpf_comp_jin(struct sock_filter *filter, unsigned long mask,
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unsigned char jt, unsigned char jf);
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/* Functions called by syscall_filter.c */
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#define ARCH_VALIDATION_LEN 3U
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#define ALLOW_SYSCALL_LEN 2U
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size_t bpf_arg_comp(struct sock_filter **pfilter,
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int op, int argidx, unsigned long c, unsigned int label_id);
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size_t bpf_validate_arch(struct sock_filter *filter);
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size_t bpf_allow_syscall(struct sock_filter *filter, int nr);
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size_t bpf_allow_syscall_args(struct sock_filter *filter,
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int nr, unsigned int id);
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#ifdef __cplusplus
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}; /* extern "C" */
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#endif
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#endif /* BPF_H */
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