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