/* 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 /* for __BITS_PER_LONG */ #include #include #include #include #include #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 */