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Diffstat (limited to 'samples/seccomp/bpf-helper.h')
| -rw-r--r-- | samples/seccomp/bpf-helper.h | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h new file mode 100644 index 000000000..38ee70f3c --- /dev/null +++ b/samples/seccomp/bpf-helper.h @@ -0,0 +1,243 @@ +/* + * Example wrapper around BPF macros. + * + * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org> + * Author: Will Drewry <wad@chromium.org> + * + * The code may be used by anyone for any purpose, + * and can serve as a starting point for developing + * applications using prctl(PR_SET_SECCOMP, 2, ...). + * + * No guarantees are provided with respect to the correctness + * or functionality of this code. + */ +#ifndef __BPF_HELPER_H__ +#define __BPF_HELPER_H__ + +#include <asm/bitsperlong.h> /* for __BITS_PER_LONG */ +#include <endian.h> +#include <linux/filter.h> +#include <linux/seccomp.h> /* for seccomp_data */ +#include <linux/types.h> +#include <linux/unistd.h> +#include <stddef.h> + +#define BPF_LABELS_MAX 256 +struct bpf_labels { + int count; + struct __bpf_label { + const char *label; + __u32 location; + } labels[BPF_LABELS_MAX]; +}; + +int bpf_resolve_jumps(struct bpf_labels *labels, + struct sock_filter *filter, size_t count); +__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label); +void seccomp_bpf_print(struct sock_filter *filter, size_t count); + +#define JUMP_JT 0xff +#define JUMP_JF 0xff +#define LABEL_JT 0xfe +#define LABEL_JF 0xfe + +#define ALLOW \ + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW) +#define DENY \ + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL) +#define JUMP(labels, label) \ + BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ + JUMP_JT, JUMP_JF) +#define LABEL(labels, label) \ + BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ + LABEL_JT, LABEL_JF) +#define SYSCALL(nr, jt) \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \ + jt + +/* Lame, but just an example */ +#define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label) + +#define EXPAND(...) __VA_ARGS__ + +/* Ensure that we load the logically correct offset. */ +#if __BYTE_ORDER == __LITTLE_ENDIAN +#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) +#elif __BYTE_ORDER == __BIG_ENDIAN +#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) +#else +#error "Unknown endianness" +#endif + +/* Map all width-sensitive operations */ +#if __BITS_PER_LONG == 32 + +#define JEQ(x, jt) JEQ32(x, EXPAND(jt)) +#define JNE(x, jt) JNE32(x, EXPAND(jt)) +#define JGT(x, jt) JGT32(x, EXPAND(jt)) +#define JLT(x, jt) JLT32(x, EXPAND(jt)) +#define JGE(x, jt) JGE32(x, EXPAND(jt)) +#define JLE(x, jt) JLE32(x, EXPAND(jt)) +#define JA(x, jt) JA32(x, EXPAND(jt)) +#define ARG(i) ARG_32(i) + +#elif __BITS_PER_LONG == 64 + +/* Ensure that we load the logically correct offset. */ +#if __BYTE_ORDER == __LITTLE_ENDIAN +#define ENDIAN(_lo, _hi) _lo, _hi +#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) +#elif __BYTE_ORDER == __BIG_ENDIAN +#define ENDIAN(_lo, _hi) _hi, _lo +#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) +#endif + +union arg64 { + struct { + __u32 ENDIAN(lo32, hi32); + }; + __u64 u64; +}; + +#define JEQ(x, jt) \ + JEQ64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) +#define JGT(x, jt) \ + JGT64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) +#define JGE(x, jt) \ + JGE64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) +#define JNE(x, jt) \ + JNE64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) +#define JLT(x, jt) \ + JLT64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) +#define JLE(x, jt) \ + JLE64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) + +#define JA(x, jt) \ + JA64(((union arg64){.u64 = (x)}).lo32, \ + ((union arg64){.u64 = (x)}).hi32, \ + EXPAND(jt)) +#define ARG(i) ARG_64(i) + +#else +#error __BITS_PER_LONG value unusable. +#endif + +/* Loads the arg into A */ +#define ARG_32(idx) \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)) + +/* Loads hi into A and lo in X */ +#define ARG_64(idx) \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \ + BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \ + BPF_STMT(BPF_ST, 1) /* hi -> M[1] */ + +#define JEQ32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \ + jt + +#define JNE32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \ + jt + +/* Checks the lo, then swaps to check the hi. A=lo,X=hi */ +#define JEQ64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define JNE64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define JA32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \ + jt + +#define JA64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define JGE32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \ + jt + +#define JLT32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \ + jt + +/* Shortcut checking if hi > arg.hi. */ +#define JGE64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define JLT64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define JGT32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \ + jt + +#define JLE32(value, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \ + jt + +/* Check hi > args.hi first, then do the GE checking */ +#define JGT64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define JLE64(lo, hi, jt) \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \ + BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ + BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ + jt, \ + BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ + +#define LOAD_SYSCALL_NR \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ + offsetof(struct seccomp_data, nr)) + +#endif /* __BPF_HELPER_H__ */ |