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