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37 lines
2.5 KiB
C
37 lines
2.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2024 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/intrin/iscall.h"
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// returns true if `p` is preceded by x86 call instruction
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// this is actually impossible to do but we'll do our best
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privileged dontinstrument int __is_call(const unsigned char *p) {
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if (p[-5] == 0xe8)
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return 5; // call Jvds
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if (p[-2] == 0xff && (p[-1] & 070) == 020)
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return 2; // call %reg
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if (p[-4] == 0xff && (p[-3] & 070) == 020)
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return 4; // call disp8(%reg,%reg)
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if (p[-3] == 0xff && (p[-2] & 070) == 020)
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return 3; // call disp8(%reg)
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if (p[-7] == 0xff && (p[-6] & 070) == 020)
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return 7; // call disp32(%reg,%reg)
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if (p[-6] == 0xff && (p[-5] & 070) == 020)
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return 6; // call disp32(%reg)
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return 0;
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}
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