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x86/cpu: Make alternative_msr_write work for 32-bit code
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1/* Copyright (c) 2015 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7#include <linux/ptrace.h>
8#include <linux/version.h>
9#include <uapi/linux/bpf.h>
10#include <uapi/linux/seccomp.h>
af392a8f 11#include <uapi/linux/unistd.h>
4b7190e8 12#include "syscall_nrs.h"
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13#include "bpf_helpers.h"
14
15#define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
16
17struct bpf_map_def SEC("maps") progs = {
18 .type = BPF_MAP_TYPE_PROG_ARRAY,
19 .key_size = sizeof(u32),
20 .value_size = sizeof(u32),
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21#ifdef __mips__
22 .max_entries = 6000, /* MIPS n64 syscalls start at 5000 */
23#else
5bacd780 24 .max_entries = 1024,
4b7190e8 25#endif
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26};
27
973d94d8 28SEC("kprobe/__seccomp_filter")
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29int bpf_prog1(struct pt_regs *ctx)
30{
973d94d8 31 int sc_nr = (int)PT_REGS_PARM1(ctx);
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32
33 /* dispatch into next BPF program depending on syscall number */
973d94d8 34 bpf_tail_call(ctx, &progs, sc_nr);
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35
36 /* fall through -> unknown syscall */
973d94d8 37 if (sc_nr >= __NR_getuid && sc_nr <= __NR_getsid) {
5bacd780 38 char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
973d94d8 39 bpf_trace_printk(fmt, sizeof(fmt), sc_nr);
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40 }
41 return 0;
42}
43
44/* we jump here when syscall number == __NR_write */
4b7190e8 45PROG(SYS__NR_write)(struct pt_regs *ctx)
5bacd780 46{
02413cab 47 struct seccomp_data sd;
5bacd780 48
973d94d8 49 bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
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50 if (sd.args[2] == 512) {
51 char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
52 bpf_trace_printk(fmt, sizeof(fmt),
53 sd.args[0], sd.args[1], sd.args[2]);
54 }
55 return 0;
56}
57
4b7190e8 58PROG(SYS__NR_read)(struct pt_regs *ctx)
5bacd780 59{
02413cab 60 struct seccomp_data sd;
5bacd780 61
973d94d8 62 bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
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63 if (sd.args[2] > 128 && sd.args[2] <= 1024) {
64 char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
65 bpf_trace_printk(fmt, sizeof(fmt),
66 sd.args[0], sd.args[1], sd.args[2]);
67 }
68 return 0;
69}
70
4b7190e8 71PROG(SYS__NR_mmap)(struct pt_regs *ctx)
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72{
73 char fmt[] = "mmap\n";
74 bpf_trace_printk(fmt, sizeof(fmt));
75 return 0;
76}
77
78char _license[] SEC("license") = "GPL";
79u32 _version SEC("version") = LINUX_VERSION_CODE;