1 | /****************************************************************************** |
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2 | * fixup.c |
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3 | * |
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4 | * Binary-rewriting of certain IA32 instructions, on notification by Xen. |
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5 | * Used to avoid repeated slow emulation of common instructions used by the |
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6 | * user-space TLS (Thread-Local Storage) libraries. |
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7 | * |
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8 | * **** NOTE **** |
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9 | * Issues with the binary rewriting have caused it to be removed. Instead |
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10 | * we rely on Xen's emulator to boot the kernel, and then print a banner |
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11 | * message recommending that the user disables /lib/tls. |
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12 | * |
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13 | * Copyright (c) 2004, K A Fraser |
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14 | * |
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15 | * This program is free software; you can redistribute it and/or modify |
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16 | * it under the terms of the GNU General Public License as published by |
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17 | * the Free Software Foundation; either version 2 of the License, or |
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18 | * (at your option) any later version. |
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19 | * |
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20 | * This program is distributed in the hope that it will be useful, |
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21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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23 | * GNU General Public License for more details. |
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24 | * |
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25 | * You should have received a copy of the GNU General Public License |
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26 | * along with this program; if not, write to the Free Software |
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27 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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28 | */ |
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29 | |
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30 | #include <linux/init.h> |
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31 | #include <linux/sched.h> |
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32 | #include <linux/slab.h> |
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33 | #include <linux/kernel.h> |
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34 | #include <linux/delay.h> |
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35 | #include <linux/version.h> |
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36 | |
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37 | #define DP(_f, _args...) printk(KERN_ALERT " " _f "\n" , ## _args ) |
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38 | |
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39 | fastcall void do_fixup_4gb_segment(struct pt_regs *regs, long error_code) |
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40 | { |
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41 | static unsigned long printed = 0; |
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42 | char info[100]; |
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43 | int i; |
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44 | |
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45 | /* Ignore statically-linked init. */ |
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46 | if (current->tgid == 1) |
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47 | return; |
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48 | |
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49 | HYPERVISOR_vm_assist( |
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50 | VMASST_CMD_disable, VMASST_TYPE_4gb_segments_notify); |
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51 | |
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52 | if (test_and_set_bit(0, &printed)) |
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53 | return; |
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54 | |
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55 | sprintf(info, "%s (pid=%d)", current->comm, current->tgid); |
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56 | |
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57 | DP(""); |
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58 | DP("***************************************************************"); |
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59 | DP("***************************************************************"); |
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60 | DP("** WARNING: Currently emulating unsupported memory accesses **"); |
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61 | DP("** in /lib/tls glibc libraries. The emulation is **"); |
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62 | DP("** slow. To ensure full performance you should **"); |
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63 | DP("** install a 'xen-friendly' (nosegneg) version of **"); |
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64 | DP("** the library, or disable tls support by executing **"); |
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65 | DP("** the following as root: **"); |
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66 | DP("** mv /lib/tls /lib/tls.disabled **"); |
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67 | DP("** Offending process: %-38.38s **", info); |
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68 | DP("***************************************************************"); |
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69 | DP("***************************************************************"); |
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70 | DP(""); |
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71 | |
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72 | for (i = 5; i > 0; i--) { |
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73 | touch_softlockup_watchdog(); |
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74 | printk("Pausing... %d", i); |
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75 | mdelay(1000); |
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76 | printk("\b\b\b\b\b\b\b\b\b\b\b\b"); |
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77 | } |
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78 | |
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79 | printk("Continuing...\n\n"); |
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80 | } |
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81 | |
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82 | static int __init fixup_init(void) |
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83 | { |
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84 | HYPERVISOR_vm_assist( |
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85 | VMASST_CMD_enable, VMASST_TYPE_4gb_segments_notify); |
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86 | return 0; |
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87 | } |
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88 | __initcall(fixup_init); |
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