| 1 | |
| 2 | Generic support for BUG()
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| 3 |
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| 4 | This respects the following config options:
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| 5 |
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| 6 | CONFIG_BUG - emit BUG traps. Nothing happens without this.
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| 7 | CONFIG_GENERIC_BUG - enable this code.
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| 8 | CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
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| 9 | the containing struct bug_entry for bug_addr and file.
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| 10 | CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
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| 11 |
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| 12 | CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
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| 13 | (though they're generally always on).
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| 14 |
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| 15 | CONFIG_GENERIC_BUG is set by each architecture using this code.
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| 16 |
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| 17 | To use this, your architecture must:
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| 18 |
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| 19 | 1. Set up the config options:
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| 20 | - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
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| 21 |
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| 22 | 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
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| 23 | - Define HAVE_ARCH_BUG
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| 24 | - Implement BUG() to generate a faulting instruction
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| 25 | - NOTE: struct bug_entry does not have "file" or "line" entries
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| 26 | when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
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| 27 | the values accordingly.
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| 28 |
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| 29 | 3. Implement the trap
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| 30 | - In the illegal instruction trap handler (typically), verify
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| 31 | that the fault was in kernel mode, and call report_bug()
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| 32 | - report_bug() will return whether it was a false alarm, a warning,
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| 33 | or an actual bug.
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| 34 | - You must implement the is_valid_bugaddr(bugaddr) callback which
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| 35 | returns true if the eip is a real kernel address, and it points
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| 36 | to the expected BUG trap instruction.
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| 37 |
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| 38 | Jeremy Fitzhardinge <[email protected]> 2006
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| 39 |
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| 40 | #include <linux/list.h>
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| 41 | #include <linux/module.h>
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| 42 | #include <linux/kernel.h>
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| 43 | #include <linux/bug.h>
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| 44 | #include <linux/sched.h>
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| 45 |
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| 46 | extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
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| 47 |
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| 48 | static inline unsigned long bug_addr(const struct bug_entry *bug)
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| 49 | {
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| 50 | #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
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| 51 | return bug->bug_addr;
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| 52 | #else
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| 53 | return (unsigned long)bug + bug->bug_addr_disp;
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| 54 | #endif
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| 55 | }
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| 56 |
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| 57 | #ifdef CONFIG_MODULES
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| 58 |
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| 59 | static LIST_HEAD(module_bug_list);
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| 60 |
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| 61 | static const struct bug_entry *module_find_bug(unsigned long bugaddr)
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| 62 | {
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| 63 | struct module *mod;
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| 64 |
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| 65 | list_for_each_entry(mod, &module_bug_list, bug_list) {
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| 66 | const struct bug_entry *bug = mod->bug_table;
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| 67 | unsigned i;
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| 68 |
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| 69 | for (i = 0; i < mod->num_bugs; ++i, ++bug)
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| 70 | if (bugaddr == bug_addr(bug))
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| 71 | return bug;
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| 72 | }
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| 73 | return NULL;
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| 74 | }
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| 75 |
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| 76 | void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
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| 77 | struct module *mod)
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| 78 | {
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| 79 | char *secstrings;
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| 80 | unsigned int i;
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| 81 |
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| 82 | mod->bug_table = NULL;
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| 83 | mod->num_bugs = 0;
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| 84 |
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| 85 |
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| 86 | secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
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| 87 | for (i = 1; i < hdr->e_shnum; i++) {
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| 88 | if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
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| 89 | continue;
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| 90 | mod->bug_table = (void *) sechdrs[i].sh_addr;
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| 91 | mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
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| 92 | break;
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| 93 | }
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| 94 |
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| 95 | |
| 96 | * Strictly speaking this should have a spinlock to protect against
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| 97 | * traversals, but since we only traverse on BUG()s, a spinlock
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| 98 | * could potentially lead to deadlock and thus be counter-productive.
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| 99 |
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| 100 | list_add(&mod->bug_list, &module_bug_list);
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| 101 | }
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| 102 |
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| 103 | void module_bug_cleanup(struct module *mod)
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| 104 | {
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| 105 | list_del(&mod->bug_list);
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| 106 | }
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| 107 |
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| 108 | #else
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| 109 |
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| 110 | static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
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| 111 | {
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| 112 | return NULL;
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| 113 | }
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| 114 | #endif
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| 115 |
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| 116 | const struct bug_entry *find_bug(unsigned long bugaddr)
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| 117 | {
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| 118 | const struct bug_entry *bug;
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| 119 |
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| 120 | for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
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| 121 | if (bugaddr == bug_addr(bug))
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| 122 | return bug;
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| 123 |
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| 124 | return module_find_bug(bugaddr);
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| 125 | }
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| 126 |
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| 127 | enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
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| 128 | {
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| 129 | const struct bug_entry *bug;
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| 130 | const char *file;
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| 131 | unsigned line, warning;
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| 132 |
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| 133 | if (!is_valid_bugaddr(bugaddr))
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| 134 | return BUG_TRAP_TYPE_NONE;
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| 135 |
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| 136 | bug = find_bug(bugaddr);
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| 137 |
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| 138 | file = NULL;
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| 139 | line = 0;
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| 140 | warning = 0;
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| 141 |
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| 142 | if (bug) {
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| 143 | #ifdef CONFIG_DEBUG_BUGVERBOSE
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| 144 | #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
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| 145 | file = bug->file;
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| 146 | #else
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| 147 | file = (const char *)bug + bug->file_disp;
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| 148 | #endif
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| 149 | line = bug->line;
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| 150 | #endif
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| 151 | warning = (bug->flags & BUGFLAG_WARNING) != 0;
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| 152 | }
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| 153 |
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| 154 | if (warning) {
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| 155 |
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| 156 | printk(KERN_WARNING "------------[ cut here ]------------\n");
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| 157 |
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| 158 | if (file)
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| 159 | printk(KERN_WARNING "WARNING: at %s:%u\n",
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| 160 | file, line);
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| 161 | else
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| 162 | printk(KERN_WARNING "WARNING: at %p "
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| 163 | "[verbose debug info unavailable]\n",
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| 164 | (void *)bugaddr);
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| 165 |
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| 166 | print_modules();
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| 167 | show_regs(regs);
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| 168 | print_oops_end_marker();
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| 169 |
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| 170 | add_taint(BUG_GET_TAINT(bug), LOCKDEP_STILL_OK);
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| 171 | return BUG_TRAP_TYPE_WARN;
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| 172 | }
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| 173 |
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| 174 | printk(KERN_DEFAULT "------------[ cut here ]------------\n");
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| 175 |
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| 176 | if (file)
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| 177 | printk(KERN_CRIT "kernel BUG at %s:%u!\n",
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| 178 | file, line);
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| 179 | else
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| 180 | printk(KERN_CRIT "Kernel BUG at %p "
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| 181 | "[verbose debug info unavailable]\n",
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| 182 | (void *)bugaddr);
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| 183 |
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| 184 | return BUG_TRAP_TYPE_BUG;
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| 185 | }
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