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