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- /*
- Generic support for BUG()
- This respects the following config options:
- CONFIG_BUG - emit BUG traps. Nothing happens without this.
- CONFIG_GENERIC_BUG - enable this code.
- CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
- the containing struct bug_entry for bug_addr and file.
- CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
- CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
- (though they're generally always on).
- CONFIG_GENERIC_BUG is set by each architecture using this code.
- To use this, your architecture must:
- 1. Set up the config options:
- - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
- 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
- - Define HAVE_ARCH_BUG
- - Implement BUG() to generate a faulting instruction
- - NOTE: struct bug_entry does not have "file" or "line" entries
- when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
- the values accordingly.
- 3. Implement the trap
- - In the illegal instruction trap handler (typically), verify
- that the fault was in kernel mode, and call report_bug()
- - report_bug() will return whether it was a false alarm, a warning,
- or an actual bug.
- - You must implement the is_valid_bugaddr(bugaddr) callback which
- returns true if the eip is a real kernel address, and it points
- to the expected BUG trap instruction.
- Jeremy Fitzhardinge <jeremy@goop.org> 2006
- */
- #define pr_fmt(fmt) fmt
- #include <linux/list.h>
- #include <linux/module.h>
- #include <linux/kernel.h>
- #include <linux/bug.h>
- #include <linux/sched.h>
- extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
- static inline unsigned long bug_addr(const struct bug_entry *bug)
- {
- #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
- return bug->bug_addr;
- #else
- return (unsigned long)bug + bug->bug_addr_disp;
- #endif
- }
- #ifdef CONFIG_MODULES
- /* Updates are protected by module mutex */
- static LIST_HEAD(module_bug_list);
- static const struct bug_entry *module_find_bug(unsigned long bugaddr)
- {
- struct module *mod;
- const struct bug_entry *bug = NULL;
- rcu_read_lock_sched();
- list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
- unsigned i;
- bug = mod->bug_table;
- for (i = 0; i < mod->num_bugs; ++i, ++bug)
- if (bugaddr == bug_addr(bug))
- goto out;
- }
- bug = NULL;
- out:
- rcu_read_unlock_sched();
- return bug;
- }
- void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
- struct module *mod)
- {
- char *secstrings;
- unsigned int i;
- lockdep_assert_held(&module_mutex);
- mod->bug_table = NULL;
- mod->num_bugs = 0;
- /* Find the __bug_table section, if present */
- secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
- for (i = 1; i < hdr->e_shnum; i++) {
- if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
- continue;
- mod->bug_table = (void *) sechdrs[i].sh_addr;
- mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
- break;
- }
- /*
- * Strictly speaking this should have a spinlock to protect against
- * traversals, but since we only traverse on BUG()s, a spinlock
- * could potentially lead to deadlock and thus be counter-productive.
- * Thus, this uses RCU to safely manipulate the bug list, since BUG
- * must run in non-interruptive state.
- */
- list_add_rcu(&mod->bug_list, &module_bug_list);
- }
- void module_bug_cleanup(struct module *mod)
- {
- lockdep_assert_held(&module_mutex);
- list_del_rcu(&mod->bug_list);
- }
- #else
- static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
- {
- return NULL;
- }
- #endif
- const struct bug_entry *find_bug(unsigned long bugaddr)
- {
- const struct bug_entry *bug;
- for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
- if (bugaddr == bug_addr(bug))
- return bug;
- return module_find_bug(bugaddr);
- }
- enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
- {
- const struct bug_entry *bug;
- const char *file;
- unsigned line, warning;
- if (!is_valid_bugaddr(bugaddr))
- return BUG_TRAP_TYPE_NONE;
- bug = find_bug(bugaddr);
- file = NULL;
- line = 0;
- warning = 0;
- if (bug) {
- #ifdef CONFIG_DEBUG_BUGVERBOSE
- #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
- file = bug->file;
- #else
- file = (const char *)bug + bug->file_disp;
- #endif
- line = bug->line;
- #endif
- warning = (bug->flags & BUGFLAG_WARNING) != 0;
- }
- if (warning) {
- /* this is a WARN_ON rather than BUG/BUG_ON */
- __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
- NULL);
- return BUG_TRAP_TYPE_WARN;
- }
- printk(KERN_DEFAULT "------------[ cut here ]------------\n");
- if (file)
- pr_crit("kernel BUG at %s:%u!\n", file, line);
- else
- pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n",
- (void *)bugaddr);
- return BUG_TRAP_TYPE_BUG;
- }
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