diff options
Diffstat (limited to 'lib/bug.c')
| -rw-r--r-- | lib/bug.c | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/lib/bug.c b/lib/bug.c new file mode 100644 index 000000000..f4fcac5dd --- /dev/null +++ b/lib/bug.c @@ -0,0 +1,220 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + 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> +#include <linux/rculist.h> + +extern 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 struct bug_entry *module_find_bug(unsigned long bugaddr) +{ + struct module *mod; + 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 struct bug_entry *module_find_bug(unsigned long bugaddr) +{ + return NULL; +} +#endif + +struct bug_entry *find_bug(unsigned long bugaddr) +{ + 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) +{ + struct bug_entry *bug; + const char *file; + unsigned line, warning, once, done; + + if (!is_valid_bugaddr(bugaddr)) + return BUG_TRAP_TYPE_NONE; + + bug = find_bug(bugaddr); + if (!bug) + return BUG_TRAP_TYPE_NONE; + + file = NULL; + line = 0; + +#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; + once = (bug->flags & BUGFLAG_ONCE) != 0; + done = (bug->flags & BUGFLAG_DONE) != 0; + + if (warning && once) { + if (done) + return BUG_TRAP_TYPE_WARN; + + /* + * Since this is the only store, concurrency is not an issue. + */ + bug->flags |= BUGFLAG_DONE; + } + + 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); + + if (file) + pr_crit("kernel BUG at %s:%u!\n", file, line); + else + pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n", + (void *)bugaddr); + + return BUG_TRAP_TYPE_BUG; +} + +static void clear_once_table(struct bug_entry *start, struct bug_entry *end) +{ + struct bug_entry *bug; + + for (bug = start; bug < end; bug++) + bug->flags &= ~BUGFLAG_DONE; +} + +void generic_bug_clear_once(void) +{ +#ifdef CONFIG_MODULES + struct module *mod; + + rcu_read_lock_sched(); + list_for_each_entry_rcu(mod, &module_bug_list, bug_list) + clear_once_table(mod->bug_table, + mod->bug_table + mod->num_bugs); + rcu_read_unlock_sched(); +#endif + + clear_once_table(__start___bug_table, __stop___bug_table); +} |