239 lines
5.9 KiB
C
239 lines
5.9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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Generic support for BUG()
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This respects the following config options:
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CONFIG_BUG - emit BUG traps. Nothing happens without this.
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CONFIG_GENERIC_BUG - enable this code.
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CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
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the containing struct bug_entry for bug_addr and file.
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CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
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CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
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(though they're generally always on).
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CONFIG_GENERIC_BUG is set by each architecture using this code.
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To use this, your architecture must:
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1. Set up the config options:
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- Enable CONFIG_GENERIC_BUG if CONFIG_BUG
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2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
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- Define HAVE_ARCH_BUG
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- Implement BUG() to generate a faulting instruction
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- NOTE: struct bug_entry does not have "file" or "line" entries
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when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
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the values accordingly.
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3. Implement the trap
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- In the illegal instruction trap handler (typically), verify
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that the fault was in kernel mode, and call report_bug()
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- report_bug() will return whether it was a false alarm, a warning,
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or an actual bug.
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- You must implement the is_valid_bugaddr(bugaddr) callback which
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returns true if the eip is a real kernel address, and it points
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to the expected BUG trap instruction.
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Jeremy Fitzhardinge <jeremy@goop.org> 2006
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*/
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#define pr_fmt(fmt) fmt
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#include <linux/list.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/bug.h>
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#include <linux/sched.h>
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#include <linux/rculist.h>
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#ifdef CONFIG_SEC_DEBUG
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#include <linux/sec_debug.h>
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#endif
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extern struct bug_entry __start___bug_table[], __stop___bug_table[];
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static inline unsigned long bug_addr(const struct bug_entry *bug)
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{
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#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
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return bug->bug_addr;
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#else
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return (unsigned long)bug + bug->bug_addr_disp;
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#endif
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}
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#ifdef CONFIG_MODULES
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/* Updates are protected by module mutex */
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static LIST_HEAD(module_bug_list);
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static struct bug_entry *module_find_bug(unsigned long bugaddr)
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{
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struct module *mod;
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struct bug_entry *bug = NULL;
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rcu_read_lock_sched();
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list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
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unsigned i;
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bug = mod->bug_table;
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for (i = 0; i < mod->num_bugs; ++i, ++bug)
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if (bugaddr == bug_addr(bug))
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goto out;
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}
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bug = NULL;
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out:
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rcu_read_unlock_sched();
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return bug;
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}
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void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
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struct module *mod)
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{
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char *secstrings;
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unsigned int i;
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lockdep_assert_held(&module_mutex);
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mod->bug_table = NULL;
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mod->num_bugs = 0;
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/* Find the __bug_table section, if present */
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secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
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for (i = 1; i < hdr->e_shnum; i++) {
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if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
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continue;
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mod->bug_table = (void *) sechdrs[i].sh_addr;
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mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
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break;
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}
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/*
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* Strictly speaking this should have a spinlock to protect against
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* traversals, but since we only traverse on BUG()s, a spinlock
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* could potentially lead to deadlock and thus be counter-productive.
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* Thus, this uses RCU to safely manipulate the bug list, since BUG
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* must run in non-interruptive state.
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*/
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list_add_rcu(&mod->bug_list, &module_bug_list);
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}
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void module_bug_cleanup(struct module *mod)
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{
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lockdep_assert_held(&module_mutex);
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list_del_rcu(&mod->bug_list);
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}
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#else
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static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
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{
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return NULL;
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}
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#endif
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struct bug_entry *find_bug(unsigned long bugaddr)
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{
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struct bug_entry *bug;
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for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
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if (bugaddr == bug_addr(bug))
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return bug;
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return module_find_bug(bugaddr);
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}
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enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
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{
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struct bug_entry *bug;
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const char *file;
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unsigned line, warning, once, done;
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if (!is_valid_bugaddr(bugaddr))
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return BUG_TRAP_TYPE_NONE;
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bug = find_bug(bugaddr);
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if (!bug)
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return BUG_TRAP_TYPE_NONE;
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file = NULL;
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line = 0;
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#ifdef CONFIG_DEBUG_BUGVERBOSE
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#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
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file = bug->file;
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#else
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file = (const char *)bug + bug->file_disp;
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#endif
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line = bug->line;
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#endif
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warning = (bug->flags & BUGFLAG_WARNING) != 0;
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once = (bug->flags & BUGFLAG_ONCE) != 0;
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done = (bug->flags & BUGFLAG_DONE) != 0;
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if (warning && once) {
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if (done)
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return BUG_TRAP_TYPE_WARN;
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/*
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* Since this is the only store, concurrency is not an issue.
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*/
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bug->flags |= BUGFLAG_DONE;
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}
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if (warning) {
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/* this is a WARN_ON rather than BUG/BUG_ON */
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__warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
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NULL);
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return BUG_TRAP_TYPE_WARN;
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}
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printk(KERN_DEFAULT CUT_HERE);
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#ifdef CONFIG_SEC_DEBUG_EXTRA_INFO
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if (file)
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sec_debug_set_extra_info_bug(file, line);
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else
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sec_debug_set_extra_info_bug_verbose(bugaddr);
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#endif
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#ifdef CONFIG_SEC_DEBUG_AUTO_COMMENT
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if (file)
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pr_auto(ASL1, "kernel BUG at %s:%u!\n", file, line);
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else
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pr_auto(ASL1, "Kernel BUG at %p [verbose debug info unavailable]\n",
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(void *)bugaddr);
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#else
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if (file)
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pr_crit("kernel BUG at %s:%u!\n", file, line);
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else
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pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n",
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(void *)bugaddr);
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#endif
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return BUG_TRAP_TYPE_BUG;
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}
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static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
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{
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struct bug_entry *bug;
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for (bug = start; bug < end; bug++)
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bug->flags &= ~BUGFLAG_DONE;
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}
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void generic_bug_clear_once(void)
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{
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#ifdef CONFIG_MODULES
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struct module *mod;
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rcu_read_lock_sched();
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list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
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clear_once_table(mod->bug_table,
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mod->bug_table + mod->num_bugs);
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rcu_read_unlock_sched();
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#endif
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clear_once_table(__start___bug_table, __stop___bug_table);
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}
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