v4.19.13 snapshot.
diff --git a/lib/bug.c b/lib/bug.c
new file mode 100644
index 0000000..1077366
--- /dev/null
+++ b/lib/bug.c
@@ -0,0 +1,223 @@
+// 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;
+ 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;
+ 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);
+}