1 files changed, 246 insertions, 0 deletions
diff --git a/lib/bug.c b/lib/bug.c
new file mode 100644
index 0000000000..e0ff219899
--- /dev/null
+++ b/lib/bug.c
@@ -0,0 +1,246 @@
+// 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 relative pointers 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>
+#include <linux/ftrace.h>
+#include <linux/context_tracking.h>
+
+extern struct bug_entry __start___bug_table[], __stop___bug_table[];
+
+static inline unsigned long bug_addr(const struct bug_entry *bug)
+{
+#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+	return (unsigned long)&bug->bug_addr_disp + bug->bug_addr_disp;
+#else
+	return bug->bug_addr;
+#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;
+
+	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)
+{
+	list_del_rcu(&mod->bug_list);
+}
+
+#else
+
+static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
+{
+	return NULL;
+}
+#endif
+
+void bug_get_file_line(struct bug_entry *bug, const char **file,
+		       unsigned int *line)
+{
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+	*file = (const char *)&bug->file_disp + bug->file_disp;
+#else
+	*file = bug->file;
+#endif
+	*line = bug->line;
+#else
+	*file = NULL;
+	*line = 0;
+#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);
+}
+
+static 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;
+
+	disable_trace_on_warning();
+
+	bug_get_file_line(bug, &file, &line);
+
+	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;
+	}
+
+	/*
+	 * BUG() and WARN_ON() families don't print a custom debug message
+	 * before triggering the exception handler, so we must add the
+	 * "cut here" line now. WARN() issues its own "cut here" before the
+	 * extra debugging message it writes before triggering the handler.
+	 */
+	if ((bug->flags & BUGFLAG_NO_CUT_HERE) == 0)
+		printk(KERN_DEFAULT CUT_HERE);
+
+	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;
+	}
+
+	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;
+}
+
+enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
+{
+	enum bug_trap_type ret;
+	bool rcu = false;
+
+	rcu = warn_rcu_enter();
+	ret = __report_bug(bugaddr, regs);
+	warn_rcu_exit(rcu);
+
+	return ret;
+}
+
+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);
+}