1 files changed, 138 insertions, 57 deletions

diff --git a/lib/bug.c b/lib/bug.c
index 1077366f496b..edd9041f89f3 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -6,8 +6,7 @@
 
   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_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
@@ -47,15 +46,17 @@
 #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)
 {
-#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
-	return bug->bug_addr;
+#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+	return (unsigned long)&bug->bug_addr_disp + bug->bug_addr_disp;
 #else
-	return (unsigned long)bug + bug->bug_addr_disp;
+	return bug->bug_addr;
 #endif
 }
 
@@ -65,23 +66,19 @@ static LIST_HEAD(module_bug_list);
 
 static struct bug_entry *module_find_bug(unsigned long bugaddr)
 {
+	struct bug_entry *bug;
 	struct module *mod;
-	struct bug_entry *bug = NULL;
 
-	rcu_read_lock_sched();
+	guard(rcu)();
 	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;
+				return bug;
 	}
-	bug = NULL;
-out:
-	rcu_read_unlock_sched();
-
-	return bug;
+	return NULL;
 }
 
 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
@@ -90,8 +87,6 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 	char *secstrings;
 	unsigned int i;
 
-	lockdep_assert_held(&module_mutex);
-
 	mod->bug_table = NULL;
 	mod->num_bugs = 0;
 
@@ -117,7 +112,6 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 
 void module_bug_cleanup(struct module *mod)
 {
-	lockdep_assert_held(&module_mutex);
 	list_del_rcu(&mod->bug_list);
 }
 
@@ -129,6 +123,45 @@ static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
 }
 #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
+}
+
+static const char *bug_get_format(struct bug_entry *bug)
+{
+	const char *format = NULL;
+#ifdef HAVE_ARCH_BUG_FORMAT
+#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+	/*
+	 * Allow an architecture to:
+	 *  - relative encode NULL (difficult vs KASLR);
+	 *  - use a literal 0 (there are no valid objects inside
+	 *    the __bug_table itself to refer to after all);
+	 *  - use an empty string.
+	 */
+	if (bug->format_disp)
+		format = (const char *)&bug->format_disp + bug->format_disp;
+	if (format && format[0] == '\0')
+		format = NULL;
+#else
+	format = bug->format;
+#endif
+#endif
+	return format;
+}
+
 struct bug_entry *find_bug(unsigned long bugaddr)
 {
 	struct bug_entry *bug;
@@ -140,45 +173,71 @@ struct bug_entry *find_bug(unsigned long bugaddr)
 	return module_find_bug(bugaddr);
 }
 
-enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
+static void __warn_printf(const char *fmt, struct pt_regs *regs)
 {
-	struct bug_entry *bug;
-	const char *file;
-	unsigned line, warning, once, done;
+	if (!fmt)
+		return;
 
-	if (!is_valid_bugaddr(bugaddr))
-		return BUG_TRAP_TYPE_NONE;
+#ifdef HAVE_ARCH_BUG_FORMAT_ARGS
+	if (regs) {
+		struct arch_va_list _args;
+		va_list *args = __warn_args(&_args, regs);
 
-	bug = find_bug(bugaddr);
-	if (!bug)
-		return BUG_TRAP_TYPE_NONE;
+		if (args) {
+			vprintk(fmt, *args);
+			return;
+		}
+	}
+#endif
 
-	file = NULL;
-	line = 0;
-	warning = 0;
+	printk("%s", fmt);
+}
 
-	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;
-		}
+static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long bugaddr, struct pt_regs *regs)
+{
+	bool warning, once, done, no_cut, has_args;
+	const char *file, *fmt;
+	unsigned line;
+
+	if (!bug) {
+		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);
+	fmt = bug_get_format(bug);
+
+	warning  = bug->flags & BUGFLAG_WARNING;
+	once     = bug->flags & BUGFLAG_ONCE;
+	done     = bug->flags & BUGFLAG_DONE;
+	no_cut   = bug->flags & BUGFLAG_NO_CUT_HERE;
+	has_args = bug->flags & BUGFLAG_ARGS;
+
+	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 (!no_cut) {
+		printk(KERN_DEFAULT CUT_HERE);
+		__warn_printf(fmt, has_args ? regs : NULL);
 	}
 
 	if (warning) {
@@ -188,8 +247,6 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 		return BUG_TRAP_TYPE_WARN;
 	}
 
-	printk(KERN_DEFAULT CUT_HERE);
-
 	if (file)
 		pr_crit("kernel BUG at %s:%u!\n", file, line);
 	else
@@ -199,6 +256,30 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 	return BUG_TRAP_TYPE_BUG;
 }
 
+enum bug_trap_type report_bug_entry(struct bug_entry *bug, struct pt_regs *regs)
+{
+	enum bug_trap_type ret;
+	bool rcu = false;
+
+	rcu = warn_rcu_enter();
+	ret = __report_bug(bug, 0, regs);
+	warn_rcu_exit(rcu);
+
+	return ret;
+}
+
+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(NULL, 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;
@@ -212,11 +293,11 @@ 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();
+	scoped_guard(rcu) {
+		list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
+			clear_once_table(mod->bug_table,
+					 mod->bug_table + mod->num_bugs);
+	}
 #endif
 
 	clear_once_table(__start___bug_table, __stop___bug_table);