Merge branch 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 stackdump update from Ingo Molnar:
 "A number of stackdump enhancements"

* 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/dumpstack: Add show_stack_regs() and use it
  printk: Make the printk*once() variants return a value
  x86/dumpstack: Honor supplied @regs arg

arch/x86/include/asm/kdebug.h

@@ -26,6 +26,7 @@ extern void die(const char *, struct pt_regs *,long);
 extern int __must_check __die(const char *, struct pt_regs *, long);
 extern void show_trace(struct task_struct *t, struct pt_regs *regs,
 		       unsigned long *sp, unsigned long bp);
+extern void show_stack_regs(struct pt_regs *regs);
 extern void __show_regs(struct pt_regs *regs, int all);
 extern unsigned long oops_begin(void);
 extern void oops_end(unsigned long, struct pt_regs *, int signr);

arch/x86/kernel/dumpstack.c

@@ -205,6 +205,11 @@ void show_stack(struct task_struct *task, unsigned long *sp)
 	show_stack_log_lvl(task, NULL, sp, bp, "");
 }
 
+void show_stack_regs(struct pt_regs *regs)
+{
+	show_stack_log_lvl(current, regs, (unsigned long *)regs->sp, regs->bp, "");
+}
+
 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
 static int die_owner = -1;
 static unsigned int die_nest_count;

arch/x86/kernel/dumpstack_32.c

@@ -96,7 +96,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 	int i;
 
 	if (sp == NULL) {
-		if (task)
+		if (regs)
+			sp = (unsigned long *)regs->sp;
+		else if (task)
 			sp = (unsigned long *)task->thread.sp;
 		else
 			sp = (unsigned long *)&sp;

arch/x86/kernel/dumpstack_64.c

@@ -264,7 +264,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 	 * back trace for this cpu:
 	 */
 	if (sp == NULL) {
-		if (task)
+		if (regs)
+			sp = (unsigned long *)regs->sp;
+		else if (task)
 			sp = (unsigned long *)task->thread.sp;
 		else
 			sp = (unsigned long *)&sp;

arch/x86/mm/extable.c

@@ -1,6 +1,7 @@
 #include <linux/module.h>
 #include <asm/uaccess.h>
 #include <asm/traps.h>
+#include <asm/kdebug.h>
 
 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
 			    struct pt_regs *, int);
@@ -46,8 +47,9 @@ EXPORT_SYMBOL(ex_handler_ext);
 bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
 			     struct pt_regs *regs, int trapnr)
 {
-	WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x\n",
-		  (unsigned int)regs->cx);
+	if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pF)\n",
+			 (unsigned int)regs->cx, regs->ip, (void *)regs->ip))
+		show_stack_regs(regs);
 
 	/* Pretend that the read succeeded and returned 0. */
 	regs->ip = ex_fixup_addr(fixup);
@@ -60,9 +62,10 @@ EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
 bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
 			     struct pt_regs *regs, int trapnr)
 {
-	WARN_ONCE(1, "unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x)\n",
-		  (unsigned int)regs->cx,
-		  (unsigned int)regs->dx, (unsigned int)regs->ax);
+	if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pF)\n",
+			 (unsigned int)regs->cx, (unsigned int)regs->dx,
+			 (unsigned int)regs->ax,  regs->ip, (void *)regs->ip))
+		show_stack_regs(regs);
 
 	/* Pretend that the write succeeded. */
 	regs->ip = ex_fixup_addr(fixup);

include/linux/printk.h

@@ -108,11 +108,14 @@ struct va_format {
  * Dummy printk for disabled debugging statements to use whilst maintaining
  * gcc's format checking.
  */
-#define no_printk(fmt, ...)			\
-do {						\
-	if (0)					\
-		printk(fmt, ##__VA_ARGS__);	\
-} while (0)
+#define no_printk(fmt, ...)				\
+({							\
+	do {						\
+		if (0)					\
+			printk(fmt, ##__VA_ARGS__);	\
+	} while (0);					\
+	0;						\
+})
 
 #ifdef CONFIG_EARLY_PRINTK
 extern asmlinkage __printf(1, 2)
@@ -309,20 +312,24 @@ extern asmlinkage void dump_stack(void) __cold;
 #define printk_once(fmt, ...)					\
 ({								\
 	static bool __print_once __read_mostly;			\
+	bool __ret_print_once = !__print_once;			\
 								\
 	if (!__print_once) {					\
 		__print_once = true;				\
 		printk(fmt, ##__VA_ARGS__);			\
 	}							\
+	unlikely(__ret_print_once);				\
 })
 #define printk_deferred_once(fmt, ...)				\
 ({								\
 	static bool __print_once __read_mostly;			\
+	bool __ret_print_once = !__print_once;			\
 								\
 	if (!__print_once) {					\
 		__print_once = true;				\
 		printk_deferred(fmt, ##__VA_ARGS__);		\
 	}							\
+	unlikely(__ret_print_once);				\
 })
 #else
 #define printk_once(fmt, ...)					\