From 19d436268dde95389c616bb3819da73f0a8b28a8 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Sat, 25 Feb 2017 08:56:53 +0100
Subject: debug: Add _ONCE() logic to report_bug()

Josh suggested moving the _ONCE logic inside the trap handler, using a
bit in the bug_entry::flags field, avoiding the need for the extra
variable.

Sadly this only works for WARN_ON_ONCE(), since the others have
printk() statements prior to triggering the trap.

Still, this saves a fair amount of text and some data:

  text         data       filename
  10682460     4530992    defconfig-build/vmlinux.orig
  10665111     4530096    defconfig-build/vmlinux.patched

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/asm-generic/bug.h         | 18 +++++++++++++++++-
 include/asm-generic/vmlinux.lds.h |  5 ++---
 2 files changed, 19 insertions(+), 4 deletions(-)

(limited to 'include/asm-generic')

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 6f96247226a4..5fe9f39cec44 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -5,6 +5,8 @@
 
 #ifdef CONFIG_GENERIC_BUG
 #define BUGFLAG_WARNING		(1 << 0)
+#define BUGFLAG_ONCE		(1 << 1)
+#define BUGFLAG_DONE		(1 << 2)
 #define BUGFLAG_TAINT(taint)	(BUGFLAG_WARNING | ((taint) << 8))
 #define BUG_GET_TAINT(bug)	((bug)->flags >> 8)
 #endif
@@ -55,6 +57,18 @@ struct bug_entry {
 #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
 #endif
 
+#ifdef __WARN_FLAGS
+#define __WARN_TAINT(taint)		__WARN_FLAGS(BUGFLAG_TAINT(taint))
+#define __WARN_ONCE_TAINT(taint)	__WARN_FLAGS(BUGFLAG_ONCE|BUGFLAG_TAINT(taint))
+
+#define WARN_ON_ONCE(condition) ({				\
+	int __ret_warn_on = !!(condition);			\
+	if (unlikely(__ret_warn_on))				\
+		__WARN_ONCE_TAINT(TAINT_WARN);			\
+	unlikely(__ret_warn_on);				\
+})
+#endif
+
 /*
  * WARN(), WARN_ON(), WARN_ON_ONCE, and so on can be used to report
  * significant issues that need prompt attention if they should ever
@@ -97,7 +111,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 #endif
 
 #ifndef WARN
-#define WARN(condition, format...) ({						\
+#define WARN(condition, format...) ({					\
 	int __ret_warn_on = !!(condition);				\
 	if (unlikely(__ret_warn_on))					\
 		__WARN_printf(format);					\
@@ -112,6 +126,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 	unlikely(__ret_warn_on);					\
 })
 
+#ifndef WARN_ON_ONCE
 #define WARN_ON_ONCE(condition)	({				\
 	static bool __section(.data.unlikely) __warned;		\
 	int __ret_warn_once = !!(condition);			\
@@ -122,6 +137,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 	}							\
 	unlikely(__ret_warn_once);				\
 })
+#endif
 
 #define WARN_ONCE(condition, format...)	({			\
 	static bool __section(.data.unlikely) __warned;		\
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 0968d13b3885..51c8dbe8e8d9 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -286,8 +286,6 @@
 		*(.rodata1)						\
 	}								\
 									\
-	BUG_TABLE							\
-									\
 	/* PCI quirks */						\
 	.pci_fixup        : AT(ADDR(.pci_fixup) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start_pci_fixups_early) = .;		\
@@ -855,7 +853,8 @@
 		READ_MOSTLY_DATA(cacheline)				\
 		DATA_DATA						\
 		CONSTRUCTORS						\
-	}
+	}								\
+	BUG_TABLE
 
 #define INIT_TEXT_SECTION(inittext_align)				\
 	. = ALIGN(inittext_align);					\
-- 
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