[PATCH] Generic BUG for i386

This makes i386 use the generic BUG machinery.  There are no functional
changes from the old i386 implementation.

The main advantage in using the generic BUG machinery for i386 is that the
inlined overhead of BUG is just the ud2a instruction; the file+line(+function)
information are no longer inlined into the instruction stream.  This reduces
cache pollution, and makes disassembly work properly.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Andi Kleen <ak@muc.de>
Cc: Hugh Dickens <hugh@veritas.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/Kconfig

@@ -49,6 +49,11 @@ config GENERIC_IOMAP
 	bool
 	default y
 
+config GENERIC_BUG
+	bool
+	default y
+	depends on BUG
+
 config GENERIC_HWEIGHT
 	bool
 	default y

arch/i386/kernel/module.c

@@ -21,6 +21,7 @@
 #include <linux/fs.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
+#include <linux/bug.h>
 
 #if 0
 #define DEBUGP printk
@@ -141,10 +142,11 @@ int module_finalize(const Elf_Ehdr *hdr,
 		apply_paravirt(pseg, pseg + para->sh_size);
 	}
 
-	return 0;
+	return module_bug_finalize(hdr, sechdrs, me);
 }
 
 void module_arch_cleanup(struct module *mod)
 {
 	alternatives_smp_module_del(mod);
+	module_bug_cleanup(mod);
 }

arch/i386/kernel/traps.c

@@ -30,6 +30,7 @@
 #include <linux/unwind.h>
 #include <linux/uaccess.h>
 #include <linux/nmi.h>
+#include <linux/bug.h>
 
 #ifdef CONFIG_EISA
 #include <linux/ioport.h>
@@ -420,43 +421,22 @@ void show_registers(struct pt_regs *regs)
 	printk("\n");
 }	
 
-static void handle_BUG(struct pt_regs *regs)
+int is_valid_bugaddr(unsigned long eip)
 {
-	unsigned long eip = regs->eip;
 	unsigned short ud2;
 
 	if (eip < PAGE_OFFSET)
-		return;
+		return 0;
 	if (probe_kernel_address((unsigned short *)eip, ud2))
-		return;
-	if (ud2 != 0x0b0f)
-		return;
-
-	printk(KERN_EMERG "------------[ cut here ]------------\n");
-
-#ifdef CONFIG_DEBUG_BUGVERBOSE
-	do {
-		unsigned short line;
-		char *file;
-		char c;
-
-		if (probe_kernel_address((unsigned short *)(eip + 2), line))
-			break;
-		if (probe_kernel_address((char **)(eip + 4), file) ||
-		    (unsigned long)file < PAGE_OFFSET ||
-			probe_kernel_address(file, c))
-			file = "<bad filename>";
+		return 0;
 
-		printk(KERN_EMERG "kernel BUG at %s:%d!\n", file, line);
-		return;
-	} while (0);
-#endif
-	printk(KERN_EMERG "Kernel BUG at [verbose debug info unavailable]\n");
+	return ud2 == 0x0b0f;
 }
 
-/* This is gone through when something in the kernel
- * has done something bad and is about to be terminated.
-*/
+/*
+ * This is gone through when something in the kernel has done something bad and
+ * is about to be terminated.
+ */
 void die(const char * str, struct pt_regs * regs, long err)
 {
 	static struct {
@@ -488,7 +468,8 @@ void die(const char * str, struct pt_regs * regs, long err)
 		unsigned long esp;
 		unsigned short ss;
 
-		handle_BUG(regs);
+		report_bug(regs->eip);
+
 		printk(KERN_EMERG "%s: %04lx [#%d]\n", str, err & 0xffff, ++die_counter);
 #ifdef CONFIG_PREEMPT
 		printk(KERN_EMERG "PREEMPT ");

arch/i386/kernel/vmlinux.lds.S

@@ -57,6 +57,8 @@ SECTIONS
 
   RODATA
 
+  BUG_TABLE
+
   . = ALIGN(4);
   .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) {
   	__tracedata_start = .;

include/asm-i386/bug.h

@@ -4,20 +4,32 @@
 
 /*
  * Tell the user there is some problem.
- * The offending file and line are encoded after the "officially
- * undefined" opcode for parsing in the trap handler.
+ * The offending file and line are encoded encoded in the __bug_table section.
  */
 
 #ifdef CONFIG_BUG
 #define HAVE_ARCH_BUG
+
 #ifdef CONFIG_DEBUG_BUGVERBOSE
-#define BUG()				\
- __asm__ __volatile__(	"ud2\n"		\
-			"\t.word %c0\n"	\
-			"\t.long %c1\n"	\
-			 : : "i" (__LINE__), "i" (__FILE__))
+#define BUG()								\
+	do {								\
+		asm volatile("1:\tud2\n"				\
+			     ".pushsection __bug_table,\"a\"\n"		\
+			     "2:\t.long 1b, %c0\n"			\
+			     "\t.word %c1, 0\n"				\
+			     "\t.org 2b+%c2\n"				\
+			     ".popsection"				\
+			     : : "i" (__FILE__), "i" (__LINE__),	\
+			     "i" (sizeof(struct bug_entry)));		\
+		for(;;) ;						\
+	} while(0)
+
 #else
-#define BUG() __asm__ __volatile__("ud2\n")
+#define BUG()								\
+	do {								\
+		asm volatile("ud2");					\
+		for(;;) ;						\
+	} while(0)
 #endif
 #endif
 

lib/Kconfig.debug

@@ -285,7 +285,7 @@ config DEBUG_HIGHMEM
 config DEBUG_BUGVERBOSE
 	bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
 	depends on BUG
-	depends on ARM || ARM26 || AVR32 || M32R || M68K || SPARC32 || SPARC64 || X86_32 || FRV || SUPERH || GENERIC_BUG
+	depends on ARM || ARM26 || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG
 	default !EMBEDDED
 	help
 	  Say Y here to make BUG() panics output the file name and line number