ppc64: Update BUG handling based on ppc32

arch/ppc64/kernel/module.c

@@ -376,15 +376,57 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 	return 0;
 }
 
+LIST_HEAD(module_bug_list);
+
 int module_finalize(const Elf_Ehdr *hdr,
 		const Elf_Shdr *sechdrs, struct module *me)
 {
+	char *secstrings;
+	unsigned int i;
+
+	me->arch.bug_table = NULL;
+	me->arch.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;
+		me->arch.bug_table = (void *) sechdrs[i].sh_addr;
+		me->arch.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.
+	 */
+	list_add(&me->arch.bug_list, &module_bug_list);
+
 	sort_ex_table((struct exception_table_entry *)me->extable,
 		      (struct exception_table_entry *)me->extable +
 				me->num_exentries);
+
 	return 0;
 }
 
 void module_arch_cleanup(struct module *mod)
 {
+	list_del(&mod->arch.bug_list);
+}
+
+struct bug_entry *module_find_bug(unsigned long bugaddr)
+{
+	struct mod_arch_specific *mod;
+	unsigned int i;
+	struct bug_entry *bug;
+
+	list_for_each_entry(mod, &module_bug_list, bug_list) {
+		bug = mod->bug_table;
+		for (i = 0; i < mod->num_bugs; ++i, ++bug)
+			if (bugaddr == bug->bug_addr)
+				return bug;
+	}
+	return NULL;
 }

arch/ppc64/kernel/traps.c

@@ -28,6 +28,7 @@
 #include <linux/interrupt.h>
 #include <linux/config.h>
 #include <linux/init.h>
+#include <linux/module.h>
 
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
@@ -306,6 +307,56 @@ static void parse_fpe(struct pt_regs *regs)
 	_exception(SIGFPE, &info, regs);
 }
 
+/*
+ * Look through the list of trap instructions that are used for BUG(),
+ * BUG_ON() and WARN_ON() and see if we hit one.  At this point we know
+ * that the exception was caused by a trap instruction of some kind.
+ * Returns 1 if we should continue (i.e. it was a WARN_ON) or 0
+ * otherwise.
+ */
+extern struct bug_entry __start___bug_table[], __stop___bug_table[];
+
+#ifndef CONFIG_MODULES
+#define module_find_bug(x)	NULL
+#endif
+
+static 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->bug_addr)
+			return bug;
+	return module_find_bug(bugaddr);
+}
+
+int
+check_bug_trap(struct pt_regs *regs)
+{
+	struct bug_entry *bug;
+	unsigned long addr;
+
+	if (regs->msr & MSR_PR)
+		return 0;	/* not in kernel */
+	addr = regs->nip;	/* address of trap instruction */
+	if (addr < PAGE_OFFSET)
+		return 0;
+	bug = find_bug(regs->nip);
+	if (bug == NULL)
+		return 0;
+	if (bug->line & BUG_WARNING_TRAP) {
+		/* this is a WARN_ON rather than BUG/BUG_ON */
+		printk(KERN_ERR "Badness in %s at %s:%d\n",
+		       bug->function, bug->file,
+		       bug->line & ~BUG_WARNING_TRAP);
+		dump_stack();
+		return 1;
+	}
+	printk(KERN_CRIT "kernel BUG in %s at %s:%d!\n",
+	       bug->function, bug->file, bug->line);
+	return 0;
+}
+
 void
 ProgramCheckException(struct pt_regs *regs)
 {
@@ -330,6 +381,10 @@ ProgramCheckException(struct pt_regs *regs)
 		if (debugger_bpt && debugger_bpt(regs))
 			return;
 #endif
+		if (check_bug_trap(regs)) {
+			regs->nip += 4;
+			return;
+		}
 		info.si_signo = SIGTRAP;
 		info.si_errno = 0;
 		info.si_code = TRAP_BRKPT;

arch/ppc64/vmlinux.lds.S

@@ -65,6 +65,10 @@ SECTIONS
   __ex_table : { *(__ex_table) }
   __stop___ex_table = .;
 
+  __start___bug_table = .;
+  __bug_table : { *(__bug_table) }
+  __stop___bug_table = .;
+
   __start___ftr_fixup = .;
   __ftr_fixup : { *(__ftr_fixup) }
   __stop___ftr_fixup = .;

include/asm-ppc64/bug.h

 #ifndef _PPC64_BUG_H
 #define _PPC64_BUG_H
 
-#include <linux/config.h>
-
 /*
  * Define an illegal instr to trap on the bug.
  * We don't use 0 because that marks the end of a function
@@ -13,29 +11,48 @@
 
 #ifndef __ASSEMBLY__
 
-#ifdef CONFIG_XMON
-struct pt_regs;
-extern void xmon(struct pt_regs *excp);
-#define BUG() do { \
-	printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
-	xmon(0); \
-} while (0)
-#else
+struct bug_entry {
+	unsigned long	bug_addr;
+	long		line;
+	const char	*file;
+	const char	*function;
+};
+
+/*
+ * If this bit is set in the line number it means that the trap
+ * is for WARN_ON rather than BUG or BUG_ON.
+ */
+#define BUG_WARNING_TRAP	0x1000000
+
 #define BUG() do {							 \
-	printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
-	__asm__ __volatile__(".long " BUG_ILLEGAL_INSTR); \
+	__asm__ __volatile__(						 \
+		"1:	twi 31,0,0\n"					 \
+		".section __bug_table,\"a\"\n\t"			 \
+		"	.llong 1b,%0,%1,%2\n"				 \
+		".previous"						 \
+		: : "i" (__LINE__), "i" (__FILE__), "i" (__FUNCTION__)); \
 } while (0)
-#endif
 
-#define BUG_ON(condition) do { if (unlikely((condition)!=0)) BUG(); } while(0)
+#define BUG_ON(x) do {						\
+	__asm__ __volatile__(					\
+		"1:	tdnei %0,0\n"				\
+		".section __bug_table,\"a\"\n\t"		\
+		"	.llong 1b,%1,%2,%3\n"			\
+		".previous"					\
+		: : "r" (x), "i" (__LINE__), "i" (__FILE__),	\
+		    "i" (__FUNCTION__));			\
+} while (0)
 
 #define PAGE_BUG(page) do { BUG(); } while (0)
 
-#define WARN_ON(condition) do { \
-	if (unlikely((condition)!=0)) { \
-		printk("Badness in %s at %s:%d\n", __FUNCTION__, __FILE__, __LINE__); \
-		dump_stack(); \
-	} \
+#define WARN_ON(x) do {						\
+	__asm__ __volatile__(					\
+		"1:	tdnei %0,0\n"				\
+		".section __bug_table,\"a\"\n\t"		\
+		"	.llong 1b,%1,%2,%3\n"			\
+		".previous"					\
+		: : "r" (x), "i" (__LINE__ + BUG_WARNING_TRAP),	\
+		    "i" (__FILE__), "i" (__FUNCTION__));	\
 } while (0)
 
 #endif

include/asm-ppc64/module.h

 #ifndef _ASM_PPC64_MODULE_H
 #define _ASM_PPC64_MODULE_H
 
+#include <linux/list.h>
+#include <asm/bug.h>
+
 struct mod_arch_specific
 {
 	/* Index of stubs section within module. */
@@ -8,8 +11,15 @@ struct mod_arch_specific
 
 	/* What section is the TOC? */
 	unsigned int toc_section;
+
+	/* List of BUG addresses, source line numbers and filenames */
+	struct list_head bug_list;
+	struct bug_entry *bug_table;
+	unsigned int num_bugs;
 };
 
+extern struct bug_entry *module_find_bug(unsigned long bugaddr);
+
 #define Elf_Shdr Elf64_Shdr
 #define Elf_Sym Elf64_Sym
 #define Elf_Ehdr Elf64_Ehdr