diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
index c01718040166e2141fe68357e57fe637e9f20edf..b7d9822fd6c2679107c2979b2df88067c3957340 100644
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -1,6 +1,7 @@
 #ifndef __ASM_SH_BUG_H
 #define __ASM_SH_BUG_H
 
+#define TRAPA_UNWINDER_BUG_OPCODE 0xc33b /* trapa #0x3b */
 #define TRAPA_BUG_OPCODE	0xc33e	/* trapa #0x3e */
 
 #ifdef CONFIG_GENERIC_BUG
@@ -72,6 +73,30 @@ do {							\
 	unlikely(__ret_warn_on);				\
 })
 
+#define UNWINDER_BUG()						\
+do {							\
+	__asm__ __volatile__ (				\
+		"1:\t.short %O0\n"			\
+		_EMIT_BUG_ENTRY		\
+		 :					\
+		 : "n" (TRAPA_UNWINDER_BUG_OPCODE),	\
+		   "i" (__FILE__),			\
+		   "i" (__LINE__), "i" (0),		\
+		   "i" (sizeof(struct bug_entry)));	\
+} while (0)
+
+#define UNWINDER_BUG_ON(x) ({					\
+	int __ret_unwinder_on = !!(x);				\
+	if (__builtin_constant_p(__ret_unwinder_on)) {		\
+		if (__ret_unwinder_on)				\
+			UNWINDER_BUG();				\
+	} else {						\
+		if (unlikely(__ret_unwinder_on))		\
+			UNWINDER_BUG();				\
+	}							\
+	unlikely(__ret_unwinder_on);				\
+})
+
 #endif /* CONFIG_GENERIC_BUG */
 
 #include <asm-generic/bug.h>
diff --git a/arch/sh/include/asm/system.h b/arch/sh/include/asm/system.h
index ab79e1f4fbe060c8180bd42c68c1d1302780eeaf..f9e2ceb94d9b215e3812626963e677f07403485c 100644
--- a/arch/sh/include/asm/system.h
+++ b/arch/sh/include/asm/system.h
@@ -181,6 +181,11 @@ BUILD_TRAP_HANDLER(breakpoint);
 BUILD_TRAP_HANDLER(singlestep);
 BUILD_TRAP_HANDLER(fpu_error);
 BUILD_TRAP_HANDLER(fpu_state_restore);
+BUILD_TRAP_HANDLER(unwinder);
+
+#ifdef CONFIG_BUG
+extern void handle_BUG(struct pt_regs *);
+#endif
 
 #define arch_align_stack(x) (x)
 
diff --git a/arch/sh/include/asm/unwinder.h b/arch/sh/include/asm/unwinder.h
index 3dc551453e2895511740ed1cbc17a61023537a61..1e65c07b3e18dacade5dcaea861874272cbd8d9e 100644
--- a/arch/sh/include/asm/unwinder.h
+++ b/arch/sh/include/asm/unwinder.h
@@ -22,4 +22,10 @@ extern void stack_reader_dump(struct task_struct *, struct pt_regs *,
 			      unsigned long *, const struct stacktrace_ops *,
 			      void *);
 
+/*
+ * Used by fault handling code to signal to the unwinder code that it
+ * should switch to a different unwinder.
+ */
+extern int unwinder_faulted;
+
 #endif /* _LINUX_UNWINDER_H */
diff --git a/arch/sh/kernel/debugtraps.S b/arch/sh/kernel/debugtraps.S
index 591741383ee6addd2fe537aa800d869b24ac26c0..cb00e4a82d4d5e47048e512c8fa3a1efed52ba8b 100644
--- a/arch/sh/kernel/debugtraps.S
+++ b/arch/sh/kernel/debugtraps.S
@@ -19,6 +19,10 @@
 
 #if !defined(CONFIG_SH_STANDARD_BIOS)
 #define sh_bios_handler			debug_trap_handler
+#endif
+
+#if !defined(CONFIG_DWARF_UNWINDER)
+#define unwinder_trap_handler		debug_trap_handler
 #endif
 
 	.data
@@ -35,7 +39,7 @@ ENTRY(debug_trap_table)
 	.long debug_trap_handler	/* 0x38 */
 	.long debug_trap_handler	/* 0x39 */
 	.long debug_trap_handler	/* 0x3a */
-	.long debug_trap_handler	/* 0x3b */
+	.long unwinder_trap_handler	/* 0x3b */
 	.long breakpoint_trap_handler	/* 0x3c */
 	.long singlestep_trap_handler	/* 0x3d */
 	.long bug_trap_handler		/* 0x3e */
diff --git a/arch/sh/kernel/dwarf.c b/arch/sh/kernel/dwarf.c
index d271d04adccd91fd99108f8c5253259801f74f37..606ece37eb42341f54f58e67943fe6f19726442c 100644
--- a/arch/sh/kernel/dwarf.c
+++ b/arch/sh/kernel/dwarf.c
@@ -69,7 +69,7 @@ static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
 		 * Let's just bomb hard here, we have no way to
 		 * gracefully recover.
 		 */
-		BUG();
+		UNWINDER_BUG();
 	}
 
 	reg->number = reg_num;
@@ -232,7 +232,7 @@ static int dwarf_read_encoded_value(char *addr, unsigned long *val,
 		break;
 	default:
 		pr_debug("encoding=0x%x\n", (encoding & 0x70));
-		BUG();
+		UNWINDER_BUG();
 	}
 
 	if ((encoding & 0x07) == 0x00)
@@ -247,7 +247,7 @@ static int dwarf_read_encoded_value(char *addr, unsigned long *val,
 		break;
 	default:
 		pr_debug("encoding=0x%x\n", encoding);
-		BUG();
+		UNWINDER_BUG();
 	}
 
 	return count;
@@ -519,6 +519,7 @@ static int dwarf_cfa_execute_insns(unsigned char *insn_start,
 			break;
 		default:
 			pr_debug("unhandled DWARF instruction 0x%x\n", insn);
+			UNWINDER_BUG();
 			break;
 		}
 	}
@@ -535,8 +536,8 @@ static int dwarf_cfa_execute_insns(unsigned char *insn_start,
  *	on the callstack. Each of the lower (older) stack frames are
  *	linked via the "prev" member.
  */
-struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
-				       struct dwarf_frame *prev)
+struct dwarf_frame * dwarf_unwind_stack(unsigned long pc,
+					struct dwarf_frame *prev)
 {
 	struct dwarf_frame *frame;
 	struct dwarf_cie *cie;
@@ -558,7 +559,7 @@ struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 	frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
 	if (!frame) {
 		printk(KERN_ERR "Unable to allocate a dwarf frame\n");
-		BUG();
+		UNWINDER_BUG();
 	}
 
 	INIT_LIST_HEAD(&frame->reg_list);
@@ -605,7 +606,8 @@ struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 	case DWARF_FRAME_CFA_REG_OFFSET:
 		if (prev) {
 			reg = dwarf_frame_reg(prev, frame->cfa_register);
-			BUG_ON(!reg);
+			UNWINDER_BUG_ON(!reg);
+			UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 
 			addr = prev->cfa + reg->addr;
 			frame->cfa = __raw_readl(addr);
@@ -624,12 +626,13 @@ struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 		frame->cfa += frame->cfa_offset;
 		break;
 	default:
-		BUG();
+		UNWINDER_BUG();
 	}
 
 	/* If we haven't seen the return address reg, we're screwed. */
 	reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
-	BUG_ON(!reg);
+	UNWINDER_BUG_ON(!reg);
+	UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 
 	addr = frame->cfa + reg->addr;
 	frame->return_addr = __raw_readl(addr);
@@ -664,7 +667,7 @@ static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 	cie->cie_pointer = (unsigned long)entry;
 
 	cie->version = *(char *)p++;
-	BUG_ON(cie->version != 1);
+	UNWINDER_BUG_ON(cie->version != 1);
 
 	cie->augmentation = p;
 	p += strlen(cie->augmentation) + 1;
@@ -694,7 +697,7 @@ static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 		count = dwarf_read_uleb128(p, &length);
 		p += count;
 
-		BUG_ON((unsigned char *)p > end);
+		UNWINDER_BUG_ON((unsigned char *)p > end);
 
 		cie->initial_instructions = p + length;
 		cie->augmentation++;
@@ -722,16 +725,16 @@ static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 			 * routine in the CIE
 			 * augmentation.
 			 */
-			BUG();
+			UNWINDER_BUG();
 		} else if (*cie->augmentation == 'S') {
-			BUG();
+			UNWINDER_BUG();
 		} else {
 			/*
 			 * Unknown augmentation. Assume
 			 * 'z' augmentation.
 			 */
 			p = cie->initial_instructions;
-			BUG_ON(!p);
+			UNWINDER_BUG_ON(!p);
 			break;
 		}
 	}
@@ -805,9 +808,11 @@ static int dwarf_parse_fde(void *entry, u32 entry_type,
 	return 0;
 }
 
-static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs,
+static void dwarf_unwinder_dump(struct task_struct *task,
+				struct pt_regs *regs,
 				unsigned long *sp,
-				const struct stacktrace_ops *ops, void *data)
+				const struct stacktrace_ops *ops,
+				void *data)
 {
 	struct dwarf_frame *frame, *_frame;
 	unsigned long return_addr;
@@ -831,7 +836,6 @@ static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs,
 		return_addr = frame->return_addr;
 		ops->address(data, return_addr, 1);
 	}
-
 }
 
 static struct unwinder dwarf_unwinder = {
diff --git a/arch/sh/kernel/traps.c b/arch/sh/kernel/traps.c
index b3e0067db3583006753fb70203993eda80a439a3..881b9a32b7de25607bbafef418e4fbf707fe7563 100644
--- a/arch/sh/kernel/traps.c
+++ b/arch/sh/kernel/traps.c
@@ -8,7 +8,7 @@
 #include <asm/system.h>
 
 #ifdef CONFIG_BUG
-static void handle_BUG(struct pt_regs *regs)
+void handle_BUG(struct pt_regs *regs)
 {
 	enum bug_trap_type tt;
 	tt = report_bug(regs->pc, regs);
@@ -29,7 +29,10 @@ int is_valid_bugaddr(unsigned long addr)
 	if (probe_kernel_address((insn_size_t *)addr, opcode))
 		return 0;
 
-	return opcode == TRAPA_BUG_OPCODE;
+	if (opcode == TRAPA_BUG_OPCODE || opcode == TRAPA_UNWINDER_BUG_OPCODE)
+		return 1;
+
+	return 0;
 }
 #endif
 
diff --git a/arch/sh/kernel/traps_32.c b/arch/sh/kernel/traps_32.c
index 563426487c6bea7aafab8c98a10b137412b7dfce..05a04b6df8446416d08beb8c614570dfe05c12d3 100644
--- a/arch/sh/kernel/traps_32.c
+++ b/arch/sh/kernel/traps_32.c
@@ -136,6 +136,7 @@ static void die_if_no_fixup(const char * str, struct pt_regs * regs, long err)
 			regs->pc = fixup->fixup;
 			return;
 		}
+
 		die(str, regs, err);
 	}
 }
diff --git a/arch/sh/kernel/unwinder.c b/arch/sh/kernel/unwinder.c
index 2b30fa28b44039f631308b64cb580da29187ec67..b9c122abe251d2a17982c4a0b41126df59ee2308 100644
--- a/arch/sh/kernel/unwinder.c
+++ b/arch/sh/kernel/unwinder.c
@@ -53,8 +53,6 @@ static struct list_head unwinder_list = {
 
 static DEFINE_SPINLOCK(unwinder_lock);
 
-static atomic_t unwinder_running = ATOMIC_INIT(0);
-
 /**
  * select_unwinder - Select the best registered stack unwinder.
  *
@@ -122,6 +120,8 @@ int unwinder_register(struct unwinder *u)
 	return ret;
 }
 
+int unwinder_faulted = 0;
+
 /*
  * Unwind the call stack and pass information to the stacktrace_ops
  * functions. Also handle the case where we need to switch to a new
@@ -144,19 +144,40 @@ void unwind_stack(struct task_struct *task, struct pt_regs *regs,
 	 * Hopefully this will give us a semi-reliable stacktrace so we
 	 * can diagnose why curr_unwinder->dump() faulted.
 	 */
-	if (atomic_inc_return(&unwinder_running) != 1) {
+	if (unwinder_faulted) {
 		spin_lock_irqsave(&unwinder_lock, flags);
 
-		if (!list_is_singular(&unwinder_list)) {
+		/* Make sure no one beat us to changing the unwinder */
+		if (unwinder_faulted && !list_is_singular(&unwinder_list)) {
 			list_del(&curr_unwinder->list);
 			curr_unwinder = select_unwinder();
+
+			unwinder_faulted = 0;
 		}
 
 		spin_unlock_irqrestore(&unwinder_lock, flags);
-		atomic_dec(&unwinder_running);
 	}
 
 	curr_unwinder->dump(task, regs, sp, ops, data);
+}
+
+/*
+ * Trap handler for UWINDER_BUG() statements. We must switch to the
+ * unwinder with the next highest rating.
+ */
+BUILD_TRAP_HANDLER(unwinder)
+{
+	insn_size_t insn;
+	TRAP_HANDLER_DECL;
+
+	/* Rewind */
+	regs->pc -= instruction_size(ctrl_inw(regs->pc - 4));
+	insn = *(insn_size_t *)instruction_pointer(regs);
+
+	/* Switch unwinders when unwind_stack() is called */
+	unwinder_faulted = 1;
 
-	atomic_dec(&unwinder_running);
+#ifdef CONFIG_BUG
+	handle_BUG(regs);
+#endif
 }