3 files changed, 97 insertions, 0 deletions

diff --git a/arch/sh/Kconfig.debug b/arch/sh/Kconfig.debug
index 39224b57c6e..52a132c24aa 100644
--- a/arch/sh/Kconfig.debug
+++ b/arch/sh/Kconfig.debug
@@ -123,4 +123,15 @@ config SH64_SR_WATCH
 	bool "Debug: set SR.WATCH to enable hardware watchpoints and trace"
 	depends on SUPERH64
 
+config STACK_DEBUG
+	bool "Enable diagnostic checks of the kernel stack"
+	depends on FUNCTION_TRACER
+	select DEBUG_STACKOVERFLOW
+	default n
+	help
+	  This option allows checks to be performed on the kernel stack
+	  at runtime. Saying Y here will add overhead to every function
+	  call and will therefore incur a major performance hit. Most
+	  users should say N.
+
 endmenu
diff --git a/arch/sh/kernel/asm-offsets.c b/arch/sh/kernel/asm-offsets.c
index 99aceb28ee2..d218e808294 100644
--- a/arch/sh/kernel/asm-offsets.c
+++ b/arch/sh/kernel/asm-offsets.c
@@ -26,6 +26,7 @@ int main(void)
 	DEFINE(TI_CPU,		offsetof(struct thread_info, cpu));
 	DEFINE(TI_PRE_COUNT,	offsetof(struct thread_info, preempt_count));
 	DEFINE(TI_RESTART_BLOCK,offsetof(struct thread_info, restart_block));
+	DEFINE(TI_SIZE,		sizeof(struct thread_info));
 
 #ifdef CONFIG_HIBERNATION
 	DEFINE(PBE_ADDRESS, offsetof(struct pbe, address));
diff --git a/arch/sh/lib/mcount.S b/arch/sh/lib/mcount.S
index 71e87f9b4fd..8596483f7b4 100644
--- a/arch/sh/lib/mcount.S
+++ b/arch/sh/lib/mcount.S
@@ -9,6 +9,8 @@
  * for more details.
  */
 #include <asm/ftrace.h>
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
 
 #define MCOUNT_ENTER()		\
 	mov.l	r4, @-r15;	\
@@ -28,6 +30,55 @@
 	rts;			\
 	 mov.l	@r15+, r4
 
+#ifdef CONFIG_STACK_DEBUG
+/*
+ * Perform diagnostic checks on the state of the kernel stack.
+ *
+ * Check for stack overflow. If there is less than 1KB free
+ * then it has overflowed.
+ *
+ * Make sure the stack pointer contains a valid address. Valid
+ * addresses for kernel stacks are anywhere after the bss
+ * (after _ebss) and anywhere in init_thread_union (init_stack).
+ */
+#define STACK_CHECK()					\
+	mov	#(THREAD_SIZE >> 10), r0;		\
+	shll8	r0;					\
+	shll2	r0;					\
+							\
+	/* r1 = sp & (THREAD_SIZE - 1) */		\
+	mov	#-1, r1;				\
+	add	r0, r1;					\
+	and	r15, r1;				\
+							\
+	mov	#TI_SIZE, r3;				\
+	mov	#(STACK_WARN >> 8), r2;			\
+	shll8	r2;					\
+	add	r3, r2;					\
+							\
+	/* Is the stack overflowing? */			\
+	cmp/hi	r2, r1;					\
+	bf	stack_panic;				\
+							\
+	/* If sp > _ebss then we're OK. */		\
+	mov.l	.L_ebss, r1;				\
+	cmp/hi	r1, r15;				\
+	bt	1f;					\
+							\
+	/* If sp < init_stack, we're not OK. */		\
+	mov.l	.L_init_thread_union, r1;		\
+	cmp/hs	r1, r15;				\
+	bf	stack_panic;				\
+							\
+	/* If sp > init_stack && sp < _ebss, not OK. */	\
+	add	r0, r1;					\
+	cmp/hs	r1, r15;				\
+	bt	stack_panic;				\
+1:
+#else
+#define STACK_CHECK()
+#endif /* CONFIG_STACK_DEBUG */
+
 	.align 2
 	.globl	_mcount
 	.type	_mcount,@function
@@ -41,6 +92,8 @@ mcount:
 	tst	r0, r0
 	bf	ftrace_stub
 #endif
+	STACK_CHECK()
+
 	MCOUNT_ENTER()
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -73,6 +126,8 @@ ftrace_caller:
 	tst	r0, r0
 	bf	ftrace_stub
 
+	STACK_CHECK()
+
 	MCOUNT_ENTER()
 
 	.globl ftrace_call
@@ -100,6 +155,36 @@ ftrace_stub:
 	rts
 	 nop
 
+#ifdef CONFIG_STACK_DEBUG
+	.globl	stack_panic
+stack_panic:
+	mov.l	.Ldump_stack, r0
+	jsr	@r0
+	 nop
+
+	mov.l	.Lpanic, r0
+	jsr	@r0
+	 mov.l	.Lpanic_s, r4
+
+	rts
+	 nop
+
 	.align 2
 .Lfunction_trace_stop:
 	.long	function_trace_stop
+.L_ebss:
+	.long	_ebss
+.L_init_thread_union:
+	.long	init_thread_union
+.Lpanic:
+	.long	panic
+.Lpanic_s:
+	.long	.Lpanic_str
+.Ldump_stack:
+	.long	dump_stack
+
+	.section	.rodata
+	.align 2
+.Lpanic_str:
+	.string "Stack error"
+#endif /* CONFIG_STACK_DEBUG */