4 files changed, 40 insertions, 1 deletions

diff --git a/arch/blackfin/Kconfig.debug b/arch/blackfin/Kconfig.debug
index 3ad25983ec97..bfd712ab125c 100644
--- a/arch/blackfin/Kconfig.debug
+++ b/arch/blackfin/Kconfig.debug
@@ -2,6 +2,22 @@ menu "Kernel hacking"
 
 source "lib/Kconfig.debug"
 
+config DEBUG_STACKOVERFLOW
+        bool "Check for stack overflows"
+        depends on DEBUG_KERNEL
+        help
+          This option will cause messages to be printed if free stack space
+          drops below a certain limit.
+
+config DEBUG_STACK_USAGE
+        bool "Enable stack utilization instrumentation"
+        depends on DEBUG_KERNEL
+        help
+          Enables the display of the minimum amount of free stack which each
+          task has ever had available in the sysrq-T output.
+
+          This option will slow down process creation somewhat.
+
 config HAVE_ARCH_KGDB
        def_bool y
 
diff --git a/arch/blackfin/include/asm/processor.h b/arch/blackfin/include/asm/processor.h
index 2cb0b8711fa4..83d57a85b14f 100644
--- a/arch/blackfin/include/asm/processor.h
+++ b/arch/blackfin/include/asm/processor.h
@@ -24,6 +24,14 @@ static inline void wrusp(unsigned long usp)
         __asm__ __volatile__("usp = %0;\n\t"::"da"(usp));
 }
 
+static inline unsigned long __get_SP(void)
+{
+        unsigned long sp;
+
+        __asm__ __volatile__("%0 = sp;\n\t" : "=da"(sp));
+        return sp;
+}
+
 /*
  * User space process size: 1st byte beyond user address space.
  * Fairly meaningless on nommu.  Parts of user programs can be scattered
diff --git a/arch/blackfin/include/asm/thread_info.h b/arch/blackfin/include/asm/thread_info.h
index 642769329d12..1d380def2410 100644
--- a/arch/blackfin/include/asm/thread_info.h
+++ b/arch/blackfin/include/asm/thread_info.h
@@ -44,6 +44,7 @@
  */
 #define THREAD_SIZE_ORDER       1
 #define THREAD_SIZE             8192    /* 2 pages */
+#define STACK_WARN              (THREAD_SIZE/8)
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/blackfin/kernel/irqchip.c b/arch/blackfin/kernel/irqchip.c
index 5ad07525ea3f..1624e1129681 100644
--- a/arch/blackfin/kernel/irqchip.c
+++ b/arch/blackfin/kernel/irqchip.c
@@ -120,7 +120,21 @@ asmlinkage void asm_do_IRQ(unsigned int irq, struct pt_regs *regs)
                 desc = &bad_irq_desc;
 
         irq_enter();
-
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+        /* Debugging check for stack overflow: is there less than STACK_WARN free? */
+        {
+                long sp;
+
+                sp = __get_SP() & (THREAD_SIZE-1);
+
+                if (unlikely(sp < (sizeof(struct thread_info) + STACK_WARN))) {
+                        dump_stack();
+                        printk(KERN_EMERG "%s: possible stack overflow while handling irq %i "
+                                        " only %ld bytes free\n",
+                                __func__, irq, sp - sizeof(struct thread_info));
+                }
+        }
+#endif
         generic_handle_irq(irq);
 
         /* If we're the only interrupt running (ignoring IRQ15 which is for