sh: stack debugging support.

This adds a DEBUG_STACK_USAGE and DEBUG_STACKOVERFLOW for SH.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

6 files changed, 52 insertions, 13 deletions

diff --git a/arch/sh/Kconfig.debug b/arch/sh/Kconfig.debug
index 75ed1be8a49e..f0188e626be0 100644
--- a/arch/sh/Kconfig.debug
+++ b/arch/sh/Kconfig.debug
@@ -30,6 +30,22 @@ config EARLY_PRINTK
           when the kernel may crash or hang before the serial console is
           initialised. If unsure, say N.
 
+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 "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 and sysrq-P debug output.
+
+          This option will slow down process creation somewhat.
+
 config KGDB
         bool "Include KGDB kernel debugger"
         select FRAME_POINTER
diff --git a/arch/sh/kernel/head.S b/arch/sh/kernel/head.S
index c5e363872b91..3e7d00b7985a 100644
--- a/arch/sh/kernel/head.S
+++ b/arch/sh/kernel/head.S
@@ -11,6 +11,8 @@
  * Head.S contains the SH exception handlers and startup code.
  */
 #include <linux/linkage.h>
+#include <asm/thread_info.h>
+#include <asm/page.h>
 
 #ifdef CONFIG_CPU_SH4A
 #define SYNCO()         synco
@@ -95,7 +97,7 @@ ENTRY(_stext)
 
         .balign 4
 1:      .long   0x400080F0              ! MD=1, RB=0, BL=0, FD=1, IMASK=0xF
-2:      .long   init_thread_union+8192
+2:      .long   init_thread_union+THREAD_SIZE
 3:      .long   __bss_start
 4:      .long   _end
 5:      .long   start_kernel
diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
index c2e07f7f3496..7066611aeb72 100644
--- a/arch/sh/kernel/irq.c
+++ b/arch/sh/kernel/irq.c
@@ -60,7 +60,6 @@ unlock:
 }
 #endif
 
-
 asmlinkage int do_IRQ(unsigned long r4, unsigned long r5,
                       unsigned long r6, unsigned long r7,
                       struct pt_regs regs)
@@ -69,6 +68,22 @@ asmlinkage int do_IRQ(unsigned long r4, unsigned long r5,
 
         irq_enter();
 
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+        /* Debugging check for stack overflow: is there less than 1KB free? */
+        {
+                long sp;
+
+                __asm__ __volatile__ ("and r15, %0" :
+                                        "=r" (sp) : "0" (THREAD_SIZE - 1));
+
+                if (unlikely(sp < (sizeof(struct thread_info) + STACK_WARN))) {
+                        printk("do_IRQ: stack overflow: %ld\n",
+                               sp - sizeof(struct thread_info));
+                        dump_stack();
+                }
+        }
+#endif
+
 #ifdef CONFIG_CPU_HAS_INTEVT
         __asm__ __volatile__ (
 #ifdef CONFIG_CPU_HAS_SR_RB
diff --git a/arch/sh/kernel/vmlinux.lds.S b/arch/sh/kernel/vmlinux.lds.S
index eb860c51c697..0220d8a838a7 100644
--- a/arch/sh/kernel/vmlinux.lds.S
+++ b/arch/sh/kernel/vmlinux.lds.S
@@ -2,6 +2,8 @@
  * ld script to make SuperH Linux kernel
  * Written by Niibe Yutaka
  */
+#include <asm/thread_info.h>
+#include <asm/page.h>
 #include <asm-generic/vmlinux.lds.h>
 
 #ifdef CONFIG_CPU_LITTLE_ENDIAN
@@ -40,16 +42,16 @@ SECTIONS
         *(.data)
 
          /* Align the initial ramdisk image (INITRD) on page boundaries. */
-         . = ALIGN(4096);
+         . = ALIGN(PAGE_SIZE);
          __rd_start = .;
          *(.initrd)
-         . = ALIGN(4096);
+         . = ALIGN(PAGE_SIZE);
          __rd_end = .;
 
         CONSTRUCTORS
         }
 
-  . = ALIGN(4096);
+  . = ALIGN(PAGE_SIZE);
   .data.page_aligned : { *(.data.idt) }
 
   . = ALIGN(32);
@@ -60,10 +62,10 @@ SECTIONS
 
   _edata = .;                   /* End of data section */
 
-  . = ALIGN(8192);              /* init_task */
+  . = ALIGN(THREAD_SIZE);               /* init_task */
   .data.init_task : { *(.data.init_task) }
 
-  . = ALIGN(4096);              /* Init code and data */
+  . = ALIGN(PAGE_SIZE);         /* Init code and data */
   __init_begin = .;
   _sinittext = .;
   .init.text : { *(.init.text) }
@@ -94,7 +96,7 @@ SECTIONS
   __machvec_start = .;
   .init.machvec : { *(.init.machvec) }
   __machvec_end = .;
-  . = ALIGN(4096);
+  . = ALIGN(PAGE_SIZE);
   __init_end = .;
 
   . = ALIGN(4);
diff --git a/include/asm-sh/page.h b/include/asm-sh/page.h
index e9135532d00c..888d6fe0030e 100644
--- a/include/asm-sh/page.h
+++ b/include/asm-sh/page.h
@@ -16,7 +16,7 @@
 
 /* PAGE_SHIFT determines the page size */
 #define PAGE_SHIFT      12
-#define PAGE_SIZE       (1UL << PAGE_SHIFT)
+#define PAGE_SIZE       (1 << PAGE_SHIFT)
 #define PAGE_MASK       (~(PAGE_SIZE-1))
 #define PTE_MASK        PAGE_MASK
 
diff --git a/include/asm-sh/thread_info.h b/include/asm-sh/thread_info.h
index 5eb874b065a6..605259f88113 100644
--- a/include/asm-sh/thread_info.h
+++ b/include/asm-sh/thread_info.h
@@ -29,6 +29,8 @@ struct thread_info {
 #endif
 
 #define PREEMPT_ACTIVE          0x10000000
+#define THREAD_SIZE             (PAGE_SIZE * 2)
+#define STACK_WARN              (THREAD_SIZE / 8)
 
 /*
  * macros/functions for gaining access to the thread information structure
@@ -50,8 +52,6 @@ struct thread_info {
 #define init_thread_info        (init_thread_union.thread_info)
 #define init_stack              (init_thread_union.stack)
 
-#define THREAD_SIZE (2*PAGE_SIZE)
-
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
@@ -73,8 +73,12 @@ static inline struct thread_info *current_thread_info(void)
 }
 
 /* thread information allocation */
-#define alloc_thread_info(ti) ((struct thread_info *) __get_free_pages(GFP_KERNEL,1))
-#define free_thread_info(ti) free_pages((unsigned long) (ti), 1)
+#ifdef CONFIG_DEBUG_STACK_USAGE
+#define alloc_thread_info(ti)   kzalloc(THREAD_SIZE, GFP_KERNEL)
+#else
+#define alloc_thread_info(ti)   kmalloc(THREAD_SIZE, GFP_KERNEL)
+#endif
+#define free_thread_info(ti)    kfree(ti)
 
 #else /* !__ASSEMBLY__ */