parisc: add kernel stack overflow check

Add the CONFIG_DEBUG_STACKOVERFLOW config option to enable checks to
detect kernel stack overflows.

Stack overflows can not be detected reliable since we do not want to
introduce too much overhead.

Instead, during irq processing in do_cpu_irq_mask() we check kernel
stack usage of the interrupted kernel process. Kernel threads can be
easily detected by checking the value of space register 7 (sr7) which
is zero when running inside the kernel.

Since THREAD_SIZE is 16k and PAGE_SIZE is 4k, reduce the alignment of
the init thread to the lower value (PAGE_SIZE) in the kernel
vmlinux.ld.S linker script.

Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
index bc989e522a045c17ca4514478b7cb5ef9d77fc4d..08a332f6ee874d814df7a97615dd44821add3c13 100644 (file)
--- a/arch/parisc/Kconfig.debug
+++ b/arch/parisc/Kconfig.debug
@@ -13,3 +13,14 @@ config DEBUG_RODATA
          If in doubt, say "N".
 
 endmenu
+
+config DEBUG_STACKOVERFLOW
+       bool "Check for stack overflows"
+       default y
+       depends on DEBUG_KERNEL
+       ---help---
+         Say Y here if you want to check the overflows of kernel, IRQ
+         and exception stacks. This option will cause messages of the
+         stacks in detail when free stack space drops below a certain
+         limit.
+         If in doubt, say "N".

diff --git a/arch/parisc/include/asm/thread_info.h b/arch/parisc/include/asm/thread_info.h
index 6182832e5b6c9c166597f2627ecc9463a38a7d1b..540c88fa8f863d44adcc254fe9a3917cf015aa4d 100644 (file)
--- a/arch/parisc/include/asm/thread_info.h
+++ b/arch/parisc/include/asm/thread_info.h
@@ -40,7 +40,7 @@ struct thread_info {
 
 /* thread information allocation */
 
-#define THREAD_SIZE_ORDER            2
+#define THREAD_SIZE_ORDER      2 /* PA-RISC requires at least 16k stack */
 /* Be sure to hunt all references to this down when you change the size of
  * the kernel stack */
 #define THREAD_SIZE             (PAGE_SIZE << THREAD_SIZE_ORDER)

diff --git a/arch/parisc/kernel/irq.c b/arch/parisc/kernel/irq.c
index 8094d3ed3b646328be21fd26738298a365089555..61e51ac85659d91a70096614b6a1b435027fd059 100644 (file)
--- a/arch/parisc/kernel/irq.c
+++ b/arch/parisc/kernel/irq.c
@@ -330,6 +330,34 @@ static inline int eirr_to_irq(unsigned long eirr)
        return (BITS_PER_LONG - bit) + TIMER_IRQ;
 }
 
+int sysctl_panic_on_stackoverflow = 1;
+
+static inline void stack_overflow_check(struct pt_regs *regs)
+{
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+       #define STACK_MARGIN    (256*6)
+
+       /* Our stack starts directly behind the thread_info struct. */
+       unsigned long stack_start = (unsigned long) current_thread_info();
+       unsigned long sp = regs->gr[30];
+
+       /* if sr7 != 0, we interrupted a userspace process which we do not want
+        * to check for stack overflow. We will only check the kernel stack. */
+       if (regs->sr[7])
+               return;
+
+       if (likely((sp - stack_start) < (THREAD_SIZE - STACK_MARGIN)))
+               return;
+
+       pr_emerg("stackcheck: %s will most likely overflow kernel stack "
+                "(sp:%lx, stk bottom-top:%lx-%lx)\n",
+               current->comm, sp, stack_start, stack_start + THREAD_SIZE);
+
+       if (sysctl_panic_on_stackoverflow)
+               panic("low stack detected by irq handler - check messages\n");
+#endif
+}
+
 /* ONLY called from entry.S:intr_extint() */
 void do_cpu_irq_mask(struct pt_regs *regs)
 {
@@ -364,6 +392,7 @@ void do_cpu_irq_mask(struct pt_regs *regs)
                goto set_out;
        }
 #endif
+       stack_overflow_check(regs);
        generic_handle_irq(irq);
 
  out:
@@ -420,6 +449,4 @@ void __init init_IRQ(void)
        cpu_eiem = EIEM_MASK(TIMER_IRQ);
 #endif
         set_eiem(cpu_eiem);    /* EIEM : enable all external intr */
-
 }
-

diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
index 64a999882e4fb8d0d584da223c7b1f43842e8d2c..4bb095a2f6fc2266388723cbb2634518a9570e44 100644 (file)
--- a/arch/parisc/kernel/vmlinux.lds.S
+++ b/arch/parisc/kernel/vmlinux.lds.S
@@ -95,7 +95,7 @@ SECTIONS
        NOTES
 
        /* Data */
-       RW_DATA_SECTION(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
+       RW_DATA_SECTION(L1_CACHE_BYTES, PAGE_SIZE, PAGE_SIZE)
 
        /* PA-RISC locks requires 16-byte alignment */
        . = ALIGN(16);