Commit 9372450c authored by Helge Deller's avatar Helge Deller
Browse files

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: default avatarHelge Deller <deller@gmx.de>
parent c207a76b

arch/parisc/Kconfig.debug

+11 −0
Original line number Diff line number Diff line
@@ -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".

arch/parisc/include/asm/thread_info.h

+1 −1
Original line number Diff line number Diff line
@@ -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)

arch/parisc/kernel/irq.c

+29 −2
Original line number Diff line number Diff line
@@ -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 */



}

arch/parisc/kernel/vmlinux.lds.S

+1 −1
Original line number Diff line number Diff line
@@ -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);

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