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SubjectRe: stack overflow on Sparc64
From
From: David Miller <davem@davemloft.net>
Date: Fri, 20 Jun 2008 14:41:28 -0700 (PDT)

> Next week I'll make one of my primary projects the implementation of
> IRQ stacks for sparc64.

Next week came real fast :-)

Amazingly this patch worked the first time I booted it up on my
dual-cpu workstation (using SMP + PREEMPT). I'm worried that maybe
gcc can do some clever things and not allow my extremely simple
approach to work, but anyways it might work for you and it's worth
giving a try.

sparc64: Implement support for IRQ stacks.

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc64/Kconfig.debug b/arch/sparc64/Kconfig.debug
index 6a4d28a..df80962 100644
--- a/arch/sparc64/Kconfig.debug
+++ b/arch/sparc64/Kconfig.debug
@@ -41,4 +41,11 @@ config FRAME_POINTER
depends on MCOUNT
default y

+config IRQSTACKS
+ bool "Use separate kernel stacks when processing interrupts"
+ help
+ If you say Y here the kernel will use separate kernel stacks
+ for handling hard and soft interrupts. This can help avoid
+ overflowing the process kernel stacks.
+
endmenu
diff --git a/arch/sparc64/kernel/irq.c b/arch/sparc64/kernel/irq.c
index b441a26..24820fa 100644
--- a/arch/sparc64/kernel/irq.c
+++ b/arch/sparc64/kernel/irq.c
@@ -674,10 +674,42 @@ void ack_bad_irq(unsigned int virt_irq)
ino, virt_irq);
}

+#ifdef CONFIG_IRQSTACKS
+void *hardirq_stack[NR_CPUS];
+void *softirq_stack[NR_CPUS];
+
+static void *set_hardirq_stack(void)
+{
+ void *orig_sp, *sp = hardirq_stack[smp_processor_id()];
+
+ __asm__ __volatile__("mov %%sp, %0" : "=r" (orig_sp));
+ if (orig_sp < sp ||
+ orig_sp > (sp + THREAD_SIZE)) {
+ sp += THREAD_SIZE - 192 - STACK_BIAS;
+ __asm__ __volatile__("mov %0, %%sp" : : "r" (sp));
+ }
+
+ return orig_sp;
+}
+static void restore_hardirq_stack(void *orig_sp)
+{
+ __asm__ __volatile__("mov %0, %%sp" : : "r" (orig_sp));
+}
+#else
+static void *set_hardirq_stack(void)
+{
+ return NULL;
+}
+static void restore_hardirq_stack(void *orig_sp)
+{
+}
+#endif
+
void handler_irq(int irq, struct pt_regs *regs)
{
unsigned long pstate, bucket_pa;
struct pt_regs *old_regs;
+ void *orig_sp;

clear_softint(1 << irq);

@@ -695,6 +727,8 @@ void handler_irq(int irq, struct pt_regs *regs)
"i" (PSTATE_IE)
: "memory");

+ orig_sp = set_hardirq_stack();
+
while (bucket_pa) {
struct irq_desc *desc;
unsigned long next_pa;
@@ -711,10 +745,40 @@ void handler_irq(int irq, struct pt_regs *regs)
bucket_pa = next_pa;
}

+ restore_hardirq_stack(orig_sp);
+
irq_exit();
set_irq_regs(old_regs);
}

+#ifdef CONFIG_IRQSTACKS
+void do_softirq(void)
+{
+ unsigned long flags;
+
+ if (in_interrupt())
+ return;
+
+ local_irq_save(flags);
+
+ if (local_softirq_pending()) {
+ void *orig_sp, *sp = softirq_stack[smp_processor_id()];
+
+ sp += THREAD_SIZE - 192 - STACK_BIAS;
+
+ __asm__ __volatile__("mov %%sp, %0\n\t"
+ "mov %1, %%sp"
+ : "=&r" (orig_sp)
+ : "r" (sp));
+ __do_softirq();
+ __asm__ __volatile__("mov %0, %%sp"
+ : : "r" (orig_sp));
+ }
+
+ local_irq_restore(flags);
+}
+#endif
+
#ifdef CONFIG_HOTPLUG_CPU
void fixup_irqs(void)
{
diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c
index 84898c4..56e22f4 100644
--- a/arch/sparc64/mm/init.c
+++ b/arch/sparc64/mm/init.c
@@ -49,6 +49,7 @@
#include <asm/sstate.h>
#include <asm/mdesc.h>
#include <asm/cpudata.h>
+#include <asm/irq.h>

#define MAX_PHYS_ADDRESS (1UL << 42UL)
#define KPTE_BITMAP_CHUNK_SZ (256UL * 1024UL * 1024UL)
@@ -1817,6 +1818,18 @@ void __init paging_init(void)
if (tlb_type == hypervisor)
sun4v_mdesc_init();

+#ifdef CONFIG_IRQSTACKS
+ /* Once the OF device tree and MDESC have been setup, we know
+ * the list of possible cpus. Therefore we can allocate the
+ * IRQ stacks.
+ */
+ for_each_possible_cpu(i) {
+ /* XXX Use node local allocations... XXX */
+ softirq_stack[i] = __va(lmb_alloc(THREAD_SIZE, THREAD_SIZE));
+ hardirq_stack[i] = __va(lmb_alloc(THREAD_SIZE, THREAD_SIZE));
+ }
+#endif
+
/* Setup bootmem... */
last_valid_pfn = end_pfn = bootmem_init(phys_base);

diff --git a/include/asm-sparc64/irq.h b/include/asm-sparc64/irq.h
index 0bb9bf5..d71b5ff 100644
--- a/include/asm-sparc64/irq.h
+++ b/include/asm-sparc64/irq.h
@@ -90,4 +90,10 @@ static inline unsigned long get_softint(void)
return retval;
}

+#ifdef CONFIG_IRQSTACKS
+extern void *hardirq_stack[NR_CPUS];
+extern void *softirq_stack[NR_CPUS];
+#define __ARCH_HAS_DO_SOFTIRQ
+#endif
+
#endif

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