arm64: remove irq_count and do_softirq_own_stack()
sysrq_handle_reboot() re-enables interrupts while on the irq stack. The irq_stack implementation wrongly assumed this would only ever happen via the softirq path, allowing it to update irq_count late, in do_softirq_own_stack(). This means if an irq occurs in sysrq_handle_reboot(), during emergency_restart() the stack will be corrupted, as irq_count wasn't updated. Lose the optimisation, and instead of moving the adding/subtracting of irq_count into irq_stack_entry/irq_stack_exit, remove it, and compare sp_el0 (struct thread_info) with sp & ~(THREAD_SIZE - 1). This tells us if we are on a task stack, if so, we can safely switch to the irq stack. Finally, remove do_softirq_own_stack(), we don't need it anymore. Reported-by: Will Deacon <will.deacon@arm.com> Signed-off-by: James Morse <james.morse@arm.com> [will: use get_thread_info macro] Signed-off-by: Will Deacon <will.deacon@arm.com>
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@ -11,8 +11,6 @@
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#include <asm-generic/irq.h>
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#include <asm/thread_info.h>
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#define __ARCH_HAS_DO_SOFTIRQ
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struct pt_regs;
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DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
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@ -181,19 +181,20 @@ alternative_endif
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.macro irq_stack_entry
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mov x19, sp // preserve the original sp
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this_cpu_ptr irq_stack, x25, x26
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/*
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* Check the lowest address on irq_stack for the irq_count value,
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* incremented by do_softirq_own_stack if we have re-enabled irqs
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* while on the irq_stack.
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* Compare sp with the current thread_info, if the top
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* ~(THREAD_SIZE - 1) bits match, we are on a task stack, and
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* should switch to the irq stack.
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*/
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ldr x26, [x25]
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cbnz x26, 9998f // recursive use?
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and x25, x19, #~(THREAD_SIZE - 1)
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cmp x25, tsk
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b.ne 9998f
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/* switch to the irq stack */
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this_cpu_ptr irq_stack, x25, x26
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mov x26, #IRQ_STACK_START_SP
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add x26, x25, x26
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/* switch to the irq stack */
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mov sp, x26
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/*
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@ -405,10 +406,10 @@ el1_irq:
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bl trace_hardirqs_off
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#endif
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get_thread_info tsk
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irq_handler
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#ifdef CONFIG_PREEMPT
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get_thread_info tsk
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ldr w24, [tsk, #TI_PREEMPT] // get preempt count
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cbnz w24, 1f // preempt count != 0
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ldr x0, [tsk, #TI_FLAGS] // get flags
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@ -25,24 +25,14 @@
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#include <linux/irq.h>
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#include <linux/smp.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/irqchip.h>
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#include <linux/seq_file.h>
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unsigned long irq_err_count;
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/*
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* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned.
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* irq_stack[0] is used as irq_count, a non-zero value indicates the stack
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* is in use, and el?_irq() shouldn't switch to it. This is used to detect
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* recursive use of the irq_stack, it is lazily updated by
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* do_softirq_own_stack(), which is called on the irq_stack, before
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* re-enabling interrupts to process softirqs.
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*/
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/* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. */
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DEFINE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack) __aligned(16);
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#define IRQ_COUNT() (*per_cpu(irq_stack, smp_processor_id()))
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int arch_show_interrupts(struct seq_file *p, int prec)
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{
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show_ipi_list(p, prec);
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@ -66,29 +56,3 @@ void __init init_IRQ(void)
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if (!handle_arch_irq)
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panic("No interrupt controller found.");
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}
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/*
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* do_softirq_own_stack() is called from irq_exit() before __do_softirq()
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* re-enables interrupts, at which point we may re-enter el?_irq(). We
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* increase irq_count here so that el1_irq() knows that it is already on the
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* irq stack.
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*
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* Called with interrupts disabled, so we don't worry about moving cpu, or
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* being interrupted while modifying irq_count.
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*
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* This function doesn't actually switch stack.
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*/
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void do_softirq_own_stack(void)
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{
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int cpu = smp_processor_id();
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WARN_ON_ONCE(!irqs_disabled());
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if (on_irq_stack(current_stack_pointer, cpu)) {
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IRQ_COUNT()++;
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__do_softirq();
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IRQ_COUNT()--;
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} else {
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__do_softirq();
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}
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}
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