arm64: use an irq stack pointer (f60fe78f) · Commits · 戴 / test

We allocate our IRQ stacks using a percpu array. This allows us to generate our IRQ stack pointers with adr_this_cpu, but bloats the kernel Image with the boot CPU's IRQ stack. Additionally, these are packed with other percpu variables, and aren't guaranteed to have guard pages. When we enable VMAP_STACK we'll want to vmap our IRQ stacks also, in order to provide guard pages and to permit more stringent alignment requirements. Doing so will require that we use a percpu pointer to each IRQ stack, rather than allocating a percpu IRQ stack in the kernel image. This patch updates our IRQ stack code to use a percpu pointer to the base of each IRQ stack. This will allow us to change the way the stack is allocated with minimal changes elsewhere. In some cases we may try to backtrace before the IRQ stack pointers are initialised, so on_irq_stack() is updated to account for this. In testing with cyclictest, there was no measureable difference between using adr_this_cpu (for irq_stack) and ldr_this_cpu (for irq_stack_ptr) in the IRQ entry path. Signed-off-by:

Mark Rutland <mark.rutland@arm.com> Reviewed-by:

Will Deacon <will.deacon@arm.com> Tested-by:

Laura Abbott <labbott@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: James Morse <james.morse@arm.com>

arch/arm64/include/asm/stacktrace.h

+5 −2

Original line number	Diff line number	Diff line
		@@ -36,13 +36,16 @@ extern void walk_stackframe(struct task_struct tsk, struct stackframe frame,
		int (fn)(struct stackframe , void ), void data);
		extern void dump_backtrace(struct pt_regs regs, struct task_struct tsk);

		DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
		DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);

		static inline bool on_irq_stack(unsigned long sp)
		{
		unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack);
		unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);
		unsigned long high = low + IRQ_STACK_SIZE;

		if (!low)
		return false;

		return (low <= sp && sp < high);
		}

arch/arm64/kernel/entry.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -276,7 +276,7 @@ alternative_else_nop_endif
		and x25, x25, #~(THREAD_SIZE - 1)
		cbnz x25, 9998f

		adr_this_cpu x25, irq_stack, x26
		ldr_this_cpu x25, irq_stack_ptr, x26
		mov x26, #IRQ_STACK_SIZE
		add x26, x25, x26

arch/arm64/kernel/irq.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -32,6 +32,7 @@ unsigned long irq_err_count;

		/* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. */
		DEFINE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack) __aligned(16);
		DEFINE_PER_CPU(unsigned long *, irq_stack_ptr);

		int arch_show_interrupts(struct seq_file *p, int prec)
		{
		@@ -50,8 +51,17 @@ void __init set_handle_irq(void (handle_irq)(struct pt_regs ))
		handle_arch_irq = handle_irq;
		}

		static void init_irq_stacks(void)
		{
		int cpu;

		for_each_possible_cpu(cpu)
		per_cpu(irq_stack_ptr, cpu) = per_cpu(irq_stack, cpu);
		}

		void __init init_IRQ(void)
		{
		init_irq_stacks();
		irqchip_init();
		if (!handle_arch_irq)
		panic("No interrupt controller found.");

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