From d224a69e3d80fe08f285d1f41d21b590bae4fa9f Mon Sep 17 00:00:00 2001 From: James Morse Date: Fri, 18 Dec 2015 16:01:47 +0000 Subject: [PATCH] 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 Signed-off-by: James Morse [will: use get_thread_info macro] Signed-off-by: Will Deacon --- arch/arm64/include/asm/irq.h | 2 -- arch/arm64/kernel/entry.S | 19 +++++++++--------- arch/arm64/kernel/irq.c | 38 +----------------------------------- 3 files changed, 11 insertions(+), 48 deletions(-) diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h index 3bece4379bd9..b77197d941fc 100644 --- a/arch/arm64/include/asm/irq.h +++ b/arch/arm64/include/asm/irq.h @@ -11,8 +11,6 @@ #include #include -#define __ARCH_HAS_DO_SOFTIRQ - struct pt_regs; DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 0667fb7d8bb1..c0db321db7e1 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -181,19 +181,20 @@ alternative_endif .macro irq_stack_entry mov x19, sp // preserve the original sp - this_cpu_ptr irq_stack, x25, x26 - /* - * Check the lowest address on irq_stack for the irq_count value, - * incremented by do_softirq_own_stack if we have re-enabled irqs - * while on the irq_stack. + * Compare sp with the current thread_info, if the top + * ~(THREAD_SIZE - 1) bits match, we are on a task stack, and + * should switch to the irq stack. */ - ldr x26, [x25] - cbnz x26, 9998f // recursive use? + and x25, x19, #~(THREAD_SIZE - 1) + cmp x25, tsk + b.ne 9998f - /* switch to the irq stack */ + this_cpu_ptr irq_stack, x25, x26 mov x26, #IRQ_STACK_START_SP add x26, x25, x26 + + /* switch to the irq stack */ mov sp, x26 /* @@ -405,10 +406,10 @@ el1_irq: bl trace_hardirqs_off #endif + get_thread_info tsk irq_handler #ifdef CONFIG_PREEMPT - get_thread_info tsk ldr w24, [tsk, #TI_PREEMPT] // get preempt count cbnz w24, 1f // preempt count != 0 ldr x0, [tsk, #TI_FLAGS] // get flags diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c index ff7ebb710e51..2386b26c0712 100644 --- a/arch/arm64/kernel/irq.c +++ b/arch/arm64/kernel/irq.c @@ -25,24 +25,14 @@ #include #include #include -#include #include #include unsigned long irq_err_count; -/* - * irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. - * irq_stack[0] is used as irq_count, a non-zero value indicates the stack - * is in use, and el?_irq() shouldn't switch to it. This is used to detect - * recursive use of the irq_stack, it is lazily updated by - * do_softirq_own_stack(), which is called on the irq_stack, before - * re-enabling interrupts to process softirqs. - */ +/* 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 IRQ_COUNT() (*per_cpu(irq_stack, smp_processor_id())) - int arch_show_interrupts(struct seq_file *p, int prec) { show_ipi_list(p, prec); @@ -66,29 +56,3 @@ void __init init_IRQ(void) if (!handle_arch_irq) panic("No interrupt controller found."); } - -/* - * do_softirq_own_stack() is called from irq_exit() before __do_softirq() - * re-enables interrupts, at which point we may re-enter el?_irq(). We - * increase irq_count here so that el1_irq() knows that it is already on the - * irq stack. - * - * Called with interrupts disabled, so we don't worry about moving cpu, or - * being interrupted while modifying irq_count. - * - * This function doesn't actually switch stack. - */ -void do_softirq_own_stack(void) -{ - int cpu = smp_processor_id(); - - WARN_ON_ONCE(!irqs_disabled()); - - if (on_irq_stack(current_stack_pointer, cpu)) { - IRQ_COUNT()++; - __do_softirq(); - IRQ_COUNT()--; - } else { - __do_softirq(); - } -} -- 2.20.1