arch/x86/kernel/irq_32.c

   1 /*
   2  *      Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
   3  *
   4  * This file contains the lowest level x86-specific interrupt
   5  * entry, irq-stacks and irq statistics code. All the remaining
   6  * irq logic is done by the generic kernel/irq/ code and
   7  * by the x86-specific irq controller code. (e.g. i8259.c and
   8  * io_apic.c.)
   9  */
  10
  11 #include <linux/seq_file.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/kernel_stat.h>
  14 #include <linux/notifier.h>
  15 #include <linux/cpu.h>
  16 #include <linux/delay.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/percpu.h>
  19 #include <linux/mm.h>
  20
  21 #include <asm/apic.h>
  22 #include <asm/nospec-branch.h>
  23
  24 #ifdef CONFIG_DEBUG_STACKOVERFLOW
  25
  26 int sysctl_panic_on_stackoverflow __read_mostly;
  27
  28 /* Debugging check for stack overflow: is there less than 1KB free? */
  29 static int check_stack_overflow(void)
  30 {
  31         long sp;
  32
  33         __asm__ __volatile__("andl %%esp,%0" :
  34                              "=r" (sp) : "0" (THREAD_SIZE - 1));
  35
  36         return sp < (sizeof(struct thread_info) + STACK_WARN);
  37 }
  38
  39 static void print_stack_overflow(void)
  40 {
  41         printk(KERN_WARNING "low stack detected by irq handler\n");
  42         dump_stack();
  43         if (sysctl_panic_on_stackoverflow)
  44                 panic("low stack detected by irq handler - check messages\n");
  45 }
  46
  47 #else
  48 static inline int check_stack_overflow(void) { return 0; }
  49 static inline void print_stack_overflow(void) { }
  50 #endif
  51
  52 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
  53 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
  54
  55 static void call_on_stack(void *func, void *stack)
  56 {
  57         asm volatile("xchgl     %%ebx,%%esp     \n"
  58                      CALL_NOSPEC
  59                      "movl      %%ebx,%%esp     \n"
  60                      : "=b" (stack)
  61                      : "0" (stack),
  62                        [thunk_target] "D"(func)
  63                      : "memory", "cc", "edx", "ecx", "eax");
  64 }
  65
  66 static inline void *current_stack(void)
  67 {
  68         return (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
  69 }
  70
  71 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
  72 {
  73         struct irq_stack *curstk, *irqstk;
  74         u32 *isp, *prev_esp, arg1;
  75
  76         curstk = (struct irq_stack *) current_stack();
  77         irqstk = __this_cpu_read(hardirq_stack);
  78
  79         /*
  80          * this is where we switch to the IRQ stack. However, if we are
  81          * already using the IRQ stack (because we interrupted a hardirq
  82          * handler) we can't do that and just have to keep using the
  83          * current stack (which is the irq stack already after all)
  84          */
  85         if (unlikely(curstk == irqstk))
  86                 return 0;
  87
  88         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
  89
  90         /* Save the next esp at the bottom of the stack */
  91         prev_esp = (u32 *)irqstk;
  92         *prev_esp = current_stack_pointer();
  93
  94         if (unlikely(overflow))
  95                 call_on_stack(print_stack_overflow, isp);
  96
  97         asm volatile("xchgl     %%ebx,%%esp     \n"
  98                      CALL_NOSPEC
  99                      "movl      %%ebx,%%esp     \n"
 100                      : "=a" (arg1), "=b" (isp)
 101                      :  "0" (desc),   "1" (isp),
 102                         [thunk_target] "D" (desc->handle_irq)
 103                      : "memory", "cc", "ecx");
 104         return 1;
 105 }
 106
 107 /*
 108  * allocate per-cpu stacks for hardirq and for softirq processing
 109  */
 110 void irq_ctx_init(int cpu)
 111 {
 112         struct irq_stack *irqstk;
 113
 114         if (per_cpu(hardirq_stack, cpu))
 115                 return;
 116
 117         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 118                                                THREADINFO_GFP,
 119                                                THREAD_SIZE_ORDER));
 120         per_cpu(hardirq_stack, cpu) = irqstk;
 121
 122         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 123                                                THREADINFO_GFP,
 124                                                THREAD_SIZE_ORDER));
 125         per_cpu(softirq_stack, cpu) = irqstk;
 126
 127         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 128                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 129 }
 130
 131 void do_softirq_own_stack(void)
 132 {
 133         struct irq_stack *irqstk;
 134         u32 *isp, *prev_esp;
 135
 136         irqstk = __this_cpu_read(softirq_stack);
 137
 138         /* build the stack frame on the softirq stack */
 139         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 140
 141         /* Push the previous esp onto the stack */
 142         prev_esp = (u32 *)irqstk;
 143         *prev_esp = current_stack_pointer();
 144
 145         call_on_stack(__do_softirq, isp);
 146 }
 147
 148 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
 149 {
 150         int overflow = check_stack_overflow();
 151
 152         if (IS_ERR_OR_NULL(desc))
 153                 return false;
 154
 155         if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
 156                 if (unlikely(overflow))
 157                         print_stack_overflow();
 158                 generic_handle_irq_desc(desc);
 159         }
 160
 161         return true;
 162 }