arch/x86/kernel/irq_32.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
   4  *
   5  * This file contains the lowest level x86-specific interrupt
   6  * entry, irq-stacks and irq statistics code. All the remaining
   7  * irq logic is done by the generic kernel/irq/ code and
   8  * by the x86-specific irq controller code. (e.g. i8259.c and
   9  * io_apic.c.)
  10  */
  11
  12 #include <linux/seq_file.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/kernel_stat.h>
  15 #include <linux/notifier.h>
  16 #include <linux/cpu.h>
  17 #include <linux/delay.h>
  18 #include <linux/uaccess.h>
  19 #include <linux/percpu.h>
  20 #include <linux/mm.h>
  21
  22 #include <asm/apic.h>
  23 #include <asm/nospec-branch.h>
  24
  25 #ifdef CONFIG_DEBUG_STACKOVERFLOW
  26
  27 int sysctl_panic_on_stackoverflow __read_mostly;
  28
  29 /* Debugging check for stack overflow: is there less than 1KB free? */
  30 static int check_stack_overflow(void)
  31 {
  32         long sp;
  33
  34         __asm__ __volatile__("andl %%esp,%0" :
  35                              "=r" (sp) : "0" (THREAD_SIZE - 1));
  36
  37         return sp < (sizeof(struct thread_info) + STACK_WARN);
  38 }
  39
  40 static void print_stack_overflow(void)
  41 {
  42         printk(KERN_WARNING "low stack detected by irq handler\n");
  43         dump_stack();
  44         if (sysctl_panic_on_stackoverflow)
  45                 panic("low stack detected by irq handler - check messages\n");
  46 }
  47
  48 #else
  49 static inline int check_stack_overflow(void) { return 0; }
  50 static inline void print_stack_overflow(void) { }
  51 #endif
  52
  53 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
  54 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
  55
  56 static void call_on_stack(void *func, void *stack)
  57 {
  58         asm volatile("xchgl     %%ebx,%%esp     \n"
  59                      CALL_NOSPEC
  60                      "movl      %%ebx,%%esp     \n"
  61                      : "=b" (stack)
  62                      : "0" (stack),
  63                        [thunk_target] "D"(func)
  64                      : "memory", "cc", "edx", "ecx", "eax");
  65 }
  66
  67 static inline void *current_stack(void)
  68 {
  69         return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
  70 }
  71
  72 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
  73 {
  74         struct irq_stack *curstk, *irqstk;
  75         u32 *isp, *prev_esp, arg1;
  76
  77         curstk = (struct irq_stack *) current_stack();
  78         irqstk = __this_cpu_read(hardirq_stack);
  79
  80         /*
  81          * this is where we switch to the IRQ stack. However, if we are
  82          * already using the IRQ stack (because we interrupted a hardirq
  83          * handler) we can't do that and just have to keep using the
  84          * current stack (which is the irq stack already after all)
  85          */
  86         if (unlikely(curstk == irqstk))
  87                 return 0;
  88
  89         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
  90
  91         /* Save the next esp at the bottom of the stack */
  92         prev_esp = (u32 *)irqstk;
  93         *prev_esp = current_stack_pointer;
  94
  95         if (unlikely(overflow))
  96                 call_on_stack(print_stack_overflow, isp);
  97
  98         asm volatile("xchgl     %%ebx,%%esp     \n"
  99                      CALL_NOSPEC
 100                      "movl      %%ebx,%%esp     \n"
 101                      : "=a" (arg1), "=b" (isp)
 102                      :  "0" (desc),   "1" (isp),
 103                         [thunk_target] "D" (desc->handle_irq)
 104                      : "memory", "cc", "ecx");
 105         return 1;
 106 }
 107
 108 /*
 109  * allocate per-cpu stacks for hardirq and for softirq processing
 110  */
 111 void irq_ctx_init(int cpu)
 112 {
 113         struct irq_stack *irqstk;
 114
 115         if (per_cpu(hardirq_stack, cpu))
 116                 return;
 117
 118         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 119                                                THREADINFO_GFP,
 120                                                THREAD_SIZE_ORDER));
 121         per_cpu(hardirq_stack, cpu) = irqstk;
 122
 123         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 124                                                THREADINFO_GFP,
 125                                                THREAD_SIZE_ORDER));
 126         per_cpu(softirq_stack, cpu) = irqstk;
 127
 128         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 129                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 130 }
 131
 132 void do_softirq_own_stack(void)
 133 {
 134         struct irq_stack *irqstk;
 135         u32 *isp, *prev_esp;
 136
 137         irqstk = __this_cpu_read(softirq_stack);
 138
 139         /* build the stack frame on the softirq stack */
 140         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 141
 142         /* Push the previous esp onto the stack */
 143         prev_esp = (u32 *)irqstk;
 144         *prev_esp = current_stack_pointer;
 145
 146         call_on_stack(__do_softirq, isp);
 147 }
 148
 149 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
 150 {
 151         int overflow = check_stack_overflow();
 152
 153         if (IS_ERR_OR_NULL(desc))
 154                 return false;
 155
 156         if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
 157                 if (unlikely(overflow))
 158                         print_stack_overflow();
 159                 generic_handle_irq_desc(desc);
 160         }
 161
 162         return true;
 163 }