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/irq.h>
  15 #include <linux/kernel_stat.h>
  16 #include <linux/notifier.h>
  17 #include <linux/cpu.h>
  18 #include <linux/delay.h>
  19 #include <linux/uaccess.h>
  20 #include <linux/percpu.h>
  21 #include <linux/mm.h>
  22
  23 #include <asm/apic.h>
  24 #include <asm/nospec-branch.h>
  25
  26 #ifdef CONFIG_DEBUG_STACKOVERFLOW
  27
  28 int sysctl_panic_on_stackoverflow __read_mostly;
  29
  30 /* Debugging check for stack overflow: is there less than 1KB free? */
  31 static int check_stack_overflow(void)
  32 {
  33         long sp;
  34
  35         __asm__ __volatile__("andl %%esp,%0" :
  36                              "=r" (sp) : "0" (THREAD_SIZE - 1));
  37
  38         return sp < (sizeof(struct thread_info) + STACK_WARN);
  39 }
  40
  41 static void print_stack_overflow(void)
  42 {
  43         printk(KERN_WARNING "low stack detected by irq handler\n");
  44         dump_stack();
  45         if (sysctl_panic_on_stackoverflow)
  46                 panic("low stack detected by irq handler - check messages\n");
  47 }
  48
  49 #else
  50 static inline int check_stack_overflow(void) { return 0; }
  51 static inline void print_stack_overflow(void) { }
  52 #endif
  53
  54 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
  55 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
  56
  57 static void call_on_stack(void *func, void *stack)
  58 {
  59         asm volatile("xchgl     %%ebx,%%esp     \n"
  60                      CALL_NOSPEC
  61                      "movl      %%ebx,%%esp     \n"
  62                      : "=b" (stack)
  63                      : "0" (stack),
  64                        [thunk_target] "D"(func)
  65                      : "memory", "cc", "edx", "ecx", "eax");
  66 }
  67
  68 static inline void *current_stack(void)
  69 {
  70         return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
  71 }
  72
  73 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
  74 {
  75         struct irq_stack *curstk, *irqstk;
  76         u32 *isp, *prev_esp, arg1;
  77
  78         curstk = (struct irq_stack *) current_stack();
  79         irqstk = __this_cpu_read(hardirq_stack);
  80
  81         /*
  82          * this is where we switch to the IRQ stack. However, if we are
  83          * already using the IRQ stack (because we interrupted a hardirq
  84          * handler) we can't do that and just have to keep using the
  85          * current stack (which is the irq stack already after all)
  86          */
  87         if (unlikely(curstk == irqstk))
  88                 return 0;
  89
  90         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
  91
  92         /* Save the next esp at the bottom of the stack */
  93         prev_esp = (u32 *)irqstk;
  94         *prev_esp = current_stack_pointer;
  95
  96         if (unlikely(overflow))
  97                 call_on_stack(print_stack_overflow, isp);
  98
  99         asm volatile("xchgl     %%ebx,%%esp     \n"
 100                      CALL_NOSPEC
 101                      "movl      %%ebx,%%esp     \n"
 102                      : "=a" (arg1), "=b" (isp)
 103                      :  "0" (desc),   "1" (isp),
 104                         [thunk_target] "D" (desc->handle_irq)
 105                      : "memory", "cc", "ecx");
 106         return 1;
 107 }
 108
 109 /*
 110  * allocate per-cpu stacks for hardirq and for softirq processing
 111  */
 112 void irq_ctx_init(int cpu)
 113 {
 114         struct irq_stack *irqstk;
 115
 116         if (per_cpu(hardirq_stack, cpu))
 117                 return;
 118
 119         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 120                                                THREADINFO_GFP,
 121                                                THREAD_SIZE_ORDER));
 122         per_cpu(hardirq_stack, cpu) = irqstk;
 123
 124         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 125                                                THREADINFO_GFP,
 126                                                THREAD_SIZE_ORDER));
 127         per_cpu(softirq_stack, cpu) = irqstk;
 128
 129         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 130                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 131 }
 132
 133 void do_softirq_own_stack(void)
 134 {
 135         struct irq_stack *irqstk;
 136         u32 *isp, *prev_esp;
 137
 138         irqstk = __this_cpu_read(softirq_stack);
 139
 140         /* build the stack frame on the softirq stack */
 141         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 142
 143         /* Push the previous esp onto the stack */
 144         prev_esp = (u32 *)irqstk;
 145         *prev_esp = current_stack_pointer;
 146
 147         call_on_stack(__do_softirq, isp);
 148 }
 149
 150 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
 151 {
 152         int overflow = check_stack_overflow();
 153
 154         if (IS_ERR_OR_NULL(desc))
 155                 return false;
 156
 157         if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
 158                 if (unlikely(overflow))
 159                         print_stack_overflow();
 160                 generic_handle_irq_desc(desc);
 161         }
 162
 163         return true;
 164 }